Suburban Furnace Loud only when burner is on. Flame Adjust?

[ChucksterCF]

I have a 2016 Coachman Freelander. Florida RV. The furnace may not have ever been used by the previous owner as they only went on 2 trips. This morning I fired up the furnace to take the chill out. Blower sounded normal then once the furnace lit there was loud low pitch humming sound. Exactly like the sound of the water heater when the flame is not adjusted properly..


The big question. Is the FLAME roar normal? Its loud outside the RV and inside. Much louder than the blower. How do I adjust it the flame if this is not a normal sound?


I believe I have Suburban SF-20Q or SF-42Q

[Kahoona]

These furnace flames are loud. Yours could have a problem though because it sat too long without use. Spiders like to nest in the mixture adjustment area. This post may help. You are looking for any obstruction. Then you will want to adjust the air/ fuel ratio, but only if it needs it. If the flame is mainly blue then you are fine.



https://www.irv2.com/forums/f54/subu...ame-65563.html

[ChucksterCF]

Originally Posted by Kahoona

These furnace flames are loud. Yours could have a problem though because it sat too long without use. Spiders like to nest in the mixture adjustment area. This post may help. You are looking for any obstruction. Then you will want to adjust the air/ fuel ratio, but only if it needs it. If the flame is mainly blue then you are fine.



https://www.irv2.com/forums/f54/subu...ame-65563.html

I dont see any place where I can see the flame.. or do any adjustments.

Not like my water heater where I could see it and adjust the air slider. It sound like the water heater roar when the not adjusted properly.

By the way I just ordered some dauber screens for it.

[Fiesta48]

Some are so load I've move to a different site, especially for long term.
Most are not getting enough oxygen. Opening the door usually stops the low pitch noise.

[Old-Biscuit]

Suburban Furnace does NOT have an 'adjustment' for air/fuel mixture

Gas flow pulls the required ratio of air via venturi
Proper gas flow is key to good combustion

Obstructed orifice is most likely cause of improper mixture
You need to clean orifice by soaking it in alcohol and then air dry (not with high pressure or poking anything thru it)

Obstruction in Intake vent...same result

High LP System Pressure also.....loud flame
*S/B 11"WC (0.39 psi) with furnace in service



Suburban SF-20Q or SF-42Q---which is it??
1st one is a 20,000btu furnace
2nd one is 40,000btu furnace
They are Loud too begin with
***Water heater only uses a 8,000btu/10,000btu/12,000btu burner for comparison

Link in above posts is for a Suburban Water Heater.....air shutter no longer used for many years