Problem with a honeywell sundial wiring centre

[Orac]

Hi Guys!

I've got a problem with a Honeywell Sundial Wiring system which has me scratching my head. The room thermostat is switching correctly (so I'm getting 240v to the roomstat terminal labelled 3), but the switched live to the boiler is staying firmly off. The unswitched live is fine, and if I wire both the unswitched and switched inputs for the boiler to the unswitched live, then the boiler is operating correctly. Surely, with power to Room Stat terminals 1 and 3, I should have power to the S/L for the boiler? I sort of wish it just had a good old-fashioned terminal block to wire everything into rather than one of these "easier" honeywell boards, but I've inherited the installation from someone else...

If it helps, links L1, L2 and L4 have been cut.

Any suggestions welcome

Orac

 

[Simon F]

welcome along Orac.
what's happening at the motorised valve??

 

[kozak1968]

Could be 2 port valve not opening enough to make the micro switch contact which tells the boiler to fire up.

 

[Orac]

The valve appears to be operating correctly; and, as I say, if I connect the boiler's switched input to the permanent live, it fires up. Or are you saying that the S/L gets its power via the valve. I've got power to the gray wire on the HTG terminal block, but none of the others

 

[Simon F]

where the boiler gets power depends on the set up and whats on demand,
what do you have, 2x2 port or mid position valve
the orange wire gives power to boiler, for a 2 port this is heating or water.
a mid position valve wiring is a completely different story.

 

[kozak1968]

Grey is permanent live, valve opens and makes contact sending power down orange. Honeywell had a problem a few years ago with their valves.

 

[chris watkins]

As above, or micro switch is not making. Take the cover off the 2 port & have a look the brass paddle should push on the micro switch & you should hear an audible click. You could also try manually pushing the little switch with an electrical screwdriver to see if boiler comes on. (not two long or it will overheat mind)

 

[Orac]

Thinking about it, and comparing with the "simple" 10-way connector, I should be expecting power back from the Orange cable of the HTG valve, shouldn't it. Hmm...

 

[Whn1]

Yes you should.

 

[Whn1]

Are you sure you've wired it to the s/l into the boiler, some boilers have a 230v out too.

 

[Blake]

Yes you should.

Which should be linked to pump live and SL on boiler, unless pump is controlled by pump overrun on the boiler.

No3 on the room stat should be connected to white on 3 port.

 

[Orac]

Thanks everyone, I think we have a diagnosis. The valve was indeed sticking almost all of the way across, and all switches on correctly if I encourage it across with the end of a screwdriver. Replacement valve I guess; can't imagine a squirt of WD40 will do 🙁. When it is working, the boiler it is connected to - a Vokera Mynute 35 - is sometimes stopping with an alarm 79 "Flow temperature too high or temperature differential between primary and return too high". Do we think that might also be caused by a sticky valve?

Orac

ps. I'm *very* impressed at how fast you can get effective help on this forum on a Sunday evening 🙂

 

[Orac]

Are you sure you've wired it to the s/l into the boiler, some boilers have a 230v out too.

It's got a permanent and a switched live into the boiler as it manages its own pump overrun. Vokera Mynute HE 35

 

[Blake]

May indeed be the cause of the problem, although that fault is common to the Vokera's. Change the valve and if the problem persists its a job for a GSR engineer I'm afraid.

 

[Orac]

May indeed be the cause of the problem, although that fault is common to the Vokera's. Change the valve and if the problem persists its a job for a GSR engineer I'm afraid.

The Vokera's still in warranty, and one of their engineers is coming to sort the AL79 on Thursday. Given the weather I was keen to get the other intermittent fault sorted, and am very happy to have got what looks like a diagnosis (and a work around, albeit involving a screwdriver, until I get the valve replaced)