# Webasto Thermotop C



## bentfinger (Oct 17, 2011)

Can anyone advise me how and where to connect my Thermotop to the vehicle engine cooling system in order to warm the engine for cold starting from the Thermotop.
I should think the hot feed pipe will need to be tee'd into the bottom hose at the engine block end, but am a bit confused about the return pipe.
Also does anyone know where I can buy quality tee connectors. My bottom hose will need a 38mm outside diameter tee.


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## PAT4NEIL (Jul 21, 2007)

I have also been researching this and the answer is don't connect it directly.

You need to keep the engine coolant and the cabin heating coolant seperate .

Some people do connect the two into one big circuit but you often incur problems.

For example If you have a vehicle radiator or hose leak it will make your habitation heating un useable, and vece versa.

You will also have probelms with having two header ( Expansion ) tanks in the system. The vehicle engine one will probably be too high for the cabin heating.

Lastly any engine crap floating about in the cooling system is now going to help to clog up your cabin system

So the solution is that you indirectly connect them via a "PLate heat exchanger so that heat is transfered from one to the other ( either way ) without mixing any fluids .

You will however, need to add a suitable electric water pump in the engine circuit that can be used when the vehicle is stationary to circulate the water around the engine as it would usually rely on a mechanical one that pumps the water around the system when the engine is running.

This method will allow you to heat the engine from the cabin and the heat the cabin and hot water from the engine.

Hope this helps

Neil

Exchanger 

Pump


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## teemyob (Nov 22, 2005)

*alde*

I don't think the poster is talking about ALDE or wet heating.

TM


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## BillCreer (Jan 23, 2010)

Hi,
Yes I think the Thermotop is just for heating the engine coolant for cold mornings. As the cab heater will be nice and warm it will supplement the habitation heater though.


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## BillCreer (Jan 23, 2010)

These people should be able to hep you.


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## PAT4NEIL (Jul 21, 2007)

The Thermotop C by Webasto is a 5.2KW water heater that is used for heating the habitation area via a wet radiator system, It heats the hot water and can be used to pre heat an engine in addition. 

If the OP is just looking to pre heat the engine then 5.2KW is a bit over the top. 

The thermotop C is usually used just like the ALDI heaters but is a Diesel Furnace instead of a gas one. 

My understanding from the Original Post ( I might have got it wrong ) was it was to be used to heat everything including the engine. 

These cost about £1000 which is a lot of money to just pre heat an engine. 

Neil


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## wray90 (Nov 3, 2008)

From what I understand the Thermo Top C just heats the engine coolant, which will heat the engine & the cab heater element. 
If you want to be able to just heat the cab, Webasto do a motorcaravan kit so that you can heat the cab or the the engine & cab.
It is also possible to integrate this into an Alde system.
See attached Webasto information sheet!
Last year I did look at fitting a Thermo Top C into my Alde heating system (which has a plate heat exchanger linking the engine coolant to the Alde system) but was quoted £1900+VAT so never got around to doing it!


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## trek (May 1, 2005)

To answer bentfingers question - 

Note this is for engine preheat & the cab heating combined as the heater will be inserted into the engine cooling system

it is not for the caravan side of things - which of course it can do - but thats not what the OP is asking for

simply fit it in series with the pipe going from the engine to the dash heater matrix !

in my opinion you need to find the two pipes in the engine compartment near the bulk head at the rear of the engine that feed the dashboard internal heater matrix .

find out which is the flow from the engine to the heat exchanger 

from cold you may be able to detect which of the two pipes warms up the quickest, then break into this and insert the Webasto (or Eberspacher ) ensuring that the webasto's own pump will pump in the same direction as the flow from the engine into the dashboard heater matrix

you do this easily with lengths of hose running from wherever you site the webasto and without cutting the original engine coolant hose (so it can all be removed when you come to change the van) just remove the identified hose from a fitting, connect one of the hoses from the webasto to that fitting and the other webasto hose to the hose end that you had disconnected using a straight coupler - remember to ensure that the webasto pump pumps in same direction as the flow when the engine is running

In operation on a cold morning when you want to prewarm the engine AND heat up the cab you just fire up the webasto - if its been wired up correctly to the heater matrix fan / blower will start up when the webasto is running & blow hot air into the cab space - if the air is set to demist it will easily clear ice & snow from windscreen, the warm water then passes through the heater matrix off around the engine to warm that for easy starting & back to the heater

its a fantastic piece of kit & once bought you keep it & just remove it from the old vehicle & fit it to the new one 

just this weekend I removed my thermotop P (I originally bought the P for a Iveco camper) from my 1.3 litre punto as I'm changing it & will fit it onto the next car, its great going out on an icy morning to a warm car thats all de-iced by the heater & has a warmed up engine that starts straight away

but the odd thing about this is that the seats remain cold until your backside warms it up - maybe some seat warmers next time


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## trek (May 1, 2005)

see page 37 in the english section of the thermo top C installation instructions

also added a document that shows tips on how to connect the fuel source - often the trickiest part in my opinion


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## bentfinger (Oct 17, 2011)

thanks for all that guys. I originally fitted the Thermotop 4 years ago for water and space heating in the back, and has been very good. And always had the intention of connecting it to the engine, but put it off as not being important then.
And of course have left things rather late because I now want to drive the van up to the north of Norway this winter.
So I have decided it really is too late to start messing with the cooling system in this way.
Instead I'm getting an electric heater fitted into the bottom hose, which should be a more straight forward job.
So, just another project for another day.


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## trek (May 1, 2005)

Hi Bentfinger 

from what you have just told us I assume you still have this webasto fitted to the caravan for the habitation (heating && hot water)

& that you intend to use this one heater for the engine as well as continuing to use it for the rear


I originally assumed you were fitting one from scratch just for the engine 


-So what you need is a heater exchanger a 12v pump and some piping 

the one side of the heat exchanger fits in series into your original caravan heating circuit 
the other side you plumb into the cab dash heater matrix & include the pump - all in series with the heater matrix 

so to heat the engine you switch the rear heating on and also the 12v pump


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## PAT4NEIL (Jul 21, 2007)

Didn't I suggest this earlier but was shouted down telling me I had mis understood the original question..

Oh well

Neil


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## bentfinger (Oct 17, 2011)

Trek & pat4neil, ok cheers for that. I will be doing this next year. 
1-- will a plate heat exchanger allow heat to flow both ways--from the thermotop to warm the engine, but also from the engine to warm the back of van.
2-- the thermotop has a built in pump and sends the water around now, will that be enough to pump around the engine as well without fitting an extra pump.


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## BillCreer (Jan 23, 2010)

PAT4NEIL said:


> Didn't I suggest this earlier but was shouted down telling me I had mis understood the original question..
> 
> Oh well
> 
> Neil


Hi Neil,

I am in awe of your telepathic ability.


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## PAT4NEIL (Jul 21, 2007)

Bentfinger

You will still need an additional 12 volt pump as per my original link if you want to keep the circuits seperate and want to pre heat th engine from the webasto

Neil


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## trek (May 1, 2005)

Bentfinger 

Yes to Question 1:
NO to Question 2:

don't combine both engine & heating circuits into one !


your engine coolant system is under pressure 

your existing caravan wet heating system is not

keep them as separate circuits 

but link them together using the heat exchanger that has previously been mentioned ( I bought mine from ALDE UK)

as has also been mentioned the 12v pump built into the webasto will circulate the water/antifreeze mix around the caravan heating circuit when the webasto is running

the extra separate pump will pump the engine coolant around when the engine is not running but when you want the caravan heating to pre-warm the engine or get the residual heat out of the engine when you first stop on a site 

to get the rear caravan heating to work when the engine is running ( the new extra pump would be left switched off & would not be used during this operation) you would also need to switch on the webasto's pump but not the webasto - so an new switch & 12v supply would be required to get the webasto's pump independantly of the webasto itself


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## trek (May 1, 2005)

Bentfinger

you asked for a source of T pieces

I have used on my car Tefen connectors - they are plastic & come in various sizes

buy them at your local motorfactor if your lucy or online eg:-

Tom Parker :TEFEN connectors

or use the orginal Webasto or Eberspacher connectors but these can be expensive & difficult to source

try ebay or look online for a German retailer
eg:-
Ersatzteilbox German online retailer
this company also sell various valves / one way valves / themostatic valves that control the direction of flow and allow different circuits to be constructed -but these can get complicated & are not cheap


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## bentfinger (Oct 17, 2011)

ok guys, well thank you very much for all that. You have all given me a lot of information and also the confidence to do it. 
But it will have to be next year now


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