Outside AC fan not spinning, buzzing sound, Trane XE1200

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Old 06-12-15, 07:04 PM
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Outside AC fan not spinning, buzzing sound, Trane XE1200

My outside AC fan is not spinning and just emits a continuous buzzing or humming electrical sound. I tried giving it a spin with a stick in either direction, and the fan spins easily and freely, but it still doesn't kick on.

Could this be a bad capacitor, contactor, something else? The model is a Trane XE1200. Any help is appreciated. Thanks.
 
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Old 06-12-15, 07:17 PM
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I would visually inspect the capacitor top for swelling.
Also look for burned wiring.

Trane crank case heaters tend to short out and trip the breaker. You can sometimes look down and see the short by the compressor.
 
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Old 06-13-15, 07:13 AM
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Ok, I disconnected power, opened the lid and inspected the capacitor. I don't really see any swelling or rust. Here are some pics Trane XE1200 - Album on Imgur of the capacitor, contactor, and what appears to be a second capacitor (in black) towards the bottom.

Should I replace the top silver capacitor? This Trane XE1200 model TTP024C100A3 calls for a 35/4 MFD 440 volt, Round, w/o resistor. Is this the correct replacement http://www.supplyhouse.com/Titan-Pro...citor-440-370V
 
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Old 06-13-15, 07:44 AM
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Is the contactor pulled in with a cooling demand present?



I'd check the breaker. If you have a service disconnect by the condenser, and it is not a square D breaker type disconnect, I would turn it off and reset the breaker to allow you to see what happens when it tries to start.

Did you get that cap value from the side of your dual capacitor or from a website?
 
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Old 06-13-15, 07:53 AM
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Capacitors commonly swell on top when they fail like this one...



This doesn't always happen. If your 35 plus 4 microfarad cap read 35 plus 1 it might not swell up yet but your fan motor wouldn't run and the compressor would eventually drop out on thermal protection.

Many meters will measure 35 microfarad. If you were to measure a dual cap you would remove power, isolate, and measure C to Herm for 35 and C to Fan for 4 uF.



I would want to know if the condenser even has 240 volts before replacing a cap that is not swollen.
 
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Old 06-13-15, 08:52 AM
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I saw the capacitor specification in the parts document that was on the inside of the unit. It lists the capacitor sizes for the various models. I would double-check the numbers against the actual capacitor before ordering through.

Here are some pics of the fuses AC 25AMP Fuse - Album on Imgur

They read 25 AMP Time-Delay Current Limiting Class RK5. Should I just try replacing the fuses first? Is this correct Cooper Bussmann Dual Element Class RK5 25 Amp 250V Fuse-FRN-R-25 - The Home Depot

Looks like they're $10 at home depot. This would be easier than testing a multimeter on the live wires or capacitor. I suppose if replacing the fuses still doesn't work, the next step would be to check if the contactor pulls in, as shown in your picture.
 
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Old 06-13-15, 09:03 AM
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Klein Tools 600 Amp AC Digital Clamp Meter with Temp-CL200 - The Home Depot

If you replace the fuse without correcting the problem it will pop again.

If you had a meter, you could measure the resistance across each fuse to see if it has blown.
(At least one has blown and you probably have a short near the compressor)

The CL200 will measure up to 100 microfarad. This should cover any run cap you would run across but not most start caps.

http://service.kleintools.com/instru...structions.pdf
 
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Old 06-13-15, 11:15 AM
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I just tested the fuses with a digital multimeter and they both went towards 0 on ohms. Also tested with the audible continuity check and both beeped, so it appears the fuses/breaker are not the problem.

I'll check the contactor to see if it pulls in when the thermostat is on.
 
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Old 06-13-15, 11:46 AM
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Is the contactor getting 24 volts to the coil and 240 volts between L1 and L2?

That yellow wire is one of two 24 volt connections on the contactor.

It looks like you popped the top of of the condenser instead of removing the 2 service panels to get that picture. It would be hard to check it that way. I would snap a few pics of the compressor area and put the top back on to check it. (Though it seems that a shorted crank case heater would have popped that small fuse before tripping the breaker)

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Old 06-14-15, 06:15 AM
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You're correct, I had opened the top and not the service panel. Good eye!

Ok, so I went and opened the service panel and just finished testing the voltage. The contactor did not depress. Further, it sounds like that is where the buzzing is coming from. Even after giving it some taps with power off (seemed to move freely), it would not depress with power on. I then made the following measurements:

With the thermostat and power active, T1 and T2 are 0. Of course, because the contactor is not depressing.

Across the yellow and brown (blue) control lines, it measured 12v.

Shouldn't it measure 24v? I traced the control lines into the house, here are some pics of the control wiring http://imgur.com/a/wB5Qa. The first 2 are the contactor. The 3rd is the yellow and blue control wires for the contactor. The 5th and 6th pics are the control wiring in the basement where the thermostat ties to the air handler. Thanks.
 

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Old 06-14-15, 07:12 AM
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We need to isolate the contactor for a couple of tests.

Turn off 240 volt power to the condenser outside for these tests.
Leave the indoor unit with power.

I would disconnect the 2 wires from the house to the condenser and measure for 24 volts AC.

If you have 24VAC to the condenser, turn off the stat, unplug the two 24 volt wires to the contactor and measure resistance across the 24 volt coil to the contactor.

It should be 13 to 16 Ohms plus whatever you read when you touch the two meter leads together.
 
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Old 06-14-15, 07:42 AM
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Ok, I disconnected L1 and L2, and measured between the yellow and blue control wires, still reads 14v.

I also tested the voltage on the thermostat between the red and green wires, it's also reading 14v. I also measured inside the basement air handler http://imgur.com/ScpHGfm between the top R and G, it's also reading 14v.
 
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Old 06-14-15, 07:55 AM
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Did you disconnect the control wire to the condenser before measuring for 24 volts?

If you measure 14 volts at the two control wires when they are not connected to the condenser it points to a problem at the other end.
 
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Old 06-14-15, 07:57 AM
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I just updated the prior post before your reply. Here is what I did:

I disconnected L1 and L2, and measured between the yellow and blue control wires, still reads 14v.

I also tested the voltage on the thermostat between the red and green wires, it's also reading 14v. I also measured inside the basement air handler Imgur between the top R and G, it's also reading 14v.
 
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Old 06-14-15, 08:00 AM
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You disconnected the high voltage L1 and L2?
I wanted to see if a 6 Ohm low voltage coil was creating a voltage drop.
I meant to disconnect the 2 low voltage wires to see if the voltage jumps up to 24 volts.
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Disconnect the red wire on R and the white wire on B at the indoor unit and measure for 24 volts AC.
 
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Old 06-14-15, 08:12 AM
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Here is what I have:

L1 and L2 are disconnected outside.
Yellow and Blue control wires are disconnected outside.

Red R and White B on the indoor unit are disconnected.

Red to White (B) measures .41v.
Red to Green measures .11v.
White (B) to Green measures .52v.

The other wires on the indoor G to Y1 measure 0.
 
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Old 06-14-15, 08:32 AM
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Are you using the same scale on your meter to measure for 24 volts that you used for 240 volts?

The lower scales can get damaged if someone connects them to 240 volts when set for 24 volts on some non-prograde meters.

Do you have a float switch under the indoor unit?



We will probably need to access the indoor unit controls.
Does the indoor unit have 240 volts AC.
 
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Old 06-14-15, 08:58 AM
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The multimeter has auto-range sensing up to 300v, so I don't think there a setting for a specific voltage.

With the Red and White wires disconnected, when I measured from the R brass connection (behind the screw) to G, I got 14v as we saw before. So it appears that the power comes from the R connection screw (not actually the wire).

Could this mean something is wrong with the transformer, that it's not correctly sending 24v? I'll check for a float pan switch. For the indoor unit, the breaker for "Air Handler" is a 240v breaker, but the one that controls the 24v (what we're seeing as 14v) labeled "Furnace" is a 120v breaker.
 
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Old 06-14-15, 09:10 AM
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Here are some pics - Album on Imgur, so measuring from the R brass connection to G gives 14v. I also disconnected the green wire from G. Measuring directly from the brass connection R to brass connection G gives 14v.

I also took a shot of the bottom of the indoor unit. Doesn't look like a float pan switch would be under there?
 
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Old 06-14-15, 11:21 AM
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The condensate pump that your drainline runs to will have a float switch.
Does it appear to be wired to the low voltage circuit?

Can we see a picture of this 120 volt transformer that is controlling a 240 volt air handler?
Sounds kinda unusual.
 
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Old 06-14-15, 12:38 PM
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> Does it appear to be wired to the low voltage circuit?

Some pics - Album on Imgur of the breaker and air handler. When I flip off the 20amp breaker labeled "Furnace/Heater" the thermostat wire goes to 0v. When the breaker is on, the wire is 14v. So this breaker is controlling the ac thermostat line. I also tested a different thermostat (one of the heater ones) just to see if it was also controlled by this breaker, however the other thermostat measures 26v even with that breaker off. So the heating thermostats must be controlled by a different breaker.

> Sounds kinda unusual.

Should the breaker for the thermostat line also be a 240? I just figured the 240 breaker is for the air handler and the 120 breaker is separate just for the thermostat wire.

This just made me realize something. I had recently purchased this house and the electric service had been upgraded to 200amp with a new breaker box. The breaker that is controlling the thermostat is a 120v breaker labeled "Furnace/Heater", even though it is controlling the A/C thermostat. I'm wondering if the electrician may have accidentally wired the AC thermostat line to a 120 when it should be 240? In the pics, the shut-off switch for the air handler has 2 wires feeding into it, they both trace to the breaker box. So, maybe that is going to the 240v air handler breaker.

I'm thinking of calling the electrician tomorrow to see if any of this rings a bell. Maybe he'll remember why he labeled the breaker "Furnace/Heater" if it's controlling the ac stat.
 
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Old 06-14-15, 01:29 PM
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I see 2 blue wires on the pump but cannot see if they are connected to anything.

I would find the transformer, measure the voltage to it and see if it is wired for the voltage that it is getting.


Universal transformers can be wired differently to work with 120, 208 or 240VAC.

Black and white are usually 120 volt.
orange is 240 volt and red is for 208 volts.

Common varies. Sometimes it is black and sometimes it is white.
 
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Old 06-14-15, 04:39 PM
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You're right about the blue wires on the condensate pump, they just sit there on top of it, not connected. Inspector said nothing about those?

I opened the transformer panel and here are the pics - Album on Imgur

I didn't see any available contact points to test with a multimeter. The wires look like they have crimp caps on them, and the transformer (I'm guessing the bottom black object) doesn't appear to have exposed contact points.

I found a legend on the inside of the panel (last 2 pics) that reads 200/230V power supply and also 24V line.

On pic 3, you can see the output wires from the transformer as black + red stripe and black + blue stripe. The red stripe feeds to the R on the stat board. The blue strip feeds to the B on the stat board.

On pic 6, you can see the input wires to the transformer, 2 thick black wires in a nut combined with a white wire that feeds into the transformer. To the left of those is a thick red wire combined with a thinner red wire that feeds into the transformer.

I found an inspection receipt from 4/2014 when the AC unit was maintenanced by a service company and considered OK. The breaker box was re-wired 10/14 and it would have been too cold to test the AC then. It's possible something was wired wrong at that point and only just discovered now, upon turning the AC on.
 
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Old 06-15-15, 09:04 AM
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Update: Fixed!

Just posting the conclusion to this mystery of the 14v thermostat line. With Houston204's in-depth help, our assumptions were correct! As hinted in the last pics, the transformer was indeed rated for 240v and was only receiving 120v. This explains why it was outputting 14v instead of the required 24v. I bet I would have caught this earlier if I had measured L1 and L2 on the condenser.

I called the electrician who re-wired the breaker box (original was on vacation, so partner came out). He confirmed our suspicions that the 120v breaker labeled "Furnace/Heater", that was apparently controlling the 14v AC thermostat line, was wired to the AC transformer. In addition, the 240v breaker that was labeled "Air Handler" had the wrong label and didn't actually control the air handler at all. The basement air handler was only receiving 120v.

The electrician un-wired the "Furnace/Heater" breaker (which is now a spare breaker) and put in a new 240v breaker for the air handler. It's now outputting a correct 24v and the AC is operating normally. The electrician also complimented our early debugging work in locating the source of this issue (the 14v coming from the transformer in the basement and what appeared to be 120 volts going into a 240 volt transformer/air handler).

Thanks again Houston204!
 
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Old 06-15-15, 07:14 PM
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That is great news

I am glad that was able to help.
 
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