Replaced Air Handler Fan Relay - Outside Unit started humming


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Old 10-16-18, 03:58 PM
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Replaced Air Handler Fan Relay - Outside Unit started humming

Hi,

First posting - so - great to be here guys!

Setup:
- Split System w. Heatpump Rheem RPFB-024JAS, First Co 24VDX0-HP Air Handler and Nest

System worked great overall - started having issues with the air handler fan not turning off anymore.
Pulled an Essex 134-20102-106 Relay and replaced it with (I believe fitting) White Rodgers 90-370.

Air handler fan is working as expected now. Right after wiring it in, I did a quick test of it coming on and off and it worked. Afterwards I didn't use the A/C at all since we have moderate temperatures these days.
Walked outside later and noticed that my outside unit was humming.
Tried heating and cooling later that day and neither one worked (the air handler fan would come on, but the outside unit wouldn't do anything. I can hear relays click but that's it.).

I don't really see how - but is there any chance I could have mis-wired anything around the air handler relay (that's all that I touched) that lead to this - or is it just sheer coincidence?

I tested some of the wires in the outside unit - I believe these results make sense - but let me know if otherwise
- Yellow wire coming into the unit has 24V if cooling is enabled, otherwise it doesn't
- Blue wire coming in has 24V constantly
- Purple wire coming in has 24V if heating is enabled, otherwise it doesn't

The humming very certainly seems to be coming from inside the unit and not from any of the relays in the circuit box.

Thanks,
Patrick
 
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Old 10-16-18, 04:24 PM
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Welcome to the forums.

I'm assuming that blue was used as the R wire. Poor choice of color.
Usually R is red and C is blue.
I'm also assuming you were measuring to ground as you didn't list a C wire.

Try disconnecting one wire at a time to the condenser and see if the noise stops.
There isn't too much that can make a humming sound.
 
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Old 10-16-18, 05:10 PM
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Thanks - Will do!

Attached is a photo of where most of those wires come into the outside unit.

Blue is where I have 24V as soon as the Air Handler has power - whether the system is on or off.
Yellow is where I have 24V when A/C is on.

Name:  wires.jpg
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Last edited by PJmax; 10-16-18 at 06:24 PM. Reason: cropped/enlarged pic
  #4  
Old 10-17-18, 05:19 AM
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Hi, is this a heat pump? Where is this purple wire connected?
Geo
 
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Old 10-17-18, 07:56 AM
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It is a heat pump yes.

Since I couldn't really make sense of what was happening, I put the old relay back.. and it's working. That means two things:
- I need to brush up on my relay / diagram reading skills
- I need to find a fitting replacement or find out how to connect the other one

Mysteriously still (probably not so much once I figured out what I mis-wired).. the air handler / fan worked completely fine with the new relay.

Be awesome if you could take a look at the attachments and let me know if they are compatible and if yes, how I'd need to wire the white rodgers one.. or if it's just totally the wrong relay.

Thanks - Appreciate every comment!
 
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Old 10-17-18, 04:30 PM
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Hi, if you can post a clear pic of the wiring Dia. showing how that relay is connected, it may be helpful.
Geo
 
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Old 10-17-18, 05:46 PM
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Couldn't see much definition on the old relay. Need larger picture

It looks like 1 and 3 are the coil on the old relay.
It looks like 2 and 4 are the NO (normally open) contacts on the old relay.

1 and 3 are the coil on the new relay.
2 and 4 are the NO (normally open) contacts on the new relay.

The new relay is 24vAC and the old one just says 24v. Can't tell if it's an AC or DC relay.
 
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Old 10-17-18, 06:12 PM
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Pete , 50 or 60 Hz would be AC.
Geo
 
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Old 10-18-18, 05:54 PM
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Thanks and sorry - here's a better version of the chart (although my original is blurry unfortunately).

This is kind of how I interpreted it @PJmax - so I figured if I just put them on the same pins than before, it should work.

@Geochurchi - I need to take a look at that next time I'm up there.
 
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Last edited by darkrothaus; 10-18-18 at 05:57 PM. Reason: respond to Geochurchi
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Old 10-18-18, 08:51 PM
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Yes..... the pin numbers match between relays.
 
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Old 10-19-18, 06:03 AM
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Hi, so after you put the old relay back in everything worked OK including the Heatpump condenser?
Its hard to believe that the fan relay would have any effect on the condenser section.
Geo
 
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Old 10-19-18, 03:55 PM
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Yes, exactly, everything works (until the relay starts hanging that is - which I'm sure is exactly when I don't need it to).
On one hand I'm glad that apparently I wasn't entirely wrong in what I've been doing but at the same time I don't know what to do next . Also since the actual fan control worked as expected with the new relay.
 
 

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