Rheem LP gas furnace model RGPN-12EARJR

Specific Inspection Topics Inspecting HVAC Systems
1

This may be a question for another message board but I thought I’d ask.

We installed a replacement furnace in my house and can only get 7" of water column on the manifold side of the valve. The install manual says it needs between 10" and 12".

Local rep says the valve needs to be replaced…we replace it with two new ones…still only 7" of water column with none of the valves adjustable (tighten screw or loosen and no difference in pressure).

We put a newer model of the gas valve on, per the local rep, with no change in performance.

Local rep then says he called the factory and they say run it with the nice blue flame we have and forget it…I am wondering.

What say you?

2

Larry,

Did anyone check the BTU input/output of the present set up to confirm that you are getting the rated input/output?

I think I would like to know that if it were mine. It is quite easy to do.

3

I don’t think my guy did that but I’ll ask tomorrow.

How is it done?

4

Basically you observe the gas consumption over a period of time(10 -30 minutes should be enough)
The burner has to be running full out and all other gas appliances turned off or at least not operating.

Then you have to know the BTU per cu ft. of your local gas supply and calulate from there.(should be appx 1000 BTU.cu.ft.)

example:
100,000 BTU/Hr rated input.
Burner on full for 15 minutes.
Used 25 cu ft.
25/ 1/4 hr x 1000= 100,000 BTU/Hr

5

Thanks, Michael, I just got back in from taking a break to stack wood. Neighbor thinks winter is coming…:shock:

Any other input as to why we can’t get the pressure needed through the valve?

6

What’s your pressure at the meter?

It should be stated on the meter.

7

It’s a LP tank and on the tank side of the valve we get 12".

8

Oops!:oops:

Forget what I said about measuring input.

You need a way to measure the actual gas used to determine if it is delivering the rated input.

BTW - Propane is 2488 BTU per Cu ft.

The nice blue flame is a good sign but it doesn’t tell you if the correct burner and orifice are in place.

9

I switched out the orifices and put in the other parts of the conversion kit, so I know that was done.

10

Larry it sounds to me as if you are having line drop. What is the size of your supply line and what is the distance from the tank to the furnace.
I ran a one inch line from my tank to the furnace approximately 75 feet and had to adjust the regulator at the tank in order to get 11 inches at the gas valve on the furnace. you can still have a blue flame with less inches of water column but the BTU output will drop and the furnace will run longer to do its job.

11

Thanks Charley.

I think we may have it figured out. It appears that the regulator on the tank is bad and fluctuating. We were able to get 11", by adjusting that, but not continually. It is running at 9 1/2" of water column now.

Tech from the LP gas company is coming out on Monday next to “upgrade the equipment”.

Thanks for the help everyone.

12

Way to go Larry. Persistance pays.:slight_smile:

13

Thanks, Michael. This certainly has been a learning experience for me and I really appreciate my 75 year old friend that has a lifetime of HVAC experience that seems to get misplaced here and there. :smiley:

14

Had to change mine two years ago they don’t as some think last for ever.

Glad you got it fixed winter is on the way stay warm. Or I should say repaired fix is what we do to cats and dogs.

15

Good find Larry. Now have a co/combustion test done on the flue gases. A few years back found bad co readings when the main blower came on. Someone at the factory left a screw out. Would have never known unless I had tested.

16

Can you explain the process a little more? What are “bad” (I’m thinking any inside the home is bad) co readings?..and did you find them at registers if they showed when the blower came on?..or was it something excessive at the flue pipe (flue gases)?

Thanks.