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HVAC, Air Conditioners, Aqua Hot, Primus, Webasto, Chassis Heaters, Furnaces and Water Heaters Questions and information about the wide variety of Heating and Air Conditioning as well as Water Heater systems available are discussed here.

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  #1  
Old 05-02-2017
DW SD DW SD is offline
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Default Webasto Thermo Top C installation - Question about Fuel pump installation

Hi All,
I've decided to piece together a Webasto Thermo Top C install for my old PT-35.
This is a small unit ~ 17.5k BTUs and very low draw > 5 amps.

One primary motivation / use case is to use it to heat the marine-style water heater via the coolant loop. I've got a nice solar setup that allows me to keep my batteries charged every day, so running the generator for a few hours to provide 110AC to the heater element isn't a good option.

Second benefit will be to use the diesel - fired heater for the hydronic heaters. I live near San Diego, rarely camp in cold temps. But, if I did, I think this would represent some benefit.

Here is my question for those who have installed similar.

The instructions (see attached) suggest the fuel pump is efficient as a pusher, but not so as a puller. Ideal would be for me to tap the pump after the racor filters. But, this would require 20' draw or so from the tank.

Will this work? Anyone done this successfully? I considered mounting the pump low on the frame with a tee after the Racor filters to take advantage of gravity.

Or do I need to Tee in at the tank pickups and then mount it low on the frame near the tank? Of course, that also necessitates an additional filter before the pump.

Thank you,

Doug
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  #2  
Old 05-02-2017
DW SD DW SD is offline
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I'm assuming those who've installed Aquahot or other diesel fired heater / engine pre-heater systems might have faced the same issue.
Thoughts welcome.

Thank you,

Doug
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  #3  
Old 05-02-2017
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Rick Rick is offline
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I tapped into the fuel supply line before the facet pump and the return at the return line at the engine return line. No problems on a SP.
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  #4  
Old 05-03-2017
DW SD DW SD is offline
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Hi Rick,
Thanks a bunch for the reply.

It sounds like your system has a fuel pump and pressure regulator. The fuel pressure, thankfully, is modulated through pulse width modulation applied to pump voltage, so there is no regulator and return line.

I wonder if my PT has a facet pump? I've never seen it or heard it (or had it go out) and I've been all over below my coach.

I was thinking of tapping in to the fuel line either for the generator or engine maybe the first six feet from the tank.

thank you again,

Doug
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  #5  
Old 05-19-2017
jfrold jfrold is offline
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Did you finish the install? How did it go? Looking for something similar in my FC.
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  #6  
Old 05-20-2017
DW SD DW SD is offline
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Sorry, no progress yet. I will soon be building a setup for bench testing. I want to make sure it works in my garage before installing and then working through issues in my RV.

I do have the unit here with most of the parts, but not plumbing. I have a wiring plug with pig tails I need to convert to a harness.

Probably a month or two is my timeline.

Doug
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  #7  
Old 09-26-2017
DW SD DW SD is offline
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Hi,
I started the process of installing the Thermo Top C. First steps... connect it up, and make it run on the bench in my garage.

I converted an empty 1 gallon ATF to a diesel gas tank, a 5 gallon bucket to a hot water tank. Pulled wiring and plumbing diagrams off the internet and went to work.

A 20 second video of it running is here: https://www.icloud.com/sharedalbum/#B0sJsHvHowNG4c

In 18 minutes, the unit raised the temperature of the water bucket from 73F to 175F. This calculated to just over 4.2k Watts. The unit is rated @ 5k watts. Part of the time was spent at part throttle during warm up and warm down. And maybe I don't have exactly 5 gallons. So that seems in the ballpark.

I also checked the current draw with an inductive unit for my Fluke.. Just about @ 4 amps.

Anyhow.... the unit was purchased one ebay for about $340 shipped and used. Which included the fuel (dosing) pump, coolant pump and harness (which I need to wire in to the bus), mount, exhaust.

I've also had to purchase fuel line 5mm - Diesel compatible (Amazon $20), Coolant flex hose ~ 3/4" - Amazon $50 and $100 or so of wiring supplies between wire, terminals, relays (one of them a programmable timer), a waterproof housing box, and a cool aluminum machined start switch for the interior.

I need to determine the hose size for the inlet / outlet coolant lines to my water heater. And then buy some Tee adaptors to adapt the 3/4" hose from the Thermo Top unit.

Then I need to determine the mounting location and then re-engineer the mount.

Note, I do not plan to heat the in-floor heaters with this unit. At least for now. If I did, I'd build a distribution manifold.

Doug
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Last edited by DW SD; 09-27-2017 at 10:15 AM.
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  #8  
Old 09-26-2017
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propellanttech propellanttech is offline
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Very cool!!
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  #9  
Old 11-04-2017
DW SD DW SD is offline
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Hi All,
I've now got the webasto Thermo Top C unit installed. I bought a programmable relay to be able to turn it on and off remotely and have it run for 60 minutes once the heater is energized. it seems like this will get very hot water in my hot water tank.

The programmable relay came from amazon @ $22. It features 25 different trigger / timer modes. I use a mode which takes a momentary ground input to toggle on / off and on will run for 60 minutes. The timer is programmable up to 1000 hours. The Webasto unit also turns itself off when coolant reaches 170F. And cycles back on when it drops to 145F.

The Webasto unit fit behind the bumper, which is a good location since its exhaust is then outboard of the coach and directly below the heater, so coolant plumbing / integration is simple.

I fed the trigger wire and a power wire for the control button (see ring on aluminum momentary mounted in the bathroom switch panel) which indicates the unit is running. (I eliminated the digicom switch, which was already disabled).

Note, I also added a coolant expansion tank and fill in the water heater compartment. I have always had trouble filling the coolant system to the top, so this serves that purpose well, too. I didn't take a photo of that, but will at a later time.

The unit draws 4.0 amps when running and about 10 amps at startup (maybe 60 to 90 seconds) while the glow plug is heating. This seems very efficient to me, when you consider the coolant pump is also part of this load.

To 100% finish off, I need to add a check valve to the coolant loop and it is completely done. Currently, the hot water takes a path of least resistance and only partially flows through the water heater coolant loop. When I pinched off one of the hoses, it worked much better. I have the check valve, but just need to drain coolant (again), and fit it in. That's another 30 minutes.

Finally, I pulled a 1/4" pipe plug from the 2nd stage main engine diesel filter console. I used a 1/4" pipe to 1/4" barb connection and ran the flexible fuel hose to the unit's pump. Will later add photos of that. I noticed now I didn't capture any of those.

If I were to use this for chassis heat, I'd look in to a manifold used in radiant heat applications. I could then open and close each loop independently. I'd guess based on BTU rating, it'd not keep up with super cold nights for the whole coach, but I bet it'd keep the rear bedroom toasty.

Cheers,

Doug
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Last edited by DW SD; 11-04-2017 at 08:56 PM.
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  #10  
Old 11-04-2017
79Ranger 79Ranger is offline
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This is a great idea, I might just go this route myself....thanks for posting!
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