best way to plumb a alternate water heater for summer

crabbydad

I currently have an indirect water heater. I was thinking about installing an electric water heater to use in the warm months to save on oil. I wanted to use the indirect as a holding tank in the summer, and in the winter close off a couple valves, and drain the electric water heater and of course turn it off. I searched online, but couldn't find any info for doing this correctly. maybe I didn't search it out correctly. anyone here ever done this or know the correct configuration?

BobC

It depends on how much hot water you use, in the summer I only use 7 therms of gas but I'm the only one in the house. It also depends on how much you pay for electricity, our beknighted utility charges us 24.6 cents per KWH - because they can.

Bob

crabbydad

good points. my oil is topped off at the end of the heating season and again at the beginning. I'll pull my oil bill for the end of the summer and see what my average cost per month is and compare to the cost of electric. thanks

ChrisJ

There's more to this though.

How much heat is the boiler wasting through it's thin insulation? How efficient is the oil burner setup? An electric water heater should be close to 100% efficient.


How often does it run and how much $$ in oil are you using all summer typically? If I recall, the typical 50 gallon electric heater claims $500 cost per year in most areas.

If it was mine, I'd much rather run a separate electric heater than the oil fired one but that's for more reasons than just cost.

Noise, wear and tear on the burner etc.

icesailor

Well, 40+ years of using electric water heaters for storage tanks on oil boilers with bad performing tankless's has worked well for me and my customers. Where I used to live, the power company was giving electricity away to get you to switch to electric heating and water heating at $.015 per KWH. Even at that price, there was no ROI by dumping oil for the summer or any other time. There's no boiler modification piping to be done, and you use the boiler tankless for the hot water supply. The electric elements are not connected to the power source.

With a family of 6, we never once ran out of hot water.

If you want to install an electric heater, do you have room for a 30 amp breaker in your electric panel?

With a water heater storage tank, it has the electrical use of a table lamp.

ChrisJ

@icesailor

Out of curiosity, does anyone make a 12,000 watt 50 gallon heater? From what I see, that would be the equivalent to my 50 gallon 40K btu/h gas heater.

vibert_c

That is surely a size large water heater. visit www.chromolox.com to see if they are made at 240 volts single phase.

icesailor

ChrisJ said:

@icesailor

Out of curiosity, does anyone make a 12,000 watt 50 gallon heater? From what I see, that would be the equivalent to my 50 gallon 40K btu/h gas heater.

They make wall hung instantaneous heaters All you need is an extra 75 to 100 amps @ 240 volts in your panel.

There's a company in Florida that manufacturers them. You can wash a horse with one. Not a lot of pressure but the water is warm, and the horse likes the warm water.

http://www.amazon.com/Stiebel-Eltron-DHC-E12-Electric-Tankless/dp/B00DSKJ38Y

ChrisJ

icesailor said:

ChrisJ said:

@icesailor

Out of curiosity, does anyone make a 12,000 watt 50 gallon heater? From what I see, that would be the equivalent to my 50 gallon 40K btu/h gas heater.

They make wall hung instantaneous heaters All you need is an extra 75 to 100 amps @ 240 volts in your panel.

There's a company in Florida that manufacturers them. You can wash a horse with one. Not a lot of pressure but the water is warm, and the horse likes the warm water.

http://www.amazon.com/Stiebel-Eltron-DHC-E12-Electric-Tankless/dp/B00DSKJ38Y

That one at Amazon is a joke with it's 1.5 GPM rating.
I was picturing a tank 12Kw heater as it should perform similar to my 40Kbtu/h 50 gallon heater.

icesailor

@ChrisJ:

"" That one at Amazon is a joke with it's 1.5 GPM rating.
I was picturing a tank 12Kw heater as it should perform similar to my 40Kbtu/h 50 gallon heater. ""

Maybe this one will work for you. 3- 4KW elements running together. You probably need a 75 amp breaker to cover the almost 60 amp draw.

Suppliers sell a lot of these water heaters. I'm sure that there is a good price point somewhere. You can probably buy a small pick-up truck full of 40 gallon residential electric water heaters for the cost of this 12KW commercial one, but we don't discuss price here. As I remember, this discussion was about buying an electric hot water heater for summer use so the OP didn't have to waste oil in the Summer months. We don't discuss pricing here. Factor in the cost of a water heater and all the appurtenant needs like plumbing so it can be switched back and forth, and wiring, and divide/compare the perceived savings in oil as opposed to the cost of the electricity and the cost of the installation, and it will show that PT Barnham was right. There's fools out there.

http://cdn.globalimageserver.com/fetchdocument-rh.aspx?name=powerpack-powerpack-asme-spec-sheet

These might be cheaper to buy, Especially if you have a 440 volt 3 phase service in your house.

http://cdn.globalimageserver.com/fetchdocument-rh.aspx?name=light-duty-commercial-light-duty-spec-sheet

SWEI

12 kW (nominal) is the largest standard heating element you can buy here. The actual limitation is 48A, above which all kinds of additional NEC requirements kick in. Higher capacities are more easily achieved using multiple 12 kW elements, which is why you see ratings of 24 kW and 36 kW from the likes of Stiebel Eltron.

Rich_49

And then there's these monsters .

http://htproducts.com/htp-commercial-electric-water-heater.html

icesailor

Electric water heaters can be a PITA. Especially if someone doesn't know the correct voltage and how electric water heaters work. "Standard" water heaters may have two 4500 watt elements, but only one runs at a time. It may appear to be a 9,000 watt/9 KW heater but it isn't. Its a 4500 Watt/4.5 KW heater if rated at 240 volts. And if you don't have 240 volts when it is running, it isn't putting out 4.5 KW. Where I lived and worked, there was a large commercial area fed with 125/208 3 phase. Restaurants were always buying new booster heaters and dishwashers. The salesperson at El Cheapo Restaurant Supply what the voltage is. "Do you have three phase? No. So they send out a 240 volt single phase heater. That now only gets 208 volts theoretically. In the evening, when the load went up, they might get 185 volts. Its called "How you get experience". Manager: That new water heater booster isn't doing the job. You screwed up the installation. "You bought it. I installed it. You bought the wrong heater. Its the wrong voltage. You bought a 240 volt single phase booster and it is running on 208 single phase. Wrong voltage for the application". But the salesperson at El Cheapo Restaurant Supply said this was the right one because I didn't have three phase, whatever that is. Before you ordered the booster or the dishwasher, you didn't ask me about it. Or the electrician.

If you're going to be blamed for someone else's mistake, you better know how to defend yourself.

SWEI

Ohm's Law at work -- that pesky V² component. When voltage drops from 240V to 208V, heat output drops by 25%.

icesailor

@Swei:

Try explaining that to a manager with a degree from some culinary school with an advanced degree in frying bacon and you have a license that says that you passed two tests to get to be a Master Plumber. The degreed Bacon/Burger flipper only calls you when his minimum wage college student, majoring in art history, can't unplug the toilet full of stomach contents from too much bar the night before. The same manager wants and needs a water heater with a 200 gallon per hour recovery at a 150 degree rise, but only wants to pay for a 40 gallon residential electric that recovers 18 GPH with a 90 degree rise, on a good day. They already bought the 40 gallon heater from El Cheapo Restaurant Supply, who threw the heater in for free with an order of square dishes (that no one wants to eat off of but their "In Vogue". And he looks at you like you are trying to take food off his table and rip him off when you tell him that a 40 gallon electric won't give him enough hot water to pass the Health Department tests for hot water.

Hint: If you've never drank coffee out of a square cup, be sure to put on a napkin bib because it WILL spill down your front and leave coffee stains on your shirt. Ever see a nursing mother, breastfeeding an infant with square breasts? And square nipples? Neither have I.

Wait, wait. It just occurred to me why they have square plates now. You tip the plate so all the juice and left over goodness will slide into the corner. And you can scrape it up with a spoon. If they gave you a spoon. They took your only spoon when they took away your empty bowl of soup of chowder.

And they EXPECT a 20% tip. Because you had the nerve to ask for another spoon.

BobC

I remember helping the factory rep install an environmental chamber with dual compressors (had to go down to -65C) we bought to do NAVMAT testing. He warned me the compressors would not operate to full capacity with 208v on them.

I had a couple of transformers wound that would give me 248v out with 208 in, I went for the 248 because I knew the line drooped to 204 in the afternoons and I had to maintain low temperatures around the clock.

I had to install additional heaters and a nitrogen boost to meet the slewing requirements of 5 degrees a minute.

Bob

icesailor

BobC said:

I remember helping the factory rep install an environmental chamber with dual compressors (had to go down to -65C) we bought to do NAVMAT testing. He warned me the compressors would not operate to full capacity with 208v on them.

I had a couple of transformers wound that would give me 248v out with 208 in, I went for the 248 because I knew the line drooped to 204 in the afternoons and I had to maintain low temperatures around the clock.

I had to install additional heaters and a nitrogen boost to meet the slewing requirements of 5 degrees a minute.

Bob

And now they have electronic phase converters that will give you any voltage you want.

Where I lived on Cape Cod, my next door neighbor raised Sheep, Goats and Alpaca's for their fleece. He found some places on the Internets that had old small wool carding machines. He went South to Georgia and brought them back. They were all 3 phase. He had a standard 150 or 200 amp single phase residential electric service for his 3 bedroom house. His electrician told him about the electronic phase converters, that the size of the converter didn't make any difference. It worked.

Sort of like the guy I recently met. The barn where my wife keeps her horse had this electric instantaneous water heater. It stopped working. Her horse is eccentric. Being related to most of the Kentucky Derby winners of the last 20 years, he's eccentric. He'd rather die than drink cold water. He might have sensitive teeth. I checked it out. The owner said that he re-set the breaker and it made all kinds of noises. The rating plate on the heater was 55 amps, the breaker was a 60 amp. His Sparky came by the next day and I was replacing the heater. I told Sparky that the breaker sounded bad and was too small, being a 60 amp breaker. His response was that HE put it in 5 years ago and it had worked for 5 years. He flipped it on and it made the same noises. It drew 55+ amps and the amperage went down. Bad breaker. Another 60 Amp breaker was procured. Just pop that new 60 amp breaker in. Same thing. Just go get credit for the 60 amp, and pop in a 75 Amp one. Life will be precious.

This is Florida. Things are different.