How does the boiler frost dump work?

[acropolis22]

Got to the storage site to check the van after being away without it during a cold snap recently. I'd forgotten to drain down. 12V was switched off. I switched on the 12V, and was about to exit the van to operate the boiler dump valve, when I realised I could hear water gushing outside. Sure enough, the dump valve had just opened. So, does this mean I must leave the 12V switched on for the dump valve to operate as designed? Never realised this. Or is something else going on?

 

[acropolis22]

On our Weinsberg,next to the dump valve (the type shown in video) there is a short cord which when pulled activates the “heating” : it opens a duct from the truma warm air system. So as long as you have the heating on low warm air is circulated around the valve keeping the temperature above the critical dump temp.

Sound idea. Will check ours again, but I've not noticed anything like that. Cheers.

 

[Lenny HB]

So now I'm wondering how people take their motorhomes on trips to the Alps in winter? Up to now all my trips have been in temperatures above 10C or so. We will be staying overnight near Dover in January, (assuming travel to France isn't banned). Is it likely the dump valve will open while the van is being used with the heating on?

Unless you have a very bad installation with the valve in a cold area it's very unlikely to dump.
If you are using the van the heating will be on in the evening, we never heat the van overnight never had a valve dump even when well below zero outside as the inside of the van will be well above the dump temperature.
If you are skiing in the Alps temperatures are going to be so low you will be running the heating 24/7 anyway.

 

[acropolis22]

Cheers. The valve is in a locker accessed from outside. It's close to the boiler, but not that close. Hard to tell what heat it might be getting. Fingers crossed. Helpful to know your experience Lenny HB This picture sort of shows where heat might be coming through from inside?

 

[Reallyretired]

My manual says that if the 12v is turned off at the Electroblock, not at the control panel, the dump valve will open. My dump valve is the one with the blue knob and button which has no 12v supply so I assume the manual is referring to the earlier type with the red pull up control, which needed 12v on to hold it closed.

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[IRHP]

Drain it, let it dump. What's the difference? You still have to refill either way. I use the van regularly throughout the year, so I don't want to keep refilling unless I have to.

There are a lot of other parts that can get damage from freezing as well as the boiler. Taps, filter, pump, pipes and fittings.

 

[Coolcats]

All you need to know is here and its not 12v its mechanical happy days

 

[ED O'DARAC]

Hi, just to say that the older Truma dump valves (Red pull-up button) needed 12v and were a pain, so Truma changed to the blue butterfly valve plus push button shown in video ( which is also a pain as it is now two-handed operation in a small space!) Both camps are correct, just choose your era and you get your answer. They can be a boiler saviour, though.

 

[bigalw35]

Agree. I always switch off the 12V when the van is in storage. But this was the first time the dump valve had operated and it threw me that water started pouring out when I switched on the 12V. As others have pointed out, almost certainly the pump pushing water through once it was re-activated.

Check whether the taps were open or not

 

[diddydave]

Our truma frost valve decided to open at Newbury and dump all the fresh water. I could not get the blue button to stay in so I took it apart and found that the shaft the button is attached too would not hold behind the plunger that’s part of the blue diamond knob at the top. So I put a cable tie around the shaft so it couldn’t pop through and hey presto it worked as a temporary measure so we could have water. No way are they worth £140 though. All cheap plastic