Getting cold - need heat

[Geoff]

Generally you have 2 options for temperature control for the Webasto itself.  The Temperature Control Thermostat comes in 167 degree or 158 degree versions.  There is also a Temperature limiter that is set for 203 degrees.  Then if things really go sideways and you manage to get to 280 degrees, the over heat fuse blows and you get to spend $100+ for a new one.


   

I blew so many overheat fuses due to air locks I installed a 205f N.C. engine overheat switch in the output hose of the Webasto.  Now I run the circulating pumps before turning on the Webasto until I can hear that all the air has been purged.

[windtrader]

In the on-hand Webasto documents, nothing provided on the internal workings of the heater. The complete repair manual is available online. I'm sure the answers lie there.

Usually it is great having documentation supplied with the conversion. Sometimes too much documentation is confusing. Finally, after reconciling the different versions of the design and the actual inspection (pictures) of the as built coach heating system, the following diagram reflects the best take of how it actually is plumbed up.
'
https://www.dropbox.com/s/wx0ujdcvsxwwlbk/Coach%20heat%20As%20built.png?dl=0

Update:
Reviewed the factory service manual. Following are references to the control aspects of the heater. There is a control unit that manage the heater through the attached sensors. It seems the magic number for heater shutdown is 167, what was mentioned earlier.

From the service manual
For control and monitoring, the heater includes:
– a control unit
– an overheat fuse (non-reset)
– a temperature limiter
– a temperature control thermostat

test switch/ timer
- test control thermostat on heater Normal operating range
- approx. 75 °C (167 °F) or higher
open (no heat required)
- approx. 68 °C (155 °F) or lower
closed (heat required)

Since the heater operates in the 68 °C
(155 °F) to 75 °C (167 °F) On to Off / Off to On
range, and the vehicle engine may be hot [e.g.
coolant above 75 °C (167 °F)], the heater will
not start until the coolant temperature is below
68 °C (155 °F). THIS IS NORMAL and does not
indicate a problem.

[richard5933]

Richard, I think the interior thermostat only controls the heater fans.  The Webasto should be independently controlled by an off on switch that cycles based on coolant temperature.  There is nothing wrong with my system, I was just wondering about what everyone else posted that doesn't ring true.   

Like I said, they are all installed differently. On ours when the temp setting on the thermostat was met the control box on the Webasto had the power cut and it went into a controlled shut down procedure. Only if the engine pre-heat was turn on did the thermostat act like yours.

But, if your system is installed in a way that the thermostat only controls the fans your Webasto will certainly cycle on/off quite often when the interior fans are not running. There will be nothing to dump the heat from the loop. If your high & low temp settings on the coolant loop are close together you can expect an even shorter on/off cycle. It won't take very much firing of the Webasto to bring the coolant temp in the loop to the upper limit.

If you ever plan to dry camp and run the Webasto just on 12v this setup will drain your batteries pretty quickly. Not sure if there are changes on your system that can be made to reduce power consumption. Not sure if you need or want to make the changes. That's up to you.

Also, if you get air locks in the system between running the unit then you might have a leak somewhere or may not have fully purged the air from the many places it can be trapped. On ours, once I got the air purged from the system I did not encounter any additional air locks. This did require me to burp a few of the lines and the move them around to encourage air to go to the bleed point.

[Geoff]

Thanks for the advice, Richard.  However, I have had my Webasto for over 15 years and I know exactly how it operates.  I do my own maintenance and repairs and it works exactly like it should.  I don't have any problems anymore.  Again, thank you for your help!!

[thomasinnv]

Every aquahot/hydrohot or hurricane packaged system operates the same way as far as what the thermostats do. The main diesel switch turns on the system, control thermostat is mounted on the burner unit or the tank and controls the burner according to coolant temp, wall thermostat controls zone pump and fan. Having the wall thermostat control the burner operation is not optimal system design and no manufacturer of packaged systems will build it as such. The only reasonable exception imho would be a home built system with a single heat zone and no buffer tank.

Having said that, everyone has their own ideas and opinions. Your bus, your way.

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