Boiler wiring problem controls guys needed

Wangerman · 30 Dec 2010

I posted this in the plumbing forum without reply thought it was the best place but obviously not can you boy helps I am not overly clued up on boiler controls

My old boiler timeclock with stat is playing up and I want to replace it it has no makers name but says VRT-QT under the cover

It is wired in 3 core and earth as follows

Green/yellow is neutral side of timeclock or terminal 2
Red is terminal 1 or live of timeclock
Yellow is wired to terminal 3
Blue is wired to terminal 4

I want to replace this with a honeywell ST699 programmer and T6360 wall stat but am not sure help

Boiler is a valiant vcw 282 gb

Forgot to say boiler is a combi so no hot water control required just need a stat to regulate temp and a clock to override it when heating is being called for out of timed hours

Many thanks in advance as always

electronicsuk · 30 Dec 2010

Perhaps you can post a picture of the timeclock? Somebody might be able to identify it.

I assume you are mistaken in saying that green/yellow is being used as a neutral conductor. It certainly shouldn't be, and if it is, you could be in for a little more work in rectifying that problem before you even get to fitting a new clock.

Wangerman · 30 Dec 2010

electronicsuk said:
Perhaps you can post a picture of the timeclock? Somebody might be able to identify it.

I assume you are mistaken in saying that green/yellow is being used as a neutral conductor. It certainly shouldn't be, and if it is, you could be in for a little more work in rectifying that problem before you even get to fitting a new clock.

Nope green and yellow are being used as neutral I am going to use 5 core flex to get over this issue

Can't post a picture as I have just moved house and the camera is all boxed up somewhere sorry

I think the clock came originally as part of a boiler pack with the vaillant when it was installed although it does not say Vaillant on it

electronicsuk · 30 Dec 2010

It seems that VRT-QT4 is probably the model number, but it's that old that the Vaillant archive site doesn't have anything other than operating instructions. No wiring diagram, unfortunately.

If it's an S-plan system and you only have four wires, two of which you have already identified, then the other two must be CH and HW demand. With a multimeter and a little playing about with the programmer, I'm sure they can be easily identified. Failing that, trace the wiring back and see which valves it's connected to.

Wangerman · 30 Dec 2010

electronicsuk said:
It seems that VRT-QT4 is probably the model number, but it's that old that the Vaillant archive site doesn't have anything other than operating instructions. No wiring diagram, unfortunately.

If it's an S-plan system and you only have four wires, two of which you have already identified, then the other two must be CH and HW demand. With a multimeter and a little playing about with the programmer, I'm sure they can be easily identified. Failing that, trace the wiring back and see which valves it's connected to.

I afraid you have lost me there with "S" plan. The hot water is instantaneous so the clock which has a built in stat only controls the room temperature and the heating times. It is a rotary clock with pull out segments

ericmark · 30 Dec 2010

I have looked for info on your boiler but nothing and I do see neutral on earth wire as a problem so look at something like this

because it uses a pair of batteries does not require neutral and it does both time and temperature in one unit. Instead of switching on and off it changes the temperature so no need for frost stat.
And simple two wire connection.

electronicsuk · 30 Dec 2010

Wangerman said:
electronicsuk said:

It seems that VRT-QT4 is probably the model number, but it's that old that the Vaillant archive site doesn't have anything other than operating instructions. No wiring diagram, unfortunately.

If it's an S-plan system and you only have four wires, two of which you have already identified, then the other two must be CH and HW demand. With a multimeter and a little playing about with the programmer, I'm sure they can be easily identified. Failing that, trace the wiring back and see which valves it's connected to.

Click to expand...

I afraid you have lost me there with "S" plan. The hot water is instantaneous so the clock which has a built in stat only controls the room temperature and the heating times. It is a rotary clock with pull out segments

Ah, it's a combi boiler then? Or electrically heated cylinder?

If there is no separate zone valve for the HW, I wouldn't expect it to be necessary to have more than 3 cores + earth at the programmer. Live, neutral, CH demand and Earth is all you should need.

To confirm, are you absolutely sure that green/yellow is being used as Neutral? How so if you don't have a wiring diagram?

Wangerman · 30 Dec 2010

electronicsuk said:
Wangerman said:

electronicsuk said:

It seems that VRT-QT4 is probably the model number, but it's that old that the Vaillant archive site doesn't have anything other than operating instructions. No wiring diagram, unfortunately.

If it's an S-plan system and you only have four wires, two of which you have already identified, then the other two must be CH and HW demand. With a multimeter and a little playing about with the programmer, I'm sure they can be easily identified. Failing that, trace the wiring back and see which valves it's connected to.

Click to expand...

I afraid you have lost me there with "S" plan. The hot water is instantaneous so the clock which has a built in stat only controls the room temperature and the heating times. It is a rotary clock with pull out segments

Click to expand...

Ah, it's a combi boiler then? Or electrically heated cylinder?

If there is no separate zone valve for the HW, I wouldn't expect it to be necessary to have more than 3 cores + earth at the programmer. Live, neutral, CH demand and Earth is all you should need.

To confirm, are you absolutely sure that green/yellow is being used as Neutral? How so if you don't have a wiring diagram?

Yeah sorry about that it is a combi a very old one but a combi all the same.

I am assuming the earth is being used a neutral as it is connected into the neutral terminal on the time clock.

I already have the new clock and stat given to me by an old friend and was hoping to use it so I could fit the stat remotely

Thanks for your help so far

Steve · 30 Dec 2010

why do you want an ST699? They are for Y or S plan systems. Not for combis. They are also daftly expensive for some reason!

electronicsuk · 30 Dec 2010

Best bet would be to trace the wiring back and see how things are connected in the wiring centre, assuming there is one. You're going to have to do this anyway if you end up replacing the cable, so it may as well be done now.

Wangerman · 30 Dec 2010

Steve said:
why do you want an ST699? They are for Y or S plan systems. Not for combis. They are also daftly expensive for some reason!

Because I was given it brand new in the box but if it is fit for purpose then I have lost nothing

Wangerman · 30 Dec 2010

electronicsuk said:
Best bet would be to trace the wiring back and see how things are connected in the wiring centre, assuming there is one. You're going to have to do this anyway if you end up replacing the cable, so it may as well be done now.

Lovely I will take a look tomorrow

Thank you

electronicsuk · 30 Dec 2010

Wangerman said:
Steve said:

why do you want an ST699? They are for Y or S plan systems. Not for combis. They are also daftly expensive for some reason!

Click to expand...

Because I was given it brand new in the box but if it is fit for purpose then I have lost nothing

You will be able to use it, although the hot water part of the programmer will obviously be redundant. A programmable thermostat would be a far more elegant solution.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Boiler wiring problem controls guys needed

Similar threads