Hydronics frustration cold air no hot water

ShawnLayne

I have a 10 year old home with 2 furnaces and 2 60g gas water heaters. When I turn one of the 2 furnaces on, I lose hot water at all taps within a couple minutes. Also, the furnace struggles to keep the house up to temp. It mostly blows cool air. Both water heaters are tied together in a series. I've been told they are in a "closed system". I've had plumbers and HVAC guys out multiple times and nobody can fix it. It seems to me that something has to be wrong with the one furnace/air handler because not only does it blow cold air, but it prevents the faucets from getting hot water. The instant I shut this unit off, I have an endless amount of hot water. Just seems like a simple valve not opening/closing to me. I'm to the point I just want to buy an entire new system because nobody can give me a straight answer.

nicholas bonham-carter

Terminology

Do we understand that you have forced air furnaces, which may be robbing gas pressure somehow when they run, preventing the gas hot water heaters from making hot water?

Or do you have hot water heaters which supply hot water to fan-coils in an air handler setup, with added controls to produce domestic hot water, through a heat exchanger?

This sounds inefficient at the best when working, costing more for gas than a regular boiler with indirect, and output to the coils. Were the bills high?--NBC

Harvey Ramer

Well

Make and model # of all equipment. Airhandler, heatpump/AC, gas water heater?



If it is a natural draft conventional gas water heater. It's just not going to work. Sorry.



Harvey

icesailor

Information

Post photos of the whole thing. Water heaters, air handlers "furnaces", whatever is there.

heatpro02920

Like the others said

we need to know what type of system it is? Did it work for 10 years or has this been an issue the entire 10 years?



If it is a pair of hydro airs running off of a pair of medium/large water heaters, it is most likely something odd that should be redone properly.. Sounds like this is the case because why would you need dual direct fired 60's?



If it is a more conventional system where you have 2 individual gas fired furnaces and 2 dhw water heaters, then it is a gas problem... BUT since you said it happens instantly when you turn the system off I am thinking it is an odd water heater fired heating system, where they have bronze or ss circs and run high pressure to the air handlers and take the dhw off of the same system... This is not a good idea for a lot of reasons...



If that is the case, your best option would be to get a boiler installed, preform a heat loss, check the btu rating of each air handler, and have a boiler installed to match with 2 zones, and let one of them 60s handle your DHW needs...