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Author Topic: Webasto DBW 2020 Parts?  (Read 3189 times)
alltech
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« on: December 07, 2006, 03:50:40 PM »

I recently bought a webasto dbw 2020 heater to install in my coach, but it didn't come with a circulating pump.

Its a 24 volt webasto, up here in Canada they want $750.00 for the pump.

Does anyone have a good source for these circulating pumps? I think the model is a U 4814

Thx Ross
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Paso One
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« Reply #1 on: December 07, 2006, 04:01:31 PM »

I'm Looking at doing the same thing for a webasto 2010 I was told a circulation pump like you would use for your water supply Sure-flow wired into the controller would work. I haven't checked out the motor draw comparison to the two pumps. The circulation pump starts before they fire up and continues to pump till after the pilot goes out.  Some trucks I'm told just put the pump on a toogle switch and manually control the pump. FYI the pump at the local friegtliner dealer is $325.00  Canadian $$ for the 12 volt pump.
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« Reply #2 on: December 07, 2006, 05:10:21 PM »

Paso One: I might be able to help you. Give me a phone call at 780-980-5031 (Edmonton) between 7 and 9 PM
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gumpy
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« Reply #3 on: December 08, 2006, 05:11:39 AM »

You might want to look at the specs on the water pump before hooking it up to a webasto. I may not be able to handle the high temperatures.

I suggest looking at a March pump. I'm using some of them on my Aquahot (2010 head) system. Have two 24v units for my interior heating system, and one 12v (came with the aquahot) that I've hooked up for engine preheating.

craig
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Craig Shepard
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H3Jim
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« Reply #4 on: December 08, 2006, 06:31:04 AM »

Dick Wright sell pumps for these systems.  He is knowledgable about what pump  is best for a given application. 541-744-4333

Also M&P pumps  Circulation pump part number 33157 is $146.  It has 1" barbs, 24 volts, pumps between 5 and 25 gals a minute depending on head pressure.   Check out their web  page, but if you want one of these its best to talk to a tech person.  http://www.mppumps.com/topics/about.htm
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Jim Stewart
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alltech
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« Reply #5 on: December 08, 2006, 08:22:38 AM »

Thx for the Help

My plans are to use the circulating pump to heat a larger tank of ucar-therm(environmentall friendly anti-freeze) an then use that to circulate to my zones in the coach. I will also stick two heat exchangers in the tank one for engine heat and one for hot water.

The Idea was that the engine can provide the heat to the tank when going down the highway, and the engine glycol and coach heat glycol could remain seperate.
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« Reply #6 on: December 08, 2006, 09:10:51 AM »

Might want to check the specs on that environmentally friendly stuff and see if it will withstand the high temps of a Webasto, and also see what the gel point it.

I started with propylene glycol (rv antifreeze) in mine. It came out after it warmed up from the first cold spell. It was so iced up it would not even pump when I turned on the system. It also broke down in the high temperature.

So now I have 18 gallon jugs filled with what looks like a nearly clear liquid on top, and a dark sludgy stuff on the bottom. I don't know if it affected the antifreeze properties of the stuff yet. Waiting for it to get a bit colder here and then I'm going to set some outside to see what it does. I'm hoping it will not freeze solid and I can at least use it to winterize with. Not really a big concern, though, as it only cost me about a buck a gallon (found a really good sale in the spring).

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Craig Shepard
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Jeremy
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« Reply #7 on: December 08, 2006, 09:21:43 AM »

The Idea was that the engine can provide the heat to the tank when going down the highway, and the engine glycol and coach heat glycol could remain seperate.

Out of interest, what advantages do you see in seperating the two systems?

I had a look at the OEM coach heat system in my coach the other day, and there are two huge heat exchangers plumbed into the engine cooling system about halfway down the bus. Even if the fans are not running they must absorb a lot of engine heat; People often refer to having disconnected or removed the standard coach heat system as part of their conversions - I wonder now if they are often the same people who experience overheating problems.

Jeremy
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« Reply #8 on: December 08, 2006, 09:33:46 AM »

Separate systems allow for use of the RV / envinmentally friendly anti-freeze in your heating / domestic hot water heating system.  Somewhat mprotant if you developea leak in your domestic hot water heat exchanger.

It also separates the bus engine cooling sytem from your 90 feet of heating system for the coach, so if a leak develps, your bus engine is still driveable.

It does increase the complexity, and it does require a separate expansion tank for the domestic system (that's higher than anything else in the system). 

I don't think those heat exchangers make much difference in kee[ping a bus engine from overheating.  Sure, you can turn the bus heat on to dump some heat, but typically that would be in the summer going up a grade, and thats not something you would comfortably do. If you're that close to the edge with yoru cooling, your should probably be looking at other solutions.
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Jim Stewart
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« Reply #9 on: December 08, 2006, 09:53:53 AM »

Just a few comments here...

Separate systems allow for use of the RV / envinmentally friendly anti-freeze in your heating / domestic hot water heating system.  Somewhat mprotant if you developea leak in your domestic hot water heat exchanger.

This isn't necessarily a concern, since by code any heat exchanger must provide two discinct separations between the two fluids. So, putting a coil of copper tube through your water heater is not acceptable, but wrapping the same copper coil around the outside of the water heater is, because you have the copper, and the steel tank jacket separating the two liquids.

Quote
It also separates the bus engine cooling sytem from your 90 feet of heating system for the coach, so if a leak develps, your bus engine is still driveable.

This is somewhat important. Isolation valves should be used so that the system can be isolated from the engine should a leak occur when the two systems use combined reservoir.  It's also nice to have separage isolation valves on the individual heating loops, in case one of them develops a leak. You won't have to shut down the whole system in that case.

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It does increase the complexity, and it does require a separate expansion tank for the domestic system (that's higher than anything else in the system). 

It does require an expansion tank, but it does not necessarily have to be the highest point. If you use a pressurized system, then the tank can be lower. This is effectively the same as an automobile cooling system which uses a pressure cap on the radiator to release liquid when it heats up and expands and suck it back in when it cools down. AquaHot systems use this same technique. Also, using a pressurized system eleminates air from the system, which promotes corrosion in steel components.

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I don't think those heat exchangers make much difference in kee[ping a bus engine from overheating.  Sure, you can turn the bus heat on to dump some heat, but typically that would be in the summer going up a grade, and thats not something you would comfortably do. If you're that close to the edge with yoru cooling, your should probably be looking at other solutions.

Agreed. But someone once suggested modifying air flow through the heater core in the summer so it could be used as a 3rd radiator. I thought that was one of the more interesting ideas I'd heard for a long time. Not really feasible in my current coach, but something to think about. If you could pull a damper that would direct air from the front of the bus through the heater core and down through the floor or out the sides, it might give you just a little more cooling capability. You'd need to modify the electric water valve control, too, to ensure full flow through the core.
Cooling some of these coaches is marginal at best, even with upgraded radiators, smaller pulleys, and all.

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Craig Shepard
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« Reply #10 on: December 08, 2006, 09:58:51 AM »

Ok, thanks - I take the point about not poisoning yourself if the antifreeze leaks into the domestic water. I had assumed I would be doing a lot of plumbing for my heating system (although perhaps not 90 feet); having seen the standard bus heat though, I suspect I would be better off routing the warm air from that through the plinth panels of the cabinets, rather than piping hot water all over the place and having heaters mounted in diffrerent locations. I guess there are some things you cannot do with hot air though (underfloor heating, or water-heated towel rails etc).

The existing system in my bus is probably a standard configureation - it has a heat exchanger on both sides, with air ducts the whole length of the interior walls. One wall heats fresh air from outside, with the other one re-circulating the interior air. Seems to be a sensible way of doing it, and the existing ducts can very easily be incoporated into the planned furniture.

Jeremy
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« Reply #11 on: December 08, 2006, 10:05:40 AM »

Regarding the pressurized system, its way easier to get the air out when you first fill it if you have the expansion tank as the highest point.  Take the cap off when you are filling.

Per David at Aquahot, if the pump has more than 4 feet of head pressure, it will chase all the air out as the fluid circulates.  but the key to this is to have it going from high pressure to no pressure.  The no pressure means the cap is off, and if its not the highest point, you will have issues.

The  code about having two distinct separations makes sense, however when I took the cover of my Seaward 11 gal domestic hot water heat exchanger, it appears that the pipes from the hot water heating system go directly into the tank, and do not circulate around it.  that would mean it has only one separation.  It's possible that there is a more complex inner structure that I couldn't see, but it does make me question  it.
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Jim Stewart
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« Reply #12 on: December 08, 2006, 10:23:41 AM »

Regarding the pressurized system, its way easier to get the air out when you first fill it if you have the expansion tank as the highest point.  Take the cap off when you are filling.

Per David at Aquahot, if the pump has more than 4 feet of head pressure, it will chase all the air out as the fluid circulates.  but the key to this is to have it going from high pressure to no pressure.  The no pressure means the cap is off, and if its not the highest point, you will have issues.

Keep in mind that as you push the air out of your system, you're pushing cold fluid and the level of the tank drops as you fill the heating loops. It's only when you heat up the reservoir and expand the coolant within that the pressure tank comes into play. It's important that the pressure cap be at the highest level of the reservoir, and as the coolant expands, it pushes out any air that is in the reservoir to the expansion tank, which must already have some fluid in it. If the coolant in the reservoir continues to expand, it will also flow to the expansion tank. Then, as the coolant cools after shutting it down, or by circulating through the heating loops, the coolant will contract, and create a suction which will pull some of the coolant back into the reservoir from the expansion tank.  Now you have an air free system.

Even if you can't chase all the air out of the lines on initial fill, it will eventually be absorbed into the liquid, and be brought back to the reservoir, where it will collect, and be expelled through the pressure cap as described above.


Quote
The  code about having two distinct separations makes sense, however when I took the cover of my Seaward 11 gal domestic hot water heat exchanger, it appears that the pipes from the hot water heating system go directly into the tank, and do not circulate around it.  that would mean it has only one separation.  It's possible that there is a more complex inner structure that I couldn't see, but it does make me question  it.

I've wondered about that myself.

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Craig Shepard
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alltech
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« Reply #13 on: January 06, 2007, 09:10:11 PM »

Does anyone know how most Webasto's are manifoled in to coach heat,hotwate,r and engine heat

Thx Ross
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