Water source HVAC & Hot water problem - No one could fix for 3 years... - Plumbing Zone - Professional Plumbers Forum

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Old 02-21-2019, 11:41 PM   #1
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Default Water source HVAC & Hot water problem - No one could fix for 3 years...

- Cross posting at **********************************


I'm a home owner of a town house in San Diego, CA who is having terrible issue for multiple years.
I will really appreciate if someone can give any kind of advice on this.

Here the problem goes.

Facts :
The house has 'AO smith GPVT 50. Build date 1/21/2015' water heater in garage.
The water heater is also used for HVAC. I believe it's called water source HVAC.
The water heater has a pipe to the HVAC and the pipe has value so I can open/close.

Problem (short version) :
If I open the value furnace works so air vents blow hot air BUT all water taps/shower in the house lose hot water. It drops to ~85F within a minute or so even when furnace isn't running.
If I close the value furnace won't work so no hot air BUT we get hot water. Hot water temp stays very stable.

Longer version :
I bought and moved in 2016.9 and very soon noticed that there is problem with hot water.
I called plumber A - A said there is no problem with heater. Just crank up water heater setting.
The issue prolonged so I called another plumber (B), (B) found the value and closed and said he doesn't know what it's for.
At this time I didn't know this will stop the furnace. It's San Diego so we never used furnace..
In 2017.11 we moved out and rent the house out.
Tenant soon reported furnace isn't working in 2018.1. of course.
So I called another plumber (C) and explained the problem.
(C) installed a check value on one of pipes above the water heater and then problem disappered!
In 2018.12 there was an water leak incident in one of show so plumber (D) fixed water leak and did build back.
(D) changed shower value inside the dry wall.
After fixing the water leak tenant is reporting the hot water problem again and closing value give them hot water back.
Called plumber (E) he changed shower catridege in whole house but didn't help.
Called water heater expert (F) he said there is no problem with wather heater but said there is problem with water source HVAC.
Called water source HVAC expert (G) he now says there is no problem with HVAC but he think water heater needs more power.

I think there is no problem with water heater. As soon as I close the value the water temp goes very high.
So I wonder if there is cross connection within the HVAC or some flow problem..

Any thoughts? Or anyone in San Diego area can help fix this?
So far 7 different plumbers/HVAC guys couldn't fix for 3 years.


The value on the top left is the one I open/close.
I don't know what the top right one is (what is it?) but that's the one (C) installed check value.
Bottom right is the cold water inlet pipe.

Last edited by Tango; 02-22-2019 at 07:43 AM..
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Old 02-22-2019, 07:42 AM   #2
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