Gas furnace failing ....strange

[andy hancock]

I have a unusual symptom and problem with our RV furnace.  With recent night time cooling we started setting our thermostat at 64 degrees before bedtime.  We wrote up to a very cool 5th wheel.  I found the gas furnace had failed and required reset by turning the thermostat off and restarting.  It was before sunrise and I restarted the furnace a couple times without success.  The fan would start and the furnace would shutdown consistently at the 120 second time.  I understand that this eliminates the sail switch which would cause fan shutdown at 30 seconds and indicates possibly a gas supply or other problem at ignition. 

Now this is the bewildering part of the problem.  The outside wall of the 5th wheel that has the furnace and propane compartment faces the East.  After the sun hits that east facing side of the 5th wheel for just a few minutes........the furnace fires up and works reliably every time.  The 7 gallon propane bottle is full. 

So I don't feel the problem is within the furnace with the most probable cause being the regulator?  Why would the sun hitting that east side of the 5th result in everything working? This has happened several mornings in a row......so it's consistent. I think the next step may be checking the gas pressure in the 5th wheel before and after sunrise? I don't have the gas meter for this test.......11 inches of water.

So hoping someone may have had a similar issue or experience?  I don't want to overreact and tear into the furnace needlessly.  It works perfectly after the sun hits that east side of the 5th wheel.  Your suggestions and ideas are very welcome and appreciated.

[Kirk W]

The first thing that I'd like to know is the make and model of the furnace that you have. If you do not already have one, I suggest that you visit Bryant RV Service website and download a copy of the service manual. 

While I do have some suspicions, they may conflict with your previous conclusions, so feel free to ignore them. In my years of experience, one of the things I have learned is that if the propane bottle is nearly empty, it will sometimes produce a poor supply with temperatures low and improve when it warms, so I would at least consider that. You have not said how low the night temperatures are. Another possible cause would be that your propane regulator is getting oil contaminated, as that could cause the regulator to be off when temperatures are low and that oil is stiff. It could also be a failing regulator. I really don't see much value in checking the propane pressure at night. A good RV tech will check the pressure at the inlet to the furnace with some other propane appliance burning such as the water heater or stove top. That would normally show any regulator problems. All of this assumes that you have determined that the furnace is not the cause of the problem. 

[andy hancock]

Kirk..........Thanks so much for your comments.  I do appreciate it.  The same symptom occurred again this morning with outside temp at 45 degrees. I have not heard about the oil contamination of the regulator and that does make sense. I built a homemade manometer today and hooked into one of the cook stove burners.  The pressure goes immediately to 13.25 inches of water which seems a sight high?  But we are currently at 6.700 foot elevation which may effect that?  When the two remaining burners are turned on the pressure drops to 9.5 inches and holds that until I turn them off.  From what I've read, that is in the OK range?  It immediately returns to 13.25 inches when I turn the two burners off.  That was this afternoon with outside temps are 83 degrees.  The weather forecast for tonight is for temps in the 30s........ so I will check it again tomorrow morning. I did order a new regulator yesterday.  I read where they should be replaced at minimum around 10 years.  This is a 2012 5th wheel and I''m sure the regulator is original.  But unless the pressures are different tomorrow morning, my first thought is that the regulator is not the problem? 

Again thanks for you thoughts and insight.......I will keep posted so that someone may learn from this.

[RV_]

When you take your propane cylinders to fill them up, do you ever lay the cylinders on their sides?

[Darryl&Rita]

Loose wiring connection inside the furnace cabinet. Pull the connector off the module, and reseat. Wait until morning.

[andy hancock]

RV_.......no I do not lay the propane bottles on their side.  I understand that is a no-no. I haven't shared that I have a second source of propane with a site mounted tank.  I've tried both and the symptom is the same.

Darryl&Rita.......good suggestion and if the pressures at good tomorrow morning early, I'm thinking I will open up the furnace and start working though it.  I will try your suggestion.

[Kirk W]

From the RV Doctor website....

Quote

I’ve stated that all propane appliances manufactured for RV use are set to operate at an operating line pressure between 10 and 14 inches of water column. All appliance makers and RV industry educators proclaim the propane system operating pressure should be adjusted annually to 11.0 inches of water column. Why 11.0 inches? It’s due to something called regulator lock-up pressure. That pressure contained in an RV gas system that has an open service valve on the propane container, and all the appliances turned off. In other words, there is pressure, but no flow of propane. In a properly adjusted system, the lock-up pressure, that pressure required in a gas system to close the seats inside a two-stage regulator and stop the flow of gas, is typically 1.0 water column inch above the set pressure.

 

If the regulator is set at 11.0 inches of water column and the lock-up pressure raises it to 12.0 inches of water column, as it should; that falls right in the proverbial center of the 10-14 inches the appliances were designed for. In other words… its optimum setting.

 

Therefore, in addition to a visual inspection, the pro tech will adjust the operating pressure to 11.0 inches of water column and measure the additional lock-up pressure to verify the condition of the regulator. As it states in the RVIA textbooks used to train professional service technicians,

 

[Wrknrvr]

  The pressure should be about 10.5 at the very least . Much rather see the pressure at 11.5 when in operation.

 

  If you try your furnace what happens to the pressure.   Go to Bryantrv.com and see what the operating pressure should be. You may find out how to adjust the regulator. If it does not move when adjusting. Then replace it..

 

 

   Vern in a T-shirt 

[GlennWest]

Trash in orfice.Mine has done this twice. 

[mptjelgin]

What is the perceived issue with transporting propane bottles on their side? I am not aware of that being an issue. Stand them up to use them for sure, but transportation?

[Kirk W]

11 hours ago, mptjelgin said:

What is the perceived issue with transporting propane bottles on their side?

The vapor pickup tube is located to be used with the tank in a vertical position. If the tank is transported on the side that tube and the connections to it, all up through the valve will be filled with liquid. If any liquid gets into the pressure regulator it will damage it. A propane dealer's tech told me that he would place any bottle carried on it side in a vertical position for at least 3 days before use. 

[mptjelgin]

Interesting. I know that the tank should be vertical for use, but I've heard seconds or minutes rather than days for the interval between not-vertical to vertical.

There is no porous media like an acetylene tank (which I think many folks use as a basis for this "must be kept vertical" discussion) so I can't imagine that it takes much time at all for the liquid to settle. 

I've used a 30-pound tank to refill one-pound bottles dozens of times (I know, gasp) and you turn them upside down to get liquid from bottle to bottle. But after turning them back upright I've been able to use them for gas almost immediately. 

On edit - It occurs to me that the portable, vertical tanks don't use pick-up tubes at all.  They have the OPD assembly and a little tube that goes down to the screw-port that some technicians open when filling the tank to see liquid at the 80% level, but no pickup tube. So no tube to be filled with liquid propane. 

Edited September 8, 2020 by mptjelgin

[Dutch_12078]

16 hours ago, Wrknrvr said:

  The pressure should be about 10.5 at the very least . Much rather see the pressure at 11.5 when in operation.

 

  If you try your furnace what happens to the pressure.   Go to Bryantrv.com and see what the operating pressure should be. You may find out how to adjust the regulator. If it does not move when adjusting. Then replace it..

 

 

   Vern in a T-shirt 

Just to be clear, that ~11 pressure measurement is in inches of water column, not PSI. It equals about 0.4 PSI.

[Dutch_12078]

16 hours ago, mptjelgin said:

What is the perceived issue with transporting propane bottles on their side? I am not aware of that being an issue. Stand them up to use them for sure, but transportation?

I was taught in the propane refiller certification class I took, that vertical tanks stored horizontally in a vehicle could vent a small amount of liquid in situations such as a hot day that would instantly expand into a large amount of vapor that could cause a serious explosion if ignited. Liquid propane expands to 270 times its volume as it turns to vapor.

[GlennWest]

when my office is clogged my fan ran a lot longer than 30 seconds. Not a big deal to remove unit and clean it out on most campers

[mptjelgin]

1 hour ago, Dutch_12078 said:

I was taught in the propane refiller certification class I took, that vertical tanks stored horizontally in a vehicle could vent a small amount of liquid in situations such as a hot day that would instantly expand into a large amount of vapor that could cause a serious explosion if ignited. Liquid propane expands to 270 times its volume as it turns to vapor.

Thank you for the information. I can see where storing a tank in a hot vehicle and having it vent itself would be a serious problem.  And venting liquid rather than gas would be even worse. But assuming that isn't the case do you know of an operational issue with having a vertical tank on its side and then turning it upright for use? 

[Darryl&Rita]

2 hours ago, mptjelgin said:

Thank you for the information. I can see where storing a tank in a hot vehicle and having it vent itself would be a serious problem.  And venting liquid rather than gas would be even worse. But assuming that isn't the case do you know of an operational issue with having a vertical tank on its side and then turning it upright for use? 

Only if the float jams. Then the bottle gets a bump against the floor to get it to drop.

[Dutch_12078]

3 hours ago, mptjelgin said:

Thank you for the information. I can see where storing a tank in a hot vehicle and having it vent itself would be a serious problem.  And venting liquid rather than gas would be even worse. But assuming that isn't the case do you know of an operational issue with having a vertical tank on its side and then turning it upright for use? 

As Darryl said, a possible stuck float is the only other issue I'm aware of. Here's a link to what can happen when you forget there's a propane tank on the back seat though...

https://globalnews.ca/news/6486541/porpoane-tank-explodes-vehicle-halifax-store/

[andy hancock]

Update on our furnace issue.......I have checked the operation with my manometer two mornings in a row.  And with two different outdoor temperatures.  This morning with a 27 degree outdoor temperature the pressures were as followers.  No gas appliances on it was at 10.75 inches.  With furnace only it dropped to 8.5 inches.  Furnace and two cook top burners on it dropped to 7.0 inches.  Two burners only 9.0 inches.  Another observation as I have watched this closely.  The regulator window that shows "red" or "green" depending on gas on or off is not working.  It only shows a black window.  So I have myself convinced that the problem is the regulator and maybe Kirk's comment about the regulator being oil logged is a possibility to explain the morning sun on the side of the 5th wheel. My new regulator arrives tomorrow and I will update after it's installed.  The regulator is 8 years old so within the recommended replacement interval. 

[Kirk W]

3 hours ago, andy hancock said:

My new regulator arrives tomorrow and I will update after it's installed. 

I'll look forward to hearing. 

[andy hancock]

Update on my propane problems....In changing out the old regulator for the new one, I found this heavy accumulation in the outlet port of the old regulator.  It is lumpy and waxy in consistency and very close to a teaspoon of it.  This outlet port connects to a 5 foot rubber hose that connects into the 5th wheel black iron propane distribution piping. I cleaned up this mess as much as I could and installed the new regulator.  Unfortunately I have the same symptoms.  With no gas appliances on, the pressure stabilizes at 11.5  inches of water column.  But when I start the furnace, the pressure drops to 6 inches and when I add a couple stove burners, it drops even lower towards 5 inches. 

That outlet port on the regulator points downward and directly into the rubber hose.  Now I'm thinking that if there is that much accumulation of this waxy "stuff" in that port, the old regulator must be full of it and also the rubber hose could be partially plugged with it.  If the rubber hose is partially plugged.......even if the regulator opened up in attempt to maintain 11 inches as the furnace came on, a partially restricted hose would not allow free flow of propane resulting in my pressure drop.  So I'm thinking I will replace the rubber hose or at least run something through it to check for this waxy stuff. From what I read, it's not unusual to have a percentage of brand new regulators not function properly but it is set properly to get 11.5 inches with no flow. I'm calling out the propane service who supplies our larger site tank and see if it could be the source of this contamination.  This 2012 5th wheel has been used for fulltiming for 6 years and part time for 2 years so there has been a lot of propane run through the system......with no problems. 

Any thoughts or advice is welcome!!!!!  What is this waxy stuff? 

[Wrknrvr]

 I would test pressure at exit of regulator.  Make sure the connection to the gas bottle is not really tight. I have seen where a tight fitting where the line hooks to the tank be a problem. Do you have two tank, turn them both on. Do you have a bottle on both sides of rv. I have seen those regulars go bay and cause problems.

 

   Just saying,    Vern in a T-shirt 

[Kirk W]

I think I would start by taking the rubber hose off and if it has any significant amount of that gunk in it I’d replace it. Look also for signs of that stuff in the iron pipe. What you describe sounds very much like a flow restriction in your gas line somewhere. I would also take a look at the fittings that connect to each propane appliance to see if there are signs of that same gunk, especially if you find any in the iron pipe. 

[andy hancock]

Update to my propane issue.  Today I took the rubber hose that feeds from the regulator to the black iron distribution pipe.  You can see that 4 foot hose in the picture.  It comes out of the regulator on the bottom where I found all that waxy junk. I put the hose in a hot water bath with Dawn dish soap for 5 minutes, ran a wire through it then blew it out with compressed air.  There was some oil (maybe a tablespoon) in it but no heavy waxy material that I found in the regulator.  The black iron distribution pipe runs along the 5th wheel frame for 8 feet and all connections come off the top.  I was able to remove the ends and blow compressed air through it.  I got approx 4 or 5 tablespoons of amber colored oil but again no heavy waxy material.  I then reconnected everything, opened the valve on our onboard tank.........went inside and tested the pressures.  Everything was perfect.  The immediate pressure was 11.5 inches and when I started the furnace, the pressure only dropped to 11 inches.  With furnace and two stove top burners on....the pressure dropped to 10.5 inches and stayed there. 

I called the propane service who provides our onsite propane tank (100 lb tank) and asked if the tank they supplied (which was a used tank) could possibly have an unusual amount of heavy oil in it.  I asked how often they purge their tanks when refilling to remove the build up of oil. Our problem started when the onsite tank got down to 30% full.  Without answering my question, they volunteered to  bring me a different tank.  I asked if I could have a "new" tank and they didn't want to agree to that and said I could buy a tank if I wanted a new one.

I was hoping that when I resolved this it might be of use to others who might encounter a similar issue.  But.....I'm not sure I know exactly what the problem was.  I replaced the regulator, cleaned the rubber hose, blew out the black iron distribution pipe and I'm using propane out of our onboard 7 gallon tank.  But ....it feels good to have it fixed......it's getting cold at night here. Thanks for all the input from all of you.

[fly2low]

I'd call that success.  Ya did good