# Geothermal and domestic hot water



## 1703 (Jul 21, 2009)

I didn't really know where to put this so I'll put it here. Move it need be.

I got a call a month ago- water heater not working right.

I go out and find a geothermal system with two water heaters piped in series, an electric being used for storage and a gas.

The first pic is how it was piped. 

What I found was the gas heater would not maintain a constant temp like it should. 

I got to running some water in an adjacent shower. while I was running water, the geothermal unit was cycling. If you look at the first pic, the supply and return from the Geotherm is tee'd into the hot and cold of the first heater. The wh used as a storage tank was full of warm water. When the pump on the geotherm would run while the shower was running, cold water was pulled from the cold inlet and sent back to to the hot outlet and then into the gas water heater. No warm water from the storage tank was pulled into the gas heater. When the pump turned off, then warm water from the storage tank was then pulled into the gas water heater. I began to wonder if I was getting some sort of thermal stacking in the gas water heater, causing issues with it.

I then looked through the HO's paper work for the geothermal and found a piping diagram that showed the return from the furnace going into the bottom of the storage tank (second pic). This made sense to me- in theory the warmest water in the storage tank would be at the top and this would then go into the gas water heater regardless of whether the goetherm pump was running.

I made the changes to the piping as per the manufacturer's piping diagram showed.

I called the HO a few times after the work was done to make sure the problem was solved, which they acted like all was well.

What I didn't know was the HO then went back to the builder's plumber and HVAC contractor and told them they had to pay my bill.

The HVAC contractor told the HO I shouldn't have changed it and it needs to be put back the way it was. 

I understand the basics of how these systems work, but am hardly an expert.

So geothermal experts- is one way right and the other wrong? Should I not have piped it the way the manufacturer shows it piped?


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## Protech (Sep 22, 2008)

Your way is better, but not the best. I'll get back with ya after work.


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## LEAD INGOT (Jul 15, 2009)

This is how I do them.


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## ckoch407 (Sep 30, 2009)

They should tell the HVAC guy off. The way they had the hot from the thermal unit connected to the hot outlet of the first heater ( or cold inlet of the gas heater, however you wanna look at it ) defeats the whole purpose of the first tank.


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## vinpadalino (Aug 27, 2010)

What about adding a 3 way valve? You would have to re pipe it though.


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