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Old 11-01-2016, 12:17 PM   #1
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Series water heater questions


We moved into a new construction home a few months ago and have two electric water heaters setup as a series in the basement. Since its just me and my wife, we don't' use need both the heaters so I turned off the upstream heater and the downstream heater has been satisfying our demand just fine. I have a few questions regarding this setup.

1. Is there a downside to leaving the upstream heater off as far as damage to the heater or any other issues?
2. I want to setup a fail safe so is there a way to set the system where if the downstream heater fails, I can simply switch to the upstream? I want to do this w/out switching to the parallel configuration. What would the approximate costs be?

Picture of the heaters is attached.
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Old 11-01-2016, 03:28 PM   #2
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Re: Series water heater questions


After thinking about this, I guess the only way to do what I want is to convert to a parallel system. I'm wondering how much it costs to convert to a parallel setup.
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Old 11-01-2016, 03:48 PM   #3
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Re: Series water heater questions


I'm not familiar with multiple water heater systems so I don't have an answer to Q1.

It seems that with your current set-up the water is circulating through both tanks. With a parallel set-up, I'm not sure how the water would circulate and if this would create problems. If you wanted to hold one of the tanks in standby, you could install some Ts and gate valves to both link and isolate the hot and cold lines and take one of the tanks completely out of service, but it would have 'old' water standing in it.
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Old 11-01-2016, 04:31 PM   #4
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Re: Series water heater questions


No harm to the water heater.

As for what it would cost. Only a plumber in your area can tell you that.

But its easy to DIY, and ave money.
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Old 11-01-2016, 04:35 PM   #5
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Re: Series water heater questions


Quote:
Originally Posted by lenaitch View Post
I'm not familiar with multiple water heater systems so I don't have an answer to Q1.

It seems that with your current set-up the water is circulating through both tanks. With a parallel set-up, I'm not sure how the water would circulate and if this would create problems. If you wanted to hold one of the tanks in standby, you could install some Ts and gate valves to both link and isolate the hot and cold lines and take one of the tanks completely out of service, but it would have 'old' water standing in it.
Ayuh,..... I like this idea, except I'd just drain the unused tank so's the water in it don't get stale,....
Probably wouldn't rust out as soon either,...

Donno what any of the options might cost in yer area,....
I like most of the other posters on this forum, Do it Ourself's,.....
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Old 11-01-2016, 07:55 PM   #6
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Re: Series water heater questions


I'd leave it as is, but add a by-pass on each. (so series unless something goes wrong, then you can isolate and by-pass)

The material costs for PVC valves and tees and pipe is fairly cheap. The labour, not so much.

My home system is actually parallel instead, since I added gas to replace the electric. Kept the electric as backup. Valves to it are shut off and so is the breaker. It'll sit that way for years without issue. If I ever need it, I'll let it heat to above 130*F and flush it a few times to give it a mix.

Cheers!
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Old 11-01-2016, 10:59 PM   #7
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Re: Series water heater questions


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,....
Probably wouldn't rust out as soon either,...,.....
Believe it or not, once the free oxygen in the water is used for any oxidation, The process comes slows, and comes to a nearly complete stop. With the tank full of air, you'll never run out of free oxygen. The only alternative would be a nitrogen holding charge, which sounds unpractical, which is why I just use water.

Cheers!
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Old 11-03-2016, 09:30 AM   #8
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Re: Series water heater questions


For being able to isolate a failed heater, you need valves on both the cold inlet and hot outlet of the water heater. Meanwhile some city codes do not allow a valve on the hot outlet.

For this failsafe setup you should have an expansion tank between the cold shutoff and the water heater for each water heater, to provide some protection against accidentally firing up the heater when the valves are closed.

Also desirable for all-electric heaters is a lockable shutoff switch for each if the tank is drained.
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Last edited by AllanJ; 11-03-2016 at 09:33 AM.
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Old 11-03-2016, 06:47 PM   #9
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Re: Series water heater questions


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Originally Posted by AllanJ View Post
For being able to isolate a failed heater, you need valves on both the cold inlet and hot outlet of the water heater. Meanwhile some city codes do not allow a valve on the hot outlet.

For this failsafe setup you should have an expansion tank between the cold shutoff and the water heater for each water heater, to provide some protection against accidentally firing up the heater when the valves are closed.

Also desirable for all-electric heaters is a lockable shutoff switch for each if the tank is drained.
Good points!
I let out a few gallons out of mine for the air buffer. AFAIK our codes don't prohibit the outlet valve, but I can understand the logic, even if I don't totally agree. (our commercial appliances all have isolation valves by design, sorry, my resi experience is very limited.)

I really like the lockout idea. Maybe just a simple red breaker tag and lockout would be just fine for such an application? They are not so expensive and real easy to add and remove.




Cheers!

Last edited by supers05; 11-03-2016 at 06:49 PM.
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