Domestic hot water setup

[ExxWhy]

I've been thinking about a new domestic water setup. I currently have an 80 gal electric tank that is around 20 yrs old and is surely on it's last legs. I also have a Biomass 40 and 500 gallons of storage running a baseboard hot water system. Plan A would be a 40 gal indirect tank feeding a 40 gal electric tank. During the heating season, the majority of the day my tank temps are below 150 and often closer to 100. Thus the indirect would only be a pre-heater during those times, yet that alone should take a big bite out of the electricity demand. I could run the boiler as desired/needed in the summer for hot water, or be totally lazy and run on the electric alone. (Once a week I am guessing?)

It is only 2 of us here now, but it is a 4 BR, 2 BA house.

Am I overlooking any problems with the concept? Is there a better way?

 

[andym]

I've been thinking about a new domestic water setup. I currently have an 80 gal electric tank that is around 20 yrs old and is surely on it's last legs. I also have a Biomass 40 and 500 gallons of storage running a baseboard hot water system. Plan A would be a 40 gal indirect tank feeding a 40 gal electric tank. During the heating season, the majority of the day my tank temps are below 150 and often closer to 100. Thus the indirect would only be a pre-heater during those times, yet that alone should take a big bite out of the electricity demand. I could run the boiler as desired/needed in the summer for hot water, or be totally lazy and run on the electric alone. (Once a week I am guessing?)

It is only 2 of us here now, but it is a 4 BR, 2 BA house.

Am I overlooking any problems with the concept? Is there a better way?

I'm not a boiler guy, but it may be cheaper to just install a heat pump water heater. The electric usage is advertised as around 120 per year. Plus in the summer it provides 'free' air conditioning. It's what I'm planning to get when mine goes out.
FWIW.....

 

[maple1]

I have a flat plate heat exchanger that re-circulates through my 80 gallon electric water heater. When heating season stops, the elements kick in. When this water heater gets to needing replaced I will check out a heat pump unit.

 

[jebatty]

I've posted this before, and the info still applies. For an electric HW heater, insulate it (6" minimum, top, bottom and sides), all the hot water pipes that you can, and install U-shaped heat traps on both the hot and cold water lines. For our household of two, with 100 gal HW heater, those steps cut our electric bill for HW heating in half, total average of 100kWh/month, or about 3 kWh/day. That's about 36 cents/day ($130/year) based on our full rate electric cost, but for us actually about 22 cents/day ($80/year) because we only use electricity for HW during off-peak times.

 

[andym]

I like the two previous comments, but I will add this: heating water with wood is just plain cool (bad word choice I know) no matter how you handle the off season. Payback may be minimal, but there's something about being able to switch off the electric WH in october.......

 

[peakbagger]

My original move into solar was a flat plate SHW system complete with Rheem storage tank so that is my 6 month hot water solution. Its DC pump with solar panel so as long as the sun it out its free to run. I would not recommend buying a new setup but if you keep en eye out on craigslist, old SHW panels and systems appear on occasion sometimes for free if you remove them. The usual failure point is the controllers followed by the storage tanks. My winter hot water heater is a salvaged indirect water heater that is hooked up as a zone off my wood boiler. The water from the SHW panels is just not hot enough in winter so I use it as preheat to the indirect system. It works slick. Worse case is the Rheem SHW tank does have one electric element. It was not hooked up for 20 plus years but when I added a minisplit for heat in shoulder seasons I on occasion would be heating with the minisplit over several cloudy days and end up without enough hot water. In that case I flip the breaker to turn the element on andI have hot water. I generate power with solar so its effectively "free" to use the backup power. Not worth heating my boiler up to temperature just to heat hot water.

 

[hedge wood]

ExxWhy
I run a flat plate with a pump on both sides and a thermostat that turns the pumps on and off feeding the hot water from the Garn. I run my Garn year round. I have air to water heat exchanger's in my furnaces so I run higher storage temps than you but in the summer I will let my storage run down to maybe 120 before firing. I have a forty gallon propane water heater set on low and it will rarely kick on if I keep my storage at 120 or above. I would think with two people you should be able to get by with a 40 gallon electric set on low and let the wood boiler do most of the heating threw a flat plate.

 

[E Yoder]

A flat plate is the cheap simple way to go these days it seems.

 

[Woodman1]

ExxWhy
I run a flat plate with a pump on both sides and a thermostat that turns the pumps on and off feeding the hot water from the Garn. I run my Garn year round. I have air to water heat exchanger's in my furnaces so I run higher storage temps than you but in the summer I will let my storage run down to maybe 120 before firing. I have a forty gallon propane water heater set on low and it will rarely kick on if I keep my storage at 120 or above. I would think with two people you should be able to get by with a 40 gallon electric set on low and let the wood boiler do most of the heating threw a flat plate.

Yes this is the same setup I use with wood boiler and storage. 5 person household equals 5 showers per day and a daily dishwasher and washing machine load. It works out to a $50.00 per month savings with electric at $0.15 per kwh

 

[salecker]

You aren't actually saving $50.00...
Unless you have figured out how much extra wood you are using .

 

[Woodman1]

You aren't actually saving $50.00...
Unless you have figured out how much extra wood you are using .

That is very true. I meant my electric bill goes up by $50.00 per month when I quit heating. I've never made hot water in the off season