Good Sam Club Open Roads Forum: suburban furnace tripping on high temp
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Class A Motorhomes

Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > suburban furnace tripping on high temp

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next
xtal_01

Vermont

New Member

Joined: 12/08/2017

View Profile



Good Sam RV Club Member

Offline
Posted: 12/17/19 08:21pm Link  |  Quote  |  Print  |  Notify Moderator

Hello,

I have a Bounder RV with a year old Suburban SF-35Q furnace ... about a weeks run time on it.

A few weeks ago I replaced the propane regulator.

At the time, I noticed the unit was tripping out ... I suspected on high temp.

I was also having an ignition problem (would not lit after ignition).

So, I bough a Dinosaur board. This fixed the ignition problem.

Now I can say for certain, the safety circuit is tripping (board has an indicator).

I tested the sail switch ... seems fine.

I replaced the high temp switch ... we are still tripping out.

So, I pulled the ducting off the rear port on the furnace .... ran it with no line ducting on it ... just dumped the warm air into the basement ... worked. Ran for an hour with no trip.

So, I put hard piping (house type galvanized steel) onto the furnace ... just some straight and 4 bends ... this is the line that comes across the RV and into the washroom. there is a small Tee to bleed air below ... I left inline as it was.

Trips out again on high temp!

Tried pulling two of the duct lines off the plenum coming off the top of the furnace ... still trips out

Tried opening one of the other side ports on the furnace ... still trips out.

I did put a manometer on the regular ...

old ... 12" wc static ... 10 - 11 while running (just bleed some off as it is in the shop and not on the furnace).

New 15" WC static ... 13" when the furnace is on.

motor is a constant 6.5 amps

It even tripped with the outside cover off so I now it is not the return air.

OK, I am stumped ... I have been at this for days standing in the snow.

I did everything I can think off ... I checked with the factory. They said it should not be tripping the high temp switch.

I am getting desperate ... suppose to be leaving on a trip this weekend.

Any suggestions ?????

Thanks .... Mike

MountainAir05

New Mexico

Senior Member

Joined: 01/27/2007

View Profile


Offline
Posted: 12/17/19 08:27pm Link  |  Quote  |  Print  |  Notify Moderator

size of ducting coming out. Heating can be large, Ac is the one you have to stay close to.

Did you get a output temp with the duct and return
did you get a return air temp with the duct and without when dump into basement. Just sound like you are not getting enough air thru the system duct. Which would be maybe a loose fan on the shaft.

time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 12/17/19 08:50pm Link  |  Quote  |  Print  |  Notify Moderator

Can you add a couple of additional 4" ducts? This what fixed mine.


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up

xtal_01

Vermont

New Member

Joined: 12/08/2017

View Profile



Good Sam RV Club Member

Offline
Posted: 12/17/19 10:00pm Link  |  Quote  |  Print  |  Notify Moderator

I should have added that this is a 20 year old (1999) RV so I am a bit surprised to have this issue "pop up".

No, I did not take any temperatures ... guess I should do that tomorrow.

I guess that for the past 10 years (that is how long I have owned the RV ... even lived in it for three years full time) I could have missed it but I think this problem just started .. hard to tell since the furnace does not shut down, fan keep going ... re-starts after the high temp switch cools off.

I though for sure that the longest duct had just failed after this many years and replacing it would do the trick.

Now with the longest duct connected in hard smooth pipe ... two open 2" holes in the top plenum and a side port (never opened before) now open you would think this problem would have gone away.

Maybe opening up the back port a bit (the one near the high temp switch ... the middle one is used now which is almost in line with the high temp switch) would let more air by it.

Even with just the 2" bleed Tee open in the basement, it is actually much warmer down there now than upstairs in the cabin.

Thanks .... Mike

garyemunson

Reno, Nevada

Senior Member

Joined: 09/27/2015

View Profile



Good Sam RV Club Member

Offline
Posted: 12/18/19 04:16am Link  |  Quote  |  Print  |  Notify Moderator

I added 2 extra registers to mine and solved the problem. Luckily my duct was rectangular metal right under the floor and I was able to just cut down into it.

Bruce Brown

Northern NY

Moderator

Joined: 06/01/2001

View Profile



Good Sam RV Club Member


Posted: 12/18/19 04:23am Link  |  Quote  |  Print  |  Notify Moderator

Any chance its just a bad switch?


There are 24 hours in every day - it all depends on how you choose to use them.
Bruce & Jill Brown
2008 Kountry Star Pusher 3910


xtal_01

Vermont

New Member

Joined: 12/08/2017

View Profile



Good Sam RV Club Member

Offline
Posted: 12/18/19 06:42am Link  |  Quote  |  Print  |  Notify Moderator

I did replace the switch ... but it could be a second bad one.

I ordered two to I can change that out this morning.

I am thinking of trying to open up the port next on the far side of the unit (second closest to the high heat switch).

Maybe this will give enough air flow.

maybe a floor register right off the unit and try moving the pipe that goes across to another port.

I worked on it till 2 last night ... running out to look at it again ... trying to beat the snow and 9 deg temps (way tooooo cold here in VT) heading our way tomorrow.

Thanks ... Mike

dougrainer

Carrolton, Texas

Senior Member

Joined: 06/11/2007

View Profile


Offline
Posted: 12/18/19 07:16am Link  |  Quote  |  Print  |  Notify Moderator

How long does it take for the Hi Limit to trip? Have you checked the INTAKE from outside to make sure there is no restriction? A partial restriction would cause lack of some air to the burner, but usually this will cause a rich condition and black sooting. I would suspect a bad motor, not running at correct RPM's, but enough to make the sail switch close. With inadequate volume of air, the furnace burner casing will run hotter. The reason I suspect the motor is you stated that until now, the furnace ran correctly even before you attempted the ducting modifications. Doug

Old-Biscuit

Verde Valley

Senior Member

Joined: 06/20/2009

View Profile



Posted: 12/18/19 08:08am Link  |  Quote  |  Print  |  Notify Moderator

Propane System Pressure 13"WC with furnace running??????

Too High/Overfiring


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
On the Road Debt Free April '07
Off the road still Debt Free Jan. '14

xtal_01

Vermont

New Member

Joined: 12/08/2017

View Profile



Good Sam RV Club Member

Offline
Posted: 12/18/19 09:12am Link  |  Quote  |  Print  |  Notify Moderator

Well yes and now on the motor .... I assume it ran correctly but maybe I just never noticed that the burner came on and off while the furnace was running. I really only noticed it after I changed the regulator. So I am wondering if a low pressure regulator was masking a "real" problem.

But maybe there was a problem with the motor from day one (there is only about a week running on the furnace ... last winter).

Here is want the factory said about the regulator pressure when I wrote them: "The LP pressure should have no effect on the Limit Switch opening. Of course the LP has influence on the flame but the gas valve in the furnace is a regulator that brings that pressure down to 10.0-10.5 inches so whether your LP pressure from your tank is at 11 inches or 14 inches, the gas valve should bring it down to an operating pressure (10.0-10.5) that feeds to the orifice."

Manual says 11" min ... 14" max

So I have touched the regulator ... but maybe I should?

I am working on opening up ducting even more ... don't know if I can, not much room for more ducting in this are under the floor.

Thanks .... Mike

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next

Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > suburban furnace tripping on high temp
Search:   Advanced Search

Search only in Class A Motorhomes


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2020 CWI, Inc. © 2020 Good Sam Enterprises, LLC. All Rights Reserved.