Boiler reset on outdoor air temp

KB_2

Does it make sense to install a control on a residential boiler to reset off outside air temp. Would you use this method on only a cold start boiler even if it has an indirect water heater. Would it totally eliminate the existing aquastat and if not would the control just be wired in series with the burner circuit. In this case the sensing bulb would have to be surface mounted to the supply header.

Robert O'Brien

Of Course!

Does it make sense to install a control on a residential boiler to reset off outside air temp.

Yes

Would you use this method on only a cold start boiler even if it has an indirect water heater.


It can be used on almost any system

Would it totally eliminate the existing aquastat and if not would the control just be wired in series with the burner circuit. In this case the sensing bulb would have to be surface mounted to the supply header.

Some ODR controls incorporate limit controls,some don't and use the existing limit

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Brad White_189

Yes.

Absolutely, residential ODR is the bees knees and is practically a "must".

I am not sure if you mean a cast iron boiler, but they do have minimum water temperatures with few exceptions.

If you have a cast iron boiler, the simplest method is to use a 4-way mixing valve to separate the "boiler circuit" and the "radiation circuit. (Injection mixing is probably the best IMHO and 3-way valves can also be used, different ways to do the same thing.)

The key feature is that the boiler be maintained at a temperature above it's dew-point (say 180F high end but not less than 140 low end), while the radiation loop can go from 180 or so down to even room temperature).

If a cold-start boiler, (or any boiler so used for that matter), it must be set up for "domestic HW priority".

A condensing boiler typically has no minimum water temperature so the mixing devices to protect the boiler are not necessary.

Taco, Tekmar both have literature to illustrate the fine points, on-line.