Chassis (hydronic) heat system

[Jim Magowan]

As some of you know I have been trying to get the hydronic heat working properly in our Bird since we bought it in 02. We have finally found and to some degree corercted the problem.

The BB diagram of the chassis heat system shows coolant going from the engine to a Y. One branch of the Y goes to the hot water heater and from the hot water heater to the return line to the engine. The other branch of the Y continues on to the heating system circulating pump and continues through all the heater cores, front heat valve (Sporlan) and back to the engine.

It looks like someone assembling the coach when it was built felt it was easier to put the Y after the pump instead of in front of it. The result is that when the engine is running and the engine water pump is really moving the water we had great hot water but the coolant (water) was taking the easy path through the hot water heater and back to the engine without going on to the heaters. Putting the Y before the heater bypass as designed was to assure that water would be 'pulled' past the HWH and pushed around through the heater cores.

The initial fix was to replace the front Sporlan valve (which had to be disconnected due to an electrical conflict with the Webasto heater) with a $300 Webasto circulating pump. We now have heat! I think we still have too much water going thru the HWH instead of the heater cores. That will be dealt with by putting a ball valve (manual) in the line to the HWH that can be open, partially open or closed.

An alternative would be to put a zone valve in that would shut off the water to hte HWH when it reaches the set temperature. (I always wondered why Aqua-Hot advertize a zillion zone valves in their systems. Now I know why they use them.)

Teh initial tip off was a result of a friend who was helping me crawling under the bus and physically tracing the water lines. When he told me where the HWH bypass took off I figured we had found the culprit.

Looking back, I'd bet that Glenn Rogers would have found the problem very quickly had he been able to look at the coach in 03 when we were at Ft. Valley. Unfortunately they had him behind a desk and all he could suggest was that the gate valve for the heating system water on the engine was turned off. I think Wendell got sidetracked replacing the front heater blower motors and forgot the original problem was the hot water circulation itself and he never worked on it.

For diagnostics this a good thing to keep in mind. If the chassis heat quits and heat exchanger works great, the circulating pump is suspect.

In our search for answers we even tried to get information or a diagram from CAT showing which were inlets and which were outlets on the engine. This is a tough question. Not even CAT has answers. After I queried CAT they had a rep at NC (Anchorage CAT dealer) call me. He said he would research it and get back to me. That was so long ago I think I still had hair (maybe it wasn't that long ago but it sure seems like it) and I am still waiting for the call.

[Randy Dupree]

you have heat?
dang it Jim,now what are we going to talk to you about?heheheee!
its a weird coincidence that you live where you need heat the most,and you may have the only SP that was plumbed wrong in the world.
weird stuff right there!
please keep us informed on your new warm alaska adventures!

[Jim Magowan]

The next adventure will probably be the left front leveling jack. No problem that I have noticed when it is up but if I put it down it leaves a puddle of blood (looks like hydraulic fluid but costs like blood).

At 50 or 60 degrees I can now make it uncomfortably hot. How much heat we get at 0 may be another story. One reason I am going to put the valve in so I can get more heat to the cabin when it is realy cool.

The irony of having heat problems in an Alaska coach has been in my mind for years. Three years ago when we had -30 on the way to the Haines Bald Eagle Festival, we had the propane heaters going full blast, with a couple of plug in electric heaters (can't use electric and propane coach heaters at the same time) with fans to push heat from the back to the front and we still had to bundle up to keep warm. Ever drive up to Customs with three dogs who raise cain when anyone gets near the coach, windows frozen shut with a half inch or more of ice and they don't want you to leave your seat? When do you ever have that much fun?

Just so you don't think it's always cold here. We ran the coach air conditioner for an hour or two last month when we were driving with the sun on the windshield. I can't remember when we last used the big air conditioners. That was one problem when I tried to get service down there I think. Nobody thinks heat is much of a problem as long as the air conditioners work and most people wouldn't notice if the heat wasn't working.

I don't know if I have mentioned it before. I discovered a great tank for a coolant recovery system in the SP. A 2+ gallon Blitz gas can can be stuck in the space where the radiator overflow hose comes down, just behind (or in front if you like) of the bumper. It jams in just tight enogh to be secure without need for additional ties, can be easily removed and holds over two gallons of coolant so you don't blow it out on the ground at $12 a gallon or so.

[Randy Dupree]

Jim,i do know that its not always cold in alaska,and i know its a state as well!
we have cold weather here in Fl.
most people think its never cold here,we get several days a year when its 20 degrees.

[Jim Magowan]

Randy,
The difference is we get up to 20, you get down to 20. :-)

Jim

[Randy Dupree]

yep,and when its 20 here we are freezing!
but when its 100,and 90% humidity we are just fine,beer anyone?