Central Heating not working

[Elzee]

Hi,
I have a CH problem - it's not coming on at all (Logic Heat 12 boiler, Drayton LP522 prog, RTS1 stat, ZA5 2 way zone valve, S Plan wiring (I think), Grundfos pump).

Stat seems to have no power when prog is calling for heating (no clicking). HW seems to work fine and can get CH if I manually switch lever on ZA5 when HW is also on. I believe it is the zone valve but can't understand why the stat has no power and I can't hear relay on prog clicking when demanding CH. Manually setting the ZA5 without HW on doesn't fire the boiler

It's all been working fine before this Autumn and is in a new build house approx 3 years old.

I'm quite new to this so go easy on me please but any help gratefully appreciated!

Thanks

 

[twgas]

A few electrical tests are required, do you have a multimeter?

 

[Elzee]

Hi Mick, yes I have a multimeter

 

[D_Hailsham]

ZA5 2 way zone valve,

Only one valve?

Does it have two or three pipes connected?

 

[Elzee]

2x 2-way valves - Drayton ZA5 on the CH and Honeywell on the HW. The Honeywell seems to be working fine.

 

[MrTherm]

First, with your multimeter, check for continuity from the room stat output to the synchron motor of the ZA5 zone valve.

If the wiring appears o.k, then with the cover off the ZA5 and the room stat calling for heat, see if the synchron motor attempts to turn (with the manual lever on auto obviously) - on full travel of the synchron motor the permanent live which feeds the micro switch should make and put power on to the boiler,pump etc.

 

[twgas]

First, with your multimeter, check for continuity from the room stat output to the synchron motor of the ZA5 zone valve.

How?

 

[pallen5000]

If your roomstats not clicking anymore then it's either damaged or it's not recieving power from the programmer. I wouldn't look at the valve until you have eliminated this.

 

[Elzee]

Tested and continuity from room stat output to motor is good.

With cover off the ZA5 and programmer CH on, Stat set high as it will go there is no attempt from the motor to turn, no noise, nothing at all.

I don't believe the stat is calling for heat though because if I turn it down I can't hear the relay clicking at all (when programmer CH is on of course).

Should I test voltage at the stat when CH is on to see if the programmer is turning on the stat?

Thanks for your assistance on this chaps.

 

[Elzee]

tbh I only tested between output on the wiring centre and motor as wasn't sure how I could run my multimeter between the stat itself and valve (thought maybe I was being a bit stupid!). I have no reason to believe the cabling between is damaged at all.

 

[twgas]

With CH on at programmer AND room stat turned up check for 240v at the brown wire on the CH valve. Do this test between brown and neutral, then brown and earth.

 

[Elzee]

No voltage on either - Programmer CH on, stat right up and testing across CH valve brown and neutral and then brown and earth.

 

[twgas]

Now you need a similar test on the CH wire from prog, the one that supplies the room stat with power.

 

[Elzee]

Nothing on both again. Must be the programmer then?

 

[twgas]

Looks like it. You could link the L and 4 at the prog, when power turned on the heating should work under the control of room stat. That would confirm wiring, room stat and valve all ok.