I have a vulcan compact 60
sn# 1744
cat# 38-05
aw 166
the problem is the gas burner shuts down periodically about every 4-5 min, leaving the fan still running for a further 3-4 min, blowing out...
Hi Dave, my neighbour has a Vulcan Compact 60 that is doing the same as yours, except the cycle time is even shorter, only four minutes total. The temperature in the house barely rises and never reaches the thermostat setting. Altering the thermostat anticipator does not alter the cycle time. Therefore, as you have found, the fault is not related to the thermostat. The gas technician who inspected the heater said he could see the unit was faulting, but didn't think he could fix it. WTH? To help my friendly neighbour, I have asked numerous experienced techs since and those few who actually seem to know anything have helped me piece together what is probably (I emphasise probably) happening. Current thinking is that the fan is not blowing enough air and the heat exchanger is overheating, which trips the over temp switch (limiter), cutting off the burner. Eventually the fan cools the unit down enough to switch itself off and reset the limiter, then the cycle repeats.
The remedy is to replace the fan or replace the fan bearings, if they have become tight, as is likely the case. It might also be necessary to replace the combination fan/limiter switch, because the contacts are probably arcing due to the extra current drain of the fan with tight bearings (I know this because the arcing causes TV and radio interference to myself and others in the vicinity, which interference ceases when the heater is turned off and resumes when the heater is turned on and had about 20 minutes to heat up). Important: If no action is taken, the heat exchanger can be damaged and/or cracked, especially if the limiter contacts weld closed, which will allow the heater to exceed the limit temperature and probably crack the heat exchanger. This in turn will allow carbon monoxide fumes to enter the house via the ducts. Therefore the problem should be fixed ASAP.
I am currently trying to find someone who understands this heater to the extent described above and therefore has some chance of repairing it correctly. No success as yet, similar to your own experience.
Dave, if you discover anything at all about this fault, please let me know, as I am not going to waste my money on gas techs who are unable to fix the problem because they don't understand the system to the required degree.
Parts can be obtained from many gas supply houses. The one I normally use quoted about $300 for a fan and $150 for a fan/limit switch. This seems too expensive to me. I could get a whole second-hand unit for about $300. Will try to let you know if I make any further discoveries. Anyway, best of luck. Regards, VC60.
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