Cylinder single stat to a duel cylinder stat ?..

[Inverness]

hi, I've replaced a gravity cylinder to a unvented cylinder. I'm about to wire the duel thermostat for the cylinder. I have a live, netural and earth from the old cylinder stat. I know the live is for com. But where does the switch wire go?

 

[ShaunCorbs]

What uv cylinder you got as there's normally a wiring diagram in the book

And direct or indirect

 

[Inverness]

Indirect cylinder. I've looked at the instructions and it says com live, loop wire connected too 2 -c the switch wire to 2.
It's a Joul cylinder.
If I connected it wrong the zone valve won't open?
Also I'm another question. It's for a Worcester vertical flue going through a loft but it passes near a joist about 25mm. I've read the Worcester instruction nothing about the distances for combustible materials so I looked at
BS5440: Part 1 and IGE "Gas Installations in Timber Frame Buildings” And couldn't find any thing on this either. Any advise?

 

[ShaunCorbs]

Any chance you could post a pic of the instructions Saves me going to hunt for them

And new condensing boilers are fine just need an air gap

 

[Last Plumber]

hi, I've replaced a gravity cylinder to a unvented cylinder. I'm about to wire the duel thermostat for the cylinder. I have a live, netural and earth from the old cylinder stat. I know the live is for com. But where does the switch wire go?

They won't normally be LN+E!
There will be a switched live from a programmer to - as you say - Common normally or No1 (read MFI's)
You need to test which is the terminal that closes on demand (to live) That will be your switched live back.
You need to test what the wires are!
What system?
S plan, Y plan etc?

 

[Inverness]

S plan system. Cheers for air gap 5 mm I found it..

 

[ShaunCorbs]

so c is your switch live from your prog

2 is the call from your first stat

so link 2 to c of other stat

and then from your second stat 2 link that to your port valve open (eghh brown wire)

 

[Inverness]

I thought com was for live wire? But it's for switch wire? Is this always the case for com? Ta

 

[Inverness]

Say I have removed a old cylinder stat from a gravity cylinder. There will be 3 wires but they might not be identified in what they should be. But there should be markings on the stat so I will copy that on to the duel stat.

 

[Last Plumber]

I thought com was for live wire? But it's for switch wire? Is this always the case for com? Ta

No, not always, just in this case the live to the cylinder stat will normally be a switched live from a programmer.

 

[Last Plumber]

Say I have removed a old cylinder stat from a gravity cylinder. There will be 3 wires but they might not be identified in what they should be. But there should be markings on the stat so I will copy that on to the duel stat.

It depends. I always test everything when wiring. Especially control wiring as people use all sort of colours for all sorts of things.
If you took the earth wire from the case of the old stat (earth terminal), then it would have been used as an earth.
One of the others will be live from the prog and the other would probably have gone to Boiler?
That SL should now go to Brown on MV.

 

[Inverness]

I want to wire this to a duel thermostat for a joul unvented cylinder indirect s plan.

 

[ShaunCorbs]

Brown to common left stat / no 1 stat

Blue to right stat / no 2 stat

Link port 2 on first stat to common on second

Hope this helps

 

[Inverness]

Thanks. confussed about the link ?
Cheers

 

[ShaunCorbs]

Thanks. confussed about the link ?
Cheers

To join the two stats check my pic out

S/l out of the first stat into the common of the other