Upgrade or repair oil boiler?

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ess

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I think that once you start looking at Most folks basements you will find the vertical distance from the shower drain to the building lateral is rarely enough to install a DWR unit. Especially if the home is on a septic system and not city sewer. Typically there's 24" or less drop. I'm not saying flat out that it can't be done but it's not all that often. Also, I'd like to see some real numbers on the ROA for a unit sold and installed by a licensed plumber. I know what I charge for the installation and I'm fairly sure the ROA is a long way down the road especially if the shower is only being used a couple times a day by a couple of older people. As far as the heating system goes, his best ROA is to install the indirect and the intellicon and perhaps downfire the boiler slightly.

The cheapest DWR unit that Home Depot sells is almost 600 bucks and 72" long. The shortest is 48" and almost 900 bucks. Add 30% profit for markup! add all the other pipe! valves and fittings at probably around 200 bucks and then add a couple hours labor at another 400 bucks or so and then run the ROA

And that's a real conservative estimate because the chances of having 4 to 6 feet of un obstructed vertical stack are pretty rare. Usually Theres other drains coming into the line and if it's cast iron you can add a bunch more money to the installation because cutting the cast out and supporting the stack is going to run some bucks. If it was planned on a new installation it would make more sense. They claim 5 to 10% savings. If it's costing say 600 a year for hot water, times 10% that's a whopping 60 bucks. Against a thousand dollar plus installation bill? Still make sense? Other things to consider are the distance from the shower drains to the vertical stack. If it's a long way off the water will cool substantially on its way down the drain, drastically decreasing the efficiency of the unit. Oh yes and one more thing. A whole lot of homes don't have a 4" lateral. Generally it's 3" and only goes through the foundation 4"
http://www.homedepot.com/s/Drain%20water%20heat%20recovery?NCNI-5

So I checked the basement, and we have basically a full floor to ceiling exposed section of vertical cast iron drain pipe (about a foot from the wall? I didn't measure). There are some joins, but I think there were 4 feet of pretty basic pipe there (again, didnt measure exactly, so I guess it could be 3 feet - but I wouldn't want to say without having someone look at it in person). We are on septic, and this drain pipe is well removed from the second floor showers, so I don't know if either of those aspects will affect the usefulness of the DWR unit. I will say that having something that could help with heat recovery sounds really nice if we have to go with a heat pump or electric tank.

From looking at pictures, they all show the recovery wrap around thinner drain tubes, so it's possible that either I wasn't looking at the right stack or it's too big to work, but again, a plumber could probably tell me better.

The installation would mostly make sense for us economically if we were using it for comfort first (to make up for not having an indirect) and energy savings second. That said, if we are spending, say $200 a year on hot water with a heat pump system + DWR (quite possibly less), versus $550 -$50 for an oil indirect + DWR, then that's still a $300 / year savings or a 3-4 year to get back the money for the DWR (assuming that the heat pump hot water tank and indirect oil tank cost about the same to have installed, which it sounds like they do, give or take).

Also, I'm seeing estimates of up to 40% savings on water heating costs (which is 5-10% of total energy costs - bit of a difference). I went ahead and estimated less anyway since there are the other factors (cast iron, distance, etc.). It still seems to come out as worth pursuing, even though it's possible that it might not work in our house.

I appreciate the counter-argument, though. :)
 

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I should address the System 2000. We were the 1st company in New Hampshire to install these. At one time we were installing as many as three a week and doing an average of two electric heat to forced hot water heat conversions a week also. The System 2000 is a very good piece of equipment. It is a low mass, 3 pass steel boiler that will run at 87% efficiency all day long. Hot water is made using a stainless steel, 2 pass heat exchanger that makes hot water and stores it typically in a highly insulated 40 gallon storage tank. Its near impossible to run it out of hot water. I have nothing bad to say about System 2000. I have units still running (at 87%) after 30 years in the field and they look like they were installed yesterday except for back then they jackets were painted grey. They are a very efficient way to make hot water. Much cheaper than electric and cheaper than most indirects because the plate exchanger is more efficient at heat transfer. They are pricey though, no doubt about it. If pressed, I would estimate ROA at a bit over 8 years. The other nice thing is that should natural gas become available in your area, the system can be converted very easily just by changing out the burner.

Back to the DWR unit. I have seen a whole lot of numbers thrown out there but when I really look into those numbers I generally find that they are derived from testing applications rather than real life, in home applications. Remember that if someone flushes the toilet, it cools the drain water as will having the shower a long distance from the DWR unit. So does running a sink or washing machine so unless you isolate the shower water totally from the rest of the drainage, those efficiency numbers will be nowhere near 10% and the cost of isolating those drains will in most cases be a whole lot of money. The actual installation requires cutting a section of the vertical draqin pipe from the system and sliding the DWR unit in its place. Then the cold inlet to the water heater needs to be piped over to the DWR unit and the hot water fronm the unit tied back into the water heater inlet. Again, unless its all right next to each other this is going to run into a lot of money also. I just dont see a decent ROA on this but if anybody can prove me wrong, by all means send me a picture of the installation along with the cost of installing the unit and the actual savings derived from the installation.

DWR is not a bad thing. Commercially, in many cases like hotels, hospitals, retirement homes etc they make a lot of sense and can indeed save a lot of money but those applications are using a lot of hot water for extended periods of time. If the plumbing system was designed and installed from the get go the payback is even better but most times it id done as an after thought.

Heat pump hot water plus DWR blind estimate - about $ 5,500.00 could be a whole lot more. Probably not much less

How north of Boston are you?
 
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Reach4

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Unless you have about a 4' vertical drop from your shower drain to the building drain (and almost nobody does) heat recovery won't work. I'd estimate 90% of homes just can't use it because there is almost never enough vertical between the inlet and outlet but maybe you can get lucky.
Why would that heat exchanger need to be vertical?
 

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Because water clings to the outside of a vertical pipe as it drains which allows the most contact time. The other thing to consider with these units is that they work best when whoever is in the shower spends a lot of time in the shower which increases transfer efficiency but of course also increases the burn time of the heater itself. Nothing is for nothing.
 
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ess

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I should address the System 2000. We were the 1st company in New Hampshire to install these. At one time we were installing as many as three a week and doing an average of two electric heat to forced hot water heat conversions a week also. The System 2000 is a very good piece of equipment. It is a low mass, 3 pass steel boiler that will run at 87% efficiency all day long. Hot water is made using a stainless steel, 2 pass heat exchanger that makes hot water and stores it typically in a highly insulated 40 gallon storage tank. Its near impossible to run it out of hot water. I have nothing bad to say about System 2000. I have units still running (at 87%) after 30 years in the field and they look like they were installed yesterday except for back then they jackets were painted grey. They are a very efficient way to make hot water. Much cheaper than electric and cheaper than most indirects because the plate exchanger is more efficient at heat transfer. They are pricey though, no doubt about it. If pressed, I would estimate ROA at a bit over 8 years. The other nice thing is that should natural gas become available in your area, the system can be converted very easily just by changing out the burner.

Do you know if there's a standard estimate for gallons of oil used per year for hot water with the EK-1? If I'm remembering correctly, during the winter the hot water tank gets purge heat from the boiler, but obviously during the summer, the boiler will only be running for the indirect tank.

The conundrum becomes that the more we use the existing heat pump / add heat pumps, the less it makes sense to upgrade the boiler, except for the fact that we get extra benefits (e.g. not running out of hot water, longer lifespan) from the indirect tank that we can't get from a standalone tank. However, I need to figure out how much I'm willing to pay to get that, since replacing our current tank with even a new standard electric one would probably help us a lot. So I'm just trying to get a handle on the difference in up front charges and yearly energy costs.

(I don't remember if this forum allows specific pricing discussion, so I will keep this vague.)

Installation cost:
standard electric tank ($100 rebate, EF > 0.67) < heat pump hw tank ($750 rebate, EF > 2.3) < indirect hw tank << boiler upgrade with indirect hw "included" (e.g. EK-1)

There is a $1000 rebate for forced hot water boilers with AFUE above 90% - I guess there's the Energy Kinetics 90+ Resolute boiler, but I don't know if the increase in price over the EK-1 would wipe out the rebate. The Firebird boiler mentioned previously also has a high enough AFUE, but I don't know whether the Energy Kinetics integration would make the hot water from that system more cost effective (or if it's really the same setup for both systems and the rest is marketing).

I don't want to be guided by rebates, but it's not an insignificant percentage of the overall cost.

Energy cost / year:
heat pump hot water < electric hot water < standard indirect oil hot water
- So what I'm not sure of is where the Energy Kinetics hot water would fit in (same as standard indirect, or less)? For example, if it used about 100 gallons of oil for water per year rather than 150+, then it would likely slot in somewhere between the heat pump and the electric tank.

For the ROI at 8 years, does that include if we reduce our oil load?
Let's say we're currently using 900-1000 gallons of oil per year @ $3.70. For an ROI of under 10 years, I'd expect that we'd need to save about 250-300 gallons of oil / year, or about 25-30% (high but within the realm of possibility).

If we dropped that to 600 gallons of oil per year via insulation + ductless heat pumps, then for an ROI of under 10 years, we'd still need to save the same amount (as we'd be paying the same for the boiler installation), so the percentage savings needs to increase to 42-50% (that seems really high).

(Neither of these oil estimates specifically take into account an increase in oil usage from indirect hot water.)

However, I don't know how likely it is that we can reduce our oil usage to 600 gallons / year or how much ductless units would cost for installation / energy costs (since electricity isn't free). If we put a large ductless on the first floor and one in the basement, we could cover a decent amount of area, although we'd probably need to place a second unit on the first floor (I know, Manual J / heat loss to be sure :) ) and continue using backup heat for a few smaller rooms. There is a $500 rebate for high-efficiency ductless units, which is probably about 10% / on par percentage-wise (I'm guessing?) with the high-efficiency boiler rebate. And we could install the units over time to spread out the cost, plus of course improve insulation / air sealing.
(The other option would be to evaluate extending the Greenspeed to the first floor, which might be more practical if possible, although more disruptive in the house.)

The ductless units are very efficient and have a side benefit of air conditioning, and a downside of needing a decent amount of wall space and condenser space outside (we do have a ductless unit in our attic, so maybe they could share? If not, I'm not actually sure we have room for outdoor units for 2-3 more ductless heat pumps...). They also don't cover hot water, and I'd still want to put some (minimal if possible) money into the existing boiler to add the Intellicon HW+, fix venting, and spot troubleshoot baseboard issues.

A new oil boiler has a downside of using oil (expensive energy costs) and having expensive installation costs for what may become mostly backup heat, and an upside of the cost including improved efficiency, fixing hot water, fixing venting issues, and hopefully figuring out / fixing baseboard heat issues (all of which need to be done anyway).

Adding an indirect to the existing boiler appears to have benefits only of longer lifespan and unlimited hot water, and downsides of more expensive installation and more expensive energy costs.

As for the DWR unit, I appreciate hearing both the pros and the cons - it's giving me a lot to consider.

How north of Boston are you?

Andover - 01810
 

NHmaster3015

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Do you know if there's a standard estimate for gallons of oil used per year for hot water with the EK-1? If I'm remembering correctly, during the winter the hot water tank gets purge heat from the boiler, but obviously during the summer, the boiler will only be running for the indirect tank.

Hard to put a number on that because everyones hot water use varies. I do know that the tank is super insulated and that the exchanger has a very high transfer rate. When we do a System 2000 swap against say a Weil McLain pin type boiler with an indirect the typical savings is generally in the 20 to 30% fuel savings range.

The conundrum becomes that the more we use the existing heat pump / add heat pumps, the less it makes sense to upgrade the boiler, except for the fact that we get extra benefits (e.g. not running out of hot water, longer lifespan) from the indirect tank that we can't get from a standalone tank. However, I need to figure out how much I'm willing to pay to get that, since replacing our current tank with even a new standard electric one would probably help us a lot. So I'm just trying to get a handle on the difference in up front charges and yearly energy costs.

I doubt you would see a significant savings doing a straight up new electric water heater. New ones are not a whole lot better than 20 year old ones. Any indirect is going to save you a few bucks but probably not enough to give you a decent ROA. The new heat pump water heaters are nice although I am hearing of several issues folks are having with them concerning noise and reliability and they are a whole lot more money to purchase and install

(I don't remember if this forum allows specific pricing discussion, so I will keep this vague.)

Installation cost:
standard electric tank ($100 rebate, EF > 0.67) < heat pump hw tank ($750 rebate, EF > 2.3) < indirect hw tank << boiler upgrade with indirect hw "included" (e.g. EK-1)

There is a $1000 rebate for forced hot water boilers with AFUE above 90% - I guess there's the Energy Kinetics 90+ Resolute boiler, but I don't know if the increase in price over the EK-1 would wipe out the rebate. The Firebird boiler mentioned previously also has a high enough AFUE, but I don't know whether the Energy Kinetics integration would make the hot water from that system more cost effective (or if it's really the same setup for both systems and the rest is marketing).

I would bet that the summer cost of hot water with a system 2000 would be less than 200 dollars. Probably a lot less.

I don't want to be guided by rebates, but it's not an insignificant percentage of the overall cost.

Energy cost / year:
heat pump hot water < electric hot water < standard indirect oil hot water
- So what I'm not sure of is where the Energy Kinetics hot water would fit in (same as standard indirect, or less)? For example, if it used about 100 gallons of oil for water per year rather than 150+, then it would likely slot in somewhere between the heat pump and the electric tank.

For the ROI at 8 years, does that include if we reduce our oil load?
Let's say we're currently using 900-1000 gallons of oil per year @ $3.70. For an ROI of under 10 years, I'd expect that we'd need to save about 250-300 gallons of oil / year, or about 25-30% (high but within the realm of possibility).

If we dropped that to 600 gallons of oil per year via insulation + ductless heat pumps, then for an ROI of under 10 years, we'd still need to save the same amount (as we'd be paying the same for the boiler installation), so the percentage savings needs to increase to 42-50% (that seems really high).

(Neither of these oil estimates specifically take into account an increase in oil usage from indirect hot water.)

However, I don't know how likely it is that we can reduce our oil usage to 600 gallons / year or how much ductless units would cost for installation / energy costs (since electricity isn't free). If we put a large ductless on the first floor and one in the basement, we could cover a decent amount of area, although we'd probably need to place a second unit on the first floor (I know, Manual J / heat loss to be sure :) ) and continue using backup heat for a few smaller rooms. There is a $500 rebate for high-efficiency ductless units, which is probably about 10% / on par percentage-wise (I'm guessing?) with the high-efficiency boiler rebate. And we could install the units over time to spread out the cost, plus of course improve insulation / air sealing.
(The other option would be to evaluate extending the Greenspeed to the first floor, which might be more practical if possible, although more disruptive in the house.)

The ductless units are very efficient and have a side benefit of air conditioning, and a downside of needing a decent amount of wall space and condenser space outside (we do have a ductless unit in our attic, so maybe they could share? If not, I'm not actually sure we have room for outdoor units for 2-3 more ductless heat pumps...). They also don't cover hot water, and I'd still want to put some (minimal if possible) money into the existing boiler to add the Intellicon HW+, fix venting, and spot troubleshoot baseboard issues.

A new oil boiler has a downside of using oil (expensive energy costs) and having expensive installation costs for what may become mostly backup heat, and an upside of the cost including improved efficiency, fixing hot water, fixing venting issues, and hopefully figuring out / fixing baseboard heat issues (all of which need to be done anyway).

Adding an indirect to the existing boiler appears to have benefits only of longer lifespan and unlimited hot water, and downsides of more expensive installation and more expensive energy costs.

As for the DWR unit, I appreciate hearing both the pros and the cons - it's giving me a lot to consider.



Andover - 01810

Ductless mini's are what they are. You get that big evaporator/fan assembly hanging in the room, they make noise and they blow air out which can be uncomfortable to some. They are efficient but they have their downsides also. Some folks love them and other hate them
 

Dana

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I think that once you start looking at Most folks basements you will find the vertical distance from the shower drain to the building lateral is rarely enough to install a DWR unit. Especially if the home is on a septic system and not city sewer. Typically there's 24" or less drop. I'm not saying flat out that it can't be done but it's not all that often. Also, I'd like to see some real numbers on the ROA for a unit sold and installed by a licensed plumber. I know what I charge for the installation and I'm fairly sure the ROA is a long way down the road especially if the shower is only being used a couple times a day by a couple of older people. As far as the heating system goes, his best ROA is to install the indirect and the intellicon and perhaps downfire the boiler slightly.

The cheapest DWR unit that Home Depot sells is almost 600 bucks and 72" long. The shortest is 48" and almost 900 bucks. Add 30% profit for markup! add all the other pipe! valves and fittings at probably around 200 bucks and then add a couple hours labor at another 400 bucks or so and then run the ROA

And that's a real conservative estimate because the chances of having 4 to 6 feet of un obstructed vertical stack are pretty rare. Usually Theres other drains coming into the line and if it's cast iron you can add a bunch more money to the installation because cutting the cast out and supporting the stack is going to run some bucks. If it was planned on a new installation it would make more sense. They claim 5 to 10% savings. If it's costing say 600 a year for hot water, times 10% that's a whopping 60 bucks. Against a thousand dollar plus installation bill? Still make sense? Other things to consider are the distance from the shower drains to the vertical stack. If it's a long way off the water will cool substantially on its way down the drain, drastically decreasing the efficiency of the unit. Oh yes and one more thing. A whole lot of homes don't have a 4" lateral. Generally it's 3" and only goes through the foundation 4"
http://www.homedepot.com/s/Drain%20water%20heat%20recovery?NCNI-5

The high retail cost at Home Depot is why you buy them at EFI instead, where a 3" x 60" costs $525, and a 4" x 48" is $577, either of which have better than 50% energy return at 2.5gpm under the standard NRCAN test protocol. EFI doesn't mark-up shipping with extra handling charges- mine was shipped from their Wisconsin warehouse to MA for less than $15. They come with sufficient fittings to install them on a same-sized drain- you'd only be out more hardware money for other fittings if you were going from 3" to 4" drain and back. (Having done this more than once, I can tell you it's really no BFD, provided you have reasonable access to the drains.

Six 7-minute showers/day at 2gpm would add up to better than 80 gallons/day of 105F water made from 45F water (averaged over the year- the incoming water is colder than that in Andover in winter. That's 667 lbs of water x 60F delta for 40,000 BTU/day. Electricity in MA runs 16-22 cents/kwh. A 0.90 EF hot water heater might hit 93% efficiency in a higher-volume use like that, so every kwh is going to deliver (0.93 x 3412 BTU/kwh= ) ~3175BTU/kwh, so showers would use about (40,000/3125=) 11.7 kwh/day, (x365=) 4270 kwh/year. At 16 cents that's $683/year. If the thing returns 50% of that heat (they actually return more at 2 gpm than it does at the NRCAN tested 2.5gpm) it pays for the hardware in two years.

In the heat pump water heater case it's mostly paid back in reduced tank size/cost, but even ignoring the cost of the induced space heating load of the room energy extracted the payback is less than 4 years. With drainwater heat recovery the 66 gallon AirGenerate would have MORE apparent capacity in showering mode than an 80 gallon electric water heater without drainwater heat recovery. (It does exactly zero for enhancing tub-filling capacity though.)

At $3.50/gallon oil and 85% steady-state efficiency oil delivers at best 117,300 BTU/gallon into the indirect, so at 40,000BTU/day for showering it's taking (40,000/117,300 = 0.34 gallons/day just for showers. Times 365 that's 124 gallons/year, at $3.50 comes to $434/year. At a 50% return from the drainwater heat exchanger it pays for the hardware in less than 4 years. But the abyssmal efficiency during the 3-4 months when the boiler is only heating hot water accrue to the hot water heating, and it's really more like a 3 year return, maybe a bit less, given tht the recent 3-year average price of heating oil in MA is actually a bit higher- closer to $3.75/gallon, and the recently tested combustion efficiency of the boiler in question was 82%.

Of course the economics run longer if y'all take 2 minute showers with 1.5 gpm showerheads for 18gallons/day for 9000BTU/day of showering heat requirement. And it runs considerably longer if there's only two people taking showers.

Good point about the septic where the drain is more likely to be above slab level vs. city sewer where its often below the slab.
 

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Ductless mini's are what they are. You get that big evaporator/fan assembly hanging in the room, they make noise and they blow air out which can be uncomfortable to some. They are efficient but they have their downsides also. Some folks love them and other hate them

The visual aethetics issue is real (though you could go with a ceiling cassette or mini-ducted cassette at a small loss in efficiency), not exactly a thing of beauty, but how beautiful are radiators or fin-tube baseboards? People get used to them, or they mount them where they don't have to look at them.


But the noise issue simply isn't there with the better units. The standard wall coil units of cold climate mini-splits like the Fujitsu XLTH or Mitsubishi M-series are literally quieter than a whisper at low speed, and about as loud as your refrigerator when going full-bore. Look at the noise specifications (measured in A-weighted decibels in those, or "dbA")- at mid-speed they're in the 30-35 db(A) range which is about as loud as whisper at a distance of three to six feet. Properly sized they would be running nearly continuously at low to mid speed except when it's below 15F outside, at which point it sounds as loud as a refrigerator, but it's mostly a whoosh, without the hum/rattle of an actual refrigerator.
 

ess

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I doubt you would see a significant savings doing a straight up new electric water heater. New ones are not a whole lot better than 20 year old ones.

That would be assuming that the current one is working properly. :) We're hoping that our electric bills are high partially because our water heater is running poorly (I'm not sure how to confirm that). We could be wrong, but considering the age of the unit, I figured it was prudent at least to have a plan in case it dies, or in case we want to try draining it / doing other horribly deferred maintenance that from my (amateur) research has the potential to cause the unit to die anyway.

I would bet that the summer cost of hot water with a system 2000 would be less than 200 dollars. Probably a lot less.
At $3.70 / gallon of oil, that comes out to about 54 gallons.

So since the summer is when the boiler isn't getting benefit from running for heating the house was well, would you then bet that the yearly cost would be under $400, or around $100 - $110 gallons of oil? Less? I realize that you don't know our hot water patterns, etc.

I wish the hot water heater had a gallon counter, but let's say that we use 70 gallons of hot water / day (no hot tub!).

According to energy.gov, at the best case scenario for an Electric tank is 0.95 EF and $0.16 / kWH (I don't have our electric rate off-hand), the cost per year is $805, or $67 / month. That's actually higher than I expected for a new one.

Doing some math, assuming everything else stays the same but the EF changes to 2.3 (e.g. heat pump, no resistance heat / moisture or air inefficiencies), the cost per year would be around $368 ($31 / month).

Comparing it to oil at $3.70 (or let's say $3.75), 100 gallons is $375 ($31 / month), 150 is $563 ($47 / month), and 200 is $750 ($63 / month).

So that seems to be:

heat pump ~= best case new boiler indirect < middle case new boiler indirect < old boiler indirect < electric tank
- assuming that DWR would assist them all equally and this can be taken out of the calculations

If we could reduce the hot water further via the DWR, that would be even better, although since there don't tend to be more than 2 showers at the same time right now (because we can't, really, unless the 3rd and possibly half of the 2nd shower is chilly), that might reduce the payback a bit. I still like the concept, even though we'd have to check on the possibility of execution.
 

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Electric water heater usually either work or they don't. The only thing that might cause it to run more would be a horrendous build up of minerals and even then, probably not. Newer ones gain some efficiency because of the added insulation but yours ain't all that old and probably has about all they can cram into the jacket. Is the yellow DOE tag still on it? They have two 1500 watt elements so they are 100% efficient as any electric element heater is. I would say the average for an electric water heater is somewhere around 50 to 70 bucks a month. What is your water heating cost?
 

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nhmaster3015;415637 Back to the DWR unit. I have seen a whole lot of numbers thrown out there but when I really look into those numbers I generally find that they are derived from testing applications rather than real life said:
Remember that if someone flushes the toilet, it cools the drain water as will having the shower a long distance from the DWR unit. So does running a sink or washing machine so unless you isolate the shower water totally from the rest of the drainage, those efficiency numbers will be nowhere near 10% and the cost of isolating those drains will in most cases be a whole lot of money.[/B] The actual installation requires cutting a section of the vertical draqin pipe from the system and sliding the DWR unit in its place. Then the cold inlet to the water heater needs to be piped over to the DWR unit and the hot water fronm the unit tied back into the water heater inlet. Again, unless its all right next to each other this is going to run into a lot of money also. I just dont see a decent ROA on this but if anybody can prove me wrong, by all means send me a picture of the installation along with the cost of installing the unit and the actual savings derived from the installation.

DWR is not a bad thing. Commercially, in many cases like hotels, hospitals, retirement homes etc they make a lot of sense and can indeed save a lot of money but those applications are using a lot of hot water for extended periods of time. If the plumbing system was designed and installed from the get go the payback is even better but most times it id done as an after thought.

Heat pump hot water plus DWR blind estimate - about $ 5,500.00 could be a whole lot more. Probably not much less

How north of Boston are you?


That's a good theory, but jusst playn rong. Throw some real numbers on it, or tell us your actual experience with it.

A toilet drains in less that 10 seconds, at a huge gpm rate (= low heat exchange rate), and is usually at or near room temp, not 45F.

Sink flows are typically low compared to shower flows, and not all cold water- some are going to be at showering temp or higher. The impact to the showerer is simply not there:

Mine shares a drain with two bathrooms, and neither the antique 5 gallon flush from the upstairs bath (or the user washing his hands afterward) has no perceptible impact on the sensed temperature in the shower. This is something that occurs at my house about once a week or so.

Unless you go out of your way to run a cold sink draw continuously and at a high rate, the net impact of those other flows on the shower temperature and heat recovery is miniscule. There is no point to isolating it. In a 6 person household you'd have to orchestrate water use optimally badly to have a real impact on the heat recovery efficiency.

Street price on the ATI66 is a couple grand, maybe another $100 to have it shipped. Then figure $600 for the DWHR through EFI, maybe another $100-200 in pipe & fittings & electrical hardware, and the raw hardware cost still comes in under $3K.

That leaves a lot o' margin to come up with another $2500-2600 for installing it all.

I suppose if you went nuts isolating all the drains & potable runs so that there isn't any possibility of other flows interacting with the heat exchanger you could run the bill up that high, but there really isn't any point to doing that isolation. The output of the HX is pretty tepid- if somebody can't stand brushing their teeth with 73F water it could be an issue (it would mean they couldn't brush their teeth in the summer without purging the cold line with new incoming water, and could never tolerate visiting Florida. :) ) But that's about it for the un-intentended consequences of not isolating it.
 

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I wish the hot water heater had a gallon counter, but let's say that we use 70 gallons of hot water / day (no hot tub!).

According to energy.gov, at the best case scenario for an Electric tank is 0.95 EF and $0.16 / kWH (I don't have our electric rate off-hand), the cost per year is $805, or $67 / month. That's actually higher than I expected for a new one.

Doing some math, assuming everything else stays the same but the EF changes to 2.3 (e.g. heat pump, no resistance heat / moisture or air inefficiencies), the cost per year would be around $368 ($31 / month).

Comparing it to oil at $3.70 (or let's say $3.75), 100 gallons is $375 ($31 / month), 150 is $563 ($47 / month), and 200 is $750 ($63 / month).

So that seems to be:

heat pump ~= best case new boiler indirect < middle case new boiler indirect < old boiler indirect < electric tank
- assuming that DWR would assist them all equally and this can be taken out of the calculations

If we could reduce the hot water further via the DWR, that would be even better, although since there don't tend to be more than 2 showers at the same time right now (because we can't, really, unless the 3rd and possibly half of the 2nd shower is chilly), that might reduce the payback a bit. I still like the concept, even though we'd have to check on the possibility of execution.

You can do a bucket-test at your shower head to figure the gpm, and measure the incoming water temp at a tap nearest the point of entry to the house. At 8.34 lbs/gallon and 2 gpm with a 60F rise it's about 1000 BTU/minute. With 6 people showering that's likely to be more than half the total hot water use.

EF testing is done at a standard draw pattern & volume, and the total daily volume is 64.2 gallons, which would be fairly parsimonious use of hot water for a 6 person household, but typical of 3-4 person households (with large variations to the 1-sigma ticks.) With higher volume use, less of the total is going to standby loss, and the as-used EF climbs a bit. With straight electric hot water heaters the standby is low, even a cheapie has an EF of 0.90, which means only 10% of the total went to standby loss, the rest went to heating up the water. Bumping it up to an EF of 0.95 by doubling the insulation makes only a 6% improvement in the overall annual power being used.

If you double the flow on a 50% drainwater heat exchanger from 2.5gpm to 5gmp the returned heat is still going to be about 40% of the total. A 50% DWHR unit running at 1.5gpm would return about 60%. see: http://www.gfxtechnology.com/EFF.pdf

With the heat pump water heater, at least 6-7 months of the year a bit more than half the heat going into the water has to be made up by the heating system to keep the basement at temp (assuming it's installed in the basement for convenience.) If the heating system is the oil boiler parked in the garage it'll have a very different cost-basis than if the basement is heated with a 3/4 ton mini-split. The MSZ-FH09NA will run an average COP of nearly 3.5 in this climate, putting out between 10-12,000 BTU per kwh, which is pretty cheap heat compared to oil in an 82% burner where the standby losses of the boiler itself are true losses, outside the thermal envelope of the building. (Call it something like 70-75% efficiency due those losses.)
 

ess

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Electric water heater usually either work or they don't. The only thing that might cause it to run more would be a horrendous build up of minerals and even then, probably not. Newer ones gain some efficiency because of the added insulation but yours ain't all that old and probably has about all they can cram into the jacket. Is the yellow DOE tag still on it? They have two 1500 watt elements so they are 100% efficient as any electric element heater is. I would say the average for an electric water heater is somewhere around 50 to 70 bucks a month. What is your water heating cost?

It does still have that tag on it! The tag references 1994 energy prices (although maybe they just didn't update them regularly).

GE PE50M9A 50 gallon water heater (licensed from Rheem)
http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=PE50M9A
Energy factor 0.91; First hour delivery 60 gph

4828 kWH / year or $406 per year estimated - I'm assuming that's at a lower kWH rate than around here (if I do the math correctly, like 8.4 cents / kWH). I checked our bill, and we're right around 17 - 17.5 cents / kWH. If we use the described 4828 kWH / year on hot water, then that would be 4828 * .17 = $821 ($68 / month).

I don't know how to dial in as to how much of our electric bill is from the hot water heater. If we're actually at the 4828 kWH / year level, then at this time of year the hot water heater would be about a quarter of our electric bills. (I kind of hope it's more so that we can save more when it's replaced...)
 

ess

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You can do a bucket-test at your shower head to figure the gpm, and measure the incoming water temp at a tap nearest the point of entry to the house. At 8.34 lbs/gallon and 2 gpm with a 60F rise it's about 1000 BTU/minute. With 6 people showering that's likely to be more than half the total hot water use.

I did that at one point, and I think we have a 1.5 gpm and a 2.5 gpm (which I'll switch out at some point). The kids are too little for their own showers right now, but that will change in the future, so it's good to be prepared. I think that's why my very rough estimate was more around what might be standerd for a 3-4 person household, not to mention that I may have underestimated quite a bit.

With the heat pump water heater, at least 6-7 months of the year a bit more than half the heat going into the water has to be made up by the heating system to keep the basement at temp (assuming it's installed in the basement for convenience.) If the heating system is the oil boiler parked in the garage it'll have a very different cost-basis than if the basement is heated with a 3/4 ton mini-split. The MSZ-FH09NA will run an average COP of nearly 3.5 in this climate, putting out between 10-12,000 BTU per kwh, which is pretty cheap heat compared to oil in an 82% burner where the standby losses of the boiler itself are true losses, outside the thermal envelope of the building. (Call it something like 70-75% efficiency due those losses.)

I think it's coming down to a choice between:
1) Heat pump hot water system, add at least a ductless unit in the basement (and possibly others over time) and try to use the oil boiler as little as possible / put only enough money into it to fix a couple of lingering issues. If the Airgenerate is ducted to use outside air instead, then that might help as well.

1830 x .17 = ~$311 / year electricity costs, not counting basement heat loss that needs replacing and if the backup resistance heating for the hw heater kicks in.

or

2) Indirect hot water system after upgrading the boiler, assuming that the efficiencies and savings will be high enough (e.g. no more than 100-120 gallons of oil for hot water / year). Has a side benefit of overlapping with some of the work we'd probably need to do on the boiler / baseboard setup anyway (vent fixes, smart controls, etc.), which mitigates installation costs a bit.

I can't see any way that we'd get the current boiler to an efficiency level that an indirect tank would be cost effective, and straight electric units just seem too costly over time.

In either case, investigation of DWHR seems rational, either to offset increasing oil costs or to provide better recovery for the heat pump unit.
 

NHmaster3015

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Ok, I went back to the 1st post. You have a HydroTherm boiler......... Its crap. Its a single pass, pin exchanger 60 year old technology boiler. Its AFUE claims are suspect and most likely manipulated in the lab it was tested in. It no doubt is capable of mid 80's for combustion efficiency but that has little to do with the boilers ability to transfer heat efficiently. In short, best bang for the buck, System 2000 or the Firebird boiler with an indirect. Estimated fuel savings? At least 15% and probably closer to 30% add Intilicon or similar control and I'd be real suprised if you didn't see 30%
 

ess

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Ok, I went back to the 1st post. You have a HydroTherm boiler......... Its crap. Its a single pass, pin exchanger 60 year old technology boiler. Its AFUE claims are suspect and most likely manipulated in the lab it was tested in. It no doubt is capable of mid 80's for combustion efficiency but that has little to do with the boilers ability to transfer heat efficiently. In short, best bang for the buck, System 2000 or the Firebird boiler with an indirect. Estimated fuel savings? At least 15% and probably closer to 30% add Intilicon or similar control and I'd be real suprised if you didn't see 30%

I am so not surprised, as everything else put in by those same people was basically the cheapest crap they could find.

I don't know about the Firebird, but doesn't the Energy Kinetics have smart controls / ODR stuff built in (like the Buderus high efficiency ones with Logamatic)? Would there still be benefit to adding an after-market control like the Intellicon HW+?
 

NHmaster3015

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I am so not surprised, as everything else put in by those same people was basically the cheapest crap they could find.

I don't know about the Firebird, but doesn't the Energy Kinetics have smart controls / ODR stuff built in (like the Buderus high efficiency ones with Logamatic)? Would there still be benefit to adding an after-market control like the Intellicon HW+?

Both come with smart controls. You won't need the Intelicon
 
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