SOLVED - Wiring in Drayton Digistat +3 from old Honeywell

[palmermj0]

Hi all

I hope someone can help?

I'm trying to wire in a Drayton Digistat +3 22083, however the wiring instructions has lost me!

This is my Honeywell

Untitled

• palmermj0
• 8 Feb 2015
• 1

The blue & yellow/brown are live and when it calls for heat the red then becomes live. Is this correctly wired?

The Digistat has:

1- C
2- On
3 - Off

Any ideas?

Thanks in advance

 

[D_Hailsham]

Untitled

• palmermj0
• 8 Feb 2015
• 1

The blue & yellow/brown are live and when it calls for heat the red then becomes live.

Are you sure? Terminal 1 should be live (when CH is on at the programmer); terminal 3 should only become live when the thermostat closes, i.e temperature drops.

 

[palmermj0]

Thanks for looking.

I have double checked and this is what I found:

When the boiler programmer is on (Thermostat closed):
T 2 - Live
T 3 - Live
T 4 - Nothing
T 1 - Nothing

When the boiler programmer is on (Thermostat open):
T 2 - Live
T 3 - Live
T 4 - Live
T 1 - Live

 

[D_Hailsham]

What are you using to check if the terminal is live? A meter or a neon test screwdriver? If a meter, what is the second lead connected to?

 

[palmermj0]

Both

Using the Earth

 

[stem]

Normally, I would say after looking at the colours of the wires and the terminals they are connected to at the thermostat, that it is wired in the usual way as follows.

Terminal 2 = Neutral (Blue)
Terminal 3 = Switched Live (Yellow with brown sleeve)
Terminal 1 = Live (Red)

For the new thermostat you would then put the red in 'C' (common) and the yellow in 'On'. The neutral is not required and should be insulated and tucked safely out of the way.

However, those readings you have given are weird. Terminal 2 is a neutral and should never be live, and as D_Hailsham said, terminal 1 should be live whenever the programmer in 'on' and terminal 3 should only be live when the thermostat is calling for heat. Having said that, neon screw drivers can be unreliable because touching the end, causes you to become the second connection and can give odd indications.

If you are using a multimeter, what voltage readings are you actually getting between the terminals and the earth?

 

[palmermj0]

I have just taken the readings

Boiler on and Thermostat calling for heat:

Red - 240v
Yellow - 240v
Blue - 222v

Boiler on with no heat called:

Red - 0
Yellow - 240v
Blue - 222v

Boiler off timed and not calling heat

Red - 0
Yellow - 12v
Blue - 12v

Any ideas?

thanks

 

[stem]

Sorry, none of that makes any sense to me especially if everything is working. I've tried different scenarios, such as the yellow and red being transposed at the other end, which may explain some of the readings, but not a neutral which should be virtually 0 V having not only a fluctuating reading, but one that reaches 222 V, I suspect that there may be several things having an effect here but unfortunately without testing the whole installtion personally, I can't say what they may be.

Although if I've understood you correctly there even seem to be different results from the same test.

Boiler on and Thermostat calling for heat:

Red - 240v (T1)
Yellow - 240v (T3)
Blue - 222v (T2)

Should be the same as

When the boiler programmer is on (Thermostat closed):
T 2 - Live
T 3 - Live
T 4 - Nothing
T 1 - Nothing

I've posted a link to this thread over on the electrics forum so hopefully someone over there may have a look and see something I've missed.

 

[EFLImpudence]

You would get voltage on the neutral if it is not connected at the other end.

Is there continuity between neutral and earth?
There should be at all times - but can't be if you are reading the voltage.

If you have live and switched live transposed that would explain why the neutral does not have the voltage all the time.
Edit - that is when programmer calling but thermostat not.

 

[stem]

You would get voltage on the neutral if it is not connected at the other end.

Agreed. When the contact is closed, the blue wire would be connected to a live via terminal 3 through the accelerator, but if the wire is not actually connected to neutral, no current is flowing and hence no volt drop and the 222 V reading. I missed this because at the time I was assuming the live and switched live were the right way around. But then if..

you have live and switched live transposed that would explain why the neutral does not have the voltage all the time.

That suggests the results are as a result of two faults.

However, I can't see how that would explain why during the original test copied below, there's not a Live on T1, because if the thermostat is closed, it should be connected to T3 which would be the transposed Permanent Live

When the boiler programmer is on (Thermostat closed):
T 2 - Live
T 3 - Live
T 4 - Nothing
T 1 - Nothing

 

[EFLImpudence]

But as you pointed out we also have this for the same situation.

Boiler on and Thermostat calling for heat:

Red - 240v (T1)
Yellow - 240v (T3)
Blue - 222v (T2)

So - who knows?

 

[winston1]

The blue is not a neutral, it is a switched wire. You need to look at the wiring of the whole system not just one part of it.

 

[EFLImpudence]

Is this not it?

[/img]

 

[stem]

That's how it should be.

Terminal 2 = Neutral (Blue)
Terminal 3 = Switched Live (Yellow with brown sleeve)
Terminal 1 = Live (Red)

But that wouldn't give the readings posted.

 

[stem]

The blue is not a neutral, it is a switched wire.

I'm not sure how you work that out, because that would mean of the three wires one is live and the other two are two switched lives, one of which has been connected to a neutral terminal, but as you say...

You need to look at the wiring of the whole system not just one part of it.

....what is, or is not connected to the other end is the deciding factor in this case.

I'm wondering if the thermostat was already in place and a boiler change has taken place and it has been incorrectly reconnected at the other end.