Heating Wiring Problem - cylinder thermostat not working

[dfreitag]

By the way this is the manual I found online..

https://www.vaillant.co.uk/downloads/z/ecotec/ecotec-installation-servicing-2-2005-261445.pdf

 

[dfreitag]

And sorry, I forgot to reply.

It was working just fine until I decided to have a Nest Thermostat installed, and it was downhill from there..

It seemed to be working fine for a while, but maybe I just didn't notice the boiler running & overheating constantly at first..

 

[Aaron b]

sure - do you mean the boiler label (below)?

I WAS TOLD THIS PCB IS NEW!! I paid £250 for it... did the guy rip me off bringing me a used one??

View attachment 100150

I just loaded a manual from Google instead of their website and it looks more like yours. It appears that it doesn't accept any switched live but expects a switched signal between 3 and 4. The orange and grey cores are the switched ones from the valves and could be used for that.

Do you have a meter to test that there is 230v on terminal 4?

 

[dfreitag]

I just loaded a manual from Google instead of their website and it looks more like yours. It appears that it doesn't accept any switched live but expects a switched signal between 3 and 4. The orange and grey cores are the switched ones from the valves and could be used for that.

Do you have a meter to test that there is 230v on terminal 4?

Ok, I see..

I don't have a meter at the moment, but can go buy one if it will help!

 

[dfreitag]

one like this?

Digital Multimeter Car Battery Circuit Multi Tester Voltmeter Ammeter OHM AC/DC Voltage DC Current Continuity Resistance Diodes Transistor Electrical Test Meter with Test Leads Backlight LCD : Amazon.co.uk: DIY & Tools

Free delivery and returns on all eligible orders. Shop Digital Multimeter Car Battery Circuit Multi Tester Voltmeter Ammeter OHM AC/DC Voltage DC Current Continuity Resistance Diodes Transistor Electrical Test Meter with Test Leads Backlight LCD.

www.amazon.co.uk

 

[diditrain]

sure - do you mean the boiler label (below)?

I WAS TOLD THIS PCB IS NEW!! I paid £250 for it... did the guy rip me off bringing me a used one??

View attachment 100150

The white flex appears to be connected in all the right places, albeit sub-standardly.
I would turn the heating and hot water to the off position and then check to see if there is any voltage between neutral and the grey wire. The boiler and pump should only fire up when there is a demand for either heating or hot water or frost protection situation, which is highly unlikely at the moment, due to all the glorious sunshine.

 

[diditrain]

sure - do you mean the boiler label (below)?

I WAS TOLD THIS PCB IS NEW!! I paid £250 for it... did the guy rip me off bringing me a used one??

View attachment 100150

Also the pump usually runs on for a few minutes after the demand for heating or hot water has ceased, in order to take the excess heat away from the boile.

 

[dfreitag]

OK, just bought a meter.

V~ 200 and on 4 and 3?

I just loaded a manual from Google instead of their website and it looks more like yours. It appears that it doesn't accept any switched live but expects a switched signal between 3 and 4. The orange and grey cores are the switched ones from the valves and could be used for that.

Do you have a meter to test that there is 230v on terminal 4?

 

[dfreitag]

The white flex appears to be connected in all the right places, albeit sub-standardly.
I would turn the heating and hot water to the off position and then check to see if there is any voltage between neutral and the grey wire. The boiler and pump should only fire up when there is a demand for either heating or hot water or frost protection situation, which is highly unlikely at the moment, due to all the glorious sunshine.

Hi, thanks

ok, so on the meter V~ 200 and on the blue (N) and grey wire (4) on the PCB?

Thank you

 

[dfreitag]

Right. So measured between the blue (N) and grey wire (4) on the PCB - and it's always 244V

No matter if the boiler is running or not.

 

[diditrain]

Right. So measured between the blue (N) and grey wire (4) on the PCB - and it's always 244V

Even when you have turned your heating and hot water to the off position?

 

[dfreitag]

Even when you have turned your heating and hot water to the off position?

Yes - heating and hot water being off (on the Nest)!

 

[diditrain]

Yes - heating and hot water being off (on the Nest)!

I would now test between neutral and brown of both of your zone valves when heating and hot water is still in the off position. Hopefully you won’t have 230 volts there. I would then separate the oranges on your zone valves and measure between neutral and each of the oranges in turn to see if one of your zone valves has an issue. Could be a micro switch issue In one or both of your zone valves.

 

[dfreitag]

I would now test between neutral and brown of both of your zone valves when heating and hot water is still in the off position. Hopefully you won’t have 230 volts there.

I have 244V

I would then separate the oranges on your zone valves and measure between neutral and each of the oranges in turn to see if one of your zone valves has an issue.

They both have 244v



any ideas?

 

[diditrain]

I have 244V

They both have 244v



any ideas?

If you have 244v between neutral and the terminal where your brown of the zone valves are connected in your wiring centre, when the heating and hot water are in the off position, then you have a problem possibly from the nest end.

 

[dfreitag]

If you have 244v between neutral and the terminal where your brown of the zone valves are connected in your wiring centre, when the heating and hot water are in the off position, then you have a problem possibly from the nest end.

I see...

So it could be the Nest's fault after all? (I spoke to Google who wants a "diagnostic" in order to send a replacement..)

Assuming you have seen the photo of the cabling at Nest? That seems correct?

Many thanks for your help!

 

[diditrain]

I see...

So it could be the Nest's fault after all? (I spoke to Google who wants a "diagnostic" in order to send a replacement..)

Assuming you have seen the photo of the cabling at Nest? That seems correct?

Many thanks for your help!

You shouldn’t see 230v between neutral and brown when your heating and hot water are in the off position.

 

[dfreitag]

OK, so I checked again (my heart sunk before)

and

b/w Neutral and Brown on both ZV = 0v

b/w Neutral and Orange on both ZV = 244v

All while heating & HW OFF


Apologies, about the wrong info earlier...

 

[Aaron b]

I would remove the permanent live from the valves by disconnecting the orange from the top of 11 and move it to the spare of 5. The spare black looks like it goes to the boiler. I'd connect that to 5 in the junction box and connect the black to 3 in the boiler.

 

[diditrain]

OK, so I checked again (my heart sunk before)

and

b/w Neutral and Brown on both ZV = 0v

b/w Neutral and Orange on both ZV = 244v

All while heating & HW OFF


Apologies, about the wrong info earlier...230v should only be present between neutral and orange when you select either heating or hot water after the valve has motored open