Wiring Diagram for Older Style Landis & Gyr CH Thermosta

[OhNoNotAgain]

Help please! I have an old brown box style thermostat on the wall in the hallway. I thought it was redundant as I had a new wireless thermostat fitted to a new gas CH boiler a few years ago.

Today I disconnected the thermostat wiring and my CH boiler has stopped working (apart from running for a minute every now and then, but no heat getting to rads). So, unless it's coincidence, it seems that the old thermo needs to be connected in order to run the CH gas boiler.

Problem is ... I never noted the wiring sequence and don't know which terminal the Blue, Yellow/Green, Red & Yellow wires should go to. Inside the cover of the brown box there is a wiring diagram which (from left to right) reads:

2 3 1

There is a U under 2; a T above 3 (but linked to the 2); and under 1 there is an N above the L (phase).

Before a call an electrician in, any suggestions please?!
Thanks.

Alison

 

[D_Hailsham]

Today I disconnected the thermostat wiring and my CH boiler has stopped working (apart from running for a minute every now and then, but no heat getting to rads). So, unless it's coincidence, it seems that the old thermo needs to be connected in order to run the CH gas boiler.

If the wireless thermostat was correctly installed the old one should be redundant.

A bit more info about your system and we should be able to get rid of the old stat.

What boiler do you have? Make and Model
Which wireless stat do you have?
If you do not have a combi boiler, how many motorized valves do you have?

 

[OhNoNotAgain]

Thanks D!

I have a Saunier Duval Xeon 80ff boiler (approx 3 years old). It isn't a combi boiler.

A Drayton Digistat RF3 and a Danfoss 3 Port Valve HSV3 is fitted.

I'm wondering if it was coincidence that when I disconnected the wall thermostat yesterday the boiler stopped supplying CH. Yesterday I got a small tingle from the yellow wire and a bit more of a shock from the red wire, so that's what made me wonder if the old wall thermostat was somehow still involved. I'm turning off the mains elec every time I touch it now!

Today I bought a Drayton RTS1 room thermostat and tried wiring it in using the diagram provided. The boiler still didn't work... but maybe the problem lies elsewhere ...

Having read your message, I went into the airing cupboard to look at the 3 Port Valve and the lever seemed to be stuck on Auto, so I pushed it to Man and back and it has freed up (don't know if this was wise! Was it just stuck?)

I thought the boiler was not supplying hot water, but the pump is running occasionally and there is very hot water in the pipes and tank. I fiddled around with the Digistat and from time to time the red warning light comes on and stays on for a while. The boiler runs occasionally, but only for a few minutes.

The plumbers who replaced the boiler and controls didn't have their heart in the job, and I had to get another plumber to sort out problems that they left. Even before this the system was prone to be 'airy', and I bleed the top radiators every so often.

Any advice would be appreciated.

 

[D_Hailsham]

I have a Saunier Duval Xeon 80ff boiler (approx 3 years old). It isn't a combi boiler.

Just in case, the User/Installation manual is Here

A Drayton Digistat RF3 and a Danfoss 3 Port Valve HSV3 is fitted.

You should also have a thermostat on the side of the HW cylinder. If there isn't one, that could explain your problems.

I'm wondering if it was coincidence that when I disconnected the wall thermostat yesterday the boiler stopped supplying CH. Yesterday I got a small tingle from the yellow wire and a bit more of a shock from the red

You should not be getting anything from these wires. They should have been disconnected at the other end as they are now redundant. If you can, try and find the other end and tell me what they are connected to.

Yesterday I bought a Drayton RTS1 room thermostat and tried wiring it in using the diagram provided. The boiler still didn't work... but maybe the problem lies elsewhere ...

You do not need this stat.

Having read your message, I went into the airing cupboard to look at the 3 Port Valve and the lever seemed to be stuck on Auto, so I pushed it to Man and back and it has freed up (don't know if this was wise! Was it just stuck?)

The valve needs to be on Auto. Do not lock it in the Man position

 

[OhNoNotAgain]

Thanks for the link to the boiler manual.

There is a thermo on the side of the HW cylinder. It's set at 55 C.

The lever on the 3 port valve is 'locked' on the auto position.

The wiring from the old room thermo leads up the wall and into a blanked off terminal box inside the airing cupboard. Inside there is a see-through plastic terminal connector with 11 terminals to the top and another 11 to the bottom. 3 cables go into and out of the box: 1 to the 3 port valve, another to the pump, and the last is the wiring we are interested in, from the old wall thermo which goes into the Landis & Gyr thermo on the side of the HW cylinder.

The old wiring from the old room thermo splits into 4 separate terminals at the bottom of the connector strip and the corresponding new style wiring comes out of the corresponding 4 terminals from the top of the connector strip: old red to new brown; old blue to new blue; old yellow to new black; and old yellow/green to new yellow/green. Then the cable continues into the thermo on the side of the HW cylinder.

I know it has to be hot enough to kill any Legionnaire's Disease virus, but is 55 C too hot a setting? After the new boiler was installed hot water was coming out of the overflow pipe from the roof tank!! I called the plumbers back, but they did nothing about it. My brother took a look and turned back the pressure of the pump, thinking that it was building up and discharging into the overflow (?) tank and then the overflow pipe. I haven't noticed the problem since, but there are some water gurgling noises at night from the loft!

Thanks for your time and help talking me through this problem!

Alison

 

[D_Hailsham]

There is a thermo on the side of the HW cylinder. It's set at 55 C.

The recommended temperature to kill Legionnaires virus is 60C

I am trying to work out the wiring as it seems a bit strange, to say the least! You mentions an 11 terminal strip with 11 terminals at top and 11 at bottom. Can you confirm that it is one strip and that each top terminal is connected to the corresponding bottom terminal, i.e they share the same brass connector inside the strip.

Can you provide a list showing which wire connects to each terminal?

The lever on the 3 port valve is 'locked' on the auto position.

That's OK

After the new boiler was installed hot water was coming out of the overflow pipe from the roof tank!! I called the plumbers back, but they did nothing about it. My brother took a look and turned back the pressure of the pump, thinking that it was building up and discharging into the overflow (?) tank and then the overflow pipe. I haven't noticed the problem since, but there are some water gurgling noises at night from the loft!

Are you talking about the small tank in the roof? This is the Feed and Expansion tank. It does two jobs: provides the cold water to fill the boiler and rads; provides a space for any excess water when it expands in the system due to heating. If the level in the tank is too high when the system is cold, the level will rise to the overflow and be discharged to the outside. When the system cools at night the level will drop and the ball valve may open to refill the tank. You should check that, when the system is cold, the water level in the F/E tank is about 3 inches above the outlet pipe at the bottom of the tank. If it is any higher, the ball valve needs adjusting to lower the level and any excess water baled out.

The other thing to check is the vent pipe. This is the pipe which loops up and hangs over the F/E tank, a bit like an old fashioned umbrella handle. Check that water is not coming out of this pipe when the system is on. If it does, it could indicate a blockage somewhere.

 

[OhNoNotAgain]

Can you confirm that it is one strip and that each top terminal is connected to the corresponding bottom terminal, i.e they share the same brass connector inside the strip. Yes, that's an accurate description!

Description of wires to terminals:
(no numbering on the strip, so I've added that to help, and it reads from left to right, and the first is the coloured wire on the top (ie going to the Pump, HW Cylinder Thermo or 3 Way Valve) and the second those wires on the bottom of each terminal (ie coming in from the controls)

Pump Wiring
1. Brown: Red
2. Blue: Black
3. Yellow/green: Yellow/green

HW Cylinder Thermo
4. Brown: Red
5. Blue: Blue
6. Black: Yellow
7. Yellow/green: yellow/green

3 Way Valve
8. Brown/white: Red
9. Blue:Blue
10. Orange:Yellow
11. Grey: Red

Yes, the old problem was boiling water gushing up into the feed and expansion tank in the loft. But since the pump was turned down it has been fine, only the gurgling noises. I'll take a look up there to check out the other things you suggest.

I've reset the HW cylinder thermo to 60 C.

Thank you.[/b][/quote]

 

[D_Hailsham]

I am still confused as I don't know where some of the wires come from. So here is your list with ??? added. Please give as much info as possible.

Sorry there are so many questions and no solution, but your wiring does not conform to any standard configuration.

Which programmer/time switch do you have?


Pump Brown - 1 - Red to/from ???
Pump Blue - 2 - Black to/from ???
Pump Yellow/green - 3 - Yellow/green to/from ???

HW Cylinder Thermo Brown - 4 - Red to/from ???
HW Cylinder Thermo Blue - 5 - Blue to/from ???
HW Cylinder Thermo Black -6 - Yellow to/from ???
HW Cylinder Thermo Yellow/green -7 -: yellow/green to/from ???

3 Way Valve Brown/white - 8 - Red to/from ???
3 Way Valve Blue:Blue - 9 - Blue to/from ???
3 Way Valve Orange - 10 - Yellow to/from ???
3 Way Valve Grey - 11 - Red to/from ???

 

[OhNoNotAgain]

Hi D

Thanks for persevering with this query - you're probably as fed up and mystified by it as me!

It's a Drayton wireless Digistat RF3 programmer.

In answer to your queries, the wiring runs into the connector strip from the following :

Pump Brown - 1 - Red to/from boiler
Pump Blue - 2 - Black to/from boiler
Pump Yellow/green - 3 - Yellow/green to/from boiler

HW Cylinder Thermo Brown - 4 - Red to/from old wall thermostat
HW Cylinder Thermo Blue - 5 - Blue to/from old wall thermostat
HW Cylinder Thermo Black -6 - Yellow to/from old wall thermostat
HW Cylinder Thermo Yellow/green -7 -: yellow/green to/from old wall thermostat

3 Way Valve Brown/white - 8 - Red to/from boiler
3 Way Valve Blue:Blue - 9 - Blue to/from boiler
3 Way Valve Orange - 10 - Yellow to/from boiler
3 Way Valve Grey - 11 - Red to/from boiler

Thanks.

[/b]

 

[D_Hailsham]

It's a Drayton wireless Digistat RF3 programmer.

If that is the only timer you have, no wonder there is a problem. The Digistat RF3 is a single channel programmer, intended to control only the central heating side, not the HW side as well. Whoever did the wiring on your system has tried to cannibalise the system so that the heating works with just the one programmer.

You really need a second single channel timer to control the HW side. It does not have to be anything fancy; something like a Honeywell ST9100.

Here is the wiring diagram copied from the boiler manual.
Please check which boiler terminal each of your many wires marked "to/from boiler" is connected to. The pump connections are probably OK. It's the rest I am worried about. There should not be so many wires going to the boiler; and the HW stat and old room stat should not be connected together. Where is the new stat connected? You have not said.

Pump Brown - 1 - Red to/from boiler
Pump Blue - 2 - Black to/from boiler
Pump Yellow/green - 3 - Yellow/green to/from boiler

HW Cylinder Thermo Brown - 4 - Red to/from old wall thermostat
HW Cylinder Thermo Blue - 5 - Blue to/from old wall thermostat
HW Cylinder Thermo Black -6 - Yellow to/from old wall thermostat
HW Cylinder Thermo Yellow/green -7 -: yellow/green to/from old wall thermostat

3 Way Valve Brown/white - 8 - Red to/from boiler
3 Way Valve Blue:Blue - 9 - Blue to/from boiler
3 Way Valve Orange - 10 - Yellow to/from boiler
3 Way Valve Grey - 11 - Red to/from boiler

 

[diverdee]

have u touched any wiring apart from the wall theromstat ? if not connect red and yellow together and wireless stat should work again. the blue is neutral to make the old thermo read true and yellow green is earth for the body of the old stat

 

[D_Hailsham]

connect red and yellow together and wireless stat should work again.

If you do that you will short out the HW thermostat, which then will not work!
The wireless stat has not been wired in to the terminal strip, so how is it connected?

HW Cylinder Thermo Brown - 4 - Red to/from old wall thermostat
HW Cylinder Thermo Blue - 5 - Blue to/from old wall thermostat
HW Cylinder Thermo Black -6 - Yellow to/from old wall thermostat
HW Cylinder Thermo Yellow/green -7 -: yellow/green to/from old wall thermostat