Replacing Furnace?

I have a RUUD "Deluxe Glasslined Electric Ignition" gas furnace, model UGDA-12EA-GS, serial number: "SNxxxxx M3983 1974". 125000 input BTU for a 2000 SQ house. How can I tell age and efficiency of the furnace? Is it make sense to replace it with a 80% or 90% furnace?

 

At 19years old, your unit still has some life left in it and its probably about 80% efficient. Pretty sure the last 4 didgits of the model number stands for the week and the year of manufacture 39th week of 1983)

 

Thanks for the information. If this unit is built in 1974 (last four digits?), it would be almost 28 years old. If its 80% efficiency, I might keep it, but if it is around 60%, I would replace it. I am planning to have my old gas AC replaced. I have 1500 SQ living space plus 500 SQ unheated basement in DC area. I mighy be able to replace it with less BTUs.

 

Sorry, but I was not clear with the numbers. The manufacture date I'm quite sure, is the four didgits following the "M" in the serial number. I think this is correct but you ought to check with a local Ruud dealer or the Ruud web site. If you're going to replace, go with the same size.

 

If you are going to replace it -
DON'T just replace with the same size.
Most systems are oversided. Do it right & have a load calculation done on your home. Then install the proper size. Money saved on size can be used for upgrade in efficiency or accessories.

 

ahasbeen
You are right about the date, I found date on wiring diagram, which is 11-15-82.
Can I replace furnace later without replacing AC?
rclhvac
I agree with you, I have read a lot about "oversize" in the old days. Besides, I have replaced old windows with energy efficient ones. The outside walls were not insulated (frame structure with hollow walls), I put insulation when I replaced siding.
Thanks

 

You can replace the furnace only. But you may want to consider replacing the indoor coil at the same time to save on installation cost. Then you just have to replace the outdoor unit at a later date. Or replace complete system & reap the savings over the next few years

 

Good suggestions. In fact, my old gas AC uses water cooled linesets and indoor coil and they must be replaced. Two contractors give me quote for 2.5T AC. I used an online size calculator for Washington DC area and 1500 SQ living space, and got 2.73T AC and 60000 BTU heat. Does it seem resonable?
It seems to me that my old 125000 BTU furnace is either oversized or low efficiency.
Goodman web site has a lot of data sheets for matching coil with furnace. Their furnaces for 2.5T coil range from 40,000 to 100,000 BTU, widths are either 14" or 17-1/2". My old furnace has 21" width. Is it a problem to use 17-1/2" wide cased coil over 21" wide furnace?
Thanks

 

Seems about right to me - just rember the 60000 heating is out put raring. You will be looking at about a 70000 - 80000 furnace.
Also look into the new dual fire furnaces for added comfort. Your new furnace will be 14.5 -17.5 wide. A transition from the new equipmet to the duct work will take care of size difference.

 

(What? No html???)


Gas a/c? Really?

Pardon my ignorance, I'm not experienced in this area.

Did you mean gas furnace with air conditioning unit? Or really a gas fired a/c system (which, by the way, is a possibility although I've never seen it on an a/c unit).

 

Gas ACs are also called absorption AC, they use gas boilers rather than compressors, see "www.robur.com/Company/history.html"
Gas ACs use R174 (ammonia), not CFC/HCFC or HFC. They also need electricity for water pump and fan.

 

Is it OK to have a narrower cased coil (17"W) over a wider furnace (21"W)? (my old 125000 BTU furnace is 21" wide)
Goodman data sheet shows 17"W cased coil over 14"W or 17"W furnaces, but not 21"W furnace.
With all the facts, do you recommend to keep or to replace my old furnace?
Thanks