central heating only comes on with h water, stumped engineer

[bonkersbill]

Hi, my Y plan ch will only comeon warm to hot when hw is on, i had engineer out who said everything was working but was scratching his head as to where the return pipe was to the boiler and said he could do no more. i had danfoss hsa 3 which got very warm whether connected to the valve or not so i repalced it, , still the same, i replaced ch thermostat and programmer, no change, after months of messing i realised i had removed a rad and had joined the in pipe to the out, i've now put in a valve in the off position and thought this must be the problem, now i get very hot rads when hw is on with ch on but the boiler will only come on for 30 seconds when ch comes on on its own, any ideas as this has been a pain for nearly 2 years and noone seams toknow what to do.

 

[MANDATE]

A 3 port valve works over two sections. First section depends on room stat and power to valves white wire (which in your case seems ok).
Second section depends on power from programmer and cylinder stat to feed valves grey wire. (if these power sources are missing valve cant move across second section)
It would appear valve is not moving further than mid point, or if it can be proved that it is moving to CH only position then the micro switch in actuator head is the most likely cause why the boiler/pump don't function.

 

[bonkersbill]

Hi and thanks for your reply, i have removed the hsa 3 and the valve does move from mid position diagonal when both hw and ch are on to the bottom position, the flat part of the valve at the bottom, hw only flat part moves to the side, so as far as i can see the valve is being moved and water is being pumped around as i can hear the grundfos super selectric pump working

 

[bonkersbill]

is the micro switch in the hsa 3? if so this is a brand new one that i fitted with out any change, i do know about new parts not working as i am an auto electrician but i also understand the odds of this hsa 3 having the exact same fault are very slim. As i said the boiler does come on for about 30 secs but i have found that it doesnt always come on.

 

[Agile]

All I can say is that a competent heating engineer should be able to identify the problem.

You dont say if this started suddenly or it has always been like this. Or if it only started when you started fiddling with the pipework.

I have no idea what your probem is. Most of these fauts are obvious on site but guessing would be a waste of time.

Tony

 

[MANDATE]

Just wondering if the whole valve was changed or just the valve head.
If it was just the head, it's possible the valve spindle is too stiff for the motor to drive it. Don't forget the motor is also pushing against a 'return spring'.
With the head removed you can try turning the spindle with finger and thumb.
Also you can try the various positions with the head off to see if the head gear moves fully across to the CH only position.
If it does move fully across, the next test would be to see if the valves 'orange' wire becomes live.
It's this orange that powers up the boiler in the CH only position.
In the other two positions where HW is involved it's the cylinder stat that supplies the power.
So its a case of Does the valve move fully across and provide power at the orange (if it does move fully and no power, then micro switch in head at fault)
If it does not move fully across then it could the first micro switch faulty, or stiff spindle or missing or fault with wire from programmer HW OFF terminal.
Simple test here with both CH and HW off, the required wire from programmer will make the 'grey' of valve live.
There is however another wire that feeds the grey that comes from the satisfied terminal of the cylinder stat when the HW is on.
These two wires may be joined at the stat and only one wire going to the grey.
If you read how a 3port valve works, it's easier to understand what causes the problem, mind you it's not so easy to understand the working.

 

[oilhead]

Is the live feed to the grey wire a separate live feed or is it taken from the switched live from the room stat?

 

[MANDATE]

Hi oilhead. not clear who your query is addessed to?
There are two live feeds to the 'grey' wire of valve and none of them are related to the room stat.
When HW becomes satisfied the cylinder stat breaks contact to boiler and makes contact to the 'grey' which powers the motor from mid position onwards. While doing this the valves orange wire becomes live via a micro switch and re fires the boiler.
The problem here is that if HW has not been selected, cylinder stat is not live and neither is the grey.
To resolve this the HW programmer switch is two way so with HW OFF the power at programmer is diverted to the 'grey'. That may be direct or it may go via the wire from cylinder stat.
The room stat provides power direct to the valves 'white' wire.
So its 'white' from HW to mid point and 'grey from mid point to CH

 

[oilhead]

Mandate,
In a perfect world I agree with your comment about wiring, but when too few cores are installed, some people decide to feed the grey with a link from the roomstat switched live, and the result is what is happening to the O.P. That is what I was trying to ask.

 

[bonkersbill]

Hi and thanks for all the details, i have had another engineer out, 3rd one and again he cannot find out what is wrong, he says everything appears to be working but the boileris either not coming on when ask by CH or it comes on then turns off after about 30 seconds, im not paying for another so it looks like im going to have to do it my self.
i need to clarify a couple of things 1st, when the valve is in the verticle this is HW position, diagonal Mid and horizontal CH only, is this correct?
The valve spindle moves easily with my fingers, the danfoss moves to all the positions when boiler is working, i have noticed that when CH and HW not in use the danfoss comes to a rest in different positions. The orange wire is connected to a brown and on the opposite side is a blue, there is no white wire but there is a white and brown, this is connected to a blue, according to the engineers these are becoming live when they should, i have had 3 electrical screw driver testers and have yet to make one light up, so i dont know if you are supposed to do something when you conect it to a live.Any more help in answering my questions and trying to figure out whats wrong will be much appreciated.

 

[Agile]

Hi and thanks for all the details,

i have had another engineer out, 3rd one and again he cannot find out what is wrong, he says everything appears to be working but the boileris either not coming on when ask by CH or it comes on then turns off after about 30 seconds, im not paying for another so it looks like im going to have to do it my self.

You should never have paid anyone who was unable to diagnose your problem!

If they dont have the requiired skills they should not have agreed to come to you!

All you need is just ONE competent heating engineer!

Tony

 

[Dodgemonkey]

Hi Bonkersbill,
Not sure if this'll help you, but I had a similar problem a couple of years ago with my Y Plan, so's to speak. My Honeywell 3 port gave up the ghost after about 7 years of duty so I replaced it. In the process of doing so, I reconfigured all the wiring to the wiring centre in an effort to smarten up the Governor's airing cupboard.
My fault centred around how I rewired the room stat to the Centre. I'd put the earth wire into the room stat terminal marked "earth", but it should have gone into terminal L3, with the earth terminal not used. This arrangement causes the earth to become a common, and thus facilitate interlock when Heating and Hot Water temps are achieved.
Of course this may not be where you are with your system, but I thought I'd mention it because the fault seemed identical.
Good luck with the fix, I'm sure you'll get to the bottom of it.

Mike

 

[dormermike]

Hi and thanks for all the details,

i have had another engineer out, 3rd one and again he cannot find out what is wrong, he says everything appears to be working but the boileris either not coming on when ask by CH or it comes on then turns off after about 30 seconds, im not paying for another so it looks like im going to have to do it my self.

You should never have paid anyone who was unable to diagnose your problem!

If they dont have the requiired skills they should not have agreed to come to you!

All you need is just ONE competent heating engineer!

Tony

Agreed on this - if the problem is not fixed don't pay.

 

[jackthom]

Hi and thanks for all the details, i have had another engineer out, 3rd one and again he cannot find out what is wrong, he says everything appears to be working but the boileris either not coming on when ask by CH or it comes on then turns off after about 30 seconds, im not paying for another so it looks like im going to have to do it my self.
i need to clarify a couple of things 1st, when the valve is in the verticle this is HW position, diagonal Mid and horizontal CH only, is this correct?
The valve spindle moves easily with my fingers, the danfoss moves to all the positions when boiler is working, i have noticed that when CH and HW not in use the danfoss comes to a rest in different positions. The orange wire is connected to a brown and on the opposite side is a blue, there is no white wire but there is a white and brown, this is connected to a blue, according to the engineers these are becoming live when they should, i have had 3 electrical screw driver testers and have yet to make one light up, so i dont know if you are supposed to do something when you conect it to a live. Any more help in answering my questions and trying to figure out whats wrong will be much appreciated.

You need to place a finger on the metal contact at the opposite end of the mains tester screwdriver to complete the neon circuit.

Needless to say if you aren't confident with mains electricity this sort of work isn't recommended.

 

[bonkersbill]

Thanks all for taking an interest, i agree about not paying if not fixed but after spending 2 hours trying to find the problem and finding out what does work has helped me get to grips with what i can do to find the problem my self, i did not think £20 was bad for a call out.
Thanks for your input Dodgemonkey, i have taken the room stat cover off and there are 4 wires, live to No 1, neutral to 2, i guess an earth to 3 (green) and a definate earth (green stripped) to the earth, do i take it you had both that look like earths connected to the earth?