New boiler/system changes

Users who are viewing this thread

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
I am largely handling some of the changes to my dad's hydronic heating system from over 1000 miles away. He is in central NY. Design temps must be subzero there. I am not DIYing this, but there seems to be significant boiler knowledge here. Please read on if you have the stamina.

Right now there is a 55 YO Crane Sunnyday boiler in place with an oil burner. Sunnyday has a DHW coil built in. I have oil use records going back several years. Gas has been in the house for some years running, sadly, only the dryer. Heavy rebates may be available (50% perhaps, 10% minimum) for an efficient boiler replacement. I've been learning about modulating and condensing systems. Apparently, the current boiler output is about 74 k. Heat losses have been estimated @ main 16 k, basement 12K and sun room 12 k for three separate zones.

Sun room is not used in very cold weather and has an exterior-grade door between it and the rest of the house. All zones are served with aluminum fin radiators. One exception is that in a kitchen reno the radiation was removed and a toe-kick heater was installed near the end of the main loop. It has been broken for a long time and installed in a less than accessible area. (A cabinet floor will have to be cut out to get to it. I suppose it should be fixed to lower the return water temp as much as possible.

Significant upgrades to the house have been made since built, insulation blown into walls, attic insulation improved substantially and windows improved. Basement was finished and split into a separate loop. (It was heated before the finishing off.) The sun room addition was built, well insulated and windowed, but heat was added later. Likely the radiation matched the need in that room pretty closely. Ditto for the basement, but the main zone is probably over-radiated for 180 F water.

Note that the three controls on the current boiler, according to a 15 YO grandson that is local, are set to 180, 170 and 160. I am guessing that 180 is the safety and the rest are high and low. The hour stays warm. There are three pumps, some combination of old modular, maybe B&G and some newer, smaller style.

It is a rural area and a BPI-trained and program-registered contractor must be used to get the rebates. Selection is limited. I got some proposals from some contractors before I knew of this requirement. I may be struggling with the decision of whether it is worth it to install a modulating boiler and the highest efficiency boiler or go with a cast iron boiler like the Weil Mcclain GV90+. I believe that the GV90+ meets efficiency (90+%) requirements for the program, but nothing much lower in efficiency does.

So far, everyone seems to want to oversize the boiler if the heat loss is correct. A Navien at 80 k is the smallest and some proposals, Triangle Tube, GV90+, Rinnai, and Baxi have specified boilers that are way larger than 73 k even though a smaller boiler in that line is available that is STILL larger than 73 k. I think that I am going to have to work hard to hold these guys' feet to the boiler and make them do this properly.

I know that a condensing boiler will not be any more efficient than a non condensing boiler if it is toggling on and off too much and I want to avoid that. I know that the zoning does not help with keeping the return water temp low. I know that with a modulating boiler, the more it turns down, the better shape I will be in. I don't yet know if any condensing boiler can be made to work well with the system. If not, I might as well choose the least complex, most robust boiler. I don't know what the best way to pipe the supply might be. I suppose that the contractor should be able to figure out how much of the time a modulating/condensing boiler will be in an efficient mode based on heat loss, boiler capacity and the radiation capacity. I don't know how best to handle the DHW supply. The way the the house is laid out, we may have to use the existing chimney with plastic pipe inside it to get the flue gas out. Adding a second vent for a separate hot water heater could be difficult with that constraint.

I'd love any general advice you may offer and any critique of my commentary. I have what might be a very naive question. The basement and main floor presumably need to be in separate zones for comfort since heat loss will not vary that much in the basement and will on the ground floor. There is not much of a thermal barrier between them, just a suspended ceiling under the joists. Given that is true, they should not be combined. If return water temperatures are too high to condense with a high efficiency boiler, could the zone that is not demanding heat serve as a heat "dump zone" to lower the return water temperature? It seems like it would not raise the temp in that zone excessively while increasing the efficiency of boiler.

Thanks, very much, for reading.
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
To properly size a modulating condensing boiler you have to know the amount of radiation (and type) on the zone with the LEAST amount of heat emitter. In this case it sounds as if all zones have only fin-tube baseboard(?), with the exception of the toe-kick heater.

The MINIMUM firing rate is more critical than the maximum rate, since that is what determines at what temperature it will begin short-cycling on the zone with the least amount of baseboard.

With a cast-iron boiler the length of baseboard per-zone is also an important consideration, but not the whole-shebang.

The other critical piece is the whole house heat load, which can be calculated from fuel use history and and weather data, to know that the high-fire output of the boiler is sufficient to cover the load. With a cast-iron non-modulating boiler oversizing it by more than 1.7x will result in lower than rated efficiency, and the smaller you can go the longer the burn cycles will be, limiting the short-cycling potential. If the total amount of baseboard would result in such low return water temperatures when using a right-sized non-condensing boiler the system plumbing has to be designed to boost the temp of the water entering the boiler.

If you have a fuel use history on it, about how many gallons/year, and what's the ZIP code (for design temperature purposes.)

Modulating condensing boilers are truly tiny, and can be made to fit almost anywhere, so don't assume you'd have to run the venting up the existing chimney. Sometimes they are monsterously oversized 3-4x simply to be able to have satisfactory potable hot water delivering using an embedded coil, but a 74K output boiler would be pretty marginal on HW service in mid-winter. Right sizing the boiler for the space heating load, and heating the domestic hot water with and "indirect" tank operated as a separate zone will be more efficient for both space heating and hot water. In most cases the zone contoller would have to give priority to the indirect HW heater, suppressing calls for heat from space heating zones until the HW heater's call for heat is satisfied, but even a tiny 50-60 KBTU/hr boiler and a 40 gallon indirect would be sufficient for 95% of all homes in NY.
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
BTW: You are correct to zone the basement separately from the first floor, since the heat loss characteristics of basements are non-linear with outdoor temp, whereas above-grade floors generally are. This is due to the fact that the fraction of the heat loss to the soil doesn't change with outdoor temp, and drifts with the season.

Who did the heat loss calculations, and what was the method they used?
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
Thanks so much for your oh so detailed response. A comment that I should have added to the original post is that the ROI for any investment beyond the boiler should be very short. We are depending on the fuel cost/btu differential to pay for the boiler. Note that the rebate caps at $5000 rebate/10,000 total cost and we are likely to fill that up but try not to go over with system wide improvements to optimize to any new boiler type. Dad does not expect to be in the house much longer due to his condition/age. He is having some problems. It might be nice to think about adding radiation and whatnot, but that is just not in the cards.

Heat loss calculations were done by a n energy evaluator with the New York State Home Performance with ENERGY STAR (HPwES) Program. That is the program with the rebates. I can’t say what methods were used. I was not there, but dad said that he looked over the structure as carefully as possible, without making destructive observations, and made measurements. A blower door test could not be done due to vermiculate between two layers of glass batts/rolls in the attic (vermiculite that I helped put down in the late 60s or early 70s).

No matter where the boiler is placed in the unfinished part of the basement there may not be a way to get out the side that is not under a window, or next to a sidewalk, patio, deck or gas meter. There is the snow depth to deal with too. I’d love say that the chimney could be taken below the roof level with the next roof replacement, but it may not be practical to go horizontal with the new flue gas.

Dad’s DHW needs are pretty low. A combination boiler will probably suffice. In some ways I’d hate to hamstring the house with respect to hot water production for the next owners, but if it adds a lot of cost and puts us above 10K for a system, the next owner might have to make the adjustment so dad does not have to invest. The only thing I worry about is “cold water sandwich”. I was cozying up to a Triangle tube proposal with its tiny, integral tank for that reason, but the boiler looks too big. Dad is quite used to letting his shower head dribble while he soaps up.

Yes, it is all fin-tube except the toe kick near the end of the main floor zone.

I had hoped to have this done by mid fall, but got delayed several times. I’ll be up there between the holidays so I can take some measurements with the existing set-up. I hope that I can kick the process too.

Here are some fuel records. I hope that the column format is preserved in the posting process. Does it make more sense to concentrate on the winter months to eliminate the DHW contribution? Zip is 13830. Locals say that the climate data is often too mild compared to reality. Very local farmers say that they have to plant corn seed with a shorter season that anyone surrounding. My personal observations indicate that Spring comes late and Fall early there.

DEL DATE GALLONS
1/27/11 176.9
3/10/11 205.6
5/12/11 196.6
11/3/11 151
12/22/11 135.5
1/31/12 165.6
3/14/12 161.4
6/18/12 162.9
11/8/12 156.3
1/3/13 204.6
2/7/13 163.9
3/28/13 206.4
8/20/13 163.1
12/4/13 158.3
1/9/14 163.5
2/13/14 187.8
3/20/14 171.7

Is my idea of piping the two largest zones so they could be connected end to end in a reversible order completely nuts? I have no idea how much cost that might add to the project for the valves and controls. It just seemed like it might be a way to make the system more efficient by lowering the water temperature more without overheating the zone that might otherwise be inactive.

Have you seen this study? I have digested some of it. Given that the climate is a just a little milder in Tompkins County it should be pretty applicable to a modern house/new construction. I have been trying to digest it keeping in mind that I am dealing with a 55 YO house.

Optimizing Hydronic System Performance in Residential Applications L. Arena and O. Faakye Consortium for Advanced Residential Buildings
http://www.nrel.gov/docs/fy14osti/60200.pdf
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
The 99% design temp of nearby Ithaca is 0F, and of nearby Oneonta it's -4F. Lets assume a 99% outside design temp that splits the difference, call it -2F. (It'll be "Good 'nuff for the girlz I go with." :) ) Assuming a base-65 balance point, that's 67F heating-degrees

Downloading a daily base 65F HDD spreadsheet from weatherstation station KNYOXFOR3 Oxford-Guilford from degreedays.net and using a presumed combustion efficiency of 85% (which is on the high side for a boiler that old, even if it has a much newer burner) and 138,000 BTU/gallon, I ran a fuel-use against degree-days calc for the periods

12/4/13-1/8/14: 163.5 gallons /1544 HDD which works out to 518 BTU per degree-hour

1/9/14 - 2/12/14: 187.8 gallons / 1656 HDD which is 544 BTU / degree-hour

2/12/14 - 3/19/14 171.7 gallons /1506 HDD which is 557 BTU/ degree hour

So @ -2F with 67 heating degrees that works out to 34,676 BTU/hr or 37,136 BTU/hr or 37,334 BTU/hr. Unless there was auxilliary heating in use (a wood stove, perhaps), the real heat load is probably between 30-35K, since the boiler isn't likely to be hitting 85% efficiency.

All of which is well below the calculated ~40,000 BTU/hr, which is pretty typical. They may have used a slightly cooler design temp, but it's certainly in the right ball-park- they're not crazy. Most load calculation methods overshoot fuel-use derived methods by 15-25%, largely due to slightly conservative assumptions about air leakage & R-values when making those calculations. Call it ~35K @ -2F, or ~36K @ -4F, but it's not likely to really be as high as 40K.

It would be crazy to put in anything but the smallest boiler that covers it. A 73K boiler would be 2x oversized at the max-fire, but the minimum fire is the most important thing. One the low end of the low-fire input boilers that work the Lochinvar WH-055 is a 55K boiler with a min-fire input of about 10,000 BTU/hr output about 9500 BTU/hr that would probably work with your zone setups as-is, and with the min-fire output being about 1/4 of your peak load it could be set up to modulate in condensing mode most of the time without much short cycling.

Combi boilers are often a PITA, since even a min-fire on most of them would be more than half your actual heat load, and even if you combined all the zones it wouldn't modulate much. (IIRC the Baxi has a min-fire that's something like 30K.) The cost of re-designing the whole system and reconfiguring the zoning or setting up more sophisticated controls could cost as much or more as adding an indirect-fired HW heater, so really the right thing to do is go with a smallest of the line modulating condensing boiler with a indirect HW heater, and size the HW heater for the biggest tub you have to fill (a 30-40 gallon unit would do most homes), and be done with it.

Unless you are there to do all the necessary system tweaking to get the boiler's outdoor reset curve dialed in there is a world of ways to screw that up. Finding a truly competent designer/installer is critical. You know the size of boiler that you need- call the local boiler distributors in that part of NY for recommend a contractor, and get bids from them, for the most appropriate model in their lineup that YOU select. There are many decent boilers out there that fill the bill, but I don't know of any off hand that modulate below 10KBTU/hr other than the Lochinvar.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
Thanks so much, Dana, for your detailed analysis. You’ve applied Occam’s razor and come up with a efficient solution, probably both from the installation cost and running cost standpoints. I think that your solution makes the most sense for the house and for our situation. I will be chewing on your response further. How well do these boilers condense when in the water heating mode? This would certainly qualify as sweating the little stuff in a comparison to the cost of heating water with the current system J~ I don’t remember the boiler model I was looking at recently that impressed me with a particular feature. You can set the DHW temp as low as desired, but it will periodically heat up on a timed basis to kill off Legionella. I giggled with delight at that.


I am going to throw in the possibility that the entire difference between fuel consumption (35-37k) and the evaluator’s estimate (48k) can be found in the variable use of the sun room. That is something that I don’t have data for. Typically, unless there is crowd visiting or the sun is very strong, on cold days the door is closed and the t-stat is set to 50F. The only auxiliary heat would be electric heater used to get that room up to temperature quickly when dad decided to open the door.


The high/low per degree day figures are below an 8% spread. That seems a pretty low divergence given everything that can feed in. I am going to say that even Oneonta @ -4 is high by a few degrees for a design temperature. Double-digit negative lows are not at all unusual. I recall as low as -40 now and again on unofficial thermometers which makes -20 a virtual certainty. I am not sure how that fits into 99% design. Even with those corrections, I’ll bet a 55K boiler could meet the need.


I have been looking mostly at combination boilers, since that was presented to me. I had no idea that non-combos might be available rated at a lower output. The Baxi combi that we were quoted has the largest ratio that I have seen @ 1/7. My notes indicate that is a low of 17k. That is not nearly the attractive 9500k of the Lochinvar. Judging from my reading, that brand has a rep of being very good and pricy. With an indirect added on…. Well, I’ll keep my fingers crossed that it won’t take us over budget. Unfortunately, there is only one contractor approved by the program within an hour drive. (Fortunately, that one is a mile away.) I’ll have to continue to feel them out and decide if my confidence in them holds up or we’ll chance engaging someone else further away. The evaluator falls into that class. Early on, I told him that he was too far away, but maybe we will re-engage. He seems knowledgeable and was helpful.



Again, many thanks
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
It looks like I can't get a program-certified installer in that area for Lochinvar. I am scanning an Energy Star web site that lists condensing boilers. I am sure that some are rebadged and I am looking at duplicates in some cases. Other modulating 50 k boilers are Dunkirk, LAARS, Lennox, Navien, Olsen, and Utica. I've noticed previously that most throttle to 1/5. Triangle Tube stands out at 1/4 and Navien's 50k at 1/7 and their 80 K at 1/10... up to 1/15 with their biggest boiler in the NHB series.

With some of these, the onboard controls are not nearly as versatile as the Lochinvar. It would take some head-scratching to know if there is any advantage to those options.

I guess I will be calling to see what they install if the rebate program comes through. Since it might be worth $5000, it is an important consideration.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
I looked over the energy evaluation again because I remembered that there was something that looked like a “fudge factor”.

Heating Safety Factory: 1.10
Distribution Safety Factor: 1.10

I don’t know if these two safety factors add up to 120%, multiply to 121% or you take the larger one, 110% L

Here is some additional information Dana, perhaps that answers your “method” question, TREAT?

Required Heating Equipment Output Capacity: 47,451 Btu/hr
Available Heating Equipment Output Capacity: 73,800 Btu/hr
Total Flow: 5 GPM (but lists main floor flow 2 and two other loops 1 gpm each).
Baseboard Capacity: 575 Btu/Hr-Ft
Heating Equipment Efficiency: 82%
Calculated Distribution Efficiency: 99%
Supply Temperature: 180 F
Temperature Drop: 20 F

Required equipment output capacity includes diversity, distribution losses and equipment safety factor.

Overall distribution CFM/GPM for heating/cooling includes equipment safety factor, distribution losses and diversity.

TREAT load sizing has been tested in minimize calculation time mode and results were compared to Manual J. TREAT heating and cooling loads proved to be slightly more conservative. Please use professional judgment in applying the results to sizing heating and cooling systems.
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
It's common to have seasonal lows that are between 5 & 15F colder than the 99% temperature bin.

It looks like you have a hard requirement for a max-fire output of at least 47.5K to qualify for the subsidy, which COULD be a 50KBTU/hr mod-con, provided you have sufficient radiation to emit 47.5KBTU/hr at a condensing temperature.

Another way to deal with short-cycling issues with low-mass radiation like fin tube is to use an inherently self-buffering system like the HTP Versa Flame combi heater, or design a system around the HTP Phoenix Light Duty. Since the minimum burn time is defined by the thermal mass of the water in the tank, you can still run the heating system in condensing mode without short-cycling the system. These are more expensive than just the raw components for a mod-con + indirect solution, but are well-engineered units, far easier to design into a retrofit l0w-mass radiation environment without screwing up. At your loads the smallest version is the one you want- it has 130,000 BTU/hr (input) at the high end, so there's no question that it'll more cover the fudge-factor oversizing requirement, but you can still run it at condensing mode with a tiny zone with only a 10' stick of fin-tube without short-cycling the thing to death, and you don't have to redesign or reconfigure the zoning & controls.

Since you are not there to manage the re-design or system tweaking it's probably a safer bet than contractors of unknown competence installing low-mass condensing combis where the amount of l0w mass radiation on the zones are critical.

Do you have a list of baseboard lengths, per zone yet? Running the sanity checking napkin math on the zone with the least radiation would be prudent before embarking on a l0w-mass boiler path.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
Thanks, the HTP option is interesting. I'll be in the house for a week just after Christmas. I can check measurements then and maybe I can give the project a push (along with backup genset installation that I have been working on). I could have passed these rad lengths along earlier. I hope they are for fins and not for some with just tube:
location/load/ft baseboard

first floor/16 k/30 feet
basement/11.5 k/22
sun room/12 k/23

I don't think that I am withholding much else :-o
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
Just the lengths of finned baseboard convector counts- no need to add up the plumbing, which emits some, but only a tiny fraction of what the baseboards deliver.

To get to even the edge of condensing to get even 89-90% efficiency the water entering the boiler coming back from radiation has to be under 125F, which means the average water temp (AWT) across the radiation from the warm side output to the return has to be something like 130F, definitely under 140F.

The output of fin-tube baseboard at an AWT of 130F is about 250-300 BTU/hr per foot, at an AWT of 140F you're looking at 300-350 BTU/hr per foot.

Here's the napkin math on it:

With a 22' baseboard zone you need a boiler with a min-fire output strictly less than 350BTU/ft-hr x 22' = 7,700 BTU/hr to operate in condensing mod without constantly cycling on/off during calls for heat.

To hit 95% efficiency you'd be looking for an AWT of 12o-125F, at which point the baseboard puts out 200-225BTU/ft-hr, for a min-fire output of no more than 225 x 22' = ~5,000BTU/hr to avoid short-cycling.

Even at 180F AWT you get about 600 BTU/ft, which is only 13,200 BTU/hr for the 22' zone. The whole 75' of baseboard can only emit 45,000 BTU/hr @ 180F AWT, so the radiation is substantially undersized even for 73.8K existing boiler(!). The cast iron beast has at least some thermal mass, but unless it has retrofit heat purging controls operating with very large temperature swings it's probably been operating at painfully short 2-3 minute burn cycles (or even shorter), which takes a toll on operating efficiency, and wears out the ignition & burner equipment prematurely.

It also means you'd need to run an AWT of about 190F to actually deliver the fudge-factor requirement of 47,500 BTU/hr with the existing radiation, which would require a higher output temp than most of these boiler can deliver, but let's hope the inspectors don't do the napkin math on the radiation. The oil burner can run that hot, most mod-cons won't.

Plumbed all together as a single zone you could do OK with a low-mass combi or mod-con with ~15,000 BTU/hr min-fire, but the heat loss characteristics of a basement are SO different from that of a sun room it would be less than satisfactory, since there would be no good/cheap/easy way to assure reasonable room-to-room temperature balance. Keeping it zoned as-is, and using a buffering thermal mass approach is probably the cheapest & best way forward.

With your radiation you can't get there from here on modulation alone- it needs some thermal mass, either a buffer tank (or massive high-volume hydraulic separator) + mod-con, or a self-buffered modulating condensing combi like the HTP Versa.
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
If you can't find a contractor for the HTP Versa, you may want to forgo the the subsidy, and go with a pretty-good mid-efficiency cast iron boiler that's closer to being right-sized. The 3-plate direct-vented Burnham ESC3 comes with decently smart controls, and isn't ridiculously oversized for the heat load or total radiation. It may cycle some on zone calls, but it won't be terrible. It's still getting onto 2x oversized for the total heat load (and still way oversized for a single zone's radiation), but with smarter controls it'll probably cycle a lot less than the current oil boiler, and will come close to hitting it's 85% efficiency numbers.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
I feel like the project just took a large step backwards to find out that I am so radiation-limited. A 50% rebate up to $5,000 is a big deal to leave on the table. I don't know what the efficiency of the boiler needs to be to qualify for the program. If above 90 makes it, the Weill-Mcclain GV90+ cast iron/stainless qualifies and is available with 65 MBTU output. I find it hard to believe that the radiation matches the current building characteristics given the changes it has seen since it was built. The sun room and basement should be a good match to current, but the first floor should be in excess. Maybe the energy rater just counted baseboard and was done with it. If so, I am very disappointed. That is what is is beginning to look like.

I assume that if the HTP equipment that you mention needs an indirect tank to make DHW and provide radiator heat. If that is the case, the water in the HTP would have to be a lot higher than required for heating the house most of the time in order to get the DHW up to reasonable and Legionella-safe temperature. In the HTP literature, for both the VERSA and Phoenix, I see some outdoor reset curves, but no information about water temp vs. (condensing) efficiency. It seems like it can't be different as that would mean changing some physical laws.
 

Dana

In the trades
Messages
7,889
Reaction score
502
Points
113
Location
01609
The HTP Versa does NOT need an indirect tank- it is a well engineered combi heating + hot water system in a package.

With outdoor reset controls on the Versa it's space heating end will be in condensing mode most of the time, and it's hot-water end will condense all the time. The designers of that system are pretty sophisticated, and have been at it for quite some time. It's the temperature of the water entering the burner that determines the condensing efficiency, not the output temp. For natural gas that entering water temp only has to be 125F or cooler to condense, which is above the Legionella-growth range. Most existing systems have sufficient radiation to deliver the average winter heat load at condensing mode, even if they won't be condensing at the 99% outside design temp load.

The zone radiation to load ratio here is all pretty similar at about 525 BTU/ft of baseboard @ -4F. At an inside design temp of 68F that would be a 72F delta. So the load is roughly 525BTU/72F= 7.3 BTU/hr per degree of delta from 68F. The binned hourly mean-temperature in January for that location is about 23F, which is only at 45F delta, so you're looking at an average requirement of 45F x 7.3= 328 BTU/ft, which takes an AWT of about 140F. During the warmer part of the day in January it'll be condensing, not so much at night, but at the warmer averages of December & February it'll flips to condensing most of the time. If you tweak the reset curves carefully you'll do better than 90% average for the season, but probably not 95% with that radiation.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
Thanks, Dana, I think that I was looking at the HTP Phoenix when I asked about a heat exchanger. I had not looked at the Versa boilers. You offer lots of food for thought. I hope that I can find an HTP installer nearby. I also hope that that installer will be willing to determine if the current radiation will deliver enough heat to keep the house warm enough with 160 F water.

I am going to try to call HTP again. I got a call from a rep in the wrong state that was very anxious to be helpful until he found out that I was out of his area. He promised to put me in touch with the rep in the right area, but someone must have dropped the ball 'cause I've not heard anything in about two weeks.

It seems like with these boilers the return water from the space heating system and the supply water for the DHW must be used in the final part of the HX rather than the water in the tank. If not, I don't see how the combustion efficiency could be so high.

HTP might benefit from some controls that would allow the temperature to be set below Legionella-safe temperatures with a program to heat above that once a day to sanitize the stored water. On the other hand, maybe the marginal improvement in efficiency would not merit the expense.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
I finally found some videos on the HTP site in the knowledge base. It looks like they use the inherent tendency of the water to stratify with temperature gradient to get low temp at the cold end of the HX, nice.

A lower capacity unit would be sweet.
 

Beads

All thumbs
Messages
45
Reaction score
1
Points
8
Location
New Orleans
Versa-Hydro seems more flexible than most for venting. The PHE130 can use up to 85' combined venting and exhaust with 2" pipe and up to 125' with 3" pipe.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks