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Which webasto thermo top C water heater is really marine?


wetfoot

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I am getting quite confused trying to buy a Thermo top C water heater for a 50 ft wide beam canal boat.

I know I need a Thermotop C heater that will tolerate a lower battery voltage for use in a canal boat rather than a vehicle.

I understand that vehicle types will shut down at around 11.8v so that there is still some PD left to start the engine whereas 'marine' ones have a different ECU and can go as low as 10.5v running on leisure batteries. I want the latter one, the one that goes down to 10.5v..

 

But this is where the confusion sets in.

 

ButlerTechnik sell a 'marine' one referred to as the Thermo Top C 300 here with a Webasto product code of 41K5083C.

They also sell one that does not include the word 'marine' as product code 9003168C

 

Page 30 of Webasto's catalogue here  agrees that the 41K5083C is a marine kit and the 9003168C is for vehicles.

 

However, it also says on page 33 that the Thermo Top C 300 is for motorhomes  so I'm confused as to whether the 300 really is a marine model or not.

 

To add to the confusion, page 30 of  Webasto's catalogue also lists what it calls a Thermo Top C Narrowboat kit with a product code of 41K5037C

So Now I'm confused as to the difference between a 'marine' one and a 'narrow boat' one.

 

Several other sellers sell what they call 'Thermo Top C marine' without even mentioning 300.

 

Is there anyone on this forum that really understands all this and can tell me exactly which model to get for the narrow boat running off two big lithium leisure batteries?

 

(I did try to contact Webasto themselves but they don't seem to want to talk to private customers, just re-sellers)

 

 

 

 

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One thing to bare in mind is that, as I understand it, the firmware can be deprogrammed to marine spec. so as long as the auxiliaries like the exhaust are suitable then some vendors may be selling ex vehicle units that have been reprogrammed.

Edited by Tony Brooks
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58 minutes ago, wetfoot said:

 

I understand that vehicle types will shut down at around 11.8v so that there is still some PD left to start the engine whereas 'marine' ones have a different ECU and can go as low as 10.5v running on leisure batteries. I want the latter one, the one that goes down to 10.5v..

You do. But you do understand that if you do that to your batteries you will also need new batteries, right? It's about meeting the lower threshold voltage to allow the unit to start as they are quite voltage sensitive.

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I always fail to understand why peeps want a unit that will run at 10.5 volts? At 10.5 volts you will need to replace batteries as often as diesel. I never run my webasto pr anything else for that matter below at worst 12.1 usualy higher than that. If you think you need to run one down at 10.5 then what you realy need to address first is your battery bank/storage/charging.

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56 minutes ago, mrsmelly said:

I always fail to understand why peeps want a unit that will run at 10.5 volts? 

I'm not surprised that you fail to understand why peeps want a unit running at 10.5v nobody would!

 

I don't want  it to run at 10.5v  - I'll be running it on standard 12v Lithium leisure batteries which I hope never drop too much below 12V.

 

The issue with the vehicle version appears to be that the ECU assumes you are using the same 12v lead acid battery as that used for starting the engine. So the heater ECU will turn off the heater if the PD drops below 11.8v in order to save the battery and allow you to still start the engine. (a PD of 11.8v can happen quite normally in a vehicle, especially during starting on on heavy drain)

 

The marine ECU assumes you are running on leisure batteries that are not also used to start an engine and so it is more forgiving and doesn't shut down the heater until the PD drops to an alarmingly low 10.5v, something I hope my lithiums never do, although they could drop below 11.8v during normal operation. 

 

So maybe instead of saying I need one that can go down to 10.5v maybe I should have said I don't want one that shuts down at 11.8v

 

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I had experience of fitting the vehicle kit to narrowboats when they first became available. They are more reliable running on red diesel than Eberslashers.

This was because they were considerably cheaper. We did not use the fuel pickup fittings or the exhaust "silencer" ( useless anyway, far too noisy)

We made a proper fuel connection and fitted a car exhaust silencer.

They worked fine, very quiet, but on hire the complaint was that they only worked with the engine running or for a short time after running.

This was due to the leisure batteries not being fully charged or discharging by the hirer running the inverter and lots of lights, pre LED days.

Reprogrammed to the lower knockoff voltage they were fine.

They need substantial battery cables to avoid volt drop when the ignition is running.

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