Need help understanding Vacuum switch...

[fmt2bx]

Hi, Newbie here. We got this used Whitfield Advantage 2T pellet stove when we purchased our home. I am going through it now, just to make sure that everything is in order. Spent a lot of time, cleaning, I replaced a few things like motor gaskets, door seal. Also tested the stove, all seems to be working just fine right now.

There is one thing tho that I cannot comprehend. On the exhaust housing is a nipple which connects to the vacuum switch. How come the rubber line doesn't fill up with smoke and ashes??? Don't see how this creates any sort of vacuum..(???) Also, for testing purposes, I ran the stove (outside) with the rubber line disconnected. It keeps running????? I can select any heat setting and it keeps running just fine. It never stopped the auger like it is suppose to do. (???) anyone with some explanation would be really appreciated.. (posted some pictures)

Thank you

 

[JRemington]

The only explanation I have is the connections are stuck in the closed position.

 

[heat seeker]

If there are three terminals on the switch, the wires could be on the Normally Closed terminals, thus falsely indicating vacuum.

When the exhaust motor runs, it draws air through the stove, creating a low pressure inside the stove. The pressure reduction is very slight, not enough to feel, but enough to trip a sensitive switch. Note the large diameter of the switch, allowing for a large diaphragm to develop enough force to operate the switch.

Suggest you eyeball the switch to see how many terminals it has. The wires should probably be on the Normally Open terminals, if it has them.

The hose would not fill with ash or smoke, because there is no significant airflow through it. That said, it is still possible for the stove end nipple to clog with ash, and the hose to crack and split from heat exposure over time.

I hope this makes things a bit clearer for you.

BTW, this switch is an important safety device; don't run the stove without it working properly, except for testing while you're standing right there.

 

[Pelleting In NJ]

Since the nipple is on the output side of the exhaust fan, the switch must be sensing the positive pressure of the blower, and actually is designed to trip if the flue is blocked, which would cause the positive pressure to rise, and then trip the pressure switch to shutdown the stove. The switch is normally closed, in series with the auger motor. If the flue pressure gets too high, the switch opens.

 

[fmt2bx]

If there are three terminals on the switch, the wires could be on the Normally Closed terminals, thus falsely indicating vacuum.

When the exhaust motor runs, it draws air through the stove, creating a low pressure inside the stove. The pressure reduction is very slight, not enough to feel, but enough to trip a sensitive switch. Note the large diameter of the switch, allowing for a large diaphragm to develop enough force to operate the switch.

Suggest you eyeball the switch to see how many terminals it has. The wires should probably be on the Normally Open terminals, if it has them.

The hose would not fill with ash or smoke, because there is no significant airflow through it. That said, it is still possible for the stove end nipple to clog with ash, and the hose to crack and split from heat exposure over time.

I hope this makes things a bit clearer for you.

BTW, this switch is an important safety device; don't run the stove without it working properly, except for testing while you're standing right there.

Thank you for the reply. The switch only has 2 terminals. I disconnected the terminals and the switch is closed. Might be stuck in that position (?). Not good if that is the case. Could lose the blower motor and the stove wouldn't shut down.(?)


So if that the case that a vacuum switch could fail in Closed position, what kinda test could i do from time to time to make sure it operates safely?

Thanks

 

[fmt2bx]

Since the nipple is on the output side of the exhaust fan, the switch must be sensing the positive pressure of the blower, and actually is designed to trip if the flue is blocked, which would cause the positive pressure to rise, and then trip the pressure switch to shutdown the stove. The switch is normally closed, in series with the auger motor. If the flue pressure gets too high, the switch opens.

Yes you are right. So if the exhaust blower fails then it won't stop running the auger. Right?
Thanks again for the reply

 

[heat seeker]

That makes sense. I've never seen a setup like that. That would explain why the stove runs without the hose. The hose is a safety item, too, and should be replaced.

That setup would not stop the auger if the blower motor quits, however, so it doesn't seem like the best setup to me. The auger would continue to feed pellets, with bad consequences.

 

[fmt2bx]

That makes sense. I've never seen a setup like that. That would explain why the stove runs without the hose. The hose is a safety item, too, and should be replaced.

That setup would not stop the auger if the blower motor quits, however, so it doesn't seem like the best setup to me. The auger would continue to feed pellets, with bad consequences.

I agree. I ll do some more testing on the vacuum switch and see what I can find . I am going to replace it anyway but it bothers me.
I ll open the switch and see what's going on in there. I ll report here later.

Thanks again for your help.

 

[johneh]

A quick test of vac switch
Open door Auger should stop
and the fire goes out !!
If the auger keeps going replace vac switch

 

[Overfireinthehole]

How long did it run for? If I remember right on those the stove doesn’t check if the vacuum switch is closed until it’s ignited and run for a few minutes. Also, that should be a pressure switch not a vacuum switch because it’s tied in after the blower.

 

[johneh]

From the manual
PRESSURE SWITCH The Positive Pressure Switch is located on the Exhaust housing and is designed to shut down the auger motor in the event of flue blockage. Some other possible causes are as follows:

 

[Pelleting In NJ]

Yes, with a positive pressure switch type of design, if the exhaust blower fails, the stove will continue to run. It only protects against flue blockages.
To test it, block the flue and see if the auger stops.

My Ecoteck has the same design, but the control board also has an RPM feedback signal from the blower motor, so if it stops rotating, or rotates too slow, the control board will shutdown the stove.

Honestly, I think all stoves should be designed to detect a blockage AND a non-functioning exhaust blower motor. Not sure how many stove manufacturers only put one of these safety systems in their stoves.

 

[Traveler12]

I agree. I ll do some more testing on the vacuum switch and see what I can find . I am going to replace it anyway but it bothers me.
I ll open the switch and see what's going on in there. I ll report here later.

Thanks again for your help.

I also have an Advantage II-T. That missing hose is part of a critical safety feature. The installer for my stove (hired by the previous owner of my house) thought he was being clever by leaving off the clamps on that hose while working on the stove. Cheap generic rubber hose (looked like the stuff used with windshield washers on cars) dried up and was loose (without clamps), so a chimney blockage could never be detected. I once woke up late at night to the house filled with smoke and exhaust gases because the pressure switch (not vacuum) never tripped.

After I replaced that hose, the pressure switch was working as it should and did properly shut the stove down again another time.

Sounds like yours has never been activated, so it’s probably still in like new condition. You won’t see any quick reactions to the pressure switch being activated unless if you’re watching the auger motor very closely. The shutdown process requires the timers to time out before turning off the fans.

If you feel you must test it, best way would be to unplug the AC power, pull the wires off the switch, find a low pressure air source (not vacuum) within range of the pressure switch specs, and get on the pressure switch tabs with an ohmmeter. If you don’t know what that is, don’t touch it, just reconnect the hose.

Suggest that you check eBay for high-temp silicone pressure hose (Whitfield part no. 12056003), and you should find more than one seller with something intended for that very same pressure switch. They’re not expensive. I found eBay more convenient and much cheaper, since every other web based supplier wanted to sell me large quantities that I didn’t need.

And don’t forget the clamps on both ends to ensure that the hose will stay there.

 

[johneh]

I also have an Advantage II-T. That missing hose is part of a critical safety feature. The installer for my stove (hired by the previous owner of my house) thought he was being clever by leaving off the clamps on that hose while working on the stove. Cheap generic rubber hose (looked like the stuff used with windshield washers on cars) dried up and was loose (without clamps), so a chimney blockage could never be detected. I once woke up late at night to the house filled with smoke and exhaust gases because the pressure switch (not vacuum) never tripped.

Not to be critical just for your information
I have never seen a vac. hose with clamps!
The hose should be inspected every year and replaced or trimmed as necessary
The stove should have been cleaned (total tear down clean long before an exhaust blockage
See your manual for the amount of fuel used between full cleanings
A Clean stove is a happy stove!!

 

[Overfireinthehole]

The older whitfields usually had a zip tie or hose clamp on the end.