LP Furnace question 2000 Adventurer 32V

joemcgin · 09-07-2013, 09:54 AM

Hi all,

Was down preparing the coach for the fall and thought I'd fire up the LP Suburban SF-25 furnace and only seem to get heat out of the floor register's. The burner lights fine and the exhaust and intake vents are all clear. It does not seem to be a strong flow from the floor vents and was wondering what to expect from the LP Blower. The electric heat pump blows fine from the ceiling vents as expected. After about 10 minutes the coach does start to warm up, but heat doesn't really seem to be blasting out of the floor vents. We haven't had to use the LP furnace since we bought the coach so we don't really know what to expect. Thanks.

jesilvas · 09-07-2013, 03:55 PM

They usually aren't very strong. You can go to the furnace and make sure that all the ducts are on good and nothing is leaking air, but that's about it.

sswilson · 09-07-2013, 04:02 PM

Have you checked or replaced your filter? Are you somehow blocking the cold air return to the furnace? If the fan sounds okay, those two things could be slowing the air flow down. I have a 35U and have a filter under the bed and cold air return on the wall near make up mirror area.

joemcgin · 09-07-2013, 04:12 PM

Thank you for the replies. I changed the AC air return filter under the bed last month. Both vents at the rear of the coach are free from obstructions. I don't know of any cold air intake location inside of the coach and nothing in my manuals about one.

sswilson · 09-07-2013, 04:20 PM

The cold air returns I speak of are not from the outside but the openings where the furnace draws air from inside the coach. Sounds like you checked them and they are okay.

mel s · 09-07-2013, 04:25 PM

Quote:

Originally Posted by jesilvas

They usually aren't very strong. You can go to the furnace and make sure that all the ducts are on good and nothing is leaking air, but that's about it.

jesilvas

----X2!
Mel
'96 Safari

sswilson · 09-07-2013, 04:29 PM

Just to clarify, I have a screened area on the side of the cabinet in the bedroom that is what i call the cold air return for the furnace. It just picks up previously heated air and returns it for reheating in the furnace. System does not work as efficiently without this return and will slow down the flow. I do not know your model, but Winnebago should be able to tell you where it may be. I have always found them very helpful.

jesilvas · 09-07-2013, 04:34 PM

Just go outside, find the outside vents. Then go inside to the exact same place, and pull a cover off, it'll be there.

wa8yxm · 09-07-2013, 04:55 PM

Here is how you tell if the air flow is strong enough.

(I will give you the furnace cycle)

Thermostat calls for heat
Mother board (Control board) fires up the BLOWER
***SAIL SWITCH CLOSES*** when air flow is high enough
Mother calls for Propane and begains ignightor.
Flame happens
A: Mother switches from IGNIGHTION to flame sense
B: Mother senses flame from seperate flame sensor
Flame continues till T-Stat says "WARM ENOUGH"
Mother shuts down propane, flame off
Mother shuts down blower (After a short cool down)

Re-The A and B above
Some systems have a single wire and "probe" that is both the ignightor and the flame sensor

Some have 2 wires and two probes.

Since the flame comes on, the air flow is enough to close the sail switch and you do not have a problem.

sswilson · 09-07-2013, 04:55 PM

There should not be a cover on a cold air return vent. It should usually be a screened area that covers a duct back to the furnace. This is what allows or makes the air move properly in the coach and it should not be real close to the furnace itself.

mel s · 09-07-2013, 05:34 PM

Quote:

Originally Posted by sswilson

There should not be a cover on a cold air return vent. It should usually be a screened area that covers a duct back to the furnace. This is what allows or makes the air move properly in the coach and it should not be real close to the furnace itself.

My Suburban SF-42F LP furnace is under my street side refrigerator.
The wooden return/cold air louver is 6 inches in front off the furnace, (toward the curb side)..... however, the nearest of the 5 heat registers IS 5 feet from the return air louver.

BTW, For my furnace, Suburban specifies that no filter, (and no screen), be used in the cold air return, the heat ducts and/or the registers.

Mel
'96 Safari Sahara

sswilson · 09-07-2013, 05:43 PM

I agree that there should not be any obstruction in the cold air return. Mine is a decorative screen so it is not just a hole in the wall. The unfortunate part is that you are unsure what it is, you could block it off by setting a box (example) beside it. This will prevent the proper circulation of heated air and maybe make the flow thru the heat vents less than what they should be.

Sammie · 09-07-2013, 06:01 PM

Quote:

Originally Posted by joemcgin

Thank you for the replies. I changed the AC air return filter under the bed last month. Both vents at the rear of the coach are free from obstructions. I don't know of any cold air intake location inside of the coach and nothing in my manuals about one.

Joe, I had a 2000 Winnebago Adventurer 32 ft. and the cold air return for the Suburban floor furnace is straight above the furnace itself on the bedroom floor. The only return air filter is the one located near the back of the coach and it is for the air conditioner. I found that when using the floor furnace, the further forward you go, the less the airflow you will get from the floor duct openings.

Sammie

Hikerdogs · 09-07-2013, 07:55 PM

If the furnace starts moving warm air the fan is blowing at the proper speed. Before the furnace ignites the blower starts. It has to blow hard enough to open a door at the exit end of the heat exchanger. When the door is open it closes a sail switch that allows the gas to flow and the igniter to work. If the blower isn't moving enough air to open the door and make the switch the furnace will not start.

joemcgin · 09-07-2013, 08:35 PM

I get hot air coming out of the furnace exhaust vent on the rear of the coach on the outside of the bedroom wall. 2 vents there; 1 exhaust vent & the other I'm assuming is the outside air intake to the furnace. Will have to check the coach after it gets out of the shop for a bad fuel pump. No access to it while its in the shop. Thanks again all.

Dispatcher · 09-08-2013, 06:19 PM

I recently purchased a 2000 35U Adventurer and the furnace operated as described in the original post when I took posession.

My low air volume was caused by a massive air leak at the furnace housing. I removed the outer cover and there was a one inch gap all the way around between the furnace housing and the rear cap. (My furnace is mounted in the rear) I bought a rubber garage door seal from a hardware store and fabricated a seal between the body and the furnace.

Now when the furnace runs it must draw air from inside the coach creating a negative pressure which allow's heated air to enter the coach. This is the way it is designed to operate. Before the repair the furnace was drawing air from outside and trying to force it into an enclosed space, resulting in the poor performance.

joemcgin · 09-08-2013, 09:25 PM

Does the LP Furnace air return on this model (32V) use the same return as the AC that is positioned on the passenger side of the Coach under the Queen bed? That is the only return I can recall seeing. The furnace itself is at the very rear of the Coach mounted underneath the Queen bed storage area. Just want to be sure we're talking about the same thing. I will also check into the Vent Cap seal as well. Thanks for the suggestions.

DAN L · 09-09-2013, 12:05 AM

Quote:

Originally Posted by joemcgin

Hi all,

Was down preparing the coach for the fall and thought I'd fire up the LP Suburban SF-25 furnace and only seem to get heat out of the floor register's. The burner lights fine and the exhaust and intake vents are all clear. It does not seem to be a strong flow from the floor vents and was wondering what to expect from the LP Blower. The electric heat pump blows fine from the ceiling vents as expected. After about 10 minutes the coach does start to warm up, but heat doesn't really seem to be blasting out of the floor vents. We haven't had to use the LP furnace since we bought the coach so we don't really know what to expect. Thanks.

here is a link to the manuals.
i installed registers with closeable dampers from home depot in the rear most areas. that helped get more air to the front registers.

Service Documents

winnie32v · 09-09-2013, 06:04 AM

As long as you're checking out the Heating system, I expect that your unit has a Motoraid Coach heater.
Be sure to check out the Dash Switch for the Aux Blower Motor. It should work on both Lo & Hi.

This pushes hot air through the Same duct system that the rear furnace uses.

I had to replace mine due to the well-known design flaw in the bird cage assy. Not fun, but educational..........

If you need any further info, please email me.

Keep us posted.
Thanks,
paul

joemcgin · 09-09-2013, 06:12 AM

That Aux heater worked a few weeks ago. Made a screeching noise when I hit the switch when I bought the Coach in April but after hitting a bump the noise went away.