0

Morning, folks. And thanks in advance for any assistance you can provide.

We have an in-line duct fan in the attic. It assists in moving air from the central HVAC system into our addition. It is hooked up to a 24v/12v relay to control on/off and controlled by two 24v connections. The first comes form the furnace and the second comes form a thermostat in the addition. When the HVAC is active AND the thermostat in the addition is triggered, it completes the circuit and the fan is powered.

To the point, the fan finally failed and needs to be replaced. I'd like to replace the relay at the same time. The HVAC contractor I called out wants nearly $700 to do the job, with the fan costing around $350. I just don't have that kind of money right now, but we're cold!

Now, I can buy a fan similar to what was installed for between $80-$150. I can replicate the wiring as it was previously done. I'm fine with the duct work, and I'm fine wiring something to voltage. I can also replicate the wiring as it was done for the old fan. But I need to make sure I'm going about it the right way. So, I have a few questions if you're willing:

  1. Should I just pay them the $700 and be done with it? Am I too far out of my depth? Am I likely to be bumping up against so many safety and code issues that I should just pay to have it done?
  2. Many of the in-line duct fans I've seen plug directly into a 120v outlet. I was thinking I could just rig the relay to energize a 120v outlet and plug the fan into that. In this way, I can just plug a new fan in if/when needed. I know codes differ from location to location. But is controlling a 120v outlet with thermostats and a relay ever OK?
  3. Let's say #2 is a no-go. I need to identify a proper relay. Can I use any old 24v to 120v relay to power the fan?
  4. I'd love for all of this to be stuffed into a junction box, but it looks like any relay I see is mounted outside of the junction box. I assume this is to keep the low voltage and line voltage separate. So I take it that it's never OK to hide the relay inside a junction box?

I know enough to know that I'm probably out of my depth here. I just want someone else to confirm it before I spend half of next month's mortgage payment on a fan. Of course, "Don't pay those bloodscuckers, dude. This is super easy and I'm going to show you how" would be even better. Thanks in advance!

EDITED TO ADD IMAGES

Relay Fan1 Fan2

Editing to add "schematic" to the degree that you can call this a schematic. Hopefully it provides enough information.

Amature Schematic

  • If you are just swapping out the fan, why do all the rewiring? – Yehuda_NYC Jan 7 '18 at 18:10
  • 1
    Yes, if it ain't broke, why do you want to fix it? – Harper Jan 7 '18 at 19:58
  • 1. i wouldn't, this is DIY turf. 2. I see no electrical/safety problems with that, but you can use a UL-approved smart outlet of some sort if in doubt, or a dusk to dawn outlet control and a 24v lamp. 3. yes. 4. not bare relays, but there are some approved switches, like sonoff, that are double insulated. – dandavis Jan 7 '18 at 21:23
  • Yehuda_NYC: Because I pulled the fan and the relay out without making a note of how it was wired in the first place, of course! :) – JD_HART Jan 8 '18 at 20:34
0

Should I just pay them the $700 and be done with it?

Depends on ..

Am I too far out of my depth?

Can you operate a screwdriver, watch you tube, turn off a circuit breaker .

Am I likely to be bumping up against so many safety and code issues that I should just pay to have it done?

Only the fan matters - UL Listed, GFCI Circuit if the location has high humidity like a shower (probably already is if that is the case)

Many of the in-line duct fans I've seen plug directly into a 120v outlet. I was thinking I could just rig the relay to energize a 120v outlet and plug the fan into that. In this way, I can just plug a new fan in if/when needed. I know codes differ from location to location. But is controlling a 120v outlet with thermostats and a relay ever OK?

Why do this you don't need to! Your current fan is 120V or possibly but not likely 220v - just use the three wires on your current fan (Black , White , and Green/copper) which are probably wire nutted in a junction box by the fan motor and swap out with a new fan.

You can probably buy a new fan of the exact same type as yours online for $100.. Do an online search of the model number found on the motor faceplate.

Let's say #2 is a no-go. I need to identify a proper relay. Can I use any old 24v to 120v relay to power the fan?

Your HVAC relay that is 24V - that is the solenoid side - not the load side - the load side is 120V or 220V and is what turns on your fan.

I'd love for all of this to be stuffed into a junction box, but it looks like any relay I see is mounted outside of the junction box. I assume this is to keep the low voltage and line voltage separate. So I take it that it's never OK to hide the relay inside a junction box?

You misunderstand: the relay is inside the junction box with Low voltage on the COIL side (which pulls in the contact side) and 120VAC or 220VAC on the Contact side. This is perfectly fine and good that they did this.

Here is an electrical Diagram of what you probably have and should see.. Fan with Relay

  • thanks. First, yes, I'm comfortable with the electrical. It's the code I'm concerned about. But this is also HVAC, about which I know nothing and want to make sure that there aren't any special considerations. The idea of using an outlet was just to address the fact that the cheaper fans have a standard plug on the end and are not hardwired. Unfortunately, I did look up a direct replacement for the fan, and it's in excess of $350. That's why I'm looking to the cheaper DIY route. Thanks for all the help! – JD_HART Jan 8 '18 at 20:42
  • @JD_HART - take a picture of your motor faceplate and the fan itself .. post that here .. $350 is most likely an HVAC dealer price - sometimes you buy the motor and the other pieces you can re-use ..The faceplate will list Manufacturer, Model, Voltage, FLA etc.. – Ken Jan 10 '18 at 22:34
  • Yes, I've uploaded images of the fan and relay to the original post. I was thinking about replacing them with a Fantech FG-8 for FG-8XL <fantech.net/products/fans--accessories/circular-duct-fans/…> and this relay <customer.honeywell.com/en-US/pages/…> What are your thoguhts on that? – JD_HART Jan 12 '18 at 21:10
  • @JD_HART looking at your picture (hard to read the text), the Model of the motor looks like 4C445A - tell me if that is correct. If so this motor and blower assembly can be had for $125.00 (as it is NLA from grainger where it was listed $51.00) a cross reference amazon.com/R7-RB445-Rotom-Replacement-Blower-Dayton/dp/… or here electricmotorwarehouse.com/… for $110 Another issue you have is that motor is rusty, meaning Moisture. How is moisture getting into contact with motor or condensing on it. – Ken Jan 13 '18 at 2:47
  • 1
    Thanks, Ken. Yes, in my semi-informed parlance switch=relay. As for the thermostat, I used images of the items I actually plan to use or have wherever possible. That's the actual thermostat! At some point I'll replace the thermostat. I'm going to order the parts indicated and give this a shot. Thanks a ton, and I'll check back in once I've completed the install! – JD_HART Jan 20 '18 at 15:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.