Economizing with dual gas hot water heaters


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Old 09-03-12, 02:25 PM
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Economizing with dual gas hot water heaters

Hi,

I'm a first time poster and glad to be here.

I have purchased a larger home that was owned by a family of five. It has twin 40 gallon gas hot water heaters that are ganged together to draw water equally(?) from each and replenish equally as well. There are also twin electric vents. These heaters and powered vents seem run quite frequently. Now, there are only two of us in this house. Is there any way one could economize and not have both of these running with the frequency that they do?
 
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Old 09-03-12, 02:55 PM
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I'd think you could just turn off the supply valve to one, turn the thermostat off and cut the power for the exhaust fan (might not be needed if it's controlled by the WH) and you would be good to go.

All depends on how it's plumbed. From what I understand, most setups like this are piped so one can be completely isolated for repair or replacement while the other continues to supply hot water. It will depend on what you have.

There might be things you would need to do like flushing or sterilizing before placing it back in use if needed.

Oh...and Welcome to the Forums! What part of OH...I'm an old Buckeye from 20 miles North of Dayton.
 
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Old 09-03-12, 03:21 PM
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Thanks Gunguy45. There is a reasonable amout of plumbing to both units. I think I will post a photo that might add some detail that I may be ommitting.

I just moved to Richfield, OH (inbetween Cleveland and Akron) from Chambersburg, PA, from Manitowoc, WI, from Edgewood, KY.
 
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Old 09-04-12, 03:51 PM
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Here is a photo of the existing coupling of the water heaters. Could it be as simple as closing the in and out valves and draining one of them? Would it make sense to alternate them every so often? Might there be long term negative effects from not using one of them?
 
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Old 09-04-12, 04:11 PM
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Yeah...that's a good looking install. Nice and clean and good valves.

Yes...it could be as simple as you describe...but I wish one of our plumbing experts would weigh in. I don't know if you should drain and flush or just leave it...or drain and leave it empty (as empty as possible).

I'd be inclined to think drain and flush, then add some sterilizer......but that would involve breaking connection it appears.

If you are on city water...I think I would alternate every few months...like daylight savings time. I'd still do a good flush thru a tub spout before using each one as your primary.

Before you decide...I'll PM one of our Pro's if they don't post.
 
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Old 09-04-12, 04:28 PM
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Boy! I can't thank you enough for how quick you respond Gunguy45. It doesn't look like there is an easy way to open a connection in the system. Everything is crimped. The only accessible screw in item in that relief valve with the lever on the side near the top of the tank. If one of your buds has any ideas I sure would appreciate you passing them on.

By the way, I'm on a well. I also need to correct the size of these. They are 50 gallons each. I hope I'm not asking for help only to save pennies. It just seems a waste to have 100 gallons of water being heated 24 hours a day for two people.

I could ask the kids to return home..............
 
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Old 09-04-12, 05:41 PM
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Looks like an alright install. The only issues I see is no expansion tank/tanks. There may be one but the tank/tanks should be installed in such a way that it cannot be isolated from the HWH. I say this because both heaters together are most likely 80k btu.

I also say this because without the exp tank I believe code dictates you cant have two valves at each heater. Basically if someone shut those valves, and the heater went in runaway mode, plus if the relief valve failed, you now have a rocket ship............Death or serious injury could occur.

Possibly one of the other members can verify my statements above.

Second, and not really major, the tee where the two heaters combine on the hot water outlet should be installed an even distance from each heater. This allows both heaters to draw evenly. Same for the inlet tee, but I cannot see that one.

Looks like they piped the circ line evenly.

With that said I would drain the heater you are not using completely. When you want to put back on line use a transfer pump to add some bleach to the drain valve. You will need to open the relief valve to do this. Then shut the drain valve, relief valve and fill with water, Let it sit 24 hours before bringing it on line.

About a pint of bleach should be plenty.

I would also fix the issues, but that's just myself. Were permits taken out for these heaters when they were installed?

One more thing, the reason you may have these two heaters is because you have a large soaking tub in the home? Code dictates that you need to be able to fill these large tubs with hot water. One heater will not cut it. But in that reality what you do is your business in that sense.

Just bringing what I know to the table.... Anyone?
 
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Old 09-14-12, 10:00 PM
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How many bathrooms does your house have? How many showers/tubs? And hot tub?

You have two higher efficiency gas water heaters with power dampers units sitting there. While they are considered efficient the stand-by losses are significant.

My estimate is that you are spending at least $200 annually to have a second tank in place.

I can't see how the hot water lines are connected to the hot water pipes. You want to be sure that you don't have cold water mixing from the disabled tank with water from the active tank. Otherwise you get water delivered at temperatures that are too low.

If you want to disable the system. I would shut of the water connections and drain one of the tanks. See whether that causes any issues on the hot water supply side in the home.

I am not sure why someone would install a second gas tank in series. It does not make any sense besides being a better way if maintenance work was required often. If someone wanted to be efficient I recommend either one large tank (if the demand justifies it) or use a gas water heater with an electric thermal storage tank. Electric tanks loose less energy than gas models. The gas water does the efficient heating. The electric does the efficient "storing".
 
 

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