Webasto confusion. HELP!

merl

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Hi all.
I wonder if anyone with experience with using a Webasto dual top heater in the winter can help.
My problem/concern centres around the instructions saying that the heater will automatically drain the hot water storage tank if the temperature drops below 6deg C under certain heater settings which aren't particularly clear. It also says that there is an 'anti freeze mode' where the heater "functions in the same manner as for winter, heating with hot water production mode, but with values below the air and water temperature". Again not really clear.
Can anyone with experience of using a dual top Webasto in a cold climate pass on their experience of how to prevent frost damage to the unit and ensure there's not an 'automatic' loss of all stored water.
Thanks, Merl
 

witzend

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When using my van during freezing conditions I leave the heating on overnight and to stop the water dumping on my older type valve it just requires a clothes peg on the valve to stop it dropping and allowing the water to escape.
Picture is of the newer type valve which can also be blocked but I can't advise how
3010431-800px.jpeg
 

SimonM

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When using my van during freezing conditions I leave the heating on overnight and to stop the water dumping on my older type valve it just requires a clothes peg on the valve to stop it dropping and allowing the water to escape.
Picture is of the newer type valve which can also be blocked but I can't advise how
View attachment 103737
It looks similar to mine, does it have a plunger that comes out when the blue knob is turned?

If so, on mine I have a piece of dowel against the wall wedging it shut. A bit bodgey but it works.
 

witzend

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images.jpg
Heres the earlier valve pull the red knob up an secure with a clothes peg
 

merl

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Our heater is underslung and I cant see any control valves as pictured.
FWIW I tried the 'drain function' that's controlled from the main control knob and although the control panel appeared to show the correct light sequence for a 'drain down' I didn't get any water out of the unit at all. I'm sure that my underslung unit either doesn't actually drain at all or the function has been disabled either from the manufacturers or by the previous owner, this notion is further supported by the van being supplied with a device that attaches to a male thread of a washing machine type valve on the water system and has a schrader valve on the other end which allows the tank to be blown out and emptied with pressure from a tyre inflator.
Thanks for the replies, my mind has been put to rest. Just got to remember to keep the heating ticking over CONSTANTLY when using the van in potentially freezing conditions and drain the tank when laying up.
Cheers everyone.
 

Mpdyork

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If you have no water showing when switched to drain down it’s more than likely the drain it’s self is stuck due to limescale buildup. The unit will also dump water if voltage drops below a predetermined point again to protect the unit. If you’ve never had the unit serviced I would recommend viewing webasto website full instructions are given on descaling unit. To give you more info I would need to know what controller etc you have fitted as there a few different options. FYI I am an approved service agent for webasto. HTH oh and please don’t “override” the system as these tanks easily split with frost and are very expensive to replace
 

merl

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Hi Mpdyork, thanks for the reply.
The unit is described as a 'Dual Top'. A pic of the control panel is attached.
I cant find any info on my unit or descaling on the webasto site anywhere, I'm probably not looking in the right place?
Previous posts have lead me to the conclusion that the I actually need to block off the drain outlet anyway so to be honest so I'm not particularly bothered about getting the automatic drain facility functioning 'properly' because ultimately I'll need to disable it anyway!
I'm the 2nd owner of the van so obviously don't know it's use history, it's 9 yrs old, 26k miles and the interior condition indicates that the van hasn't been used a lot, the tap spout outlets don't have any limescale deposits so I'm thinking that the limescale build up in the boiler will be slight at worst? I'm obviously quite wary about putting chemicals etc through the system if there's no genuine benefit to be had.
From your experience what happens / fails when a unit isn't descaled?
Merl
 

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merl

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Draining isn't an issue, as mentioned the previous owner left a device for 'blowing' water out of the system with a tyre inflator, it's called a Floe
https://www.autoleisure.co.uk/winte...n_ZJE-bj_4ok9w12SSRQhBSKzGzines8aAkHDEALw_wcB Also my heater doesn't have the option to heat the water electrically so there's no Immersion elements to get scaled up.
The Webaso instructions are typically vague about the descaling process, it suggests using wine vinegar or Kettle clear diluted 2:1 and ''filling the boiler and system" but I expect filling the heater with the solution won't be particularly easy and will involve removing the 'suction' pipe to the water pump from the existing water storage tank and connecting to the wine vinegar source. After 1-2 hours of low heating of the solution the instructions say "Check whether the scale deposits have completely dissolved". Hmmmm? X Ray vision needed for that one Webasto!
The instructions recommend periodic descaling depending on the hardness of the water, it mentions a drop in efficiency due to limescale but nothing else as a downside. Descaling will ultimately mean I'll be introducing a corrosive substance not only into the boiler but the pump, pipework, taps etc and I'm not sure how comfortable I am with doing that to a system that's working fine for me right now.
When the weather improves I'll get on my back under the van and take a look at the heater and inspect the drain outlet pipe, I've a feeling that I'll find that it's been intentionally blocked to prevent the tank from auto draining and the Floe unit then being used to drain the heater and negate the need to clamber under the van over and over removing the blocking device, draining electronically and then clambering back under to re-instate the blocker.
If I'm wrong I'll consider my options further, I may simply leave the thing alone TBH.
 

Mpdyork

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The floe device I think will be tapped into the cold supply from my experience, so will blow through if both taps are open. if you wish to inspect the drain valve you would have to remove the end cover and associated pipe work not an easy job to carry out off your back. As you say it may be better to leave it be, especially if your not familiar with the workings of the unit. I would be cautious though of any “blocking” device as if there is an overtemp situation the pressure has to go somewhere!
 
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