no c/h but h/w is fine

[Big_Phil]

Hi I have the same symptoms as others on this site but my observations are slightly different than others.
My system is a domestic one with a Potterton 50e boiler. The 3 way valve is the (much maligned by most of the engineers on this website)switchmaster. Pump is the Grunfos 15/50 and the thermostat is another switchmaster. Controls are a recently upgraded to (18 months ago) Danfoss FP715si. Not sure if the system is open or closed loop but we have tanks in the loft. Boiler was installed 15 years ago but seems to be ageing well. some periferals have be upgraded over the years
All was working ok until last night and it was pointed out to me that the central heating was not working but we had plenty of hot water. Just what we needed on the coldest night of the winter so far. I did some basic observations and then trawled the net for inspiration. It would appear that the only issue is that the switchmaster 3 port valve is set to heat the hot water only and when i turn it a bit (like i have seen the servicing people do)to prompt it to go to the central heating part it does one revolution, past the central heating settings and settles on the hot water bit again before allowing the boiler to start again thus only heating the hot water.
However i noticed that the 3 port switch can be removed from the plumbing and the valve bit beneath is able to be turned to align up to any of the positions. With the synchro motor aligned to hot water and the valve set to heating and hot water the radiators are back on as a temporary measure. The adjustment of the thermostat does not seem to make any impression on the operation of the 3 way switch or anything else. Please help with any advice and experience you may have. Phil

 

[MANDATE]

Well it seems your problem is the 3 port mid position valve.
It gives no problem when on HW only because the valve does not play a important role, The valve is turned by a spring loaded quadrant and HW is the rest position. ie a motor drives it forward but the return spring forces it back.( providing it's not stuck). It works in conjunction with the cylinder stat which fires the boiler. so rarely any problem with HW.
For the valve to malfuction it could be down to.
(a) faulty room stat
(b) faulty wiring
(c) faulty motor due to
(d) stiff spindle
(e) faulty micro switch
I've experienced (e) about three years ago and last month (c) & (d)
On both occassions a replacment actuator head has been fitted to rectify the problem. as well as freeing the spindle.
My valve is a potterton but all spring load valves work on the same principle
This problem has been covered many times on this forum, so there's plenty for you to read on this subject if you want to find out exactly how it functions.

 

[twgas]

Well it seems your problem is the 3 port mid position valve.
It gives no problem when on HW only because the valve does not play a important role, The valve is turned by a spring loaded quadrant and HW is the rest position. ie a motor drives it forward but the return spring forces it back.( providing it's not stuck). It works in conjunction with the cylinder stat which fires the boiler. so rarely any problem with HW.
For the valve to malfuction it could be down to.
(a) faulty room stat
(b) faulty wiring
(c) faulty motor due to
(d) stiff spindle
(e) faulty micro switch
I've experienced (e) about three years ago and last month (c) & (d)
On both occassions a replacment actuator head has been fitted to rectify the problem. as well as freeing the spindle.
My valve is a potterton but all spring load valves work on the same principle
This problem has been covered many times on this forum, so there's plenty for you to read on this subject if you want to find out exactly how it functions.

i believe switchmaster valves are not spring return and are now obsolete so a complete change will be needed if its nakkered, first you need to check for mains power being in the right place at the right time

 

[Big_Phil]

Hi and thanks for your replies so far.
It would appear that it would be a good start to change over to the Honeywell 4073 type first when i find out what pipe sizes the existing one has ( i am currently at work so cant measure it).
There seems to be little room above the pipework on the existing arrangement to the ceiling -does it need clearance above the silver box for electrics or levers to be moved?.
As far as the testing of the microswitch and mains voltage - i take it that is internal to the switchmaster box of tricks - any advice on this as to what goes wrong?
Another thing which i forgot to mention yesterday is that the pump which was set to the slowest speed and works fine as it pumps still but when i change the speed to the faster ones the shaft stops - is this a reason to change it?
Spindle on the pipework from the existing valve is able to be turned by fingertips so presume this is not a problem.
Synchro motor turns with no more noise than before.
I am still a bit worried about the lack of input from the Thermostat or associated wiring but will source a new valve first and then see if that fixes anything. Any further advice or tips welcome in the meantime.
Phil

 

[MANDATE]

One problem I encountered couple of weeks back was like you the spindle was in the CH only positon, but the actuator was off the spindle and in the mid position.
In the HW only position or mid position the boiler and pump is powered from the cylinder stat, but in the CH only position they are powered from the valves 'orange' wire.
Because the actuator was not in the CH only position the room stat had no effect and neither did the cylinder stat, because the cylinder stat when satisfied is supposed to move actuator to CH only, but it could not do that and HW became hotter than normal and it then relied on the boiler stat to cut off the boiler. All this I believe was down a stiff spindle which the motor could not cope with.
On a previous problem, with the actuator head removed the quadrant responded to whatever was selected. But whilst in the CH only position the 'orange' wire did not become live. This indicated a micro switch failure. A replacement head solved the problem and I did manage to repair the micro switch at a later date. This proved useful, cause it's just been used while waiting for another head.
If you're concerned about the room stat, then it easy to establish if it is working. The programmer CH ON terminal feeds the room stat and the room stat feeds the white wire of the 3 port valve. So a quick test on the 'white' in the terminal box, with the stat down and up will show if power is there or not.
What is not usually understood is that although the power from the white wire only drives the motor to mid point. At this point it depends on what was selected and what has been satisfied and what is still demanded.
The alternatives are (a) the actuator/valve stays at mid point or (b) the actuator picks up power supplied via the 'grey' wire and then continues over the last half of the range and whislt doing so triggers a micro switch to light the boiler.
When HW or CH are selected alone the valve position is fixed in both cases. Controlled by cylinder stat for HW and room stat for CH.
But if HW and CH are both selected, the actuator has the choice of all three positions depending upon what has or has not been satisfied.
With a cold system actuator will move to mid position for a while and then fluctuate accordingly to any of the other positions.
I should also remind you that there is still power at the valve and in the terminal box after you have put both CH and HW to the OFF position.
This comes from the OFF side of the HW switch and feeds the grey wire.
So you must remove fuse before any wires are removed.

 

[Big_Phil]

Thanks Mandate for your detailed reply. I have now found a new valve and it is on its way to me. Due to my work patterns i am on shift now until Thursday at which point i will have a go at replacing that valve. The only trouble i can foresee is the existing copper pipes being in the wrong place or the clearance between the pipes and the ceiling not being enough in which case an unsightly hole will appear in the plaster board.
The existing connections on the switchmaster VA1 are soldered into the base of the relay - are they similarly soldered into the new valve or screw connected? I have not found any references to this posted on your site so far but will continue to look now.
Will let you know how things progress but it looks as if some people have been lucky and others have had a nightmare depending on experiences and understanding.
Catch ya later
Phil

 

[MANDATE]

The valve is basically in two parts. The body which includes the valve itself fitted into the pipe work and the actuator head which slips on the spindle. The actuator head will have almost a metre of flex containing 4 wires ( 5 if there is an earth wire).
There should be a 10 terminal box quite near so all the wires can be linked, but not all 10 terminals may be used.
The colours used on these valves seem to be fairly standard.
Green/Yellow is earth, but not always needed.
Blue is Neutral as normal.
You're then left with 'white' 'grey' and 'orange'
The room stat feeds the 'white'
The 'grey' is fed from two sources. One is from the satisfied terminal of the cylinder stat. The other is from the HW OFF terminal.
The 'orange' wire leaves the actuator head to connect up the boiler, this is how the boiler lights when on CH only.
So theres no soldering needed. It's a matter of finding the correct terminals, not too difficult with a bit of testing.
Just remember programmer CH switch is normal one way and feeds the room stat. The HW switch is a bit different, it's a two way, which means there are two wires but they can't both be live at the same time.
HW ON feeds cylinder stat (not satisied terminal)HW OFF feeds the 'grey' of the valve.
Regarding pipe work, I think you'll need to read the instructions, but I think if the valve is horizonal it the actuator does not have on top, I think it may be acceptable on one of the sides which makes access easier.

 

[Big_Phil]

now that i have changed the switchmaster to a honeywell as suggested in lots of postings, pipework was a bit tight and tbh the previous switchmaster install was a bit of a bodge job to keep the pipes in the valve, so i sorted it with new pipe and fixings.
Seems that this has sorted the problem and we are now settling down to a normal running system again.
Only problem is that i have one small radiator at the top of the house which remains cold although I have bled it and it seems normal otherwise with the taps switched on etc etc.
Thanks for your help on this especially mandate as the explanations are detailed enough to be informative without going over the top.
I will be back on other subjects you can guarantee.
Cheers
Phil

 

[MANDATE]

Glad to see you have now resolved your main problem!
Regarding the cold radiator! assuming both valves are open.When you say 'top of the house' It suggests it could be harder for the pump to get water to it than others
I would first check to see if you have a by pass pipe with a gate valve on it. The pumped water will take the easiest route available and if you have a by pass valve open too much, then that may be the cause.
Likewise you may have to balance the remaining radiators by closing some of the lockshield valves a little so the cold radiator gets its fair share.
If it's not that then and the fact you've drained down, then it could be a 'air lock'.
You could try closing all hot radiators and upping the pump speed, which may be enough to move an air lock and disperse air into radiators which means they may need bleeding again.