# Installing 240V/30A FUH54 Garage Heater with External Thermostat



## OldSaltUSN (Dec 10, 2017)

I'm getting an error that I can't post links until after my first post (which I've made above), and I can't post attachments, pictures, or "cut and past" pictures into the editor. However, I figured out how to add albums, which is a whole lot more tedious than simply viewing the pictures in this post. But it'll get us there.

*Albums* 
FUH54: Three pictures
1) Show's a picture of the FUH54 unit
2) Second picture show's the (quite spacious) open electrical box of the heater
3) Third picture shows the OEM electrical diagram of the FUH54.

G73: One picture 
1) Shows a picture of someone else's modification for installing a G73 heater, including a Contactor, Transformer, and Thermostat. (Sorry, there was no write up or attribution for this; just a picture hanging out there in the internet-ether.)

So, to return to my original points:

FUH54 is 30A; CT410B is a 22A inline thermostat, and apparently it's tough to find a 30A model. The actual L1 line, I assume, is actually 120V/15A, i.e. the 240V/30A line from the breaker box is actually two 15A circuits. If that assumption were correct, then a 22A thermostat would work without a Contactor, except it is a four wire thermostat with it's own L1/L2 circuits, and I assume each of those are 1/2 of 22A, e.g. 11A max each. So, the 22A thermostat would probably be underspec for this 30A application, no matter what.

What kind of Contactor do I need? Can I wire it similar to the G73 diagram? If so, why would I need the transformer, unless it were to convert AC to low volt DC, and use a LV/DC thermostat? I would assume that the thermostat would control the open/close of the Contactor, and get it's power from the 240v/30A Contractor, so why the transformer? 

Thanks to all. Hope you can find the pictures.


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## CodeMatters (Aug 16, 2017)

Had a look at the manual for the FUH54 Garage Heater. Didn't see any 
allowance for a separate thermostat. Without specific instructions for this 
I wouldn't use one. 
I did see that it has several different internal settings for output. The highest 
being 5000W. So my first thought would to simply direct wire it with #10/2 
on double 30 breaker.


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## Jim Port (Sep 21, 2007)

A double pole 15 is not 30 amps. It is 15 amps.


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## OldSaltUSN (Dec 10, 2017)

Jim, if you're referring to my breaker, it's a 30 amp breaker.
My understanding of a 240V circuit is that it's two (15A) hots, one neutral, and one ground.

Not sure if that was what you were referring to (i.e. my terminology is incorrect), or you were describing the heater or thermostat.


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## OldSaltUSN (Dec 10, 2017)

CodeMatters said:


> Had a look at the manual for the FUH54 Garage Heater. Didn't see any
> allowance for a separate thermostat. Without specific instructions for this
> I wouldn't use one.
> I did see that it has several different internal settings for output. The highest
> ...


That's definitely the safe/easy way to go. I could do that in half an hour. Then again, a thermostat is a thermostat. Replacing the internal one with an external one shouldn't be rocket science (nor require the intervention of the manufacturer). I've seen advertising (or reviews) for the FUH54 unit that speaks of adding an optional external thermostat, but that doesn't mean that it's Marley endorsed that.

I've sent in a question about this to Marley, but they never responded. When it gets cold enough (i.e. Northern Idaho), then I guess I'll surrender and just install it "stock". :biggrin2:


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## CodeMatters (Aug 16, 2017)

OldSaltUSN said:


> That's definitely the safe/easy way to go. I could do that in half an hour. Then again, a thermostat is a thermostat. Replacing the internal one with an external one shouldn't be rocket science (nor require the intervention of the manufacturer). I've seen advertising (or reviews) for the FUH54 unit that speaks of adding an optional external thermostat, but that doesn't mean that it's Marley endorsed that.
> 
> I've sent in a question about this to Marley, but they never responded. When it gets cold enough (i.e. Northern Idaho), then I guess I'll surrender and just install it "stock". :biggrin2:


Sounds like you understand everything and need no help. No problem,
last I'll post on this thread.


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## OldSaltUSN (Dec 10, 2017)

Actually, I have one more question: What does "Heater Amps" (20.9A for 240v/5000 watts) on the Marley (Fahrenheit) table mean, in relation to the Max Fuse Size and the 22A rating of the Thermostat. Does that mean that the Thermostat rating matches the heater requirements, e.g. it could be installed without a relay or Contactor? (I know that you're recommending a stock install. I probably won't do this unless Marley support gives it's blessing. I'm still working on requirements.)

Edit: Added the picture of the table to a new Album "FUH54 Part 2" (see link at left "View OldSaltUSN's Album"). This problem adding pictures to a post is certainly "limiting" (a.k.a. frustrating).


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## Jim Port (Sep 21, 2007)

OldSaltUSN said:


> Jim, if you're referring to my breaker, it's a 30 amp breaker.
> My understanding of a 240V circuit is that it's two (15A) hots, one neutral, and one ground.
> 
> Not sure if that was what you were referring to (i.e. my terminology is incorrect), or you were describing the heater or thermostat.


That is still a 15/amp circuit. You do not add the handles together.


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## Shadow99 (Nov 3, 2017)

OldSaltUSN said:


> My understanding of a 240V circuit is that it's two (15A) hots, one neutral, and one ground.


That statement is wrong on so many levels


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## joed (Mar 13, 2005)

OldSaltUSN said:


> Jim, if you're referring to my breaker, it's a 30 amp breaker.
> My understanding of a 240V circuit is that it's two (15A) hots, one neutral, and one ground.


Couple of points that need to be made.
Two 15amp hots is a 15 amp circuit not a 30 amp circuit.
A 240 volt circuit does not require a neutral. Some 240 volt devices also require 120 volts so they require a neutral. This is properly referred as a 120/240 circuit.


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## OldSaltUSN (Dec 10, 2017)

Shadow99 said:


> That statement is wrong on so many levels


Well, I guess I'm done here. I won't embarrass myself in a chat room of experts any further.

CYA all. Thanks for all the "help".


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## OldSaltUSN (Dec 10, 2017)

Boy, DIY chatroom just "erased" over an hours work here. I can't begin to tell you how irritated I am with this site. However, since this thread shows up under "google" under "FUH54", "install", and "External Thermostat", I'll spend another hour posting this solution in case someone is looking for it. It implements a DC Thermostat versus the AC, because I could find no AC Thermostat rated above 22AMP for this 30 AMP heater. I believe a relay is required to safely install this heater with an external thermostat, and the relay I selected includes a transformer to convert the thermostat leads to DC (that's how I understand it; don't rag on me for the technical details; this solution works).

Parts:



Honeywell R841C1169 heater relay (Supplyhouse.com, $60.95)


 Honeywell Pro-1000 non-programmable, heat only Vertical Thermostat (DC) - (Supplyhouse.com, $22.95)


 Southwire Ultrawhip 10/2 wire harness, including 1/2" conduit, 6' long, with fittings (Lowes, about $12).


 18/2 Thermostat wire (50' for my application)


 FUH54 Heater (30A/5000W configuration)


 Electrical Tape, wire nuts, spade connectors, sheet metal screws, etc.


 30 AMP/240V circuit, prewired by my Electrician from main panel to a ceiling box.
 Note: SupplyHouse.com had the lowest prices I could find, by almost 50% on the Honeywell parts. Your mileage may vary.

Actions:

1) Install the Honeywell relay. There's plenty of room in the FUH54 box for it; attach with two sheet metal screws.

2) Wire the relay to the heater, replacing (and removing) the existing dial thermostat switch.
Relay wires:
a) Black 10G : Replaces black wire between switch and L1 block. Attach a female spade connector to the relay wire, and plug it in.
b) Red 10G : Replaces black wire between switch and terminal block. Attach a female spade connector to the relay wire, and plug it in.
c) Blue 10G: Splice into the large (10 gauge) black wire connecting from L2 block into a grommet inside the heater. It will not be long enough, so I replaced the L2 connection with a section of black 10 gauge wire with a female spade connector (i.e. plug it in). I cut off the existing connector on the black wire, and combined the blue, existing black, and new black (L2) wires under one wire nut, to complete the splice.
d) Red/White 18G wires: Connect to your thermostat, white to white, red to red.

3) Install your thermostat and route thermostat wires from heater to thermostat. I used spade male/female connectors (covered by electrical tape) to connect the relay wires to the thermostat wires in the box. The thermostat mount has three screws for R/W/C; connect the wires to R/W. The "C" is for a hot lead, which the Honeywell relay did not provide, so I'm operating optionally on battery power alone. (Perhaps there is a relay that provides a "C" wire, but this is the one that worked for me.)

4) Install the 10 gauge wires per Farley instructions. My 30 AMP receptacle wire includes there wires, white, black, copper (ground). The Southwire harness includes red, black, and green (ground). I tagged the red harness and white receptacle wire with black tape to indicate they are both the second "hot" wire. Inside the FUH54 box, I connected black (hot) to L2, red (hot) to L1, and green to ground (FUH54 box nut). As already noted, L1 routes to the heater element, and L2 to the fan element. The thermostat should only control L1, since L2 operates based on unit temperature, running after L1 shutdown to cool the heater.

5) Mount the heater bracket. I used a single lag bolt, per Farley instructions, in the center of the mount to enable me to pivot the fan left or right if needed. Mount the heater to the bracket, connect the thermostat wires and the harness to your 240V receptacle.

The use of spade connectors leaves the appearance clean, almost as OEM.

Note: The thermostat allows setting three options, one of which is "cycle". The default is 5, electric furnaces are recommended a 6 to 9. The setting is arbitrary. The higher the cycles, the more frequently the thermostat will sample temperature and activate the unit. The lower the cycles, the less. Use higher cycles if you want the heat as consistent as possible, e.g. 50F or 65F, at the expense of a higher electrical bill. I set mine to "3", and find the garage at 55F every time I've checked (Northern Idaho, insulated garage, 20F to 30F outside). I may change this to "1". There is also a "low temp" setting to enable the lowest temperature at 35F for garage use; I also set that.

Pictures:
See my album titled FUH54-Ext Thermostat Solution 1

Pictures include self-explanatory labels, but I'll add a few notes here. Unfortunately, I appear to have no control over the order in which the pictures appear, which may be confusing for some. Notes:



Honeywell R841C1169 heater relay3: Shows the relay install location and the spade connectors as I prepare to install the Black and Red wires using spade connectors. I connected wires first, before securing screws.

Hope this helps someone else. It took me a while to figure out the solution. Credit a guy on Amazon who had more electrical knowledge than I, and posted HIS solution in his review of the FUH54 Heater.


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## derwin424 (Feb 2, 2021)

How do I view pictures? Where are they?


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## rdy2go (Apr 18, 2009)

You may want to look at this other thread, it has discussion of a solution involving a relay installed inside the unit. 

*Thermostat for 5000W 240V heater, is 22A safe enough*


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## derwin424 (Feb 2, 2021)

did the modification as suggested. heater was working perfectly for nearly one year. Now red overheating light is coming on and heater won't start up. I called Marley but they don't want to do anything since i modified the heater. Anyone experience this? Is there a simple solution?


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## Shadow99 (Nov 3, 2017)

Apart from a defective thermal O/L, is the fan running ? Is the unit hot ?
Does the light go out after awhile when turned off ?


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## rdy2go (Apr 18, 2009)

derwin424 said:


> did the modification as suggested. heater was working perfectly for nearly one year. Now red overheating light is coming on and heater won't start up. I called Marley but they don't want to do anything since i modified the heater. Anyone experience this? Is there a simple solution?


When you say the heater does not start up, do you mean the fan does not run? As far as I know, they have a bi-metal thingy, (technical term), in the heater circuit to keep it running for a while on shut down, so the heater element is cooled. Take a look at the schematic, see if you can locate the thingy, and or measure voltage directly on fan. 

May be wait for better ideas


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## derwin424 (Feb 2, 2021)

When i turn on, the red light goes on. So, no fan. Could be the motor or the heat limiter from what i understand.


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## joe-nwt (Jul 15, 2020)

Most hi limits are either manual reset or one-shot. By time an appliance trips a high limit you don't want it auto-restarting.


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## derwin424 (Feb 2, 2021)

So, sounds like i would absolutely need another high limit unless i can reset it, and the motor? What would cause this? I installed the Honeywell relay exactly as described above and the heater was working fine, or so it seemed.


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## rdy2go (Apr 18, 2009)

derwin424 said:


> So, sounds like i would absolutely need another high limit unless i can reset it, and the motor? What would cause this? I installed the Honeywell relay exactly as described above and the heater was working fine, or so it seemed.


From the online description of the heater
_* Thermal cutout - A high limit thermal cutout automatically shuts off the heater in the event of
overheating and reactivates it when operating temperatures return to normal._

So the high limit should reset itself when working properly. 

_* Automatic fan control - All heaters are equipped with an automatic fan delay control that
delays fan action until the heating element is warm, and continues fan action until the
heating element has cooled after the heating cycle._

So there is a control element, (the thingy), which will keep the fan running for a while. It is a timer, not a temperature sensor, although it must be a thermal based.










From the schematic, which I hope it matches your unit, the fan is in series with the timer. If the motor does not run, either there is no juice through feeding the series branch, or motor or timer are dead. I would start by taking some continuity measurements, disconnecting wires as needed. I do not know how easy is to get to the motor and element area. May be you could take pictures as you go, for the world to see.

*No need to say that you need to turn the breaker off before you touch the unit. *


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