Replacement Cylinder Thermostat

[Redhotferrari]

Seco, sorry to drag this up again but still having problems with this, did what I thought was correct and wierd things started happening with the heating and H/W - Long story and wont bore you with it!

Anyway would you mind answering a couple more questions?

I think what you are saying is disconnect the old stat, being very careful with the produding wires, turn electrics back on and with the controller set to HW on constant find out which is the 'live' wire - Correct? Have a multimeter but never really used it, can you explain how to test this wire?

Once I have found this, this wire then goes to common on the new stat?

The other two wires are as you have already stated?

Bit difficult to explain but the valve is no where near the cylinder and stat, and seem to going through a couple of junction boxes to the floor below, is there a way of checking which one is which as the coloured wires going into the mid port are not the same as the stat end

Once I have assertained which is the live 'c' wire, will it cause damage/be dangerous to do the old 'try it and see' method and swap the other two wires if it does not work correctly?

Hope this makes sense

Really appreciate your time and answers on this one.

 

[Redhotferrari]

Just wondered if anyone can help with this one?

Many thanks in advance

 

[D_Hailsham]

Satchwell is now callled Sunvic. A quick google and I found the wiring for the currrent Cylinder stat. Manufacturers tend not to change terminal numbering so you should be able to rely on this.

Satchwell terminal 1 = Honeywell terminal 1
Satchwell terminal 2 = Honeywell terminal 2
Satchwell terminal 3 = Honeywell terminal C

No need for the earth, so just cut it back to the outer insulation at both ends.

 

[Redhotferrari]

Thanks for the advice, thats what I thought and did, but no luck, the heating started to do strange things, like the room stat would no longer fire the boiler, I had to push the motor arm over to manual to get it to fire, and when the hot water called for heat the central heating started to come on.................

So put the old one back on and all works fine, except the stat does not seem to work very well and heats the water well past the stat setting..

All very strange and confusing...

 

[JohnD]

No need for the earth, so just cut it back to the outer insulation at both ends.

Better still just sleeve it in Green & Yellow and fold it over to stop the sleeving falling off.

If in future someone needs an earth wire for some reason they will be realy annoyed to find you have cut it off (this applies to lots of things, not just thermostats).

 

[D_Hailsham]

Thanks for the advice, thats what I thought and did, but no luck, the heating started to do strange things, like the room stat would no longer fire the boiler, I had to push the motor arm over to manual to get it to fire, and when the hot water called for heat the central heating started to come on

It sounds as if whoever installed the system made some mistakes

Check that port B on the motorized valve is connected to the HW cylinder and port A to the CH? (The three ports should be stamped A, B and A/B). This is the normal way round, but some installers make port A the HW and B the CH.

You say you have a multimeter but don't know how to use it to test the switch. Presumably you know which lead to plug into which socket and what to set the switch to the read AC Volts? Or are you completely in the dark about using the meter?

Assuming you have basic knowledge, set the meter to AC volts (make sure it says 250 or more - often 600). Take the cover off the cylinder stat. You need to measure the voltage at each of the stat terminals. The black probe should be touched against a convenient neutral (Blue wire) though if you do not have a neutral nearby an earthed pipe will do. The red probe is touched against the terminal you are measuring. The terminal may be live so take care

Turn the CH off at the timer so you only have HW working.

When the HW is ON at the timer one terminal on the HW stat should have 240v all the time. This is the Honeywell C terminal.
When the cylinder stat is turned down one of the other terminals will read 240v. This is Honeywell terminal 2
When the cylinder stat is turned up the third terminal will read 240v. This is Honeywell terminal 1

 

[Redhotferrari]

Thanks for the detailed instructions Hailsham...Have now tested the stat and come up with the following readings:

With HW ON, CH OFF

STAT TURNED UP.

c-240v
1-240v
2-240v

STAT TURNED DOWN.

c-240v
1-.948v
2-240v

With programmer set to HW and CH OFF

STAT DOWN.

c-240v
1-.948v
2-240v

STAT UP

c-.938v
1-.938v
2-240v

Assume this is wrong as in your post c should always be live, so should the wire thats in 2 be the c terminal?

From my readings above can you work out which of the other wires should then go into 1 & 2?

Look forward to hearing from anyone with some advice!

 

[Redhotferrari]

Ant thoughts on this one guys?

 

[twgas]

STAT TURNED UP.

c-240v
1-240v
2-240v

this isnt right

STAT TURNED DOWN.

c-240v
1-.948v
2-240v

With programmer set to HW and CH OFF

STAT DOWN.

c-240v
1-.948v
2-240v

STAT UP

c-.938v
1-.938v
2-240v

these seem correct

let me have a think for a minute

 

[Redhotferrari]

Thanks TWGAS, await your thoughts!

 

[twgas]

what type of 3port valve have you got

 

[Redhotferrari]

Bulk standard Honeywell

 

[twgas]

you need to go back to wiring centre and disconnect (and make safe) the wires that are connected to no1 (call) on cyl stat,will also be orange from mv. do this one wire at a time then check for 240v at that terminal, this should tell you where the problem is.

good luck