Underperforming webasto furnace

[dpiano]

Hi all,
On our 2014 R-29, our furnace has never been adequate. Most of the year it doesn't matter but we use the boat year round.
We have re-routed the air intake from the cave, and ran it directly to the lower cabinet to the left of the oven. This was recommended by Hobson at Sure Marine in Seattle. The entire run of intake is shorter than 2 ft now, and not going through the engine room. I also put a closable vent on the v birth duct, so we can keep more heat in the main cabin. This does not change the furnace performance, open or closed.

On startup the furnace runs at high fan speed and fast clicks on the fuel pump, but after maybe 1/2 hr it will slow down, but not really get the cabin warm. Last night I ran the furnace all night at the max speed and temp setting on the "airtop evo m" control panel. In the morning, the outside temp was 40F, and inside was 58F. Not good enough. Ronnie at Ranger says he has never heard of this, and the furnace should "bake us out".

Hobson says there may be a kink in the output hoses, which I will check soon. He says there are 2 sensors in the furnace monitoring cold air in and warm air out. If there is a air hose restriction on either side, it would slow the furnace down. Ronnie says the entire run of hot air hoses are visable by pulling out the fridge, and climbing in there which I will do soon. Hobson also rcommended removing the output hose from the furnace and see if it changes performance, which I will do. I also wonder if one of the sensors is bad. Hobson also preferes using a different type of control panel which isn't as involved as this one but doesn't think the panel is the problem.
We are in Portland and there is no good furnace tech down here.

Has anyone had this problem or have any suggestions?

 

[knotflying]

sorry I can't give you a specific item to check. I went through the entire repair manual troubleshooting guide and there is no symptom that you describe. My Webasto toasts us out. We even have to open the windows at times. It definitely sounds like a restricted flow issue either on the intake or the exhaust. Keep in mind that the warm air intake and exhaust tubes are different than the combustion intake and exhaust. The warm air intake and exhaust are larger, around 2 inches or so. There should be one intake somewhere in the cabin. Have you located that and does it seem like it is functioning? It should suck a piece of paper tight to it if held against the vent.
let us know how things go.

Mike Rizzo

 

[dpiano]

Thanks Mike.
Makes perfect sense that it needs combustion air port. Never thought to look. I looked, and don't see one anywhere. Looked in the manual and it shows a port right beside the combustion exhaust. I see one; it has the copper fuel line and wiring leading into it. It's about 1" diameter with a slot on the side, but no duct leading away. With furnace running, held my thumb across to block it but felt no pressure. Time to call Sure Marine tomorrow to have a talk. It encouraging to hear it isn't just under capacity for our boat, and SHOULD work better. I'll let you know what the tech says.

Thanks again
Denis

 

[knotflying]

The 1" tube with the slot is the combustion intake. That normally is attached to a fitting that takes air from the outside not inside the cabin. There should be another hose that is covered with heat resistant insulation going to another outside fitting and that is the combustion exhaust. I would initially disconnect the intake and exhaust ducts (large ones on front and rear of heater) and see what type of performance you are getting initially. Then I would shut it down and connect only the supply hose and see how that is throwing heat through your cabin ducts. If it is working well then it is the intake that is clogged. Then reverse the process and see how the air is coming out with the supply unattached and the intake connected. I would say this process will determine if your problem is the unit or the intake or exhaust cabin air. Also, depending on how they ducted your unit, you could have a disconnected, damaged or open hose down line and I suspect that combustion is not an issue. That would show up with black smoke outside from incomplete burn.

Keep us informed.

Mike

 

[Sodapop]

I have an R29 with a Wallas heater (10,000BTU) - installed in Stbd aft hold. This past weekend spent the night out a found heating not adequate. Outside temp 38 F. I’m thinking my problem is that the ducting is not insulated as recommended by the manufacturer. I will try fibreglass wrap. Hoping this works. Just a thought - Rob

 

[SJI Sailor]

I don't know about the Wallas but just in case it helps anyone, I can share an issue we had when our C30 Webasto would not heat adequately: the duct connection to the heater -- which is buried under a hatch below the stove -- had come loose. All of the heat was going into the hull space between the hull and inner finished space.

The solution was to get a small duct extension piece and reconnect the ductwork with a bit more "give". Tough to do in the workspace, but solved it perfectly. After that we were blasted out with plenty of heat!