derating a Revolution

KBP&H_3

I also passed this Q to Burnham as I have a RV5,- the house addition was 600 sq ft less than anticipated).. Anyway, Burnham said not to change anything as the co2 and the p vent fan, and input are all related,, There is a baffle / orfice plate before the blower that is different sizes between the different boilers. They also said that the boiler needs to have a consistent temp across the cast iron.. There is also the manuf rating and warranty, I'd like to also down rate it.. but there seems to be more variables.

CC.Rob_8

derating a Revolution

The boiler in question is a Burnham Revolution RV-4. Serves two zones of fin-tube at a design load of around 33-35k BTU/hr at ~140F supply, and a 40 gal State Escort indirect which receives preheated water from a solar DHW system. It never has to do more than a 50F rise on DHW calls.

Control is a tekmar 260 with indoor feedback.

On space heating calls, the boiler never runs more than 5-6 minutes, or less than 4. Not short cycling, but not long, either.

Am contemplating having the orifices changed to reduce the input from 96k BTU/hr to something less. Perhaps up to the 20% derate allowed by code. 77k BTU/hr would still be plenty to do the 50F max rise needed for DHW, and also lengthen the runtime on space heating calls.

Is this a reasonable idea, or unnecessary?

Alternatives include a) do nothing, and b) implement a buffer tank. Using Siegenthaler's formula for buffer tank sizing, something in the 50-60 gallon size would give a long runtime and a long off-time.

Thanks for any thoughts.

CC.Rob_8

aking them

Have a query to Burnham as well. Good considerations, those. But I would think that an orifice change would at least not affect the temperature across the hx. If anything, the longer runtimes would allow more even and lengthy warmth.

Thanks.