Ok, I admit it, I'm stumped......

[Octopus]

So the back ground to the situation.

Gas /boiler mate replaces boiler and relocates it by about 2 meters.

Old cabling to boiler :

L, N, E and SL

New cabling to boiler:

L, N, E and SL - so cable just extended.

This is where it gets interesting:

The tank is a Megaflow, it has a tank stat, the SL from the tank stat goes to a Megaflow thermal cut-out connection (rather than back to the boiler & Megaflow have told me NOT to bypass it). At the thermal cut-out the connections are also to a Megaflow 2 port motorised valve (well actually its a Sunvic SZ 2302)

Here is a link showing the thermal cut-out etc wiring (about 1/2 way down).

http://interpart.partsarena.eu/System/DATA/Dx/DS1/installation/2978/I48-2978/I48-2978.htm


My problem is that the grey at the auxiliary switch is PL and whether the switch is open or closed it remains a PL connection. As the motor turns the valve there is a click and the voltage drops momentarily. I tried to call Sunvic technical but they go home at 4.30 so 4.55 was a bit late

So the Orange remains PL rather than SL and thus the boiler has a SL which is pretty much PL all the time.

The Gas/boiler man has changed the valve twice!

So can I please call on the collective knowledge of you good chaps, to point out the error in my thinking/understanding.

Tin hat well and truly on!

Here are some photo's of relevant bits:

 

[Leesparkykent]

I'm not familiar with the sunvic valve. Normally closed from the cylinder thermostat should go to one side of the thermal cutout, other side of cutout should go to the brown of the valve. Grey of the valve is permanent live, blue neutral and the orange is the switch live to the boiler which also is connected to the pump. I take it there's another valve? If there is, is it a two port or 3 port valve?

 

[dansk]

As above - Grey is PL, and Orange SL, if Orange is PL also then i suspect a duff micro switch, but seen as its been changed twice id be surprised its that.

 

[nunthe wiser]

Has the gas man changed the body of valve maybe at fully open the spindle is jamming ,and the valve not returning and so not breaking the micro switch.

 

[andyb]

Is the hot water gravity fed Murdoch? It seems like it should be looking at the drawing.

 

[Octopus]

Has the gas man changed the body of valve maybe at fully open the spindle is jamming ,and the valve not returning and so not breaking the micro switch.

no......

 

[Octopus]

Is the hot water gravity fed Murdoch? It seems like it should be looking at the drawing.

will check but I'mm 99% sure the boiler has a pump in it.

 

[andyb]

Something strange there Murdoch.
The Megaflo manual shows a 2 port valve yet the drawing you've posted for the SZ 2302 would seem to indicate a 3 port valve because it has an input for hot water and central heating.
You need to talk to the plumbers to find out if the changed anything other than move the boiler.

 

[Leesparkykent]

will check but I'mm 99% sure the boiler has a pump in it.

there will still be a pump in the system for the Heating even if the hot water Is gravity fed which if it is then it's a bit naughty of the plumber as it should of been upgraded to fully pumped when the boiler was changed under part L. Is there only the one valve?

 

[andyb]

Just Googled the SZ2302 and it says 2 port valve, so I'm confused now.

 

[Octopus]

there will still be a pump in the system for the Heating even if the hot water Is gravity fed which if it is then it's a bit naughty of the plumber as it should of been upgraded to fully pumped when the boiler was changed under part L. Is there only the one valve?

2 valves. the CH works ok when i disconnect the SL from the water!

 

[andyb]

So, if it's a 2 port valve then it looks like the feed from the tank stat (S/L) goes to the brown, and orange to the boiler. You do not connect the grey.

 

[Leesparkykent]

2 valves. the CH works ok when i disconnect the SL from the water!

so it sounds like it's not gravity and is an Splan with a high limit/themal cutout as its unvented. So when HW is turned on, on the programmer the common on the cylinder thermostat should become live, cylinder thermostat is below the water temp then normally closed on cylinder thermostat should be live, normally closed should then go through the the thermal cut out and power up the brown of the valve, valve should then motor round and close the micro switch between grey (permanent live) and orange switch live. So if the valve is staying open and closing the micro switch then the body of the valve could be stuck but the plumber should pick this up when replacing the head or the brown is picking a feed up from somewhere as it must be wired wrong as the heads been replaced a few times it sort of rules out it being a dodgy head.

 

[nunthe wiser]

With the juice of and the orange and greys of valves removed is the switch closed. If it's open and there's a live on the orange could there be link passing a feed to valve at junction box, maybe the boiler pump arrangements have been changed. Ie over run and boiler is feeding outgoing side of micro switch. Just a thought could be Pish. Not the brightest when it comes to various boiler controls.

 

[Octopus]

So, if it's a 2 port valve then it looks like the feed from the tank stat (S/L) goes to the brown, and orange to the boiler. You do not connect the grey.

Is that a fudge or should the head be swapped to the SZ 2351?

The home owner knows her house was built by bodgit and scarper so its the latest of her issues swallowing her money...