Furnace malfunction / figured out

[AntonJ]

Stopped in Marathon, TX to day trip down to Big Bend NP. It started snowing, so we decided to hunker down and wait it out. I thought I would run the furnace just in case it got cold enough to freeze the internal lines. We disconnected and drained hose.

Furnace no worky... A suburban SF-Q.

blower would come on, could hear it ignite after 15 seconds or so. Could feel a brief puff of heat out the exhaust vent and smell of propane then would go out, cycle 3 times and shut off. Repeat, repeat, repeat...

A quick google search indicated sail switch was the likely culprit. You tube looked simple. Getting the outside cover off as a first in 2 years of ownership took a while. Wiggling the tubes out of the tubes without knowing they were there was the trick. It looked nothing like the You tube videos.

More manual reading. Could not make head nor tails of the manual instructions.

Finally came back to the good ole Forest River Forum and followed the thread
by Walk the Walk on his Suburban Furnace. The part that caught my eye was an adjustment to a propane pressure. I looked for it on mine, but could not locate one.

Then the light bulb came on. A couple of months ago when I switched tanks. my regulator on one side failed. (Propane hissing out the little hole). I searched all over and found a similar Mr. Heater regulator and used it for a replacement on that side. I've been switching tanks back and forth with no problems for the stove, oven, fridge, hot water, but... I had never attempted to run the furnace off the tank on the side with the NEW regulator.

I switched tanks back to the side with the original regulator and voila' furnace workee!!!

That furnace sensor must be very pressure sensitive.

FWIW: My Mr. Big Buddy kept us from being panicked. Redundancy is useful.

Thank you Mr. Walk the Walk!

[AntonJ]

Does anybody know if this model does have a sail switch and if so, how do you get at it?

Thanks!

[Bama Rambler]

That model does have a sail switch and you have to partially disassemble the furnace to access it.

As long as the furnace tries to ignite the sail switch is working. The control board first checks that the switch isn't made and then starts the blower and checks that the switch makes before it fires the igniter. So if it ever tries to ignite, the sail switch is working.

Depending on which regulator you bought, you may not have gotten one with a high enough flow rate to handle the furnace. Those furnaces require a lot of flow in order to operate.

[AntonJ]

Thank you! That confirms our suspicions. Anton

[Larry-NC]

The SF-series furnaces are MUCH more sensitive to exact pressure than water heaters or ranges. (In fact the ranges all have a secondary regulator that makes up for a multitude of sins.)

The furnaces need exactly 11" w.c. pressure (about 1/2 psi). 14" won't work. Ask me how I know.

[TGR]

My trailer has two propane tanks and two regulators, one low-pressure regulator and one 30 psi regulator. The red 30 psi regulator is next to the tank that is away from the propane tank automatic selector valve. A standard low-pressure regulator will not work properly if it is used at a remote location.

[AntonJ]

What is 11" w.c. pressure, how do you measure it and what regulator should I buy?

[Larry-NC]

Originally Posted by AntonJ

What is 11" w.c. pressure, how do you measure it and what regulator should I buy?

What is 11" of w.c.?
Eleven inches of water column is just enough pressure to push water 11 inches up a section of vertical tubing (the column). It's around 1/2 psi. This is a tiny amount of pressure--you exert much more blowing up a balloon.

How do you measure it?
The gauge to measure it is called a manometer. There are some expensive and inexpensive gauges around. But you can build one in less than an hour which is perfectly accurate for under $5. It actually relies on the laws of physics to actually create and measure the water column.

I used scraps of wood I had to make the stand, in the shape of an inverted-T. I got 5' of tubing at Lowe's as well as the fittings needed to adapt to a flare fitting, so I could disconnect the furnace and connect the gauge in its place. It took two fittings to convert from a tubing barb to "iron pipe" threads to a flare fitting that matched the supply pipe to the furnace. I could have bought both brass fittings but the nylon one was a dollar or two cheaper.

I ruled lines across the backboard 1/2" apart and numbered them. This is because one side of the water moves down as the other moves up, so 1/2" movement on each side constitutes an inch of water column.

As you can see, I stapled the tubing to the backboard, put a little water into it, and put a few drops of blue food coloring into it for visibility. I put in enough water to raise the level to my 0" mark. Then I turned on the gas. The pressure is low enough that it just pushes the right side up to the 11" mark if it is working right. (Mine went to the 14" mark showing that the regulator was failing allowing too much gas through.)

What kind of regulator to buy?
There are really only two considerations for buying an RV regulator.

• Do you have one tank or two? If you have two tanks, you want a regulator with two ports and automatic switchover. If you only have one tank, you would get a one port regulator.
• Is your current regulator a horizontal or vertical regulator? You need to get the same, because regulators are designed to be mounted in one orientation only. Look at pictures on the internet and compare to yours to determine which you need.

Don't worry about the brand. They all seem to fail after about ten years, regardless. I think we've gotten twelve out of the last two.

[AntonJ]

Thank you for the detailed reply. We currently have 2 tanks with a manual switchover. It is the one away from the switchover that failed and was replaced with a Mr. Heater regulator with same PSI rating as the one that failed. I never paid attention to the mounting direction.

[Larry-NC]

Originally Posted by AntonJ

Thank you for the detailed reply. We currently have 2 tanks with a manual switchover. It is the one away from the switchover that failed and was replaced with a Mr. Heater regulator with same PSI rating as the one that failed. I never paid attention to the mounting direction.

A horizontal regulator usually mounted directly to a tank.

A vertical regulator often with hoses from two tanks.

These two are not necessarily recommendations, just the first of each type that I found.

[jeff64]

With a 2009 vintage rv, save yourself a whole lot of bs'ing around and put on a new lp regulator...the life span is 8-10 years, cost about $50 bucks and take about 10 minutes to change out

[Larry-NC]

Originally Posted by jeff64

With a 2009 vintage rv, save yourself a whole lot of bs'ing around and put on a new lp regulator...the life span is 8-10 years, cost about $50 bucks and take about 10 minutes to change out

The OP had already decided to do that. His last post was asking how to select one from the plethora on offer.

I'm wondering why he even kludged that funny combo together in the first place instead of doing the replacement.

[TGR]

If your OEM LP gas regulator was red, then your new regulator needs to be a high-pressure regulator and it too will be largely red. I looked at the Mr. Heater web site and saw only one stand-alone high-pressure regulator (F273719). That regulator had a red adjustment knob with a 1 to 20 psi range.

I replaced my leaking high-pressure regulator with a Marshall Excelsior MEGR-130-30 High Pressure Regulator from Amazon for <$15. I needed that one to match the inlet and outlets of the OEM regulator. You might want to contact your dealer and see what the correct regulator is for your RV and get one from them or order a similar one if it looks like the Mr. Heater regulator you have isn’t working right in your application.

[Mr. Dan]

Originally Posted by TGR

If your OEM LP gas regulator was red, then your new regulator needs to be a high-pressure regulator and it too will be largely red. I looked at the Mr. Heater web site and saw only one stand-alone high-pressure regulator (F273719). That regulator had a red adjustment knob with a 1 to 20 psi range.

I replaced my leaking high-pressure regulator with a Marshall Excelsior MEGR-130-30 High Pressure Regulator from Amazon for <$15. I needed that one to match the inlet and outlets of the OEM regulator. You might want to contact your dealer and see what the correct regulator is for your RV and get one from them or order a similar one if it looks like the Mr. Heater regulator you have isn’t working right in your application.

Yep... that's the one I used.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[AntonJ]

Hi Guys:

Sometimes I disappoint myself. As TGR said the Mr. Heater regulator has an adjustable valve.

I bought the actual replacement regulator and rediscovered that fact when I got ready to do the replacement. Then I paused and thought for a minute...

Yep, I had the valve open about halfway. Enough to run all the other appliances but not the furnace. Opened the valve all the way and guess what? The furnace ran just fine.

So now I have a spare and didn't have to spend the 15 minutes to change things out. (Trying to put a positive spin on my boneheadedness is a new activity in retirement for me)

Thanks everyone for your responses and help!

[5picker]

Originally Posted by AntonJ

Hi Guys:

Sometimes I disappoint myself. As TGR said the Mr. Heater regulator has an adjustable valve.

I bought the actual replacement regulator and rediscovered that fact when I got ready to do the replacement. Then I paused and thought for a minute...

Yep, I had the valve open about halfway. Enough to run all the other appliances but not the furnace. Opened the valve all the way and guess what? The furnace ran just fine.

So now I have a spare and didn't have to spend the 15 minutes to change things out. (Trying to put a positive spin on my boneheadedness is a new activity in retirement for me)

Thanks everyone for your responses and help!

I'm glad you seemingly have it working but I'm still somewhat confused...
If the original remote regulator looked like this red one (that leaked) it is a 50 PSI regulator.


If the Mr. Heater regulator you used to replace that red one is similar to this model with the red adjusting knob (as mentioned by TGR) it is only good for 0-20 PSI.



While you've said opening the valve the whole way has allowed the furnace to work, you really should replace it with a 50 PSI regulator as you'll likely have issues as the propane level in the tank gets lower.

The reason for the red regulator to begin with is on TT & 5th wheels where the LP tanks are on opposite sides of the R/V from each other, the tank farthest away from the change-over regulator is connected by a long hose that crosses the front of the R/V from one compartment/side to the other. DOT regulations say that hose cannot have tank pressure in it. They reduce the tank pressure (-+150 PSI depending on ambient temp) down to 50 with the red regulator.

Since you also mentioned it... the regulators are flow sensitive. They have an arrow on them somewhere indicating flow direction.

[AntonJ]

Originally Posted by 5picker

I'm glad you seemingly have it working but I'm still somewhat confused...
If the original remote regulator looked like this red one (that leaked) it is a 50 PSI regulator.


If the Mr. Heater regulator you used to replace that red one is similar to this model with the red adjusting knob (as mentioned by TGR) it is only good for 0-20 PSI.



While you've said opening the valve the whole way has allowed the furnace to work, you really should replace it with a 50 PSI regulator as you'll likely have issues as the propane level in the tank gets lower.

The reason for the red regulator to begin with is on TT & 5th wheels where the LP tanks are on opposite sides of the R/V from each other, the tank farthest away from the change-over regulator is connected by a long hose that crosses the front of the R/V from one compartment/side to the other. DOT regulations say that hose cannot have tank pressure in it. They reduce the tank pressure (-+150 PSI depending on ambient temp) down to 50 with the red regulator.

Since you also mentioned it... the regulators are flow sensitive. They have an arrow on them somewhere indicating flow direction.

Luckily, for my wife's sake, I'm smart enough to point the flow arrow in the right direction and did enough research to get the yellow /gas tape to screw things together so I got tight connections with no leaks.

The Mr. Heater regulator / valve has the same max psi as the stock regulator's psi. Since we are settled in our winter digs in Havasu now, I'll experiment a bit. That will let me know if a low level in the tank causes the furnace to not kick on.

Also, it would seem getting another 2 stage regulator for the side with switchover gizmo would be good insurance to.

Thanks to all of you offering advice. I am grateful for all the help I can get. Sometimes I am in need of adult supervision.

[jacknife]

11 inches of WP is the industry standard .

[Jcape]

What has not been said is, as the temperure gets colder, you get less pressue from your propane tanks. The furnace is set for optimal pressure and if it goes lower than that the furnace will shut off if it goes below pressure. I have had this issue and had a factory rep look at it, they can't adjust the pressure switch. What they did was give me a. New regulator, no help. What I found worked was having a full tank and it would not lose pressure. So, if you are in cold weather use one tank for normal use and keep the other one full. For the furnace and switch back and forth.

[dustman_stx]

Originally Posted by 5picker

I'm glad you seemingly have it working but I'm still somewhat confused...
If the original remote regulator looked like this red one (that leaked) it is a 50 PSI regulator.


If the Mr. Heater regulator you used to replace that red one is similar to this model with the red adjusting knob (as mentioned by TGR) it is only good for 0-20 PSI.



While you've said opening the valve the whole way has allowed the furnace to work, you really should replace it with a 50 PSI regulator as you'll likely have issues as the propane level in the tank gets lower.

The reason for the red regulator to begin with is on TT & 5th wheels where the LP tanks are on opposite sides of the R/V from each other, the tank farthest away from the change-over regulator is connected by a long hose that crosses the front of the R/V from one compartment/side to the other. DOT regulations say that hose cannot have tank pressure in it. They reduce the tank pressure (-+150 PSI depending on ambient temp) down to 50 with the red regulator.

Since you also mentioned it... the regulators are flow sensitive. They have an arrow on them somewhere indicating flow direction.

Those red step down regulators are 30psi, not 50.