Y Plan Central Heating problem

[waveneygnome]

I have a Y plan/sundial system, worked fine the last 8yrs.

Suddenly stopped producing CH. (Hot water working fine).

Plumber #1: "You need a new pump, cost you £250 +vat"
Plumber #2: "You need new 3 way control valve; I'd have to charge you £100+vat; but you could do it yourself for £50"

Naturally I chose the DIY route, bought new control head (motor & mechanism), fitted it.

1st day - could'nt get any CH at all (HW still OK)- no change (begining to think was plumber #1 correct?)

Today on return from work, jiggled wires (?me thinking it may be loose connection or something) - 5 mins later CH comes on, stays on for 12mins, then cuts out and dies.

Any suggestions?

Thanks

 

[scatmanjohn]

Find the loose connection

 

[chrishutt]

Make sure you've got all the wiring right. Mid position valves are often incorrectly wired, so just copying the connections of the old one might not be right. Also make sure all electrical connections are secure.

 

[waveneygnome]

Thanks for your advice.

I have now checked and rechecked wiring for loose connection; still no CH.

I just replaced wire for wire when I fitted new 3way valve.

If the system has been working fine for 8 yrs; how could it be possible to have been wired in wrong?

Sorry for being a pain, but this DIY is still all new to me, but I'm prepared to give it a go.

The wiring I have is in ports:

(1) Yellow to Cylider stat only

(2) Black to Cylinder stat
AND black to Programmer

(3) Yellow/Green earth power
AND Yellow/Green to pump
AND Yellow/Green to Programmer
AND Yellow/Green to 3way valve

(4) Black mains power
AND Blue to pump
AND Blue to 3 way valve

(5) Orange to 3 way valve
AND Orange to programmer
AND Orange to Cylinder stat
AND Brown to pump

(6) Grey to programmer
AND Grey to Cylinder stat
AND Grey to 3way valve

(7) Red to programmer
AND red to Cylinder stat

(8) Red mains power
AND white to 3way valve

Any help suggestions before I throw in the towel and call in the experts.

Many Thanks
WG

 

[ChrisR]

http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf

Check the white wire is 230V when ch should be on.
And grey wire 230V when hw NOT on.

 

[waveneygnome]

Hi Chris R - not sure how to check - I assume I would need some kind of electrical tester?

I spoke to the plumber #2 and he said, the next thing to check would be the room thermostat.

.....so.......I have bought a new room thermostat, fitted it, the CH fired up and ran for 6 minutes, then cut off again.....arhhhhh.

Any other suggestions?

Could plumber #1 be correct? Is it worth me fitting a new pump? Could it be the Honeywell ST1507 programmer?

(I don't believe it is the pump as I have overridden the system to provide heat to rads by (a) setting boiler temp to min (b) setting cylinder stat to 70 (c) moved 3way valve to manual (d) demanding HW = gets heat to rads and I can feel/hear pump working....or am I deluding myself and its gravity at work? - either way I have bought myself some time by keeping family warmer)

Getting frustrated now. I know I can fix this...if only I knew which bit to fix!

Thanks
WG

 

[lor]

WHY NOT PAY A PROFESSIONAL TO DO THE JOB PROPERLY,save you & your family getting wound up.

 

[ChrisR]

not sure how to check - I assume I would need some kind of electrical tester?

ANd the ability to use it, yes.

 

[waveneygnome]

Hi Lor,

I don't think you have read the whole post.

I HAVE paid 'professionals' to look at it - both have given their diagnosis and one is blatently trying to rip me off - £250 +VAT for a £36 myson pump; the other (who seems more genuine) is too busy to come out before next Tuesday.

Hence I was asking for help on this site.

 

[MANDATE]

WG Just had a look at the wiring on your terminal block which raises a few points. term 1 has only 1 wire so thats not linking anything at all.
cylinder stat has 3 terminals but you have shown 5 terminals linked to it.
There is no mention of a room stat, but there must be one.
Apart from the earth and neutral there will be 3 live wires (not all the same time) coming from the programmer ie HW ON , CH ON and HW OFF and it's important to understand and identify these.
The movement of the valve depends on the room stat and the live white wire for the first half of its travel. The second half of travel depends on the HW OFF wire or the cylinder stat 'satisfied wire' making the grey 'live'
Your problem appears to be either. No live to room stat, faulty room stat, no switched live to valve or poor neutral connection.Any of these would mean valve cannot move away from HW only positon.
Or if valve does move to mid point and will not go further because the grey is not live, then wiring between cylinder stat, valve and HW OFF is suspect.

 

[beermatt3]

What sort of motorised valve was it. If it was motor driven rather spring, or if it was one of those nasty blue/brown switchmaster valves, the wiring is total differnet.

I have got wiring diagrams for these let me and I will give them to you.

 

[waveneygnome]

Thanks for replies.

Have now called in a favour from our electrician at work. Spoke to him on phone and he thought along the same lines as MANDATE.

I popped down local plumbers merchants, bought new room stat, fitted = no joy.

Electrician from work came over and tested all connections and has downloaded wiring diagram from web - all checks out OK.

Only thing he could suggest was a fault in the programmer.

Popped down local plumbers merchants again, bought a replacement programmer (my Honeywell ST1507 no longer available apparently) slotted straight into slots and.............................

BINGO

All working fine, like a sauna in here now.

Thankyou everyone for your support and advice.


P.S. Beermatt3 - motorised valve is a Honeywell V403H
MANDATE - the room stat is wired into programmer, not 10 port box