2 Heating questions please

[poolebybirth]

when the valve shuts the heating port it will be in its relaxed position.
may have crud blocking the port from shutting fully.

no power to valve will be in rest position yes

thanks seco - i will use sentinel x400 tonight (from the mighty b & q)! and order up a new valve from screwfix.

one last point: you say grey only is valve held in last position (eg when h/w and heating both satisfied but programmer still on, but is there any voltage to orange whilst this is the case?

 

[seco services]

grey is only live from the cylinder stat satisfied or hw off at programmer.

heating don't affect the grey if on or off.

grey live will give appox 100v on orange.

http://content.honeywell.com/uk/homes/Schemes/y1.jpg

 

[poolebybirth]

if orange has 100v live when both h/w and heating are satisfied then the pump and boiler will still be on (orange live means pump and boiler live).

Also if grey only live + 100v on orange as you say (held in last position if both hw and htg sat but programmer still on) does the grey staying live counteract the orange sending power to the pump and boiler?

sorry for all these questions. just want to be sure ?

 

[MANDATE]

The power supplied to the boiler and pump comes from the cylinder stat in the case of HW only and HW & CH shared.(mid position)
In the case of CH only (HW being off or satisfied) the live grey wire takes over from the white at mid point when 1st micro switch is triggered. this is followed by the triggering of the 2nd micro switch which supplies power out from the orange wire.
Of course the orange wire and the wire from the cylinder stat are joined so makes them both live. in one case fed from mzd valve and in the other two cases fed from the cylinder stat.
The grey wire of course has two feeds coming to it. One from the cylinder stats satisfied terminal and the other from the HW OFF terminal at the programmer.
Thing to remember is that HW only and CH only if selected are fixed positions, whereas HW & CH shared if selected is only until one side or the other is satisfied, so the valve position can be at any of the three positons, depending upon what is satisfied and what is still on demand.

 

[poolebybirth]

hi-

today i bought a new honeywell mot valve - and am going to be fitting it in an hour or so.

as i have the sentinel x400 sludge remover to be added to the system, should i replace the valve now or in a week's time? what would be best?

also, will it be possible to change the valve by plugging the feed cistern vent and cold feed? i have done this to replace a trv before but never a valve? it worked fine for the trv...

about the sludge problem, i put a magnet on the tee section of cold fed pipe and it attracted to it (not hugely but quite a bit) - so this means sludge is definetely in the pipework! around the tee section it was strong. (so although as i proved by my test i didn't have a blocked cold feed, just a partial blockage/sludge problem)!

lastly, thanks seco for your help a few days ago. after reading a few posts recently i have also noticed some of my CH system water is actually black in colour. is this normal-the system is 20years approx. old... is it just the sludge that has caused this colour. or something else? surely from 20 years circulation the colour would not be clear still!

thanks again guys.