I only get heating when water's on

[LeeroyK]

Hi all,

I awoke today to find that my central heating doesn't work so started googling and it has led me here, seems like a great site for this kind of thing.

I've been reading a few posts and here's what I've deduced, please tell me your thoughts.

At first I was getting no click from the thermostat so I thought that was the culprit, then I read a post where there was nothing unless the hot water was on so I tried that. The heating comes on and rads heat up, plus the thermostat is active.

Apparently this is down to a broken motorised valve, which may need replacing or just the head.

This is where I think the diverter valve is...

Bear in mind I'm a complete layman when it comes to this kind of thing. I assume it's the bottom left hand box.

The pump appears to be functioning as the rads heat up like I said....

From the labels on the boiler I have an Ideal Classic ff250 lxff

The motorised valve is an acl 2 port 679h308 30L1

Please let me know if you think I'm on the right trail and what's involved in replacing the valve if need be.

Thanks in advance

L

 

[kevindgas]

you don't have a motorised diverter valve
what you have is 2 motorised zone valves one as you identified is an ACL (drayton) the other looks like a myson which may be a motor on motor off valve
these work differently to the ACL which is motor on, spring off

i suspect the myson one is the defective one or there is no hot water off wiring from the timeclock.

just reread the OP and have a question - did it work without hot water on originally? as some systems were wired C/H through the Hot water circuit. the cylinder stat providing the link for C/H when H/W is satisfied.

 

[LeeroyK]

Hi Kevin,

Thanks for taking the time to respond, the ACL is indeed a motor on spring off (from the sound of it, although I haven't noticed it make the sound since this problem has arisen)

Little bit of back history to try and answer your question....

My pressure exchange unit (I think that's what it is, big red thing ontop of the boiler ) was leaking about a year ago and killed the timer (by leaking onto it). I bought a new one and installed it. The guy that fixed the leak said that the loom wiring was wrong and changed it. Now I think the pump was always on from that point, I didn't get him back as funds are always tight (hence me trying to diagnose this one myself) and just got used to switching off the whole timer unit at the mains and boiler off too everytime I didn't want hw. So maybe that's a contributing factor in all this, I assume he would have switched one of the live feeds in the loom and although I'm fairly competent at fixing this kind of thing I wouldn't know which wire to switch back.

Hope that helps, thanks again for the input.

L

 

[kevindgas]

you seem reasonably competent so have a look in the wiring box that the lead from the myson valve goes into and see what colour wires there are?
blue is neutral, green or green/yellow is earth what colour are the others ? may be 3 or 4 wires but most likely 3

the myson type valve is usually held onto the brass section by 2 screws you can remove these to see which valve it is, label is on underneath of motor head.

 

[LeeroyK]

It looks like we have grey, orange, brown and blue.

So you're thinking the wiring in the loom (at the timer) is ok and to find the part number and order a new myson?

Thanks

L

 

[kevindgas]

a 4 wire valve will most likely be sprung loaded brown to activate, grey should be perm live, orange should be switched live (power to pump & boiler) blue is neutral

there should be 240 volts to brown when C/H or HW only is called for (which valve goes to which?) if there is then most likely valve but if there isn't then the problem is before the valve

does the stat on each circuit become live when the timer is set for that circuit? does the output become live on the stats when demand is requested?

 

[LeeroyK]

I really appreciate the help. So we're still fault finding and I need to break out the volt meter and test which wires are live when ch is on, hw is on and both. Will test and report back!

 

[kevindgas]

sequences of timer to boiler/pump

timer hot water
hw on - cylinder stat common (C)
cylinder stat calling (1) - brown on valve
orange on valve to boiler/pump


timer central heating
C/H on - room stat common (1)
room stat (3 or 4) to brown on valve
orange on valve to boiler/pump

grey wires should be permanently live (don't go through timeclock)

 

[LeeroyK]

Right, CH is on the ACL, this should be a hoooge image.....

http://i35.tinypic.com/b8pzt.jpg

Smaller version.....

Timer, mains on but both HW and CH off

Grey : Perm live
Brown5 Nil
Brown7 trace
Orange Yes

HW on
G: Y
B5: N
B7: Y
Or:Y

CH on
G: Y
BR5: Y
BR7: N
Or: Y

Obviously grey's perm live like you said, brown7 has no feed so that's obviously powered by pixies Seriously tho, the wierd thing is that I now have CH without HW, the only thing I've actually changed is the variable controller on the water pump, it was a notch off max so pushed it that extra click. It could be that all the poking around has moved something (although no wires are loose) maybe the valve was jammed?

Anyway, I would like to disconnect the pump from being permanently on though, that would mean I could have 'normal' central heating, set and forget.

Thanks again for all the help

 

[kevindgas]

the brown goes to the white cable bottom right so must go on to something.

the pump live should be with the orange wires in the last terminal.

where does yellow in terminal 9 come from?

yes valves do stick sometimes

kev

 

[LeeroyK]

I was only joking about the pixies The other wire goes to the water heating unit.

I don't know where the yellow in t9 comes from, how would I find out?

I'm guessing the other end of T10 must be on some kind of 'common' circuit in the timer, which I'll need to change over to the CH circuit.

Time to ruin the sealant around the timer and see if it's obvious which wire needs swapping

 

[kevindgas]

i suspect that it goes back to Hot Water Off in the timeclock if it does then thats ok as the off side isn't needed in a 2 zone valve system (used in Y plan mid position valve)
the other possibility is that it goes to the boiler with the red in term10
and isn't connected
either will be ok.

 

[kevindgas]

term 6 & 7 are cylinder common and cylinder calling but i can't say which is which as can't see the inside of stat from here! LOL

 

[bellairaphon]

is it me or does term 6 & 7 look like cyclinder stat on perm live

 

[LeeroyK]

Whipped the timer off.....

From what I can tell I need to swap one of the reds in "L" to either 2 or 4?

I stuck a little black square on the pic because the flash made it look like there was something in 1