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ChrB

Alde 3020 heating caravan when HW only selected

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Hi. First post here. Be gentle. 

We just had our first weekend in our Cadiz 3. All good except that the caravan kept getting too warm even though only hot water was selected on the Alde control panel. 

 

What seemed to be happening was that while the heating pump stayed off (as expected),  warm fluid was creeping up into the first "radiator". The one behind the seat that contains the boiler. 

The effect was more than just some warmth coming from the boiler it's self. The pipe up to, and that "rad" behind the seat, were quite hot. This heat didn't travel to any other part of the van but it meant we had to switch off hot water or have roof lights and windows open. 

 

PS. When turned on, the heating works superbly throughout the van. 

 

Any ideas? Does anyone else suffer?

Thanks.

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You say only hot water was selected on the control panel, but what was the temp setting, and in which position was the 'shower' symbol?

You should have the temp set low - say 18C or so as the heating won't come on below about 22-23C at this time of year.

The shower symbol should have only a half showing next to it else the water will get much hotter than necessary and you might get the problem you have.

Also check there is nothing incorrectly set in the sub-menus - like running on gas?

Finally if all is correctly set but you still have a problem ring Alde support - they are usually very helpful.

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It sounds like natural thermo-syphon - if the radiator pipe is above the boiler outlet this will happen - not sure how you can stop it other than adding a valve into the system which shuts when heating is off.

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Thanks for both replies. 

I did a reset which I hope cleared any odd settings.  Shower symbol was set to half (I think that's "normal" rather than "boost"?)

Temperature was indeed set to 18. Gas was set to off and electric to 2KW. The van got up to about 26 (on Alde display) because the evening was so warm. 

 

I think thermo-syphon describes perfectly what seemed to be happening. Hot water rising to that rad because it's higher and close to the boiler. 

I'll contact Alde. Thanks for the suggestion. I assume a support contact is easy to get through to using info from their website? I'll see what I can find anyway. Cheers.

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Hello. There is a non-return valve in the flow assembly that should prevent that scenario, so it would be worth asking your dealer to check that the NRV is fitted and hasn't been removed for some reason.

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2 hours ago, Alde UK said:

Hello. There is a non-return valve in the flow assembly that should prevent that scenario, so it would be worth asking your dealer to check that the NRV is fitted and hasn't been removed for some reason.

 

That won't stop thermo-syphon in the normal direction of flow.

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Thanks Alde UK

This was a private sale so I'm thinking of having a full service soon to get everything looked at anyway. I'll get it checked then. Is the valve in the boiler assembly or is it something the installer should have fitted?

 

BG I believe that the right non-return valve would not be opened by the thermo-syphon effect, there just wouldn't be sufficient pressure. But when the pump comes on, the valve will open. 

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Here's what there is. I assume that's just a short piece of pipe coupling the two rubber ones? 

 

IMG_20190902_192019.jpg

IMG_20190902_191911.jpg

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5 hours ago, Black Grouse said:

 

That won't stop thermo-syphon in the normal direction of flow.

 

It will if its crack opening pressure is greater than the very low "head" pressure developed by the thermo syphon. Their use is a classic method to stop thermo-syphoning, so I suspect that is what we could have here.. When the pump starts an adequately higher head to open it is generated.

 

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9 hours ago, Alde UK said:

Hello. There is a non-return valve in the flow assembly that should prevent that scenario, so it would be worth asking your dealer to check that the NRV is fitted and hasn't been removed for some reason.

So if the NRV is in the flow assembly, is it that alloy part in between two rubber hoses in my zoomed in picture?. Is this available on it's own? 

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Update. The non return valve was in place but is fitted inside the rubber pipe with a tywrap squeezing the pipe at either end of the valve. The plastic valve looked off straight and was quite grubby. I've cleaned it up and attempted a refit. Rads working again so I'm letting it all cool so I can try HW only. 

I note that the replacement flow assembly appears to have no tywraps but does have a crimp in the ally pipe. Has the NRV been moved into there to improve reliability? 

 

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Here's a couple of shots of the valve. It seems to be working correctly now. Time will tell, I guess. 

IMG_20190928_114240_compress89.jpg

IMG_20190928_114314_compress64.jpg

Edited by ChrB

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I had exactly the same problem. Couldn't understand why the first heating element was always giving out heat even though the hot water only was selected. A call to Alde support did diagnose the NRV as the fault. Coincidentally it started to give fault after the service engineer changed the fluid. NRV replaced FOC by servicing engineer and solving the problem .

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Hello. On the 3010-series, the NRV was cable-tied into the rubber of the flow assembly.

 

This meant that when the system was being filled on at the caravan manufacturer and the expansion tank was installed in reverse, if the technician tried to fill it normally, the NRV would be knocked loose rather than overflow the expansion tank.

 

The upside of this was if the technician wasn't attending the pump while filling, the mistake didn't result in a flooded caravan on the assembly line.

 

The downside was that the mistake would result in poor circulation and problems for the dealer, or brand new owner if it wasn't detected at PDI.

 

Over time, the problem created for the dealers/end users by a shiftable NRV was judged worse than the problem for the caravan manufacturers, whose assembly lines had grown familiar with the Alde equipment.

 

So with the 3020-series, we phased in an NRV crimped into an aluminium pipe in the flow assembly.

 

Now if a technician mistakenly tries to fill against the NRV, it won't shift, and they will be given quite a memorable lesson if they aren't watching the expansion tank.

Edited by Alde UK
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Thanks for the explanation, Alde UK. 

I can report a successful weekend away with HW turned on all weekend and no sign of the issue. So for now it appears solved. 

 

If a NRV in a crimped pipe was available separately I'd be doing the replacement. But considering the cost of the complete flow assembly, I'll take my chances for the time being. 

PS a quick Google for "plastic insert check valve" appears to bring up similar valves. Of course we don't know the exact spec required, though. 

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The NRV crimped into a 90 mm length of alu tube is part number 1900-870. The Flow Assembly, complete with NRV and automatic bleed valve is part number 1900-887. Resellers won't generally have them listed or on stock, but can order them in.

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That's great info, many thanks Alde UK

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