Diesel Hot Water System

Submitted: Saturday, Jun 20, 2015 at 00:05
ThreadID: 119238 Views:1716 Replies:1 FollowUps:7
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What is the best percentage of glycol to use in a Webasto Thermo Top 90 diesel system that heats water through a heat exchanger? I see that standard glycol is 65g/litre, but there are concentrates 5 and 9 times that. Will the concentrates heat the water faster?
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Reply By: Ozhumvee - Saturday, Jun 20, 2015 at 08:39

Saturday, Jun 20, 2015 at 08:39
I had the same problem when I installed my Thermotop about 4 years ago, couldn't get a definitive answer from anyone including Webasto.
As they can be installed in conjunction with the vehicles existing cooling system to preheat the engine and lots of Australian based vehicles run a 50/50 mix I put a good quality 50/50 premix in.
Increasing the glycol content doesn't necessarily increase the heat transfer capabilities as pure water is actually a better conductor of heat, you are basically wanting to raise the boiling point a bit and prevent corrosion.
As we rarely encounter the frigid temperatures encountered in very cold climates the 50/50 mix has worked ok for our setup in the Oka. It is standalone and not hooked into the trucks cooling system.
Peter
1996 Oka Motorhome

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Follow Up By: PhilD - Saturday, Jun 20, 2015 at 09:00

Saturday, Jun 20, 2015 at 09:00
Thanks Peter. When you say 50/50 is that the standard mix available off the shelf. I have put Tectalloy 60 in at present which has 65 g/litre of glycol from memory.
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Follow Up By: Ozhumvee - Saturday, Jun 20, 2015 at 09:19

Saturday, Jun 20, 2015 at 09:19
Yes I just bought the premixed Nulon coolant.
I installed the system and as I had no real idea of the total system coolant capacity apart from the actual header tank,thermotop and calorifier, the hoses and heater core capacities were unknown.
Add to that the header tank access is under the bed and I didn't want to make a mess it was easier just to pour the right concentration in directly from the container.
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Follow Up By: HKB Electronics - Saturday, Jun 20, 2015 at 10:41

Saturday, Jun 20, 2015 at 10:41
The same here premixed containing with anti freeze, the anti freeze to protect the unit but if you have a water heater then you would also need to drain the water so probably easier to leave the heater on a very low setting when freezing likely whilst camping. The thermo tops only heat the water to 70C from memory so boiling should not be an issue.

One thing I did notice but may be my imagination, it seems the higher the percentage of glycol the more likely you are to get seeping.

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Follow Up By: Ozhumvee - Saturday, Jun 20, 2015 at 13:16

Saturday, Jun 20, 2015 at 13:16
HKB is right, the higher the glycol percentage the higher the chances of leaks, too much and you can get problems with different metals in the system too.
The water heater never gets drained due to possibley freezing as you just run it before going to bed and it is well insulated so won't freeze in our climate.
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Follow Up By: HKB Electronics - Saturday, Jun 20, 2015 at 15:10

Saturday, Jun 20, 2015 at 15:10
My heaters under the camper so is exposed to the elements.

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Follow Up By: HKB Electronics - Saturday, Jun 20, 2015 at 15:11

Saturday, Jun 20, 2015 at 15:11
Should have added, so is the hot water heat excahnger though it is wrapped in a neoprene Jacket.

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Follow Up By: Frank P (NSW) - Saturday, Jun 20, 2015 at 15:32

Saturday, Jun 20, 2015 at 15:32
The van manufacturer (Kimbewrley Kampers) who installed mine told me they use SCA pre-mixed coolant (from Supercheap!).

I haven't had any problems in 8 years.

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FrankP

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