This is a hydronic heating system at a family member's house -- oil-fired hot water baseboards with two zones, one for each floor. The bedrooms get hot and the bathroom / dining room / living room stay pretty cold. All those rooms are on the same floor. The boiler is relatively new, I'd guess 10 years old at most. The burner is made by Carlin.
I checked and as you might expect the rooms that are getting hotter are at the beginning of the pipe loop for that zone and the ones that stay colder are at the end. The problem seems to be that the boiler is short cycling. With the house at 62° and the thermostat set to 70° the boiler will run for about 2 minutes then shut off for 7 or 8 minutes. The boiler temperature gauge goes up to about 195° before it shuts off so I presume it goes off due to the high limit on the temperature. When the gauge drops back down to around 180 it turns back on. As this goes on the pressure reading is somewhere around 20 or 25 psi and doesn’t change much.
I understand – correct me if I’m wrong – that with the boiler short cycling there isn’t really enough time for the heated water to move through the whole system, which would explain the temperature differential between the rooms. But I have no idea what would cause the short cycling. Any ideas? Thanks!