Should I stop water heater maintenance?

[Dana]

Dana, including the increase in real estate value, and the energy savings, which projects do you think would break even in 5 years?

If you need a 5 year "payback" air sealing is about the only energy related upgrade that will break even in that time frame. If you discount your labor to $0 and use reclaimed foam board for insulating a basement it might pay off in that time frame in higher-priced energy markets if 1/3 or more of the wall is above grade.

Whether or not a new or upgraded boiler increases property value at all (or by how much) is something only a local real estate company could estimate with any accuracy.

 

[DIYorBust]

Just wanted to explore that a little since you said you were looking to downsize and leave the region in 5 years. That said, as an alternative to re-lining the Chimney the economics might look better. But as an architect you probably know this already, and there's something to be said for just doing a quality job. I'd guess buyers will underestimate the value of your work and will comp you to houses that need all new mechanical, but you might find someone smart enough to pay up. At least then they can finance those improvements with the mortgage.

 

[Sponsor]

 

[Dana]

Quick question. With the current boiler oversized, would it make sense in terms of energy savings to lower the limit control to 180ºF? Would it be a good test to see if a new ModCon boiler with that as the max would be constrained by the amount of radiation in the house? Our chimney never had a cap until we added one. Our last cleaning and inspection went OK, but we were put on notice that we might eventually need a liner and that could push us to a ModCon.

An even easier, quicker and more accurate way to find out is to take 15-30 minutes to run a fuel use load calculation based on some wintertime-only gas bills.

If the fuel use numbers imply a heat load of 60,000 BTU/hr @ +15F you have more than 30% margin of radiation at 180F EWT, which is enough to sail through even the coldest Polar Vortex event cold snaps in your area.

If the numbers indicate a load of 75K @ +15F it'll still heat the place comfortably more than 99% of the time, and still keep up +5F or a bit colder. But it might lose ground during extreme weather events if it stays below +5F all day.

If you're going to keep the beastie boiler for more than a couple of years it may be cost effective to add a heat purging economizer control, which will lower the average idling temperature, which lowers the heat loss to the basement, which also lowers the average heat load to the house. But in general it's not usually worth investing anything in a boiler that old.

A simpler way to lower the idling losses is to lower the peak temperature of the boiler. With a fuel use heat load calculation we could use that to figure out a reasonable high-limit temperature to set the boiler to. As long as the entering water temperature at the boiler doesn't drop to under 130F it won't damage the boiler, but you may need to hold the line at 140F return water entering the boiler to keep flue condensation issues well controlled. At an average water temp of 150F (160F out, 140F return, or thereabout) 10" cast iron baseboard delivers about 390BTU/hr per foot, so the 175' of baseboard would be good for about 68,000 BTU/hr, which might be enough. That would reduce the peak duty cycle of the CGM-7 to about 40%, (68K/165K= 41%) but that's not a disaster as long as it's not short-cycling. Without running the math I'm guesstimating there is enough thermal mass in the system (and not too much) that it'll probably be fine to run it at 155-160F at the high-limit without condensation or short cycling issues, and the remaining question would be if it actually keeps up with the load.

Running the system with 190F water when it doesn't really need it often results in comfort problems like room temperature overshoots followed by a chill. Running it at the lower temperature is generally more comfortable, with low room temperature swings.

 

[Robert Snow]

An even easier, quicker and more accurate way to find out is to take 15-30 minutes to run a fuel use load calculation based on some wintertime-only gas bills.

If the fuel use numbers imply a heat load of 60,000 BTU/hr @ +15F you have more than 30% margin of radiation at 180F EWT, which is enough to sail through even the coldest Polar Vortex event cold snaps in your area.

Great guess on the fuel use number. I used 388CCF the month of January. So, 38.8 million BTUs in and 27.2 million out using 70% efficiency. At 65ºF base temp there were 966 degree days. January was brutally cold here, with the highest fuel bill we've ever seen.
27.2 million BTU / (966 degree days x 24 hours) = 1,173 BTU per degree hour
65ºF less 15ºF (99% for Philadelphia) yields 50º - so if I understand correctly, the heat load is 58,650 BTU/hr

I lowered the high limit from 200ºF not long after we moved in. Probably should have gone lower after the windows were replaced. Seems like condensation issues shouldn't be a problem. This information has been extremely helpful.

 

[Robert Snow]

Just wanted to explore that a little since you said you were looking to downsize and leave the region in 5 years. That said, as an alternative to re-lining the Chimney the economics might look better. But as an architect you probably know this already, and there's something to be said for just doing a quality job. I'd guess buyers will underestimate the value of your work and will comp you to houses that need all new mechanical, but you might find someone smart enough to pay up. At least then they can finance those improvements with the mortgage.

Having been here almost 30 years, the work we've done has served us and will benefit future owners. I think we spent about half the purchase price of the house in the first couple of years, dealing with a lot of deferred maintenance. We ripped out the soggy finished basement right away, which they tried to use as a selling point. We've probably spent that much again on renovations and upgrades. The location cut my wife's drive to work in half and I had a great mass transit ride into the city for all those years. I'm taking a slightly different approach now that I've retired. Prices are constrained by lenders at this point and not buyers willingness to pay more. It's not just the condition of the housing stock either.

 

[Dana]

Great guess on the fuel use number. I used 388CCF the month of January. So, 38.8 million BTUs in and 27.2 million out using 70% efficiency. At 65ºF base temp there were 966 degree days. January was brutally cold here, with the highest fuel bill we've ever seen.
27.2 million BTU / (966 degree days x 24 hours) = 1,173 BTU per degree hour
65ºF less 15ºF (99% for Philadelphia) yields 50º - so if I understand correctly, the heat load is 58,650 BTU/hr

I lowered the high limit from 200ºF not long after we moved in. Probably should have gone lower after the windows were replaced. Seems like condensation issues shouldn't be a problem. This information has been extremely helpful.

The raw combustion efficiency might still be over 70%, so it's conservative to worst case it at the full nameplate efficiency. With the full nameplate 78.5% the load becomes 58,650 BTU/hr x 78.5/70= 65,772 BTU/hr. That's probably higher than reality due to the gas used for domestic hot water, but could be somewhat lower than reality if your house leaks a lot of air. (It's probably not crazy-leaky if the window replacement job was done reasonably well, and the attic floor was sealed prior to insulation.)

Using ASHRAE's 1.4x multiplier recommendation the biggest cast iron boiler you'd ever want to install there is

---1.4 x 58,650 BTU/hr= ~82 KBTU/hr if it's close to 70% efficiency

---1.4 x 65,772= ~92 KBTU/hr of output at the 78.5% efficiency is still valid (probably not)

With a mod-con boiler 1.2x is almost always more than adequate which would put the bracket between:

--- 1.2 x 58,650 BTU/hr=~ 70 KBTU/hr

---1.2 x 65,772= ~79 KBTU/hr

So, if you were to continue with building envelope upgrades an 80-85K-in condensing boiler would get you there, but for now a 100-110K-in condensing boiler would for sure be enough, and if the boiler has a 10:1 turn down ratio would still modulate well even after a few more efficiency improvements on the house. You have sufficient radiation to deliver the full output of a 100K mod con, and even broken up into two zones a 10:1 turn down boiler wouldn't short cycle on zone calls.

Assuming a design load of 60K. with 175' of baseboard that works out to 343 BTU/hr per foot, which is going to take an average water temp (AWT) of about 145F with a return water temp in the 130s F, which will be a bit above the condensing zone, but at your average wintertime temp of ~35F your heat load would be about 35-36,000 BTU/hr or about 200 BTU/hr per foot, which the radiation would emit at an AWT of 120F, where it would be edging into the mid-90s for efficiency.

A 100K with a 10:1 turn down can modulate as low as about 9500 BTU/hr out, so with the outdoor reset curve dialed-in perfectly it would run pretty much continuously whenever the temperatures dropped into the mid-50s F or cooler, and may even beat it's AFUE tested efficiency by a percent or two. You don't have to settle for a 5:1 turn down or lower, which used to be the standard.

A few boilers that would fill the bill would be the Navien NHB-110, Lochinvar KHB-110 (or NKB-110) , HTP UFT-100W, or Burnham K2WT-100B. There are others. The fire-tube heat exchanger types like the KHB , NKB or UFT have more design forgiveness. Stainless heat exchangers have a much better track record than other materials (avoid aluminum). The HTP-UFT is substantially cheaper than most of the others and simpler to set up than most, and would be the best choice if attempting a DIY (with some pro help at the point of commissioning it.) But choosing can boil down to figuring out which vendors are better supported in your area. Since you're not really in a hurry (and may not even do the project at all) you can take your time to ponder it all. With all of these lipstick-on-mirror basic design calculations already in the can you're in a pretty good position to specify what you need to see in any proposals from installers.

 

[Robert Snow]

The raw combustion efficiency might still be over 70%, so it's conservative to worst case it at the full nameplate efficiency. With the full nameplate 78.5% the load becomes 58,650 BTU/hr x 78.5/70= 65,772 BTU/hr. That's probably higher than reality due to the gas used for domestic hot water, but could be somewhat lower than reality if your house leaks a lot of air. (It's probably not crazy-leaky if the window replacement job was done reasonably well, and the attic floor was sealed prior to insulation.)

I did factor out the gas used for water, gas drier and cooking by subracting the summer numbers. Window job was done as well as could be expected. The insane alpine pitch of the roof makes the attic a difficult problem and the roof is cedar shakes on nailing strips. The problem is that much of the second floor living space is under the sloped roof and not covered by the insulation done under the attic floor. Also the basement is rubble stone and when we moved in, the interior parging was completely gone and the mortar between the stones was falling out from ground water. After ripping out the finished basement, I parged the walls with cement plaster and after all this time, the parging is beginning to crack and fail in a few places. It would be very difficult to install basement wall insulation over what is there and it would get damp. The only other house I've owned was built in 1904 and this one is a piece of cake compared to the first.

This information has all been very useful. A new boiler would be going in during the summer if we were not preparing to move on soon. I've always known the boiler was oversized, but never put two and two together about the radiator capacity being inadequate, although now, I'm pretty sure it is just about right with the envelope fixes we've made. I think I'm now prepared to deal with boiler replacement if necessary, but will research installing an Intellicon-HW+. THANKS!

 

[Dana]

Though Intellicon was one of the first to market, are other decent alternatives, (eg Hydrolevel Hydrostat 3200, Beckett Aquasmart 7610.) Some are more of a pain to program than others, but none take rocket science. The key feature you're looking for it heat purging the boiler prior to firing on a new call for heat. Some/most will "learn" the system based on recent behavior and cut the burner in anticipation of the end of a call for heat to reduce the idling temperature of the boiler, thus reducing standby.

People with electrician skills and the ability to figure out the boiler control schematic can usually install a heat purging economizer control as a DIY for ~$150 out of pocket.

 

[Robert Snow]

People with electrician skills and the ability to figure out the boiler control schematic can usually install a heat purging economizer control as a DIY for ~$150 out of pocket.

I'm watching one on eBay that was removed from a decommissioned boiler. I suppose it will either work or not work. I looked at the installation instructions and it seems simple enough to install. When programming (DLOLIM = xxx ̊F) the default is 115ºF. I assume that if there is no temperature probe plugged into the domestic hot water port, the programming for this doesn't matter. What I'm not sure of is the (HLOLIM = xxx ̊F). Default is 145ºF which I suppose is fine if I drop the high limit from 190ºF to 175ºF on the aquastat. I want to be sure to avoid condensation. I suppose this is how the device wrings the most heat out of the boiler by stopping the boiler from firing while continuing to run the circulator pump with some kind of learning about when to start the heat based on prior cycling of the boiler. We do use setbacks at night and I wonder how the logic on these things deals with that as it happens in real time. Hoping to improve efficiency by at least 5% with those changes. I clean the burners every year and thoroughly clean the heat exchanger every five years or so. I don't think the water in the system has much oxygen in it since there has only ever been a tiny bit of air at the bleed valves upstairs. Just replaced the automatic air vent this year. I have always assumed that corrosion kills most boilers.

 

[Dana]

These things work just fine with setback strategies, and you can program out the domestic hot water control stuff. The low-limit is the most important thing to get right, which is the "purge to" temperature, then set the high limit to as high as you like- 200F is fine. With a gas burner vented into a tile lined flue 135-140F is fine. If it had a right sized metal liner 130F would be fine. The default 145F would be appropriate for oil burners, which have much more acidic exhaust characteristics.

During long recovery ramps from setbacks it might actually hit the high limit (probably will sometimes, with a boiler oversized for the radiation), but by purging to 130F or 140F at the beginning of a call for heat the system will slew through a much wider temperature range compared to the 10-25F it's constrained to for typical aquastat controls, for a much longer initial burn during setback recovery. When it hits the high limit it'll purge down to some intermediate temperature (the controller may "learn" to optimize that intermediate temperature after a few days using setback) before refiring. Then during room temperature maintenance calls for heat it will start parking the boiler at a lower temperature.

The behavior will vary bit with outdoor temperature and model or revision number but this is basically how most of them work. New cast iron boilers often come fitted with similar (or even identical) optimizing controllers since the effectiveness of heat purging control schemes to mitigate the effects of oversizing has been well proven. (<<Compare the regression curves for system #3 against the others. See also the efficiency at 3x oversizing compared to steady state combustion efficiency in Table 3.)

With heat purge controls the total number of burn cycles and the total amount of burn time will fall off. Since the boiler is about 2.5-3x oversized for the design load and more than 1.5x oversized for the radiation the fuel savings will likely be in excess of 10%, possibly more than 15%. Since you have a reasonable amount of thermal mass in the radiation (to help extend burn cycles) it probably won't hit 20% savings, but maybe.

 

[Robert Snow]

Intellicon-HW+ from eBay ($12 including shipping) arrived. Was easy to install and program. Temp sensor reports correct temp. Standby mode works by establishing continuity to the aquastat and takes the unit out of the system. It's 82ºF and too warm to really test any further until the heating season rolls aorund.

 

[Dana]

It looks like you might have just enough of a heat load on Monday night/Tuesday morning to rationalize giving it a test run early on Tuesday morning:

https://www.wunderground.com/forecast/us/pa/philadelphia

Running it for just a few hours won't tell you much about savings potential, but it'll verify that it works nominally. Sometimes eBay finds aren't fully functional, especially if it's been used. Gary in NJ seemed to have worse than average luck when scrounging around for one last year on the secondary markets. (See the last paragraph in his post #15.) If it turns out to be defective I may still have a brand new Intellicon kicking around on the basement shelves, if my visual memory isn't playing tricks on me.

 

[Robert Snow]

Reviving an old thread to report some results. I replaced the water heater anode this summer and it came out easily. It looked like it had quite a few years left in it and I replaced the plastic drain valve with a really nice ball valve. The water that came out was nice and clean. As far as the boiler goes, last winter was very mild and we didn't use much gas at all. Just fired it up again for this year.

 

[Reach4]

Reviving an old thread to report some results. I replaced the water heater anode this summer and it came out easily. It looked like it had quite a few years left in it

You had replaced the anode 8 years before?

What was that new ball valve?

 

[Robert Snow]

Actually about 9 years since the last anode rod was replaced. Water heater is now over 24 years old. New ball valve was from eBay - listed as House Mods HMP010. I'll be keeping it for the next water heater.

 

[DIYorBust]

Seems like that worked out well.

 

[MikeQ]

If you need a 5 year "payback" air sealing is about the only energy related upgrade that will break even in that time frame. If you discount your labor to $0 and use reclaimed foam board for insulating a basement it might pay off in that time frame in higher-priced energy markets if 1/3 or more of the wall is above grade.

Rooftop solar has become so inexpensive, it can payback in 5 years, depending upon which area of the country you live in.

It also adds considerable resale value to the home because you can actually see it (unlike insulation, air sealing, etc.).

 

[Dana]

Rooftop solar has become so inexpensive, it can payback in 5 years, depending upon which area of the country you live in.

That's only true in areas with optimal net-metering or other remuneration and other incentives, and a taxable income that can take advantage of the US Federal tax credits. As a general rule for most people in the US the payback is longer than 5 years even on a simple-payback model, longer still using present value calculations.

That said, with low interest financing in high electricity cost areas with net metering it can often lower the monthly cash outflow relative to paying the utility bills directly rather than making payments on the rooftop PV.

It also adds considerable resale value to the home because you can actually see it (unlike insulation, air sealing, etc.).

That's true only in select locations. Many buyers view it as potential maintenance liability &/or unsightly. The only people who can tell with any reasonable accuracy whether putting solar on YOUR house would add "...considerable resale value..." would be a local real estate broker who has dealt with more than just a few homes with solar.

Solar leases can save money on a cash flow basis too, but become cumbersome at the point of sale, adding another layer of negotiation that involves a third (or even a fourth) party. This problem is partly what Tesla's "Subscription Solar" program (not available in all states or all utilities within states where it is available) is intended to address. There is effectively $0 money down up front, and a modest (relative to the cost of an average home) fee for terminating the contract which can be done at any time. Tesla collects the tax credits & other incentives, and continues to own & maintain the system. The "subscriber" /homeowner pays a fixed monthly fee, which is usually well under the local cost of the amount of electricity produced. When initially rolled out the cancellation terms did not specify any time limits for when the system had to be removed, which is one potential fly in the ointment if the home buyer wants it gone. (That may have changed.)

The notion that some buyers will insist that a pre-existing roof top solar installation be removed as a condition of sale isn't theoretical- it happens! I personally know of at least one instance where that happened, and several others where local real estate agents advised people to not install it if they were planning to move in short years.

 

[Robert Snow]

If you look at the photo of the roof, earlier in the thread, you can see how difficult it would be to accommodate solar panels. Roof pitch is very steep @ 20/12 and the 22 year old cedar shingles are attached to nailing strips and open to the attic below. Attachment would be extremely difficult and flashing next to impossible.

 

[MikeQ]

That's only true in areas with optimal net-metering or other remuneration and other incentives, and a taxable income that can take advantage of the US Federal tax credits.

True, in many areas it takes longer than 5 years. That's why I said "depending upon what area you live". Duh!

That's true only in select locations. Many buyers view it as potential maintenance liability &/or unsightly. The only people who can tell with any reasonable accuracy whether putting solar on YOUR house would add "...considerable resale value..." would be a local real estate broker who has dealt with more than just a few homes with solar.

The only way to to determine if rooftop solar adds value (on average) is to do a study. And a number of them have already been done. Google it. Homes with rooftop solar sell for more (on average) than comparable homes without it. And this makes sense because people love to save money on their monthly energy bills. But don't believe me, Google it.

I don't know why you focus on non-typical buyers who want it removed, LOL! There are always going to be weirdo's or people who don't fall within the norm, what we are concerned with is does it make the average home worth more or less? And the answer from looking at a sample of hundreds of comparables is more.

Solar leases can save money on a cash flow basis too, but become cumbersome at the point of sale, adding another layer of negotiation that involves a third (or even a fourth) party.

I didn't mention solar leases and have zero interest in them. I'm talking about energy upgrades you can buy that can have a payback in 5 years. Solar is one of them, but you have to live in an area where this is possible. Many areas take 7-15 years before it's all gravy. Fortunately, they tend to last far longer than their 25 year warranty so even a 7-15 year payback is a smart investment.

If you have air conditioning, the length of the payback period is over-estimated because I've never seen one that took into account the reduction in cooling load that shading the roof provides.

The notion that some buyers will insist that a pre-existing roof top solar installation be removed as a condition of sale isn't theoretical- it happens! I personally know of at least one instance where that happened, and several others where local real estate agents advised people to not install it if they were planning to move in short years.

Yeah, well real-estate agents are generally not known as being the sharpest pencil in the room, LOL! Someone might take issue with the color you painted your house too. It's a fool's game to try to accommodate every weirdo out there - you have to go with the averages. That said, yes, if you're planning to move in 2-4 years it's probably not worth thinking about. The exact amount of time will depend upon the payback period for your particular system in your particular area and how much it can be expected to add to the value of your home. That should be obvious.

What's not so obvious is how quickly the payback period is shrinking. This is largely a function of the falling prices of panels and other components.