Posted by Ari on October 01, 2001 at 09:54:51:
Two problems, actually.
I have a 35 year old gas fired hot water furnace with pilot, one circulator pump, two zone valves, in a two-story house. It's used only for heat, and gets a checkup about twice a year from the gas company.
Problem 1 - When the service guy came by, he noticed the pressure gauge was running only about 4 psi (at about 80F). He said the expansion tank or auto-fill valve may be bad. I stuck a pressure gauge on the valve on top of the tank and it read 4 psi. I pumped it up to 12 psi (heat off - about 80F). It now swings between 12 psi and about 18 psi with both zones open and hot (190F on gauge). All baseboards throw heat fine. Can I assume that the tank just leaked down over time, and since I repressurized it, I'm OK? I'll monitor the pressure, and if it starts to leak down again, I'll replace the tank.
Problem 2 - When the burners kick on, there is a 'moaning' from the furnace that last about 20 seconds. It sounds like a pipe organ. It's not the circulator pump - it's definately associated with the burner/exhaust - I can actually hear it from outside the house by the chimney. I assume this is some resonance set up in the burners, and once they get warm, it goes off resonance. Any idea how to fix this? Would minor adjustments of the air valves help?
Thanks!