Pex or Silicone Hose for Webasto

[Homegrowndiesel]

Hello John

My 2 cents worth.
   Pex is made for these temps 160-180 & heater use. I used equal pex and regular heater hose, some copper & a Little Silocone which can be a pain to seal at the joints even with the best clamps.

Dont forget the circulation pumps on the heat exchangers (of either engine you want to heat) if your keeping everything (coolant systems) seperate. And do not forget a heat exchanger for your potable hot water, that one you will never regret.

Drill a 3" hole out the bottom in either bay, run the exaust straight thru & the rest is the makeup air for combustion. I like the wet bay as it keeps the tanks from freezing without a heater in that bay.

Do Not put it in the engine compartment if you are going to be sleeping overtop (the noise from a dead quiet to the webasto burn makes for a fitfull sleep). Do mount it on rubber isolation mounts to lessen the high pitched gear noise.

I ran my fuel line seperate, I have seen some that used the same line work.

I do not find many spots that have off road fuel easily available but your situation may be (is) different.

Decisions Decisions


Bill Glenn

[CindyandJohn]

Hi Bill,

Thanks for the insight. I haven't heard from you guys in a while... We need to get ourselves back down there. Cindy and I have a case of some great Vino for Roberta! We hope to come around in a couple weeks or so.  Cindy said to say hello to you guys too....

I'm leaning towards the pex... At this time I am not going to plumb in the hot water heater... I have a tankless propane that has been working well since I worked out my kinks in the feed lines.

 If the exhaust from the heater is quite high - do you think some capture of that heat could be cycled back into the system? I have been kicking the idea of mainly using the generator as my heater since I run it most of the time. The webasto is more or less a secondary heater, block heater, and a reason for me to fix my dash defrosters... I was thinking of installing in a water bay area for the heat capture, but it will most likely be inside the open area with my generator... it is a much more accessible space. so many ideas - so little time....

Thanks,
John

[rv_safetyman]

Ski, I am very surprised at the Aqua-Hot recommendation.  When I got my system from them, it came with PEX.  If you look at the Aqua-Hot installation in most new premium coaches, I think you will find that it was done with PEX. 

I used PEX on mine for the domestic and heating systems, with a little heater hose for connections.  I made some 90 degree bends with copper and hooked them in with heater hose - some heater hose over the pex (using internal ferrules).  For the engine connection, I used some very premium heater hose (did not want to take a chance there).

We are still in Europe, so I can't contact my top level Aquahot application person by phone, but I think he would confirm that they still recommend PEX.  I have written him an email with this tread link.  If he does not reply to the thread, I will post his email reply to me.

Jim

[CindyandJohn]

When using Pex - is the larger the diameter the better - 1" vs. 3/4" ? I read somewhere that the larger the Pex the higher the BTU's produced? At least that was my interpretation of the thread. Thoughts on this?

Thank you for all the greart input.

John

[JackConrad]

Not sure about producing more BTUs, but most of the diesel fired boiler systems, require a minimum amount of coolant to prevent the pump from short cycling.  Don't ask how I found out about this. Larger diameter would increase the system capacity. With 1 engine to proheat heat exchanger, 3 heat exchangers inside the bus and 1 heat exchanger in the water bay, we still had to add a reservoir.

[CindyandJohn]

Thanks for that insight Jack... I will take that advice to heart... and as with most things in a bus - Bigger is Better!!!

John

[buswarrior]

Don't be afraid to tie the Webasto fuel lines into your generator lines, and keep its exhaust seperate.

I know a coach based command vehicle application that ran two 8k generators and a 300 BTU Webasto off the same length of plain old skinny fuel line.

A Webasto doesn't need to run through a muffler, not really much sound there to muffle, and you'll introduce restriction that is verboten.

The Webasto in with the water tanks is a mixed blessing...the Webasto needs air to breath, introducing the frozen air to the tanks... and if you are tying in the generator waste heat, your goal will be to keep Webasto burn to a minimum, so it might not do the job?

I'd consider losing the heat in the exhaust from the Webasto as the cost of doing business, the generator waste heat is far more readily captured without a penalty and is available for longer amounts of time.

Adding a water bed electric heater to the water tank compartment so as to give the generator some load...and add some redundancy... how to keep the tanks from freezing under various inconvenient circumstances, or failures...

Lots more for a cold weather busnut to have fun with in the calculations!

happy coaching!
buswarrior

[rv_safetyman]

OK, we are back in the good old USA (over 24 hours of travel yesterday )

I did receive a reply from Aqua-Hot and it has some good information. 

Here is a synopsis of the reply I got from the lead Technical Sales Representative at  Aqua-Hot Heating Systems Inc.

1)  PEX is rated for ***80 PSI ***at 180 degrees. It doesn't mean that the PEX is rated at 180 degrees.  It is a qualification for pressure rating.

2)  The Aqua-Hot 675 to 375D models use a 0 pressure system. The pre 2008 units use a 13 lbs system. PEX is JUST fine!!

3)  If heater hose is used in an  enclosed living quarters AND is heated above 180 degrees, it will give off a smell and may cause headaches. (physical). The silicon heater hose is designed to resist abrasions but with temps over 180 degrees, water starts to permeate the hose and it sweats creating the same conditions as heater hose in a enclosed living quarters but more noticeable.
 
4)  The Webasto cycles between 145 to 167 degrees. The Webasto uses engine coolant which will be heated to engine temp. which can exceed 200 degrees. For the engine connection a good quality heater hose with 3/4 ID is just preferred  because of  the vibration of the engine along with the twist of the coach.

5)  Aqua-Hot uses heater hose in connections inside the cabinet of the unit and the transitions between the PEX tubing is 5/8 ID x 3/4 OD and Cozy exchangers.

6)  They recommend 5/8 ID x 3/4 OD PEX tubing .

I questioned my contact about the heater hose smell and the silicone hose issue.  In a subsequent email, he mentioned that in one coach had used silicone hose and, because of a customer complaint of headaches when the Aqua-Hot would come on, they did a thorough investigation using what sounds like a sophisticated "sniffer" and found that the silicone hose was "off-gassing".  They replaced it with PEX and the problem went away.   He has also seen the silicone hose change color from the coolant permeation.  As a longtime hose guy, I have not seen that, but my contact is very reliable and I will defer to his experience.

Jim

[CindyandJohn]

Jim,

Thank you very much for this information. I too will accept your contacts professional information... It sounds like some good Oxy Pex is the best way to go.  I agree with the connection to engine using a quality hose... that makes a lot of sense.

I will let you know how I make out.

Thank you,
John

[belfert]

How are folks dealing with the transition from PEX to heater hose connections on the heat exchangers and at the diesel heater itself?  I physically looked at Brian Diehl's system and he uses heater hose the last few inches, but he is also saying that is where the leaks are.

[rv_safetyman]

Brian, a short piece of stainless steel tubing is inserted into the PEX.  That keeps the PEX from collapsing.  The heater hose is then placed over the PEX and clamped.

The inserts that Aqua-Hot sells are really neat.  I ran out and ordered some from another source (can't remember who) and they were not as good.

Aqua-Hot uses constant tension clamps (the type you apply with pliers).  I have used them with no problem and also worm clamps.  I have had leakers in the past.  I go back and make sure the PEX is clean with no burrs and then sometimes double clamp those, or go to worm clamps and tighten them pretty good.   With worm clamps, you have to go back and tighten them periodically, as the rubber in the hose tends to "creep" a bit.

Jim

[CindyandJohn]

Is it possible to use those shark bite compression connectors to go from PEX to a barbed hose nipple? Then use hose clamps... or to use a threaded end if the heater is so equipped. Does anyone know if the shark bites are good for the heat of the system? Just more thoughts to make it easier. I know they aren't cheap but they sure are easy to install.

John

[Ednj]

John,
I have them threaded right into my hot water heat exchanger and they are working just fine.

[luvrbus]

John, find a plumber and see if he will lend you his expander and you can slip the PEX over the pipe on the exchanger and crimp it I watched a RV dealer do this because of leaks with adapters.Oh yea Jack another tool for Pex