Hotwater Heater: In Series Or Parallel?

izzy

What do you guys think? Should I install single 85 gallon hot water heater, (2) 50 gallon in series or (2) 50 gallon in parallel. Whats the pros and cons?
Geo thermal installer will run dispersion hot water thru tanks.
Electric co-op energy management coordinator claims the (2) 50 gallon tanks ran in series will be the cheaper most efficient system to own and operate for the homeowner.

Leo G

My gut feeling is that you should install 2 50 gal heaters in parallel. But as I was thinking about it you could set them up in series and the first one could be a pre heater. Set it to 100 degrees and set the second one to 130. You should have ample water. If you set them up in parallel one of them is always going to do more work than the other as the liquid resistances will be slightly different because of the plumbing.

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KillerToiletSpider

There is no such thing as a hot water heater, if the water was hot there would be no need to heat it.

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user50444

Killer,... I was going to say the same thing this morning but.... I'm not a plumber. George Carlin had taught me that one at a show a few years ago.

KillerToiletSpider

This is exactly wrong if they are piped correctly.

I'm not a plumber anymore either.

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Pipe Wrench

When you say Geo thermal you mean Solar or something else? What exactly are you providing hot water for?

izzy

Domestic hot water for a residential home. Geothermal in a nut shell is a heating and cooling system that circulates water under ground and uses the earths heat to heat and cool the house. The hot water from the geothermal is connected to the hot water heater and in theory since the water is already hot the water runs more efficient or basically doesn't work as hard. There's a lot more to it but thats a generic explanation.

protechplumbing

When he says "geothermal" he is referring to a ground source heat pump system. It's a central heating and cooling system that uses the ground or a body of water as the heat source/sink instead of air. Many geothermal units come with an optional hot water generation option thru the use of a desuperheater.

A desuperheater essentially captures the heat extracted from the building and uses it to heat the domestic water and pump it into the tank. When the heat pump is in heating mode the heat isn't "free" but it's still 4-6 times cheaper than electrical resistance heating. A backup heat source is still needed for periods of hot water demand when the HVAC unit isn't running.

I would do a single tank if possible for a variety of reasons. 1 is that the surface area to volume ratio is much better with a single tank and you will therefore get less standby loss. It also will be cheaper initially due to reduced piping / wiring. The only advantage of a dual tank setup is redundancy. If one leaks it can simply be removed from service via isolation valves and the system will still run on the other tank. If a dual tank setup is used I would definitely go with a parallel configuration.

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Plumber_Bill

[quote=izzy;787650]What do you guys think? Should I install single 85 gallon hot water heater, (2) 50 gallon in series or (2) 50 gallon in parallel. Whats the pros and cons?

We have a couple of jobs piped this way. Heaters (both) are set at 160 F.
all domestic use is tempered through mixing valve. Reduntancy is there by valve position. Can use either or when one in down.

Take a look

Attached Files

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