Sticking Honeywell fan/limit switch

StanInPa

Installed on a Beckett, hot air unit. Switch settings on new unit defaults. Bi-metal turns disc ccw when burner establishes flame, hangs up at fan on position for several minutes. Then flies all the way to limit position, so that the burner stops and the fan starts at the same time.
Then it hangs at this position till ducts cool down to almost room temperature, and disc flies cw all the way to fan stop, whereupon the burner starts up and the fan stops. Some times after call for heat is satisfied burner will shut off and fan will continue to run blowing cold air tilll I tap on the switch cover and then fan stops.

Not interested in theories about how to lubricate this unit, I can come up with those myself. If your advice contains the word "should" or the word "WD40" keep it to yourself. I'd like to hear from a pro based on actual experience if there is an aceptable remedy for this.

BTW about a month into the heating season it "fixed" itself. Damp basement with an active spring and busy sump pump.

STEVEusaPA

StanInPa said:

Not interested in theories about how to lubricate this unit, I can come up with those myself. If your advice contains the word "should" or the word "WD40" keep it to yourself. I'd like to hear from a pro based on actual experience if there is an aceptable remedy for this.

Kind of a rude way to ask for free help. don't you think?

BTW, I don't think you 'should' use 'WD'40'.

Jamie Hall

Considering that almost any suggestion I would make would contain the word "should"... forget it.

DZoro

Maybe time for a new one. They usually come in different lengths make sure you get the proper length for your furnace 5,"8",11".
D

HVACNUT

And the Honeywell fan/limit disc from a cold start turns CW. CCW during the burner off cycle. Unless of course you're in the southern hemisphere in which case you'd be correct.
Then you can try 04DW.

Either the "on" contact is faulty, not closing the circuit to the blower motor in heat mode or bad windings in the blower motor for the heating speed. When the fan/limit reaches the 2nd "off" in the CW cycle it shuts off the burner. That limit also closes a contact to cool down the HX (with a different fan speed) on the Beckett furnace. Didnt know they made a furnace.

BTW I'm not a pro and have absolutely no experience so I cant promise this is an "aceptable" remedy.

ch4man

3 paragraphs and not a single question. weird

StanInPa

HVACNUT - I'm not looking at the unit right now, but I believe you're right. I misremembered the direction of rotation. The contacts all work OK, its just that the disc physically hangs up at the fanon position until the bimetal coil builds up enough torque to flip the contact, then it goes all the way to open the limit contacts.
The fan/limit unit is only a year old, and it developed this odd behavior early on. I didn't see a way to safely disaddemble it without doing harm, and didn't want to try introducing lubrication indiscriminately.

GBart

CALL A PRO

JUGHNE

I would pull it out and look. Sometime insulation could get in the spiral element and it is binding up.
If too long the element could be touching one of the heat exchanger cells as expansion comes into play.
Or you just got a bummer, these are not used much in new equipment anymore that I see.
When that happens the quality of things drop off.
That should be all I have to offer.

EBEBRATT-Ed

what @jughne said

then pour a can of WD40 on it

neilc

EBEBRATT-Ed said:

then pour a can of WD40 on it

yeah, that's what ya SHOULD do
#smileyface