DHW questions/ideas

That's what I did. Controlled by Johnson A419, pumped on DHW side by a B&G E3Ecocirc.

Sounds like a simple dual fuel option.
Is it a fairly new tank? Any possibility for some solar, it could provide a large part of the DHW in the summer months.
When the tank is ready for a replacement, consider a solar tank with an electric element for, backup. Better yet a dual coil solar tank with solar, wood or electric input.

maple1 said:

That's what I did. Controlled by Johnson A419, pumped on DHW side by a B&G E3Ecocirc.

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I was also trying to figure out how I would handle domestic hot water in my upcoming build. Maple, are A419 and the ecocirc both on the domestic side of the heat exchanger? What circulates and controls flow on the boiler side of the heat exchanger?

Thanks, jerid

The boiler side of the FPHX is plumbed through a zone valve, same as my other heating zones. On call for DHW heat, the Johnson sends 24v to the zone valve & opens it. The end switch in the ZV then starts my main load pump (an Alpha), same as the other heating zones, as I have that end switch wired into the other ZV end switch stuff.

On the DHW side, I also have a RIB relay wired parallel to same 24v that opens the ZV. So at the same time the ZV is opening, the relay is hooking up. The other side of the relay is 110v hooked to the Ecocirc. So at setpoint, the Johnson sends out 24v. Which in turn opens a ZV, and starts the pumps on each side of the HX.

It works very good - both pumps are variable speed so I can adjust flows through each side of the FPHX. The load pump only shows 1gpm when just the DHW heating is going on. I forget what I have the Ecocirc set to, but it is on the low side. Great for maintaining stratification when heating from storage.

Having said all that - I initially did the DHW heating with just a sidearm. Which works fine when burning for heat every day or two, but doesn't when heating from storage. So, if you were only concerned with heating DHW in the heating season, that would be a lot simpler solution - but if heating DHW from storage is a possibility or wanted, a FPHX would be the way to go. If heating an exisiting DHW heater - otherwise if looking to do a new heater/tank too, an indirect type tank may be something to check out as mentioned above. Although I don't know how hot they would need the boiler water to be & how they would do with maintaining stratification when heating just from storage. I have an 80 gallon electric water heater, can go a week between burns in the summer, and my storage is down to around 120 on top before I need to burn again.

I use a sidearm hx for dhw during the heating season. Sunday morning when everyone in the house needs a shower is about the only time there is NOT enough hot water. I would like to add a fphx to my water heater. In conjunction with the sidearm, i would have endless hot water.

don't forget to use a mixing valve to keep the temps down. I have small children, so it's important that i NOT have 180* water coming out of the faucet.

I use propane during the non heating season, and i think it's time for a change! I use about $350 worth of propane just for DHW during the non heating months.

This year I am definately upgrading to a solar water pre-heater.

To the question about alpha II pumps turned on/off.....

I have one pump that runs 24/7, but my other only turns on when the thermostat in the house calls for heat. It is engineered to remember it's settings after the power is turned on/off. I LOVE my alpha's! They will pay for themselves in electricity savings within 2 years. Plus, i have a battery backup for the boiler, and these pumps will run up to 24 hours with no human intervention when the power grid fails. Traditional pumps would likely only run for a few hours with the same setup before the batteries were discharged.

My Alpha turns off & on with call for heat, it's tied to an aquastat. I just did a straight swap with a 15-58 3 speed. They can be done either way, and gotten with a plug-in cord, or as a traditional hard-wire install. It is an awesome pump - IMO should be standard issue in a setup with varying loads (multiple zones all calling at different times). So to vary flow on the boiler side of the DHW FPHX, I just throttle a ball valve there - the pump will slow down accordingly. The Ecocirc has a dial on it for speed.

Using the sidearm for DHW in the summer, I found my storage was pretty well useless for heating the DHW once it got below 150 or so on top. And at that point stratification was pretty well lost.

Man - that's harsh propane use for DHW. I would definitely do something about that. As it is here, even if I don't burn wood for DHW in the summer, it only costs around $25/mo in electricity to do it. Which kind of takes away some incentive to do it.

I can try to rough sketch it later - about to go sledding. Yee haww...

A sidearm hx is probably cheaper than a flat plate, and it circulates hot water through the tank by gravity. You can build one yourself if you know how to solder for probably less than $100 with off-the-shelf parts. Mine gets water from the boiler before it goes into the house heating system. Provides plenty of nice hot water all winter. I've built several over the years and they all worked great.

SteveStearns said:

Any ideas are welcome.

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This would only apply if your situation happens to make it possible. If you have your storage the basement and can re-locate your electric water heater into an upstairs closet space, you could locate a side-arm heater above storage and then pipe that to the upstairs water heater. Then gravity would eliminate the need for any pumps.

SteveStearns said:

Not sure how good a 40 gallon water heater would look parked in the living room?

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Sure, go for it.

SteveStearns said:

I have been looking for ideas on how to heat my domestic water. The best idea that I have come up with so far is to install a flat plate exchanger and tie it into my existing electric water heater. I am not completely sold on the idea of burning wood year round yet. However six months of no electric use for hot water is sounding good. Any ideas are welcome. Thanks

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My heating and DHW solution was to use a larger potable water tank and plumb two boilers to heat it, one a pellet boiler and the other an oil boiler. They both input about the same energy to the tank but only usually operate singlely. I just set the snap switch on the tank, a 100 gallon Triangle Tube to a setting below the pellet boiler's aquastat. If that boiler quits and the water temp drops enough the oil boiler will pick it up. The DHW is tempered through an adjustable mixing valve to 125 F or so but the tank when heated will be at 180 F. The house is heated by running that hot water through a 50 plate FPHX, so I get pellet heat in the winter along with DHW and in summer I drop the temp in the tank to about 155 and run the oil boiler to heat true DHW. I have an electric backup that can supply DHW also.

My current set up is flat plate solar hot water that circulates glycol around a electric hot water heater through a coil in the jacket. That system covers all my hot water for about 8 months a year. It has a DC pump with solar panel so there is zero electric usage. The tank does have a backup electric coil but I have never wired it up in 12 years. It runs during a power outage. In the winter I switch a couple of valves and the electric hot water tank turns into preheat for a Amtrol hot water maker that is heated off a separate zone from my heating system. It is rigged so that if the house heating is off storage, the hot water zone is inactive. I usually manually operate it at the end of running the wood boiler to use up excess heat in the boiler but it also can be automated. The Amtrol is quite small but I set the zone at 180 deg F and with typically 100 deg plus water coming from the hot water tank even in cold weather that 180 degree water lasts quite awhile. Worse case is I turn off the wood boiler circuit and the oil boiler turns on an it runs like a conventional hot water maker.

That system was built up over years with some scrounging. I wouldn't recommend it currently as with cheap solar electric panels you never make up the initial cost of solar hot water. I would rather suggest some solar electric panels on the roof and a heat pump hot water heater in the basement assuming you utility has net metering. You basically are building up a surplus of power in the summer to use in the winter and the HPHW unit runs better in the winter if there is a wood stove or boiler in the generally vicinity plus you get summer dehumidification as a bonus. Solar panels with microinverters are pretty darn close to plug and play these days so they are a relatively easy install. The key thing to check is if you have net metering and if and when the utility "zeros" the account.

Best money I've spent is on a HPWH for the summer months. Large tank is a plus.

TS

I use a 20 plate exchanger and use it as tankless water heater. I have my hot water heater bypassed all together. I have never even come close to running out of hot water. Even while the shower and washer is running. The tempature of the water coming out of the faucet is a 161 degrees. So i would highly recommend a mixing valve.

Part of my system is an electric boiler that also has an instantaneous DHW coil in it. Works great during the winter when I am burning but I am also looking at some kind of summer preheat for the well water coming into that coil. I figure that if I circulate my whole system during the summer, my cast iron rads and storage should stay roughly the temperature of the surrounding air in the house. If that is around 70 degrees, is it enough heat to run through a FPHX to preheat my well water before it gets to the boiler? How may plates would I need in the FPHX? I am not trying to create all of my hot water, just trying to help the electric boiler to burn a little less hydro.
Thanks a bunch.

Introducing fresh water into a closed heating system on a regular basis isn't a good thing.
O2 will break down all your steel components.

Willman said:

Introducing fresh water into a closed heating system on a regular basis isn't a good thing.
O2 will break down all your steel components.

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I don't think that is what he was implying - I think he was just thinking about circulating his heating fluid thru his rads in the summer to pick up a bit of house heat that the DHW coil would scrub off to preheat.

Which I don't really have an answer to - but I suspect the gain would not be a lot as there wouldn't be very much of a delta T at the DHW coil.

Yes. That's it exactly Maple. If my well water is 45-50 degrees to start and my heating fluids/rads can pick up 70-75 degrees from the house ( I don't use A/C), is there anything to be gained? How much less electricity would the electric boiler use if it was starting with water that was 10 degrees warmer?
I am just looking for a cheap easy way to save a few bucks in the summer. Maybe the easiest thing to do is just put a copper coil on my brown metal roof and run my well water through that.

How much electricity would you use now just heating DHW?

I don't really have an answer one way or the other I don't think - but our 80 gallon electric water heater only runs about $25/mo to heat our DHW when not burning wood.

This is my first year with the system. Perhaps I should take the summer to figure out what it really costs for just electricity. Then I will know whether I need to improve.