Vaillant Weather Sensor help

[ln1234]

Any ideas on which component is inside this vaillant weather sensor? It looks like moisture has got into it and damaged the component (wasn't sealed correctly), and i'm having trouble finding the replacement. From what I understand, you can't get the VRC693 (sensor) separately from the VRC430 controller.

I might be oversimplifying it, but the component looks like some sort of thermister / temperature sensor. Anyone happen to know which replacement component would work?

Cheers

 

[Beerlover]

Have you tried contacting Vaillant spares? Their number is 01773881358

 

[Agile]

Its probably just a 10k NTC thermister!

Tony

 

[ln1234]

Thanks for that - tried calling them but they didn't know the part number either, and weren't able to provide information on getting the VRC693 separately.

So is it a thermistor inside? If so, what value resistance?

Cheers

 

[BarryCambs]

I have a spare at home, so I'll have a look see if I can see any markings or measure the resistance

 

[ln1234]

Its probably just a 10k NTC thermister!

Tony

Thanks Tony - i'll have a look around farnell/maplin to see if there is anything similar available!

 

[ln1234]

I have a spare at home, so I'll have a look see if I can see any markings or measure the resistance

Thanks Barry - that would be a great help!

 

[Agile]

I think that maplin have them for less than £1

 

[ChrisOxford]

Are you sure it's faulty? Modern electronic components are usually epoxy encapsulated, and can take a lot of atmospheric abuse without failing. What does it read when you connect a meter (on highish Ohms setting) across it?

As people have said, I'm sure it's just an NTC thermistor too, but there are a lot of different variants. If you scrape the white gunge off, are there any markings (or colour bands) on it?

You may also find that the sensor and controller are matched to one another, which could explain why they're not sold separately.

Good luck,

 

[ChrisOxford]

See also this (badly translated) German thread... someone else has had the same problem and doesn't want to pay over the odds:

http://translate.google.co.uk/trans...rmistor&hl=en&sa=X&biw=1024&bih=571&prmd=ivns

If you have the patience to wade through it, there's some useful info about how the device's characteristics change with differing temperatures, which might help you select a suitable substitute.

 

[ln1234]

Thanks for all your help - I looked through that site and I think I have a bit more understanding of it.

The actual issue with the thermistor is that one of the legs has broken close to the thermistor - looks like it's corroded. There are markings on it if I peel back the epoxy a bit - the number 1825 is printed on it.

I got my multimeter out and checked the resistance across it. Luckily today is quite a warm day and the ambient temperature in the room is about 25 degrees (I understand thats how they are measured). The resistance across it is about 1015 ohms, which is roughly 1kohm from my understanding. What I haven't been able to do is work out the resistance at different temperature points.

As these are quite inexpensive, I was thinking of purchasing the following, and then checking the temperature on the VRC430 display vs my own temperature measurement outside

http://www.ebay.co.uk/itm/Disc-NTC-...Supplies_ET&hash=item43a750cb81#ht_1781wt_905

What do you think of this suggestion? Is there an alternative I should consider? The heating system is working ok at the moment (although it's displaying outside temperature as -50), so i'm ok experimenting for a bit.

Cheers

 

[Onetap]

Anyone happen to know which replacement component would work?

It is an NTC thermistor.

The temperature resistance characteristics are on P86 here;

http://www.vaillant.co.uk/stepone2/data/downloads/54/43/00/geotherm-6-10-kw-installation-manual.pdf

If you can get a matching thermistor from Maplin, it should work OK.

 

[ln1234]

Anyone happen to know which replacement component would work?

It is an NTC thermistor. I don't know the resistance offhand, but I seem to recall it has the same temperature/resistance characteristics as the VR10 sensor, which is sold as a sensor for use with hot water cylinders. You could get a weatherproof box with a couple of cable glands, with the sensor cable going through one and the VR10 sensor protruding through the other. I have something similar in the shed, which used a 10k thermistor and became redundant when replaced with the VRC device. It worked OK.

Cheers! I managed to fix it

Taking off a bit of the epoxy exposed a bit of the metal leg, so I soldered it back on and connected it back up - all works ok! My soldering skills aren't that great and it isn't that pretty but I think it should hold up. Outside temperature is currently showing as 26 degrees, which sounds about right as it's baking outside.

Thanks all for your help

If anyone is interested in the resistance readings at different temperature points I can get that.

 

[ln1234]

Anyone happen to know which replacement component would work?

It is an NTC thermistor.

The temperature resistance characteristics are on P86 here;

http://www.vaillant.co.uk/stepone2/data/downloads/54/43/00/geotherm-6-10-kw-installation-manual.pdf

If you can get a matching thermistor from Maplin, it should work OK.

Interesting that at 25 degress it should be 2700 ohms where I was getting closer to 1000 ohms. Different sensor types? or maybe i'm measuring it incorrectly.

 

[matt1e]

Interesting that at 25 degress it should be 2700 ohms where I was getting closer to 1000 ohms. Different sensor types? or maybe i'm measuring it incorrectly.

at 25 degrees it should 1020 ohms if its sensor type VRC-DCFwhich makes yours spot on if its one of them

Matt