Radiant with Bradford-White Combi-core water heater

Steve Garson_2

This should make for spirited discussion:

Five years ago, my contractor built an addition with radiant heat. The water is heated by a Bradford-White Combi-Core water heater, that has a water loop for the radiant in the water heater. I know this wastes a lot of heat through the vent, but that's what I have. The rest of the house is steam.

Realizing that these water heaters last only ten years, I am thinking toward the future. Bradford-White has another similar heater with power venting that eliminates the atmospheric heat loss.

My heat loss for the radiant heated are is only around 18,000 BTU. The water heater uses 65,000BTU with an AFUE of 82%, which I can't imagine bears any relation to that AFUE with a boiler; or perhaps it does. I am thinking that the lower efficiency of the water heater is offset by the much lower cost of the heater.

When it comes time to replace. What would you pros recommend if it were your house?

Alan(OnVacationInOregon)Forbes

Surprised

that your CombiCor has lasted so long; all the ones we installed gave up the ghost just after 1 year.

I'm a fan of water heaters for small radiant loads; conventional water heater for domestic with an external heat exchanger for radiant or to make it easy, a Taco mixing block:

http://www.blueridgecompany.com/radiant/hydronic/484

Rodney Summers

Is the Combi

your main DHW supply? Then it's still nice to have a storge tank. How about a wall hung tankless water heater with a low-boy indirect under it. WOn't take up any more space then the Combi.

Steve Garson_2

Yes, the water heater serves for DHW. Are you suggesting that the tankless feed the DHW and have a take-off feeding an indirect, with the outlet of the indirect going back to the tankless?

Brad White_19

Good thing

I am not paranoid...

You ought to know my full name (forgetting middle names) is indeed Bradford White...

So keep going... my ears were burning but for naught

ALH_4

Agree

For a load that small, I agree with Alan's take on it.

Another option, depending on your electric rate, is an EPR heater from Laing. They are very reliable and designed for smaller heating loads.

-Andrew

hr

For that size load

Which I assume is at design day? Think a small electric WH would be my choice. A 5000 watt element in a small 6 gallon tank gives you 17,000 BTU/hr.

Inexpensive, 100% efficient, etc. I highly doubt you are running 82% efficiency with any gas fired WH

hot rod

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Rodney Summers

Sort of

I'd turn the indirect into a Combi-cor. Use the indirect's internal coil as the heat exchanger for the radiant loop.
The tankless and indirect would be set up like a booster tank. Get a bronze or stainless pump to circ the DHW through the tankess and back into the indirect. You'll need a tank with a bottom drain that you could use as the 3rd tapping. The indrect's aquastats will run the bronze pump and the flow will fire the tankless. Now you have a good supply of DHW and don't have to wait for the tankless to kick in.

Steve Garson_2

So is something like a Bosch 250SX-NG (Natural Gas) Tankless Water Heater what would make sense?