Radiant with W/H Heat source

Howwen

I looked at an installation today that I need some advice on. Bock water heater propane fired at 199,000 btuh. 1 1/4" feed and return headers to 4 radiant zones of unknown length. No mixing valve on water heater. Stat set to 125 degrees. Cust. complaint: Lack of heat, sooted up water heater. My thoughts: at the least a mixing valve on the water heater, turn up to 165 or so mix down to 130 to radiant. Better: new condensing boiler.

Any ideas?

Unknown

your first idea is a good one. new boiler might be tough; does the tubing have an O2 barrier? If not, that's a large HE you'll need.

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hr

First you should

do a heatloss calc to see what the load really is! Even at 70% efficiency that heater could be oversized for the actual load.

Yes you should consider running it hot, above dew point, then adding a mix down mechanism.

The heatloss would also give you needed supply temperatures and design info for loop length, gpm, pressure drop, etc.

It's always good to have a starting point, even on repair or trouble calls like this. Don't want to guess like the previous installer

hot rod

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Howwen

Thanks for your advice.

I have asked the HO for the engineering data, it is in the garage and needs to be "dug out". What I explained to them was exactly what you said, GPM, temp, heat loss, etc.
They seem to understand. Hot Rod, what is your opinion of even using a WH as a heat source? I think it is an inefficient way to do it with regards to heating much more water than is needed. 72 gallons in the Bock alone. I value your help on this.

HB

hr

regarding WH's

First, few, if any, have the actual listings needed to be used as a closed loop heating appliance. Which is a big reason many of the internet radiant companies sell combined systems. It's the only way to get around code issues. Although I highly recommencd against combined systems.

Next, basic tank style WHs are terribly inefficient, a tank wity a large, always open, hole through the center is a very inefficient way to heat water.

Actually the tank capacity is not a bad idea for multi zoning IF it is a well insulated stoage tank, not really a center flue water heater

This leaves "upfront cost" as the only selling feature of tank style water heaters, in my opinion.

Now, if the listings, or lack of, do not concern you, the HO, or the code officials..., WH like Polaris, Voyager and other condensing style WHs are excellent low temperature radiant sources, IMO.

Efficient, large volume, fairly dependable and simple to repair, stainless steel, good track record as far as years on the market.

If only they had the ASME, or codes could be modified to accept these as low temperature, low pressure heating appliances.

They are as safe or safer in regards to pressure ratings, etc as a basic cast or copper boiler, again IMO.

Keep in mind virtually all the small condensing "boilers" on the market started as, or still are, water heaters!

hot rod

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