Help! Can I use a single water heater for two purposes?

AndrewHern

Hi everyone, I’m new to the board. Can I use a single tank water heater for both purposes of heating my home and hot water? Is it legal? Is it safe? I live in northern NJ. 

Thank you,
Andrew

Larry Weingarten

Hi and yes it can be done as long as you keep the potable water separate from the heating water by using a heat exchanger. Also, if the heating load taxes the water heater too much, it can greatly shorten the heater's life, as they aren't made to fire continuously.

Yours, Larry

Mad Dog_2

Or, the Bradford White Combi-Cor. They advertised that the internal coil could provide "space heat" and domestic hot water. Sounds good to me. I upgraded to a 75 Gallon gas model...just in case. Everything was great for a month or so. Then, the call came: The den is cold! Sure enough, the 30 feet of high output Slant Fin BB was warm, not hot, but the water heater was cranking. I upped the Water heater gas valve to the highest setting, adjusted the Mixing valve, but it wasn't helping. It was extremely cold that week, 8-10 degrees. I finally called Bradford White Tech support and pushed till I got a real engineer. After 20 minutes, he finally admitted it really was only good for radiant "heating," not "space heat!." I told him that they really needed to put THAT is the literature, that is was quite misleading. Any tank water heater at that temp simply can not recover fast enough. Lesson learned-Tuition paid..Don't ask a boy (water heater) to do a man's (Boilers) Job. Mad Dog

hot_rod

As per the 2021 IPC you can use a listed tank to do combined systems. Apollo and a few others are listed.

Most plumbers shy away from mixing potable and heating water. Health and liability reasons.

There are some aftermarket plate HX modules for separating.
At some point a separate stand alone heater may be less $$.

There are some tank type water heaters listed for hydronic applications, stand alone.

The CombiCors are an option, special order and them price is getting close to a combi boiler.

Mad Dog_2

I have a picture of a nice Combi-Cor I did with ALOT OF radiant connected to it.  It was a 50 gallon Model and heated 1/2 the house...Very happy w those Brad White Combis Mad Dog  🐕 

JohnNY

Legal in NJ, not in NYC.

jumper

In the seventies Apollo & others advertised circulating DHW through air handler for heating. Tank heater was more efficient than furnaces or duct heaters in those days. For low heating delivery and high DHW demand like ski chalet idea wasn't as dumb as it sounds. Plus coil could be used for wimpy A/C.

Jon_blaney

I use a 32 gal oil fired Bock water heater for hydro-air and heat half of my house. System has been in place for 20 years, no problem. I do not have a heat exchanger. This is a high fire tank, 104000 btus, I think.

Mad Dog_2

Yes, legal in every municipality in NYS.  Otherwise.  Mad Dog

ethicalpaul

Everything's legal in NJ!

Mad Dog_2

Gotta Love Joisey...."You from Joisey???
I'M from Joiesey!!!"  Second best place to live & work.  NY, the cool Older brother is the Best!   Ha ha   Mad Dog