Free Ruud Furnace - http://www.hvacmechanic.com/ Forums
Original message
| Tpgroceman
 |  "Free Ruud Furnace"
, posted Thu 18 Sep 01:27  
I have an old oil burner converted to gas (50% eff.) and I recieved a free Ruud furnace (UGFD10EZCMS) and would love to install it as it's a modulating 90% eff furnace, only it's too big.
I took the burner apart and pulled off one of the jets and it's a number 50, anyone know of a source for smaller ones? I could just braze it and re-drill but to what size? I need about 60K BTUH and this furnace is a 102K max 42K min.
Also if I put in smaller jets will that work? It seems that should be simple enough. Any thoughts? Oh and the furnace is 42K min which is fine but it would be nice to modulate down to 20-30K...
Thanks for any advice!
Tpgroceman
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Replies:
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| ampulman
| "Re(1):Free Ruud Furnace" , posted Thu 18 Sep 09:46
Congratulations on receiving your prize.
First off, the only way for that furnace to modulate, is to pair with the modulating thermostat, which I doubt you can buy in the aftermarket. It costs about $500 from a dealer (better not screw up that installation).
Do you have air conditioning? What size? That furnace puts out 1200 - 2000 CFM in cooling. I doubt that your duct system is designed for that level, not to mention that your a/c probably requires less CFMs.
The furnace also requires a supply side temp sensor. Don't know if that's included with the furnace (return sensor built in).
If I were in your shoes, I would try to work out a deal with a dealer to swap the unit for a smaller one and install it (warranty). Oh wait, you already disassembled it, didn't you? Good luck with that.
AM
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| | ampulman
| "Re(2):Free Ruud Furnace" , posted Thu 18 Sep 16:39
Oh, it just occurred to me:
Even if you could rework the nozzles, the gas valve is sized to deliver the amount (range) of gas, based on the nominal size of the furnace.
Likewise, the board is designed to deliver the required range of heating CFMs (as above).
AM
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| | tpgroceman
| "Re(3):Free Ruud Furnace" , posted Fri 19 Sep 16:11
The furnace isn't new but it was free to me, it came with the thermostat and the sensor you talked about, I think a better way to go is to leave the jet sizes alone and just plug 3 of the seven jets which would put me right in the zone for my house and move the temp sensors between the burn tubes if needed (are't they over temp sensors?).
I pulled the A/C unit off and will sell it on Craigs list with the big compressor box thing that sits outside for half price. There were only a few sheet metal screws holding it on. I have the paperwork for it and it says it's a 6 ton I believe.
I don't know about the duct work in my house but if the fan will modulate and run slower I'm not sure it will be a problem.
What are your thoughts? I just want to get rid of the converted to gas oil burner and have no $$ to buy something new. Does anyone in the Seattle/Tacoma area have something to trade?
Tpgroceman
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| | ampulman
| "Re(4):Free Ruud Furnace" , posted Sat 20 Sep 15:52
The return sensor is built into the unit; the supply sensor is mounted in the supply plenum, beyond the coil. You need to consult the manual for proper location as this is critical to its operation.
The sensors are not there to function as overtemp sensors (in the usual sense of the word. Actually, the sensors work in conjunction with the thermostat to adjust the firing rate to match the heat loss, and to maintain a stable heat rise. If the temperature rise is such that the maximum temperature is within reach, it will throttle down the furnace until the output matches the heat loss. The thermostat 'modulates' the gas valve based on the difference between the room temperature and the set point. The fan only adjusts to maintain the heat rise.
You still have bigger problems as I noted regarding the blower speed and the gas valve. And as mentioned, you probably won't do the heat exchanger any good.
I think you should abandon the project.
AM
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| | theduke03
| "Re(4):Free Ruud Furnace" , posted Fri 19 Sep 17:13
If what you propose was that simple then manufacturers would just make a "one size fits all" furnace and they would be adjusted for capacity at install. Since that's not the case I would strongly discourage your idea. You could end up warping or splitting the heat exchanger due to uneven heating. If the limit switch is not between 2 sections of heat exchanger being used you could burn your house down.
"My dad was the most feared furnace fighter in Northern Indiana."
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