I'm trying to adjust our boiler to stable settings after we replaced insulation, installed main venting and repaired a leak in a buried condensate return.
Federal FST-40 Scotch Marine, Heat Timer EPU-CH, Carlin 701CRD, Single-pipe steam, 24 apartments
Low-fire/high-fire pressuretrol (set between .5 and 2)
Cut-in pressuretrol (set between 2 and 3)
Outside temp sensor, heat system sensor on basement return, no thermostats
I have had trouble finding settings that keep the building at a comfortable temperature, not too hot, not too cold.
Our system heat sensor is located on a return pipe in the basement. The pipe it is attached to was well insulated a month ago. Since then, it seemed that lockout period after a heat cycle was much longer than it had been in the past. My theory is that the sensor is kept warmer longer and delays the next heat cycle from starting. I response, I turned up the system sensor knob on the Heat Timer. This increased the length of the cycle since the timer started later, after the system was up to pressure, and shortened the time between cycles. I know that the heat system sensor should be set by timing how long it takes to heat up the farthest radiator from a cold start. However, we did this before the new insulation and I don't think the result would change. So we would end up with a much lower heat system sensor setting and the too-long lockout period problem.
Current thinking: Keep the system sensor high and find the right spot through trial and error. I'm worried that the cycles are still delayed, but I haven't timed them yet or measured temperature swings.
I turned up the boiler yesterday but it didn't improve the heat. When I sat with the boiler for a while this morning, I noticed that the boiler shuts off and restarts during the heating cycle.
I watched the pressure climb up to about 1.5psi and then switch into low fire. In low fire, it continues to climb and got to 2psi after about 5 minutes, then shut off. The burner restarted a few minutes later and repeated the process.
It seems to me that the burner is restarting over and over, and losing pressure in between. Maybe this is why we're not getting better heat? I was also wondering if the system is locked out from restarting by the return sensor, so that it doesn't finish its timed hear cycle.
My current solution: 1) lower the low/high pressuretrol (.5?) so that it climbs more slowly to the cut out pressure. 2) raise the cut out pressure (2.5?) so that it shuts off on pressure later.
Is it preferable that the boiler runs continuously through its heating cycle (approximately 34 minutes today)?
It would be nice to have a steady pressure after switching to hi fire so that it doesn't .cut off on pressure. Is there a way to accomplish this? Smaller fuel nozzle for low fire? Lower initial low fire setting?
Any advice would be appreciated.
Single-pipe steam | 24 apartment, self-managed coop | Federal FST-40 Scotch Marine boiler | Carlin 701CRD burner| Heat Timer EPU-CH | Honeywell pressuretrols | Heating oil #2