Tank stat wiring

[foxhole]

After problems with system the 3-port valve was changed and the controller, I want to change the tank stat, on checking with the Hot water off all three terminal are live, when hot water is in ON position there is only one live terminal marked NC .? Is this as it should be ?
[Forgot to mention tank is currently full of hot water.]

 

[matt1e]

After problems with system the 3-port valve was changed and the controller, I want to change the tank stat, on checking with the Hot water off all three terminal are live, when hot water is in ON position there is only one live terminal marked NC .? Is this as it should be ?
[Forgot to mention tank is currently full of hot water.]

Hot water off - all three live - ok
Hot water on - two should be live at all times
com should always be live and
NC when hot water is in demand or
NO when hot water is satisfied

Either the cyl stat is wired wrong or you have a problem with the programmer or programmer wiring
Or you are mistaken with your test results

Matt

 

[foxhole]

Programmer new last week, so more likely the tank stat incorrect, just checked again and common is dead when HOT water is on, Only NC is live.
Do you think possible common and NC are wrong way round?
When HW is on it also holds off the Heating side.

 

[matt1e]

Programmer new last week, so more likely the tank stat incorrect, just checked again and common is dead when HOT water is on, Only NC is live.
Do you think possible common and NO are wrong way round?
When HW is on it also holds off the Heating side.

No it's more likely wiring has been mixed up at the controller end when it was changed, you need to check at the wiring centre and see if the grey wire connected to the valve is also live when NC is
If so then the problem is due to the wiring at the programmer

Make sure ch is turned off when you make the above checks
And if you get power to NC AND the valve grey then swap over hot water on and hot water off at the programmer

Matt

 

[foxhole]

The programmer was changed by replacing facia on backplate, no wiring was touched.
Another thing I don't understand is how I had a tank full of hot water this morning at 10am when the tank was cold last night and the HW is not set to come on till 11am.?
The heating runs from 6am so would the current wiring hold the port in the mid position allowing both HW and Heating?

 

[foxhole]

Checked wiring , when NC is live [HW on, Heating off] the port grey wiring is not live.

 

[matt1e]

Checked wiring , when NC is live [HW on, Heating off] the port grey wiring is not live.

Ok it does sound as though its wrong at the stat

Turn off both ch and HW at the programmer and check the grey again ( it should be live now)
If so then the easiest way to check all connections at the stat is to disconnect the stat Wiring and put the three cable cores into a connecter block
Leave both heating and hot water off at the programmer and test the cables in the block
The one you find live is the NO connection
Now turn on HW only, the one you find live is the COM connection
The one that's left is the NC connection

Reconnect the stat and test

Matt

 

[foxhole]

Thanks very much for reply, will try this in the am.

 

[foxhole]

Success, well nothing went bang, the common was in the wrong position, probably because the wire used was an earth cable [twin and earth]and it may have been assumed to be an earth during boiler install, though it was sleeved in the stat and at terminal to indicate otherwise.
See how we get on now, thanks for help.

 

[foxhole]

Seems I spoke too soon, no hot water , the wiring seems right and is calling for heat, but boiler not firing up and pump off.
Heating side seems fine though.?

 

[matt1e]

if the heating is working and there is no central heating then the valve must be fully open

I'm still not convinced that the wiring of the new programmer wasn't to blame, are you sure that the tests checked out concerning the grey wire?
are you using a multimeter to test with?

if so try turning the cyl stat up down with only hw switched on at the programmer, does the boiler fire?

check the lever on the valve is it loose or does it have resistance?

Matt

 

[foxhole]

if the heating is working and there is no central heating then the valve must be fully open--- WAS THAT A TYPING ERROR, CENTRAL HEATING IS WORKING.

I'm still not convinced that the wiring of the new programmer wasn't to blame, are you sure that the tests checked out concerning the grey wire?
are you using a multimeter to test with? -----TESTED WITH MULTI METER ,
THOUGH WHEN HEATING TURNS OFF AT CONTROLLER THERE IS A RESIDUAL VOLTAGE OF ABOUT 50VOLTS, but have spoken with another engineer who has same boiler and advised a capacitor needs putting on the valve wiring to cure it.

if so try turning the cyl stat up down with only hw switched on at the programmer, does the boiler fire? ---- THIS WORKED, DOES IT MEAN NO AND NC ARE THE WRONG WAY ROUND?

check the lever on the valve is it loose or does it have resistance? --Under what setting do I check this, HW on?

Matt

[/i]

 

[foxhole]

Just checked the Honewell site for tank stat instructions [none supplied with stat] and it shows only two wires used?

 

[matt1e]

Just checked the Honewell site for tank stat instructions [none supplied with stat] and it shows only two wires used?

Two wire for s plan
Three wire for y plan
You have y plan

Matt

 

[matt1e]

if the heating is working and there is no central heating then the valve must be fully open--- WAS THAT A TYPING ERROR, CENTRAL HEATING IS WORKING.

Yes mate a typo

if so try turning the cyl stat up down with only hw switched on at the programmer, does the boiler fire? ---- THIS WORKED, DOES IT MEAN NO AND NC ARE THE WRONG WAY ROUND?

Yes, swap them around

Matt