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Broughton 2

Webasto and room stat control

14 posts in this topic

Has anyone out there run a Webasto (Thermo Top C) or Eberspacher water heater through a simple on/off switch and room stat for central heating application? If so then how did you get on with it?

 

I'm interested to know mostly because I would prefer not to run the webasto water pump when it's not really necessary, i.e when a set room temp is achieved and no further heating is required.

 

I believe Webasto Air Top heaters can be run through a room stat. so why not Thermo Top?

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If you go down this route, you must ensure that the thermostat does not switch the Webasto off before it has been able to do a fuel purge. Otherwise, if you suddenly remove the power from the Webasto, you will get clouds of white smoke billowing out of the unit due to unburnt fuel vaporising, but not burning, in the still extremely hot burner unit.

 

Chris

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If you go down this route, you must ensure that the thermostat does not switch the Webasto off before it has been able to do a fuel purge. Otherwise, if you suddenly remove the power from the Webasto, you will get clouds of white smoke billowing out of the unit due to unburnt fuel vaporising, but not burning, in the still extremely hot burner unit.

 

Chris

 

Thanks Chris.

I assume a room stat could be somehow wired in to do that but how?

 

When it reaches the off time setting does a Webasto clock timer send a signal the burner to begin it's purge program? If so then could it be the signal is simply loss of current from the timer (but not loss of power to the burner) and if so then same loss of current from a stat would do same provided the stat is wired to same connection(s) at the burner as would be the timer? I'm guessing of course!

 

Alan

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Yes the timer sends a purge signal. I haven't looked into how it does this, but it will doubtless consist of a simple 0 or 1 on one of the pairs of wires. The thermostat could indeed mimic this. I will have a look at the circuit of my Webasto but it won't be for a couple of weeks.

 

Chris

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Yes the timer sends a purge signal. I haven't looked into how it does this, but it will doubtless consist of a simple 0 or 1 on one of the pairs of wires. The thermostat could indeed mimic this. I will have a look at the circuit of my Webasto but it won't be for a couple of weeks.

 

Chris

 

 

Chris

I appreciate your help and look forward to your comments in a couple of weeks time.

 

Alan

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Joanie M has a simple switch with a red LED indicator located in the bedroom to switch the Webasto on or off. This has only 3 wires, 12v in, 12v out and neg. I assume it is simply piggy backed onto the Webasto timer unit. When you switch the heating off the Webast runs on for a minute or two.

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Joanie M has a simple switch with a red LED indicator located in the bedroom to switch the Webasto on or off. This has only 3 wires, 12v in, 12v out and neg. I assume it is simply piggy backed onto the Webasto timer unit. When you switch the heating off the Webast runs on for a minute or two.

 

 

Thanks Pearley. Seems like a room stat could indeed operate the Webasto if wired in place of your on/off switch. Do you know if the 12V in and neg are direct to battery or through Webasto wiring somehow? Also where the 12V out is wired to?

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Ive tried wireing in a room stat but it works for a while and then on the 2nd or 3rd time of turning off when the temp set on the stat is reached it does not turn back on. I get the feeling I have either wired incorrectly or the webasto start timer has done its 3 starts then will not start again ? is there a way of clearing the 3 programed start times so that it just starts and stops when the temprature reaches or falls below the set temperature  ?  Any advise gratefully received ...............

thanks

Gal.

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I have one of these for hot water/heating but Webasto's/Eberspachers don't like to be run for short periods of time and/or at reduced power. As such I have set mine to operate at maximum power early in the morning to heat up the water and in the afternoon to re-heat water. If I need heating, I put it on override outside of those timeframes until the boat is warm enough. - this works as it never reaches its maximum setting of 30°C except during the summer as it's a little underpowered for the size of boat.

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5 hours ago, Gal said:

Ive tried wireing in a room stat

You must not run a Webasto/Ebberspscher from a room stat. They do not like short cycling.

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1 hour ago, WotEver said:

You must not run a Webasto/Ebberspscher from a room stat. They do not like short cycling.

Agreed 

I have no idea whatsoever as to why folk constantly want to mess around with kit on thier boats . Webasto & eberspatchers are complicated enough as it is . Start messing around with the wiring and its tantamount to inviting trouble at some point . If it starts short cycling & cokes up inside then you 'll be pulling it apart or worse - paying someone else £60 p/h to pull it apart , to replace bits  & bobs inside & clean out the carbon build . 

I pulled mine apart 3 years ago & im in no hurry to do it again .

To use it i follow this procedure : I press the ON button & leave it for one hour . 

If it aint broke ............ 

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I concur with the above. Switch it on and leave it on. If boat gets too hot we simply open the doors till it cools off again, its only background heating as the stove is for full time use. Our webasto never cycles, if yours is cycling you aint got enough radiators.

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Webasto do not make a thermostatic control for water heaters and specifically discourage their use, in fact if you fit one to a new one you will put the warranty in jeopardy. They cause short cycling and increase service costs, all the water heaters with the exception of the larger Pressure Jet models are designed to be run for a couple of hours at a time and not used like a central heating system. The wiring to fit a thermostat would be dead simple though, its simply a +dc to run and 0v to go into shutdown mode.

 

 

Edited by NMEA
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Thanks for all of your replies. I will be getting a coal/wood burning stove but not ready for it yet. I will remove the room stat and stop touching stuff that I dont understand ...............................

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