Blower fan won’t shut off

[Rizzo2121]

I'm stumped. Have a wood boiler manufactured by Northern Steel (out of business)
which was a copy of Johnson Mfg in Wisconsin 22 years old. Has a switch that shuts the blowers off and turns on light simultaneously. Uses Ranco aqua stat
One day, turned the switch off to load, blower keeped running, also found the Ranco no longer shut down the blower. There is a relay in the circuit.. replaced, same issue..
Replaced three way switch, same issue. Called Ranco, said unit reached useful life ,
replaced. You guessed it , same thing. Ranco goes right past set limit, still displays temp .
Can’t find an electric schematic. Anyone heard of such an issue or possibility of a schematic of similar design? Thanks in advance

 

[brenndatomu]

Sounds like a shorted wire(s)

 

[Rizzo2121]

That has to be it . No electrician for sure,…. ever heard of the fan motor feed operating the motor with only the common wire attached? Mine does..
Good thing end of season. Going to rewire . Thanks for the feedback

 

[brenndatomu]

ever heard of the fan motor feed operating the motor with only the common wire attached?

Now that sounds like a house wiring issue...you have voltage on the nuetral.

 

[gthomas785]

Well if it's not the switch, then I'm guessing your wires are melted somewhere causing the fan to receive constant power.

 

[sloeffle]

If it's outside, I'd bet a mouse got in there and chewed some wiring up.

 

[brenndatomu]

If it runs with only the neutral hooked up, then there is power on the neutral, (and ground is coming literally from the ground,..or possibly from a conduit) you'd have to unhook wiring coming into the boiler and then check it there to see if something is crossed up from the house/garage, or if its in the boiler wiring somewhere.

 

[hedge wood]

That has to be it . No electrician for sure,…. ever heard of the fan motor feed operating the motor with only the common wire attached? Mine does..
Good thing end of season. Going to rewire . Thanks for the feedback

If it runs with only the neutral hooked up, then there is power on the neutral, (and ground is coming literally from the ground,..or possibly from a conduit) you'd have to unhook wiring coming into the boiler and then check it there to see if something is crossed up from the house/garage, or if its in the boiler wiring somewhere.

If the wiring to the boiler is direct buy your problem may be in the ground. Years ago we had a direct bury wire go bad to a well house and had the same issue as the neutral had power to it. Caused some strange things to happen.

 

[gthomas785]

If the neutral is energized that alone would not be enough to run the fan unless the hot wire is also compromised and leaking to ground. Both of these scenarios would be unlikely to persist for a long time without either tripping a breaker or burning up. Not saying it's impossible just improbable.

If the fan is running and no other funny stuff is going on, to me it seems more likely that the "switched" hot wire going to the fan somehow contacted another wire that is hot. Another possibility is that the switch was defective but was then replaced with a wrong type or wired up wrong, or the replacement switch could be bad.

Time to break out the multimeter, disconnect all the fan leads and check voltage at the fan and also where the power is coming in. Check it line to neutral and also against a known bonded ground connection. Check continuity of the switch in both positions as well as the aquastat.

 

[brenndatomu]

If the neutral is energized that alone would not be enough to run the fan

Depending on the motor that's in it, it certainly would.

 

[gthomas785]

Depending on the motor that's in it, it certainly would.

How? Draw me a circuit

 

[Rizzo2121]

Thank you all for the feedback I’m going to remove the tinware and inspect..
Probably a good excerise anyway considering its age Again, thanks