Coolant to coolant heat exchangers

[grizzlyj]

Hi
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I seem to remember being told that Eberspacher recommend separating engine from camper as the engine will want to pressurise its system but might not be able to when you add all that extra stuff pipework?
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Our last camper had the engine combined with the camper circuit directly and I don't think, for the small amount of diesel the heater would use to heat up the calorifier once stopped, that i would combine them again at all for the quite small benefit. They stayed isolated and separate.
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Preheating the engine? That Merc engine was designed to start from low temps and didn't even have glow plugs. If you insist on being somewhere properly cold then add a separate coolant heater placed and plumbed to do just that.
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[Neil]

I personally have separated my two circuits via a plate exchanger for the following reasons

1 If I had a problem with the cabin heating and had to drain down( which does happen ) it wouldn't take the truck of the road and Vice versa.
Imagine if you eberspacher or webasto has to go for repair, is that you off the road then

2. Big cast iron engines create a black sludge of Iron particles. I didn't fancy all this crap coursing through my new eberspacher heater and heating circuit.

3. Eberspachers a Webastos are designed to work at atmospheric pressure and no more ( maybe a slightly higher header tank ). Engines have a much higher working pressure which is above the hydronic comfortable pressures.

4. Surely having it all in one circuit wastes energy unnecessarily heating up the engine all the time

5. I have cabin radiators higher than the engine expansion tank which makes it impossible to combine the circuit ( Water runs down hill ) If the header is below the heating circuit then it will fill to the brim and the you will lose the engine built in coolant expansion ability .


Joe 917 . I cant work out why your engine doesn't have a header tank for expansion .( the original 917 had one , maybe it has been removed ) If your engine over heated then i think it would blow at one of the weaker joint such as a rubber connection in the hydronic heating circuit. ( Messy ) Your system must be using a cabin radiator as its expansion tank.

It horses for courses, if it works for you then its right. But i am definitely in the keep it separate, independent and simple camp.

hope this helps

Neil

Further details of my setup are on my blog

 

[Joe917]

There is no header tank in the camper, there is one on the engine.

 

[Neil]

sorry joe, that the bit we have mis interpreted.
when you open the cap on the engine header, does the tank have about 50% air space for expansion.
What stops all the fluid in your heating circuit running down into the engine exoansion tank and filling it up to the brim.
I would of thought thst if its all one big circuit then when you take the cap of the engine expansion tank ( which is in a lower position) it would all spill out as water runs down hill.
Just cant work ot out

Neil

 

[Joe917]

No worries Niel, everyone seems to use slightly different terminology. I refer to the Factory coolant loop as "Truck" and the loop in the living area as "camper".
When I pull the cap on the truck expansion tank the coolant is at the filler height, ie correct. The truck to camper valve(T/C) is closed for this. The system has worked for 23 years(lived in full time for more than 20 years). I assume that the air in the truck expansion tank is "locked"as it is at the top of a loop. If I pull the cap with the T/C open coolant may well pour out.
As for your other concerns:
1. Truck to camper valves allow separation of the two loops for servicing.
2. Webasto heaters are designed to pump coolant for large diesels, non issue. The first Webasto on the truck lasted 23 years, replacement had nothing to do with the coolant pump or plumbing.
3. The pex pipe and fittings used all fall within the required spec for pressures and temperatures. Also our Webasto is installed at block height, well below the header tank. It may be useful to note that a 1 atmosphere difference requires 33 feet of head, 2 or 3 feet of height is insignificant as far as pressure.
4. Truck camper shut off valve cuts block out of the heating loop.
5. It may be impossible, but it works.

I offer these observations as a comment on a proven operating system installed by certified Webasto installers.

Cheers, Joe.

 

[Iain_U1250]

I used Stainless Steel braided teflon hose for most of my camper heating system. It is good for a few hundred PSI and very tough. I have three long hoses, all made from the Stain steel braided hose, then six other smaller silicon double walled hoses for the two heater matrices, the hot water tank, the rest is all stainless steel pipe. I have shut-off valves for all of them, and one for the common return line. I also have two bleed valves, to get the air out.

I can shut off the camper heating system, but not the stainless steel braided hoses, I didn't think that was necessary.

 

[drewactual]

curiously enough timing wise to seeing this thread, I've got my espar mounted and the heat exchange mounted, but awaiting wiring harness to complete the job.

f250 with a cap on back... point is to provide engine pre-heating, and warm up the bed/cap for the dogs while venturing through the UP of Michigan over the holidays. Using a d5wz for the job, and tapping into the heater core return for feed/return to the 6.4PSD. I've both a 7 day timer from espar as well as a inkbird thermostatic controller I intend to implement, allowing me several different ways to control it.

the rear heater core is mounted just above the drivers rear wheel hump, which is about level with the engine mounted degas bottle- and something I concerned about, thinking it would be difficult to purge all the air and keep it that way. I use an air-lift tool exclusively for purging the cooling system of air (use it to fill under vacuum), because arguing with trapped air in that thing is zero fun- it was a good investment.

the espar is mounted on the outside of the frame rail laterally almost dead between the front and back door- and it will be the lowest point in the cooling system. it's a pretty well protected area. the exhaust will be pointed in the general direction of the AirDog lift pump mounted slightly behind and on the other side of the frame rail- this ought to keep that filter system warmer than the clouding point but not exactly hot- the exhaust is pointed down via the little muffler, but the heat ought to reflect and come back under the truck and perform some anti-gelling magic.

at any rate, what I settled on to manage the likelihood of air becoming trapped in the top of the rear mounted auxiliary heater core was simple- and I hope it works out. I have two checks inline- one before and one after the rear auxiliary heater core.

the return of the espar/heater core is near the degas bottle and maybe three inches below the highest point. It feeds directly into the engines pump after the union. the ^checks ought to keep the auxiliary heater core purged, and the engine circuit ought not care much so long as the coolant is returned.