Fan Relay Question

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  #1  
Old 08-09-18, 12:51 PM
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Question Fan Relay Question

I have an older HVAC (HCS-2-750 furnace) which makes use of an Essex SPDT relay. See photos below. I'm not ready to replace the entire HVAC just yet but am willing to learn and DIY resolve my current issue.

The HVAC works fine however at random times the fan / blower will stop running causing the AC coils / condenser to freeze up. I've discovered if i simply tap on the Essex SPDT relay the fan will startup again and all is fine until the next random time.

A few questions:

1. From the photos below you can see the SPDT relay plugs into the white socket area. One of the sockets (for the #4 terminal) has charring around it. Why exactly did this occur? Is it due to lack of proper contact?

2. Although the fan is turning off at random times and refuses to turn back on until i give it a gentle tap, does this mean, 100% i need a replacement SPDT relay?

3. I've searched around for a replacement ESSEX SPDT relay with the following specs:

  • ESSEX 134-20103-301AC
  • 12FLA 60LRA 125VAC
  • 8FLA 48LRA 250VAC
  • 18A 277VAC
  • COIL 24V 50/60HZ

I can find this however the underside pin layout (as seen in the photo below) does not match. I'm willing to purchase a replacement but i cannot find ANY spdt replacement with the same pin layout so that i may insert it into the white socket (shown below). How do i get around this issue?


4. In the event i cannot locate a suitable replacement relay and must resort to creating a wired connection with female + male spade terminals what gauge wiring does this relay require for all terminals?


Thanks.







 
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  #2  
Old 08-09-18, 12:58 PM
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A picture from further back of the whole thing would be nice as I can't tell what that is you are working on.

You have a burned socket.... not a burned relay. You can unlock all the wires out of the socket and plug them directly unto the relay after replacing the burned terminal.

There are still a few replacement relays floating around but they are pricey.
american hvac parts/p-21813-direct-factory-replacement-blower-control-relay
 

Last edited by PJmax; 08-09-18 at 01:23 PM.
  #3  
Old 08-09-18, 04:44 PM
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Ahh "burnt socket" only. Very good idea. I can do this. Incredible how you found a relay with a similar terminal layout. I have no clue how you did that magic!!

Here are photos from farther back.






 
  #4  
Old 08-09-18, 05:47 PM
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That's an old style Coleman fan center.
You could replace the entire fan center too. Just do a search for "fan center".

White-Rodgers-90-113-Fan-Control-Center-120-VAC-Primary-24-VAC-Secondary-SPDT-Relay
 
  #5  
Old 08-09-18, 06:50 PM
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I really appreciate the extra insight into all this PJmax. Really tough to find any info on this thing yet i do have the desire to keep it going. I very much like this fan center approach. And it appears cheap.

Why would the burned socket occur? Is there something deeper beyond the relay and fan center i should be concerned about?
 
  #6  
Old 08-09-18, 07:33 PM
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The slide terminal on the relay lost its strength due to age, current flow and it may have been loose to start.
 
  #7  
Old 08-10-18, 12:41 PM
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Thanks PJmax for the Fan Center link above. To save myself the headache i think i will just order that unit and swap out my old one.

One thing though. I notice on the old relay the labelling:

ESSEX 134-20103-301AC
12FLA 60LRA 125VAC
8FLA 48LRA 250VAC
18A 277VAC
COIL 24V 50/60HZ

however your White Rogers fan center has the following printed on it:
Input: 120v 60hz
Output: 24v 40va
Relay spdt 13.8fla, 82.8lra @ 125vac
6.9fla, 41.4lra @ 250vac


I'm still trying to piece together what everything means but is the White Rodgers a compatible replacement to my old fan center + relay?

Thanks
 
  #8  
Old 08-10-18, 01:06 PM
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Yup.... the new one will be fine. A fan center is basically two things...... a transformer and a relay. That's it. The transformer is 24vac @40watts and the relay is a SPDT with plenty of current handling for the blower.
 
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