Potterton Suprima 120L

EliteHeat

OK, if the valve is not opening you have a problem either with the programmer or the room thermostat.

First of all turn off all power to the heating system, usually via a 3-amp fused spur.

Next locate and remove the cover from the wiring centre. This is usually very close to the motorised valves in the airing cupboard.

Each zone valve has 5 wires. These are neutral, earth, live, common live and switched live. The colours correspond too blue, green/yellow, brown, grey and orange. Be careful though, some installers mix up grey and orange, but I have to assume that it was wired in correctly.

The purpose of the brown wire is simply to open the valve and cause contact to be made between the common live and switched live parts of the volt-free microswitch within the valve.

The first thing to check is whether the brown has 230v to it when the programmer and room thermostat are both calling for heat.

If it is live then check the voltage on the grey wire, if this is 230v and the voltage on orange is zero then you need a new head unit for the valve if it is of the detachable sort or a complete new MV unit if it isn't.

If there is zero volts to brown then remove the front of the room thermostat from its backplate and check the voltage to the common electrical connector. If this is zero then the programmer is faulty.

If you are getting 230v to common then the room thermostat is faulty.

paragp

do i do these checks with the hw and heating on from the programmer?

espresso

paragp wrote: »

do i do these checks with the hw and heating on from the programmer?

Yes because the programmer provides the live feed to the motorised valve and then to the boiler/pump as required.

paragp

ok i have checked the brown wire and there zero volts on it.
i have also checked the thermostat and there is zero vaults

on the blue wire on the control above.

I have tried this with the heating on from the programmer. On the above control (thermostat) the blue wire is live if I check with a tester however there is zero volts showing on the multimeter.

i just want to check that the testing i did is correct, on the above control i check the voltage between the Blue and the Reb/Brown wire connections.

EliteHeat

The reason that you cannot detect a voltage on the thermotat is that it is just switching 230v. Without a neutral the multi meter cannot detect the voltage.

You need to identify the blue and brown wires from the thermostat at the wiring centre end. One of them will be supplied by the programmer and one of them will be supplying the motorised valve via the brown wire. So, you will see either brown+blue or brown+brown in the wiring centre where the common brown is from the MV.

You will always be able to accurately measure voltage via the wiring centre as neutral will be readily available.

So, again, you need to measure (with all heating controls set to run) the following:-

1) Voltage to brown at the MV
2) Voltage on grey and orange on the MV
3) Voltage from programmer to room thermostat
4) Voltage from room thermostat to MV (via brown) - same as (1)

paragp

how do i measure the voltage from programmer to room thermostat? should I be doing this at the programmer end or at wiring centre end as you suggested ?

EliteHeat

paragp wrote: »

how do i measure the voltage from programmer to room thermostat? should I be doing this at the programmer end or at wiring centre end as you suggested ?

At the wiring centre:-

1) Brown wire from MV should be switched by the room thermostat - normally open terminal
2) Common terminal on room thermostat should be supplied from programmer
3) Grey (or orange) wire on MV may be permanently live or may be switched by programmer or thermostat
4) Whatever powers the pump and boiler - orange or grey from MV - is the normally open terminal of the microswitch

I keep mentioning grey or orange as it is possible to wire the MV in either configuration. It would be best practise to wire grey to common and orange to normally open.

Sequence of operation is programmer -> thermostat -> motorised valve -> pump & boiler

BTW, it would take a heating engineer about 5 minutes to work it all out, so maybe you might be better off getting someone in

paragp

thanks eliteheat,
i'll try this out tonite

if i do get a heating engineer in to look at this, roughly how much should I expect to pay to fix the problem?

paragp

alas, after all that, it would appear that the problem might be caused by the little four legged creatures...RATS!!!!:mad: :mad:

while i was carrying out the checks i noticed that at the thermostat, where I was getting live points (using a tester) yesterday, these were not live today!! I checked at the wiring centre end and the wire at that end was live. this got me thinkng that there must be a break somewhere, which I traced to the garage and found that the wire was eaten through. The wire had been routed through the floor boards and into the garage and then up into the loft where the MegaFlow is.

I am going to try and re-route the wire tommorrow and see if this works.:o

paragp

ok, re-routed the wire, going through the ceilin joists now rather than under the floor boards, and all is working perfectly.

thanks eliteheat for all your help