Why do Webastos need "resting"

[Nickhlx]

In my quest to find out what system(s) to instal for space heating and water heating, I keep coming across the "recommendation" to "rest" a Webasto... Errr... why ?

 

I can see that if you turn a boiler off for say 12 hours every 24 hrs, the service interval ( if based on hours) will only come around half as often - so if this was the reason and you didn't "rest" it, expect to service twice as often - fair enough. But I get the impression that if you don't rest them, they will go wrong / coke up etc...

 

So I wonder if there is some procedure they go through on cooling down or on start up ?

 

That all said, I expect our use to be "normal" - i.e on for a few hours at each end of each day for most of the year, possibly a bit more over the winter months, and possibly on a low tickover to keep damp / frost at bay when away from the boat in the depths of winter.

 

Does not the normal "cycling" constitute "resting" or does it actually burn continuously, like a wick-fired oil AGA, perhaps modulated by external controls ? ( never had / seen one in action)

 

 

Thanks,

 

Nick

[chris w]

The reason (as I understand it) is to ensure the Webasto fires up at full heat in order to help reduce carbon deposits.

 

In normal use, the Webasto will come on at full bore (0.5 litres of diesel/hour) only at initial start up for about 20 minutes. Once the water gets to 62C the Webasto cuts down to half power (0.25 litres of diesel /hour). From this point onwards, it stays at half power till the water reaches 72C at which point the Webasto switches off and "idles" (just the water pump stays ON). Once the water cools back to 62C, the Webasto comes on again at half power and so on ad infinitum. Should there be a heavy demand for heat (eg: a couple of additional rads are switched on) and the water should cool to 56C, the Webasto will come back on at FULL power.

 

However, under normal circumstances, once through the initial 20 minutes or so, it never comes back on at full power. The resting peiod is to allow the water to cool right down so that the Webasto fires up next time at full power.

 

Chris

[saltysplash]

I have no idea, but i do know that my webasto on my old tub was designed for motorvehicles, ie coaches and hgv's and not designed to run for prolonged periods, having said that, the only probs i had was having to replace the fuel filter every 6 mths...an thats down to the tank, not the webasto........dont forget....like houshold domestic units, we never ever have problem with them during summer...but come winter.....they always play up when we need em the most....maybe its lack of use that causes the faults?

[Nickhlx]

Thanks for the replies...

 

I have not had a problem with our GCH boiler in ? 15 years apart from the well known PCB failure - but replaced that and no problem since ( 10 years) ( Potterton Suprima)

 

Chris.. that seems a very acceptable reason for the ? resting ?... so, can I assume a suitably big calorifier in the hot tank will hold it at full power whilst the tank heats up, returning water at below 56 deg C, whilst the hot water comes up to temp ? Or perhaps a manual over-ride switch to open up a valve to divert the returning water through the rads to ensure it is cooled enough to force it to stay in high power mode until the hot tank is up to temp ? - bit of a pain in summer - perhaps the overide can be done in the Webasto or somewhere around the circuit at say ? 63 deg C or whatever is appropriate to hold it at full power - safety over temp switches deployed as necessary ! Maybe just a timed override for say 20 mins or so?

 

I think I can see what is needed so "fiddlable" with if necessary...

 

Thanks again,

 

Nick

[denboy]

best advice don`t fit webasto or ebers