Low propane at furnace

[obscenic]

With a U-tube manometer I have measured 11" WC at the propane regulator output. When I fire up the furnace the WC drops to just about 10.5". When I measure at the furnace, at the post-valve gauge output, I see just 6" WC when the furnace fires. Any idea what could be causing this?

[westend]

Thanks for posting the outcome.
You could look on the bright side: You removed a regulator that may have failed catastrophically in the future at the most inopportune time causing all sorts of additional frustration. You have all new copper supply line. You now have the tool to do your own and maybe, other's copper repairs. You know a bit more now than yesterday.

Just saying, not a total loss.

[mrgreetis]

Glad you found the solution. Frustrating, I know, when it turns out to be "simple". But you were successful. Good job!!

[Harvard]

Hey, that is great, thanks for letting us know, some might just sink away into the cloud and not give this feedback. Good on you. 🙂 🙂 🙂

[obscenic]

Well this is embarrassing. "I know now what I new then but I didn't know then what I know now."

The "blockage" was a second regulator. When I first bought this van conversion (a 1983) I decommissioned the on board propane tank for fear of it's age (it's VERY rusted). I tapped a tee and propane quick release into the elbow just past the tank, assuming the valve on the tank was regulated to RV pressure. As it turns out, this tee (which I attach an external regulator and tank to when I use the RV) actually went to another regulator which was hidden between the running board and the tank. That second regulator was what was causing pressure to not make it through the line... since I had already snipped the old line to make it easier to remove, I had to just keep going and replace the whole run. I took out the second (failed) regulator and disconnected the propane system from the built in tank altogether. Works like a charm now. The cost of removing the regulator and solving my problem would have been about $3 for a pipe nipple. The cost because I had already started cutting the copper line became $50 for copper and $30 for a flaring tool and much time and effort.

The moral of the story is, despite how awful it is to crawl around under your low-to-the-ground van RV, a 95% inspection is never good enough. Suck it up and look at every inch of the run.

C'est la vie.

[obscenic]

Harvard wrote:


I am assuming there is part of the line you cannot see, also the hidden line is copper? Right? If that is the case the hidden line may have a kink so all you could do if replace the section. I too am very interested in how this turns out, so don't disappoint us. 🙂

There's just 3 feet where it goes above the fuel tank. That said, the rest of it has a black plastic protective cover around it so if it was crushed it might be hard to notice.

[Harvard]

obscenic wrote:
I connected the propane tanks at the halfway point down the line and now I have correct pressure to all my appliances... So the culprit is identified. I'm just not sure I want to know what the solution is. 100 PSI of air did nothing to clear the blockage. Soap and water? Any suggestions?

I am assuming there is part of the line you cannot see, also the hidden line is copper? Right? If that is the case the hidden line may have a kink so all you could do if replace the section. I too am very interested in how this turns out, so don't disappoint us. 🙂

[Cdash]

Do you have a fish tape (for pulling wire through conduit) that you can push through? Or a stiff wire?

[obscenic]

I blew both ways, same results.

[mrgreetis]

Don't know if it will work, but you might try blowing it out from that middle connection toward the tank end. Blowing toward the middle didn't work, but "back flushing" might.

Good luck!
Mike

[Cdash]

I have no help to offer, but am very interested in what you find.

[obscenic]

I connected the propane tanks at the halfway point down the line and now I have correct pressure to all my appliances... So the culprit is identified. I'm just not sure I want to know what the solution is. 100 PSI of air did nothing to clear the blockage. Soap and water? Any suggestions?

[obscenic]

I just now attempted to blow out the propane lines. The line was holding pressure so when I took the air gun off, some pressure blew back. This seems off to me, the air should flow freely.

I tested the first half of the run (tank to appliance tee's) and it has the same issue. The lines from the Tee's to the appliances themselves don't have any backpressure from the air line. There's no visible damage (I can't see 3' of it where it goes between the body and the fuel tank) to the first half of the line, but do you experts think that's the culprit?

[obscenic]

I just measured at the furnace, with each stove burner I turn on, it drops one inch WC from 10" (one burner) to 7" (3 burners). This sounds like it might be a problem with the supply between the regulator and the appliances! I've heard of oil in the lines, is that possible?


Edit: I just took two more measurements.

1. The pressure at the regulator with the burners on is still 10.5" WC... so that's bizzare.

2. The pressure at the stove when the furnace is on also drops to 7" WC.

The only conclusion I can draw from this is that there is an obstruction between the regulator and the appliances. Anyone else draw the same conclusion?

[obscenic]

Ok I thought so! I'll enquire with Atwood, as the valve is brand new. Thank you!