Using Transformer For Fan

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  #1  
Old 06-22-15, 02:07 PM
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Using Transformer For Fan

I purchased an Acme Electric TB81210 step down transform 220/440 to 120v. (http://www.acmetransformer.com/~/med...3375-22117.pdf )
I do not fully follow how to wire this in; data sheets do not give me a full enough understanding.
Clearly I'm not an electrician, but with a touch of knowledge, I'm competent to hook this up.


Here's what I'm doing:

I have a 240v AC air-handler installed (that runs a large blower motor).
I did meter test the wires to the blower and do understand what the "hot" / neutral connections are.
It's wired with a single feed, 14ga, black, white, bare wire, 600v rated.

I purchased an "inline" fan unit to increase air flow to a specific output duct on the duct system; this fan is 120v.

The goal is to "power on" the inline fan when the main blower powers on. Doing so by tapping the power at the point the blower is powered on; connecting to the transformer; then out to a typical 120v receptacle to accommodate the inline fan.

The transformer is laid out as follows:

Input Terminals: H1 H3 H2 H4
Output Terminals: X2 F1 F2 X1

I gather, for my 220v input, I must use the included terminal jumpers, H1 to H3 and H2 to H4.
I gather the 120v output wires will be attached to X2 and X1.

What I do not follow/fully understand, is what two wires attach to the input as diagrams show?
Is one the "hot" (black) and and the other the neutral(white)? ...if so, does it matter which wire goes to which input?
...or is wired with just the single black wire input (as that's all I have in my case) and the neutral(white)'s are simply wire-nutted outside the transformer?

Same question on the output side....

Any help would be greatly appreciated.
 
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  #2  
Old 06-22-15, 03:05 PM
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do understand what the "hot" / neutral connections are.
There is no neutral connection. Just two hots. The hots are interchangeable. Neutral is a term referring to the grounded conductor. On a transformer such as you have there is no grounded conductor on the secondary side (120v). So just two hots on the output (secondary) side.
 
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Old 06-22-15, 08:28 PM
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I don't particularly recommend your method in powering a remote fan. You should use 24v switching from the air handler to operate a relay controlling the 120vac to the remote fan.

With that transformer you will be putting more load on the blower fan relay which it wasn't designed to handle.
 
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Old 06-23-15, 06:07 AM
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In looking closer...

There is a 24v relay in the handler now.
There are also 3 bars; ground, #1, #2.

When the blower is activated via the thermostat, there is 120v at #1; 120v at #2, and 240v metering across #1 & #2.

Would it be reasonable to simply connect my 120v receptacle to here? Black to either #1 or #2, white/ground to the ground bar? (No transformer used)


I think getting from the panel in the garage to the air handler in the attic of the 2 story home would be extremely difficult and more cost than it's worth.
 
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Old 06-23-15, 06:42 AM
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Can you send a pic of the wiring Dia. Of the air handler? PJ's suggestion is the best way to go, power the 24 volt relay from the fan relay then run low voltage wiring to the new relay/outlet location near your new fan location.
Geo
 
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Old 06-23-15, 06:46 AM
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Ray, to many secondaries on that transformer.
Just Saying!
Geo
 
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Old 06-23-15, 06:47 AM
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You cannot obtain 120v from a hot leg and ground. Since there is no neutral there you can't directly tap 120v power.
 
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Old 06-23-15, 07:29 AM
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It's sounding like there is not good way, short of a new 120v line in?
(So much for a quick fix )

If I can manage to get a 120v line in, would it be acceptable to tap the existing 24v relay (input side) to trip a 2nd 24v relay to energize the 120v line to the inline fan?
 
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Old 06-23-15, 08:46 AM
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Just curious, what are you trying to accomplish with this additional blower?there maybe other options.
Geo
 
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Old 06-23-15, 09:14 AM
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The 2nd floor air handler ducts are all "forward facing" for the direction of air flow ...all except the supply to 1 room. It's a U-turn; essentially in the opposite direction of the airflow causing very little pressure / cooling to that room. It seemed like a simple solution to add an inline 8" round air duct blower to boost the cool air flow to that room -it's designed for that.

Having it power on only when the air handler powers on is what I need. I did look for a 240v fan, but not finding one and I already installed the 120v fan in the duct work. I've seen a few "solutions" out there such as temp sensor triggers in the duct, etc, but all that looked like over-kill. It seemed far more logical to "trigger" (and power) off of what was there.
 
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Old 06-23-15, 09:39 AM
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It's sounding like there is not good way, short of a new 120v line in?
(So much for a quick fix )

If I can manage to get a 120v line in, would it be acceptable to tap the existing 24v relay (input side) to trip a 2nd 24v relay to energize the 120v line to the inline fan?
That's the correct way to do it as well as the safe way to do it.
 
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Old 06-23-15, 05:25 PM
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I've used the approach I've listed many times. I use a RIB relay mounted to a 4" square electrical box. You make all your 120v connections inside the box. You run the two 24vac lines out a grommet in a knockout next to the relay. You can install this setup right next to your aux fan. You won't need to run a lot of expensive cable. You can use thermostat wire between this and the air handler.

The link below is just to illustrate RIB relays. Google 24vac RIB relay and they can be found in many places.

Functional Devices (RIB) RIB2401D Enclosed Relay 10Amp DPDT 24Vac/dc/120Vac at Controls Central



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  #13  
Old 06-23-15, 05:51 PM
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Works every time!!!!!!!!
Geo
 
  #14  
Old 06-25-15, 09:07 AM
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First, thank you all for your help! I've learned much; which is always a good thing.

I wish I had seen the post sooner; I would have ordered that relay and followed.
Although, I did (I believe) do nearly exactly what was suggested.

I ordered a Supco SU90340 relay. In googling, it was "suggested" this was a more durable relay than some others. It did seem like it might be overkill feature wise, but it was suggested/rated for air units.

I did manage to get a standard 120v line from the panel to adjacent to the air handler; and a few feet from the inline fan install.

Mounted the SU90340 inside the air handler.
Built a couple jumper wires and used double spade connectors to run from the primary relay trigger to the this relay's triggers.

Installed a receptacle on a wall joist; ran wire into knockout (with clamp) into air handler.
Attached the new 120v source; ground to the ground bus bar in the handler (which is screwed to case, so everything is grounded); tied the neutral (whites); and hot (black) to (line in)#1, (line out)#3 on relay.

Tested voltage under on/off conditions at relay and receptacle; all tested as expected. 24v at relay coil when activated; 120v at receptacle when activated; 0v otherwise.

Inline fan powers on / off as expected with air handler blower; activated by thermostat.

I did read about "options" such as inline fusing and "fail safe" switches. However, it seems to be applicable to heat/cooling systems rather than my cooling only system (for heat safety reasons). So did not do these options.


If any of the above seems incorrect or questionable, by all means let me know.

Thanks again for the help!
 

Last edited by NoZap; 06-25-15 at 09:08 AM. Reason: type-o
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