How does the boiler frost dump work? (1 Viewer)

[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?

 

[VXman]

Pretty sure my 12V wasn't switched on when it dumped earlier this year - might be wrong though.

 

[Coolcats]

The Truma dump valve works in the same way as anti scauld does in may showed by the use of a spring.

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[acropolis22]

The Truma dump valve works in the same way as anti scauld does in may showed by the use of a spring.

So you're saying it's nothing to do with 12V being on or off?

 

[Coolcats]

So you're saying it's nothing to do with 12V being on or off?

No not the Truma one it’s temperature sensitive, personally I like the use of a good old fashioned mechanical spring there is something quite re-assuring about it not relying on modern technology. There is a button at the base of the valve push it in and turn the tap if the temperature is to low the switch doesn’t stay in position. Once the Temperature rises just push the button turn the valve and you hear it click in to position.

 

[Coolcats]

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[Northern Boy]

My Truma dump valve opens when either the temperature drops or I take the fuse out. Turning the main 12V switch on or off makes no difference. I therefor guess the 12 volt supply to the Truma dump valve is direct from the battery via a fuse. Unlike the video above mine has a red spring loaded button on top, once lifted it stays there until as mentioned above either temperature drops or fuse is removed.

 

[Coolcats]

My Truma dump valve opens when either the temperature drops or I take the fuse out. Turning the main 12V switch on or off makes no difference. I therefor guess the 12 volt supply to the Truma dump valve is direct from the battery via a fuse. Unlike the video above mine has a red spring loaded button on top, once lifted it stays there until as mentioned above either temperature drops or fuse is removed.

Which version do you have as the current one which has been around a while has no power connection as per the video.

 

[acropolis22]

No not the Truma one it’s temperature sensitive, personally I like the use of a good old fashioned mechanical spring there is something quite re-assuring about it not relying on modern technology. There is a button at the base of the valve push it in and turn the tap if the temperature is to low the switch doesn’t stay in position. Once the Temperature rises just push the button turn the valve and you hear it click in to position.

Thanks. That all makes sense. But still not sure why the dump happened seconds after switching on the 12V. If it's temperature sensitive, and I'm not doubting you, it should have happened during the night before.

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[Chod Jacqui]

Didn't tuning on the 12v just start the water pump and the water you heard was just the now refilled boiler emptying.

 

[acropolis22]

Didn't tuning on the 12v just start the water pump and the water you heard was just the now refilled boiler emptying.

It's a thought, but there was way too much water emptying out. The boiler would have never refilled so quickly.

 

[Northern Boy]

Which version do you have as the current one which has been around a while has no power connection as per the video.

My MH is 2007 and the valve looks like these below.

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[Scotch mist]

It's a thought, but there was way too much water emptying out. The boiler would have never refilled so quickly.

probably the pump trying to fill the boiler but the water is coming out the dump valve as it was open

 

[acropolis22]

probably the pump trying to fill the boiler but the water is coming out the dump valve as it was open

Hard to remember the exact sequence of events. Pretty sure it just poured out and stopped by itself. Not ruling out what you say though.

I wonder if the temperature control had somehow jammed/seized, and me climbing into the van shook it loose?

 

[acropolis22]

My MH is 2007 and the valve looks like these below.

View attachment 561884View attachment 561885

Mine looks like the one in the video previously linked. No visible power connections.

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[Lenny HB]

Hard to remember the exact sequence of events. Pretty sure it just poured out and stopped by itself. Not ruling out what you say though.

I wonder if the temperature control had somehow jammed/seized, and me climbing into the van shook it loose?

I go with the pump theory, any water left in the pipes would just get pumped through.

 

[Spriddler]

So, does this mean I must leave the 12V switched on for the dump valve to operate as designed?

It's in storage, not being used.
Whether or not the dump valve is electrically powered, after the dump valve has opened and you've also drained the water tank and piping there's no need to leave the 12v on as there won't be any water to freeze.

 

[acropolis22]

Whether or not the dump valve is electrically powered and the dump valve has opened and you've also drained the water tank and piping there's no need to leave the 12v on as there won't be any water to freeze.

Yup. It was more the next time I was worrying about. I'm starting to lean more to the theory that several of you clever buggers have suggested. The valve had already opened, and me switching on the 12V just started the pump trying to refill the boiler. Nothing else it can be really is there? Other than my bizarre theory about the valve being stuck and me freeing it up by jumping in the van. No takers for that one?

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[Spriddler]

Other than my bizarre theory about the valve being stuck and me freeing it up by jumping in the van. No takers for that one?

Perhaps you could test that theory by not eating so many pies?

 

[olley]

My truma 4e only has a manually operated valve, you lift a little lever on top, it also acts as a pressure relief valve.
The fancy valves you guys have is an option for GB models according to the manual, which also states that frost damage isn't covered by the guarantee.

 

[acropolis22]

Perhaps you could test that theory by not eating so many pies?

I'll have you know I'm a sylph-like 10 stone.......

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[Northern Boy]

No takers for that one?

Anything is possible, I have a saying I often use which is 'If it wont work hit it with a hammer' I will add a new saying to my tool kit of life 'if the valve is stuck jump about in the van'

 

[VXman]

Surely the sensible thing to do is to drain it before leaving it in storage. Mines on the drive but I drained it to prempt a low temperature dump.

 

[Lenny HB]

Surely the sensible thing to do is to drain it before leaving it in storage. Mines on the drive but I drained it to prempt a low temperature dump.

The problem when you get caught out, in the last week we have had days at 11° followed by the next day at 4° with an overnight below zero, which is not very normal on the south coast, that get that much variation day to day.

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[pappajohn]

Pump should be turned off regardless of dump type.

Diaphragm pump.....
Once the tank and boiler are empty there's no water at the pump to activate the pressure switch so the pump will either run until next spring or burn out.
They are designed to run dry......but for how long?

Microswitched pump.
If the 12v is left on It will continue for a while, as taps are left open, then it WILL burn out.
They aren't designed to run dry

 

[acropolis22]

Surely the sensible thing to do is to drain it before leaving it in storage. Mines on the drive but I drained it to prempt a low temperature dump.

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.

 

[acropolis22]

Pump should be turned off regardless of dump type.

Diaphragm pump.....
Once the tank and boiler are empty there's no water at the pump to activate the pressure switch so the pump will either run until next spring or burn out.
They are designed to run dry......but for how long?

Microswitched pump.
If the 12v is left on It will continue for a while, as taps are left open, then it WILL burn out.
They aren't designed to run dry

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.

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[VXman]

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.

I was referring to someone who was putting it in storage. If you are prepping a car for long term storage it make sense to empty the water as part of your storage prep. What if you left water in it and for some reason it got to freezing and didn't dump?

Of course, if you are going to be using it I wouldn't drain it.

 

[acropolis22]

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?

 

[mapman]

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?

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.