Water heater options

MaxMercy

I have a DHW coil on my boiler, and it does OK except my wife complains about the showers (I run the shower slower and it works fine but my wife likes a deluge).

My boiler is new and about 110K BTU. My options are a Boilermate type storage, a heat pump hybrid electric, a tankless, and a straight electric.

I'm in CT and electricity is expensive, so I'm leaning to a storage tank, but that means I'm running the boiler just for hot water at least six months.

The tankless offers unlimited hot water which is a big bonus, but I wonder what it will cost to run it compared to the boiler which I could shut down for the summer.

Ideas?

Larry Weingarten

Hi, I’d try tiptoeing into this by trying out a good low flow shower head. Get one that gives large water droplets at good speed. It can feel like an old fashioned shower but use significantly less water. When that gets vetoed, move on to a heat pump, if you want to keep the boiler off.

Yours, Larry

Jamie Hall

Um... well, maybe. But if you chose to go with a heat pump, be very aware that if you have a large demand on it one of two things will happen: you'll run out of hot water (which she won't like much) or it will switch to electric resistance heating instead, which your wallet won't care much for - and unless it's a big one (like 80 gallon tank) you'll still run out of hot water.

This is even more true of a tankless. Be VERY aware of the maximum flow rate for a tankless. They advertsie "endless hot water" -- but only up to a certain flow. Beyond that they drop to cool... or cold. To get 5 gpm for a big shower, for instance, you are looking at a 120 ampere draw on the usual 240 volt single phase electrical service. Even if you have a 200 amp service to your house, that's a big ask.

I'd go with a nice big indirect, like a 60 or 80 gallon Superstore indirect.

mattmia2

Did he say tankless electric? I'd be very skeptical of that 5 gpm on a tankless electric at even that enormous power draw in a situation with municipal water and winter.

If you go with an indirect be very careful about making it big enough, measure your draw and do the math, don't look at the tables in the manual which are for a boiler size and a municipal water temp that do not match yours. With a large, well insulated indirect and the boiler set up as cold start it won't run much in the summer.

HVACNUT

Is there a mixing valve on the tankless coil?
The boiler is new. What aquastat came with? 
110k btu net?

Intplm.

Does the issue occur at all the fixtures!?

Does it?! Be sure, because it might be the showerhead and or the shower valve.
What type of shower valve do you have? If it's a single-handle anti-scald valve it could be a problem and need repair.

Hot_water_fan

Take a look at drain water heat recovery: no moving parts and pairs perfectly with showers. 

MaxMercy

Thanks everyone. Answers to questions asked:

The shower heads are a typical modern low flow head - nothing special.

All the fixtures affected? I'm not sure about the sinks as the volume of hot water used at the sinks is generally very low, but it affects both showers similarly.

There is no mixing valve currently installed. When I replaced the original boiler, I just plumbed it in very similarly as it came from the builder. I bought a Honeywell adjustable mixing valve when I bought the boiler but didn't get around to installing it yet. I plan to (this year, I promise!), and there are no kids in the house.

The shower valves are Symmons Temptrol and the cartridges are new(ish) and the pistons move freely. The smaller shower doesn't have a way to throttle back like the combo shower/bathtub valve does (using the tub/shower lever), so the problem is worse in that shower because of the higher flow.

The BTU I posted was a typo. It's 119K input, not 110. That's based on a .85gph@100lbs pressure (adjusted). The net is just about 100K based on 85% efficiency (which I believe to be accurate)

The new boiler acts like the old one with regards to hot water production which is surprising since the new boiler is running a lot less BTUs than the original. It has no trouble heating the house at 100K net even at sub zero temperatures and in fact is probably still a bit too big (2800 sq zone 5).

The problem isn't *bad* - I don't find it a problem if I throttle back the shower flow a bit. Even in a longish shower, it never runs out of hot water but it changes constantly as the boiler starts and shuts down. It does get to the almost lukewarm temperature before recovering during the shower as the boiler restarts, but I think I can improve both hot water and maybe reduce oil consumption by making a change to my current setup.

I thought about bumping the low limit to get it the boiler to start a bit earlier to limit the cooler swings, but I'm not unhappy with the oil consumption overall and would hate to have the boiler maintain a higher temperature the other 23:30 hours of the day, particularly on non-heating days.

The aquastat is a Hydrostat 3250+. I'd like to take advantage of some of the savings this control offers, but I think it's limited by the DHW coil setup.

Never heard of drain water heat recovery, but that is a fascinating idea.

I really appreciate the advice.

mattmia2

MaxMercy said:

The problem isn't *bad* - I don't find it a problem if I throttle back the shower flow a bit. Even in a longish shower, it never runs out of hot water but it changes constantly as the boiler starts and shuts down. It does get to the almost lukewarm temperature before recovering during the shower as the boiler restarts, but I think I can improve both hot water and maybe reduce oil consumption by making a change to my current setup.

Is the water hot enough if you keep adjusting the temp as the boiler cycles? The idea of the thermostatic valve is to produce a consistent temp from the varying temp of the boiler. With the mixing valve your problem may go away.

Is the boiler steam or hot water?

Heating an indirect tank with the boiler cold start will be a lot more efficient, especially in summer.

MaxMercy

mattmia2 said:

Is the water hot enough if you keep adjusting the temp as the boiler cycles? The idea of the thermostatic valve is to produce a consistent temp from the varying temp of the boiler. With the mixing valve your problem may go away.

It's *almost* hot enough, but not for my wife (who is not a picky person). During a shower, it can approach lukewarm at full rotation of the valve for two or three minutes, then recover to the point where I have to rotate back to the center of the valve's rotation because it will get too hot. I know I can fix this by adjusting the boiler's lower limit, but it seems wasteful.

I'll install the thermo valve before making a final decision. If the thermostatic valve happens to also reduce the flow even a little, it might be enough to keep from outflowing the coil during the boiler's low swing. That and maybe a better shower head might fix the problem.

Is the boiler steam or hot water?

Hot water.

Thanks for the help.

Hot_water_fan

@MaxMercy

From what you've described, drain water heat recovery would help if you can fit it. Basically, it warms both the cold side (reducing amount of hot water needed) and preheats the water entering the boiler so less BTUs are needed for the same GPM.

pecmsg

Get a mixing valve on it. Set it for around 110 - 120* max. 

Larry Weingarten

Hi @MaxMercy , I'm still stuck on the showerhead idea as a first step. It sounds like your present one is 2.5 gpm and a good lower flow can work at 1.5 gpm. That gallon might make a big difference in the boiler's ability to keep up. So, here are some links to different reviews of low flow heads:
https://plumbinglab.com/best-low-flow-shower-heads/#:~:text=10 Best Low Flow Showerheads Reviewed. 1 1.,Standard Flowise. 5 5. Niagara Earth. More items
https://www.treehugger.com/best-shower-heads-5086864
https://bathroomer.org/best-low-flow-shower-head/
https://www.popularmechanics.com/home/g36661091/best-shower-heads/?utm_source=bing&utm_medium=cpc&utm_campaign=arb_bg_pop_d_bm_g36661091&msclkid=7e14fe47d2a91d4ac4189c75d6d8c629&utm_term=best showerheads&utm_content=Best

Yours, Larry

mattmia2

Is there a temp limit stop in the shower valve that prevents you from rotating it to only hot water? Most modern valves have some sort of a mechanical limit instead of actually being thermostatic.

MaxMercy

mattmia2 said:

Is there a temp limit stop in the shower valve that prevents you from rotating it to only hot water? Most modern valves have some sort of a mechanical limit instead of actually being thermostatic.

The Temptrols have an internally adjustable limit - they are not thermostatic. They are pressure balancing but that's it. They're adjusted right now to get really really hot - much hotter than is comfortable during the temperature swings.

Larry Weingarten said:

Hi @MaxMercy , I'm still stuck on the showerhead idea as a first step. It sounds like your present one is 2.5 gpm and a good lower flow can work at 1.5 gpm. That gallon might make a big difference in the boiler's ability to keep up.

Thanks for the shower head recommendations Larry, I'm going to look into those as well. Lowering usage is a good idea under any circumstance.

Hot_water_fan said:

@MaxMercy

From what you've described, drain water heat recovery would help if you can fit it. Basically, it warms both the cold side (reducing amount of hot water needed) and preheats the water entering the boiler so less BTUs are needed for the same GPM.

I'm going to look into that. I have a full basement so I have the room.

Jamie Hall

One comment. If you do decide to go with some sort of drain water heat recovery scheme, be sure and check with the authority having jurisdiction in your area. Some probably won't care. Some may require specific hardware. Some will simply flat out not approve it (I never would have, back in the day).

Jon_blaney

What is your boiler fuel? Have you considered a stand-alone oil or gas WH?

MaxMercy

Jon_blaney said:

What is your boiler fuel? Have you considered a stand-alone oil or gas WH?

It's oil, and I have considered one yes, but I don't know if another burner is the best way to heat hot water.

Jamie Hall said:

If you do decide to go with some sort of drain water heat recovery scheme ... Some will simply flat out not approve it (I never would have, back in the day).

Which begs the question...

Jamie Hall

MaxMercy said:

Jon_blaney said:

What is your boiler fuel? Have you considered a stand-alone oil or gas WH?

It's oil, and I have considered one yes, but I don't know if another burner is the best way to heat hot water.

Jamie Hall said:

If you do decide to go with some sort of drain water heat recovery scheme ... Some will simply flat out not approve it (I never would have, back in the day).

Which begs the question...

Begs what question? The fact of the matter is that in some jurisdictions drain heat recovery schemes are severely limited or just plain prohibited, and it would be well to find out what's the case in yours, should you try to implement one.

MaxMercy

Jamie Hall said:

Begs what question? The fact of the matter is that in some jurisdictions drain heat recovery schemes are severely limited or just plain prohibited, and it would be well to find out what's the case in yours, should you try to implement one.

The question is why they would be prohibited. I understand they could be limited or prohibited in an given jurisdiction, but I honestly can't see any safety or environmental issue with a heat recovery apparatus, and I assume safety or environmental impact would be the reasons they would be prohibited. I'm sure I'm missing something here, but it doesn't mean it's not a fair question.

mattmia2

They would be concerned about contaminating the potable water system with sewage if it leaks.

MaxMercy

mattmia2 said:

They would be concerned about contaminating the potable water system with sewage if it leaks.

Ah. Still, contamination seems unlikely as the potable supply is pressurized and the drain is not. I guess a leak from the outer coil to the drain pipe, as unlikely as that would be, might flood a septic system eventually.

Thanks.

mattmia2

It is somewhat unlikely a leak would be detected since it would just go down the drain, then when the water system loses pressure for whatever reason sewage gets sucked in, possibly also in to the municipal water system.

MaxMercy

mattmia2 said:

It is somewhat unlikely a leak would be detected since it would just go down the drain, then when the water system loses pressure for whatever reason sewage gets sucked in, possibly also in to the municipal water system.

I see what you're saying, but that seems like powerball odds or greater if even possible since that would require two leaks, not one. From the pictures, it seems the outer copper is tightly wrapped around the copper drain tube, but it's not welded or otherwise sealed in any way other than what looks like a pretty tight fit.

I would think that a leak between the outer tubing and the inner pipe would be detected externally as I don't think the wrapped outer coil could hold the potable line pressure in, and even if the leak between the outer coil and pipe did happen, it would then require the copper drain to fail as well.

Long shot to be sure, too long for it to be a concern for me if it's not contra-code in my area. But, with just my wife and me living home now, I don't know if a two-person usage would get me a payback. Info on-line suggests a 4 person household would better take advantage of this setup.

Thanks again.

Jamie Hall

The problem is, as has been mentioned, a leak from the waste water into the domestic water system. There is a very common assumption that the domestic water system will always be above atmospheric pressure -- after all, water comes pouring out when you open the tap!

The assumption isn't true. The two most common reasons for negative pressure in water mains are fire flow testing, which should be done annually (often isn't) and fires. Leaks, although much rarer, can also do it. Both can reduce mains pressures to well below atmospheric. This is why air gaps or vacuum breakers or backflow preventers are usually required (they should be always, in my humble opinion).

Cross connections are a water supply manager's nightmare.

If you are on a private well, this is less of a problem -- for two reasons. First, a vacuum is actually rarer. Second, any contamination is your pigeon and not the whole water system.

MaxMercy

Jamie Hall said:

If you are on a private well, this is less of a problem -- for two reasons. First, a vacuum is actually rarer. Second, any contamination is your pigeon and not the whole water system.

I am on a well and septic actually. Still, I am forced to wonder if there have actually been any actual cross contamination incidents in this type of heat exchanger. It would take an extraordinary combination of factors for this to happen in my opinion, and I still believe the leak on the pressurized side would make itself known immediately.

But at least I understand the concern no matter how remote the possibility. Thanks for the explanation.

Larry Weingarten

Hi, Drain water heat recovery units all use double wall heat exchangers. Here is a manufacturer: https://renewability.com/ Ask them what restrictions are placed on their units. I believe they are required by code in some areas of Canada.

Yours, Larry

MikeAmann

@MaxMercy
I just want to point out that any heat recovered should be used to warm the cold water going to the tub/shower. That is the place that you need it. I wouldn't bother trying to warm the water going into the boiler unless the pipe runs will be very short.

hot_rod

Double wall exterior coil, there would need to be a few very unusual conditions for drain water to enter the domestic side? Looks like this brand has some listings

Im not sure UL comes into play? 

Condoman

My $0.02. I live in CT with oil hydronic and MS-40 indirect. I installed the MS-40 ten years ago and haven't been happier, especially since LOML is happy. The small amount of oil used to heat water is not a concern. I know the boiler is functioning and it keeps critters out of the flu.

MaxMercy

MikeAmann said:

@MaxMercy
I just want to point out that any heat recovered should be used to warm the cold water going to the tub/shower. That is the place that you need it. I wouldn't bother trying to warm the water going into the boiler unless the pipe runs will be very short.

That would require major re-plumbing since both showers are on the second floor otherwise the recovered heat will have to feed all second floor fixtures including the toilet.

I'll probably not install a recovery system since it's only my wife and I (they say a four person household yields a better ROI), but my drain is only about 6' away from my boiler, so I would use it to preheat the coil or a side storage tank if I decide to use one.

Thanks.

MaxMercy

Condoman said:

My $0.02. I live in CT with oil hydronic and MS-40 indirect. I installed the MS-40 ten years ago and haven't been happier, especially since LOML is happy. The small amount of oil used to heat water is not a concern. I know the boiler is functioning and it keeps critters out of the flu.

A Crown MS-40?

Is 39 gallons enough, or can indirects be sized smaller compared to a dedicated water heaters? I've heard a 60 gallon would be minimum. Thanks.

Hot_water_fan

They recommend heating both the incoming water headed to the heat source, as well as the cold side of the shower, but just one is okay too. The ROI is part energy savings of course, but you increase capacity at the same time, so that belongs in the ROI calculation too (as an alternative to standalone tank, new shower head, etc.).

Canucker

@MaxMercy Indirects can be smaller than standalone because the burner in the boiler is usually much larger. I have a 35 gallon aqua plus that supplies hot water from a 107000 input gas boiler. It has a mixing valve set to 110F and it gets stored at 140F. My incoming water at the coldest time of the year is 34F. When I haven't fallen behind on descaling the tank it can heat water from cold in about 10 minutes. If I had gotten a bigger tank it probably wouldn't fire as often during use because there is so little heat being lost between calls, even at the high storage temperature.

MikeL_2

    I like Larry's idea of lower flow rate shower heads; the design of the lower flow rate shower heads has improved substantially since they first came out. 
    Although I'm not a huge fan of a lot of the home centers plumbing ware, they do let you return most gently used purchases. I suggest buying several shower heads and try them until you find one with a satisfactory spray.
     Almost all critical plumbing codes regarding safety and maintaining sanitation are based on potential, and in my 50 plus year career I've seen potential realized enough times to understand the importance of safety & liability. 

MikeAmann

NO OFFENSE INTENDED but we are all thinking like men trying to solve a woman's shower problem. Consider what a woman might be doing in the shower and how long that might take. An unlimited supply of high pressure hot water might only make her shower time even longer.

mattmia2

Bigger indirect, in addition to a hedge against you take longer showers than those that said the 40 gallon was fine with 35 degree water, will also make it so the boiler doesn't fire every time someone washes their hands.

MaxMercy

MikeAmann said:

NO OFFENSE INTENDED but we are all thinking like men trying to solve a woman's shower problem. Consider what a woman might be doing in the shower and how long that might take. An unlimited supply of high pressure hot water might only make her shower time even longer.

LOL! But to be fair, it's not the length of the shower and indeed, often the shower is hottest right before I get out.

I've got a plan to get the boiler to fire using a flow sensor and connecting the contacts to the indirect contacts of my Hydrostat. Gotta think about this a bit more.

Canucker

mattmia2 said:

Bigger indirect, in addition to a hedge against you take longer showers than those that said the 40 gallon was fine with 35 degree water, will also make it so the boiler doesn't fire every time someone washes their hands.

Mine doesn't fire every time some one showers, (Only on multiple, concurrent showers) so I doubt it's firing because somebody washes their hands. 5 gallons makes that big of a difference, eh? I believe that a bigger indirect would minimize the number of firings is exactly what I suggested in my post.

MikeAmann

I have a Hydrostat also, and I wasn't happy that it took ECON mode hours to finally ramp up to the HI Limit with a very long call for heat. My old setup worked the opposite way - run burner up to the HI Limit and then economize on the way down. Because of my work hours, I usually turn the heat down to 55 F when I am not at the house. I used a cheap China programmable timer relay with the contacts connected to ZR ZC and set it for 45 minutes. A CFH via ZR ZC overrides ECON and automatically fires the burner up to the HI Limit. The Hydrostat automatically abandons an indirect's CFH after 45 min and reverts back to heating the house. You might consider doing the same. All your wife would have to do it hit the button to activate the timer while she is getting ready for her shower. You could even use a remote transmitter, like a car alarm.

Robert_25

MaxMercy said:

I have a DHW coil on my boiler, and it does OK except my wife complains about the showers (I run the shower slower and it works fine but my wife likes a deluge).

My boiler is new and about 110K BTU. My options are a Boilermate type storage, a heat pump hybrid electric, a tankless, and a straight electric.

I'm in CT and electricity is expensive, so I'm leaning to a storage tank, but that means I'm running the boiler just for hot water at least six months.

The tankless offers unlimited hot water which is a big bonus, but I wonder what it will cost to run it compared to the boiler which I could shut down for the summer.

Ideas?

Hello. I think you have a combination of things going on here.

1. Your aquastat low limit setting may not be high enough.
   
2. You may be exceeding the capacity of the tankless coil. Most tankless coils call for a flow rate restrictor to be installed so you don't exceed the coil's ability to produce DHW.
   
3. The lack of mixing valve is causing more variability in the temperature of the water going to your fixtures.
   

If you would like to keep the coil and avoid the expense of an indirect water heater, I suggest checking the installation manual for your boiler and see what it recommends for aquastat settings, adjust as necessary. Install a flow-control valve and mixing valve to avoid variable DHW temperature due to use of multiple fixtures.

Note that keeping the coil comes at the expense of increased fuel consumption due to keeping the boiler hot all the time.