2500Ram

Way off topic but I thought I'd ask.
Our pellet stove Quadrafire 1100i took a dive and isn't working. Everything and everyone said the board was bad so I replaced the board again, 2nd board in 2 years. Well the stove still isn't working. First board acts just like the new board. The call light for heat is on but the exhaust fan is not working, spinning VERY slow. The auger feed for the pellets is vacuum fed and if you suck on the hose the auger will start and eventually the igniter will fire but there is no exhaust fan = stinky smoke in the house.

Fast foreword I believe I have a bad startup capacitor but don't know how to test it. I've been all over the web and people say you can test them with a volt meter and other say you can't. I have 2 capacitors on the stove; while the stove is plugged in one will read 130.xx volts and the other .01volts AC. I tried using the ohm reading but don't know what I'm looking for. Everyone says just run down to Radio Shack and get a new one but I don't know if it's bad or if it's the fan but doubt they would have one anyways.

Thanks in advance.

Bill.

sherod

A cap can be checked with a multimeter, but, it needs to be removed from the circuit for accuracy.

Use Ohms function. Place the positive probe on one leg of the cap and the negative probe on the other. You may show an open. If you do, switch the leads. You should now show continuity. If you do, the cap is good.

Caps normally fail shorted. If you have continuity with both probe senarios, it is bad. Also look for swelling or use your nose for that nasty burnt smell.

Ed

Mexstan

A quick and dirty way to test the capacitor is to isolate it from the circuit by disconnecting one of the wires. You did not say how big this capacitor is (physical or otherwise), but if it is a small one soldered into a board, it could give you a bit of a problem. Once it is isolated, short the two wires together for a few seconds. Don't touch the wires with your fingers after you have shorted them together. Now get your ohm meter (not the voltmeter) and set it to the highest scale on the ohms setting. Clip one lead to one leg of the capacitor. You may need a second pair of eyes for this next step as it happens very fast. While watching the meter closely touch the second lead of the ohm meter to the second leg of the capacitor. The meter should twitch up slightly and then settle back down. Remove the second lead and do it again. This time the meter should not move. If the meter twiched up the first time and then not the second time, there is a good chance that the capacitor is good as it means that it is holding a charge. Shorting the wires together before the test discharged the capacitor and the ohm meter recharged it, albeit very slightly.
Hope this helps a bit. Let us know how it went.
BTW, unplug the unit before you work on it.

sherod

Thanks Stan, that's alot clearer than mine.

It's hard to believe I taught electronics for 15 years, isn't it

Ed

Mexstan

You are welcome. I forget to mention about it being shorted, but you covered that.

2500Ram

These cap's are about as big as a pack of cigarettes, 4 spade terminals on each pole if that helps.

So unplug and remove from the stove, short the cap with a wire and use the ohm meter to see if there is a jump = good correct?

Bill.

jrs_dodge_diesel

Most high end multimeters have a cap checker on them that will check the cap and give you a farad reading. A cap should NEVER show continuity. The cathode and anode are not directly connected and should read open with a digital multimeter. The best way to check a cap without spending a ton of money ($500+) on a high end multimeter, is to use a analog Simpson meter (a digital meter does not react fast enough to give an accurate reading) set to test resistance (Ohms Ω). You should see the needle sweep to the right indicating an open at first (as the cap charges) and creep back to the left for an open (as the flow of charge current dwindles). This check will not check to see if the cap is still within its tolerance to its farad rating.

I assume this is a large style can capacitor for an A/C system. You probably won't find it at Radio shack. An A/C parts supplier is your better bet. And they are relatively cheap.

Normally when caps fail they short out (continuity both ways between the cathode and anode), and usually stink like burnt electronic stuff.

Good luck from this Coast Guard Electronics technician (6 years so far).

2500Ram

Thanks for the info, my big dollar Fluke meter is miles away and all I have is a cheap but good digital meter $50 unit, cant find my old analog meter for the life of me. There is no electrical burnt smell at all. Please don't tell me the fan is bad now... $100 for the board and $250 for the fan Just to keep the gas bill down isn't paying this year.

2500Ram

Ok, last check. No smell what so ever, I pulled all connections from the cap's and shorted with a small piece of wire. Set the ohm meter to 200k witch left me a reading of 1xx. (x = spaces on the meter or no value) Put on the neg probe and while watching the meter put the positive probe on and had a reading from 130.0, 084.0 to the 1xx. within a second.

Just about the same readings on the other cap. I had to short the posts each time or the meter wouldn't move but after I had shorted the caps I received the same results each time.

Do they sound good to you?

jrs_dodge_diesel

It does sound like its holding a charge (which is what caps do charge and discharge at fast rates). You charge it then short the two leads together to discharge it. It sounds like its good. Looks like you also found out how a digital meter doesn't work as well as a analog for checking if it holds a charge. There is always that delay between readings. But it does sound like its good in that it holds a charge and is not shorted. Now there could be internal breakdown and the cap will "leak" its charge between the anode and cathode internally. This is a sign of a failing cap that that hasn't ultimatley failed (shorted) yet. The only way I know of to check for cap leakage is with a cap anylyzer.

Also, the charge check will not confirm that the cap is still with in tolerance to its farad rating. Usually on a cap you will see something like 380 uF +/- 10 %, which means 380 micro farads with a 10% tolerance either way.

I would like to say your cap is good, but there is the unknowns like the farad rating and leak breakdown. If you are confident that the cap is good leave the cap out of circuit and check out the motor and be sure that there is no windings shorted together and/or shorted to ground. A megger is a great tool to check for shorted or imminate failures in windings.

BTW if you have an extra cap, short the leads together before you store it. Good caps can build charge over time and if you pick it up and accidently touch the leads you could get a rather nice shock from it. Larger caps are worse with this as they can build up lethal charges for unsuspecting technicians.

sherod

What J.R. said.

J.R., you sure you never set anyone up with a cap? All in good fun? Spent 20 years in the military, and I do believe I have seen a trap or two.

Nothing wakes you up faster in the morning that a hidden cap. (within reason, not lethal)

Ed

2500Ram

Well I'm almost sure the caps are good, I disconnct the leads going to the motor and get 120v, hotwired the fan and it's doing the same thing, sloooow spin.

Anyone have $250 for a new fan. Man I can't believe these fans are so expensive.

Thanks everyone. This place is an absolute wealth of knowledge about anything and everything.

Bill.

jrs_dodge_diesel

Can't say I have made cap traps (yet ). However playing with the high voltage megger was always good for a laugh. What was your rating (job) in the military and what branch?


2500Ram

Sounds like you found your problem with your fan motor. Sounds like the windings are going out and or there is a bad bearing or two. An option instead of replacement is to take the entire blower/motor unit out and take it to a electric motor shop and have them fix it.

I had a motor/air compressor unit for a dry air antenna system that had stared blowing fuses on a regular basis. It had a cap start on it and after taking it out megged the windings and found shorted windings. Took it to a motor shop and they replaced the bearing and rewound the windings in the motor with new copper winding line and it came out cheaper than replacing the compressor. Something to look into.

BTW the cap start system was designed for motor as they have INDUCTIVE load. Which means they draw more power to start spinning than they do when its spinning at constant speed. The cap is there to provide that brief surge of power to get the motor going without blowing fuses or tripping breakers. Granted it does throw in another piece that can break but saves the hassle of reseting a tripped breaker every time the motor has to run.

FiverBob

Didn't you say the fan was turning slowly? If it is, that may indicate a bearing freezing up or needing lube. Probably a sealed bearing, but sometimes you can still lube them. I would try it before condemning it to death.

2500Ram

yes it's spinning slowly but you can turn the fan by hand while running or stopped and there is no bearing sound or resistance