Hello heating experts... this is my first post..... Thank you for providing this important service!
I have a Weil McLean VHE-6, which I installed in 1989. I tried to start my furnace for the first time this season, and found it was not working. The problem which I will describe, is new to me, and I have been unable to figure out what is wrong, so your suggestions will be greatly appreciated.
1) The furnace is off and cold, the room thermometer shows 50F, and the thermostat is set for 70F. I turn on the furnace, the circulator and the blower turns on as per normal, and then the hot surface ignitor glows normally, then the burners all fire up,,,,, everything appears normal. After running for 6 minutes, and the temperature gauge on the side of the boiler hardly moved, the burner suddenly shuts off. No error signal is made by the control module (Fenwal 35-655600-003). The blower and circulator are both still running. And there is no voltage on the gas valve, IE, the control module told it to turn off.
2) After 4 minutes, the hot surface ignitor comes on, then the burners fire up, and everything runs for 5 minutes, the water temperature is up to about 90F, then the burner shuts off! No error signal, but there is again, no voltage on the gas valve.
3) After 8 minutes of being off, the hot surface ignitor comes on, but this time the Fenwal control module error LED signals "Ignition lockout", the ignitor goes dim, and that is all that happens, until I shut off the power to the furnace and let it sit for 5 minutes.
4) Every time I re-
power the furnace, it always goes through the same three cycles, always signalling an error on the third time. The only variation is that sometimes this all takes place in about 25 minutes, sometimes it seems to take 30 minutes.......
a) The current Fenwal controller is almost one year old. (It is the 3rd one I have had. The original one lasted 18 years, the second one lasted 11 years. ) Upon opening this one, nothing looks burned, and everything is clean. I checked all the connections, especially the ground connection, as this unit uses the ignitor as the flame sensor. And the instructions caution that solid ground connections are mandatory.
b) At the start of every heating season, I remove all the burner tubes and clean them carefully. A year ago, I opened up the heat exchanger, and cleaned it all out.
c) I always keep a spare ignitor, and I put in a new ignitor, and that didn't help. Also, years ago, Weil McLean told me the hot surface ignitor must have a resistance of between 45 and 65 Ohms. My current ignitor measures 47 Ohms, and it worked fine all of last heating season.
d) Beyond the replacement of two earlier ignition control modules, the only problem I have had has been needing to replace the hot surface ignitors. They used to last for 4 or 5 years, but last year, I had two fail in less than one month! (I handle them very carefully, and don't touch them.)
e) I should not admit to this, but I have done this as a test...... when the furnace first fires up, I have "hotwired" the gas valve on. I sat there with my hand on the wire in case of any problems....... but with the gas valve "hot wired", everything ran fine, (and no error signals) until the temperature got up to 160F, when I ended my test by removing the "hot wire", and shutting off the furnace.
f) I also checked the White-Rodgers temperature control that probes into the heat exchanger, and it is set for 200F.
g) I talked to two heating contractors that I am aquainted with, and both said since the unit is so old that I should replace it! And when I pressed them for tips, they claimed they had never worked on this model, so I couldn't get anything out of them, unless I want to buy a new furnace..... As I think the unit is basically in good shape, I don't want to get rid of it, and being retired, well, money doesn't grow on trees!
So I would greatly appreciate any suggestions! (Otherwise, all I can guess to do is to replace the almost brand new Fenwal ignition control module..........)
Thank you most sincerely, Chuck