Hot water OK but Rads cold

[PaddyBourne]

Have just completed the following sequence:

Turn CH and HW off
Open Bypass stopcock
Close all TRVs (ie minimum temp setting) on rads
Turn pump from top speed (3) to minimum speed (1)
Turn CH thermostat to max (30 degrees C)
Open TRV on nearest rad (bedroom) to full (max temp)
Close bypass stopcock
Turn on CH at control box
Switch pump from low (1) to high (3) - hoping to give the system a "nudge"

Try again with different radiators.
Try again but leave pump set to (3) all the time.

Have noticed that the boiler initially fired up but doesn't seem to be bothering now unless I turn up the temp setting on the boiler itself.

Unfortunately none of the radiators got hot (the bypass did though) the pump is extremely hot.

Also there was a comment earlier about 15mm pipes. Whilst the main kit around the valve etc is either 22mm or 15mm, the radiators are all much smaller than this.

Will check the orange wire next I think.

Back soon.

 

[MANDATE]

You can gain valuable information if you can remove the head off the spindle.
You can check to see if the spindle is free and easy to move. You can observe the quadrant moving according to the various positon.
Having had a similar problem I suspect the motor may be at fault or if not the microswitch is faulty.
The motor/quadrant is designed to move over two sections.
1st section. Room stat provides power to white wire of valve to move quadrant to mid position.
2nd section. Cylinder stat or HW OFF on programmer provides power to grey wire to drive motor/quadrant from mid positon to CH only position.
When in CH only position the orange wire should have become live due to microswitch.
If microswitch is faulty, you will only get CH for a short period, that is when HW and CH is called for together, but as soon as HW is satisfied valve will attempt to operate on CH only. valve may move but microswitch will prevent boiler from working.
If this is the case, try running off some hot water. This will create a demand for HW and valve will attempt to operate in mid position. In this case the boiler is operated from the cylinder stat and does not depend on the faulty microswitch.
So does valve not move to CH only positon. (motor or grey wire?)
If it does, confirm orange wire is not live (microswitch)

 

[PaddyBourne]

Having now removed the cover and the motor (eventually), there seems to have been a slip of the motor to lever arm mechanical mating although this could have happened during my attempts to get the motor off.

I would say that the valve spindle now moves freely about 30 degrees or so (much less than a quarter turn, which is what I would have expected).

When I did the electrical tests, the orange wire seemed to be permanently live.

More confused than ever.

 

[PaddyBourne]

Have definately now cleared one fault, the bleed cap on top of the pipework between the valve and the water cylinder hot input was definately blocked.

It isn't now. Lots of air followed by lots of water. Cap now back on, red face but delighted the kids.

 

[MANDATE]

When testing the orange wire make sure HW is off, The wire coming out of cylinder stat to fire boiler when HW is 'called for' is connected to the orange wire. This can be a little misleading because it makes the orange wire live from the stat end when it should be live from the valve microswitch.
If you get hot radiators when HW and CH is shared, even though it will only be for a short period, it proves the valve/quadrant is moving to the mid point. This proves room stat is ok and white wire must come live.
It is essential for the grey to be live if the quadrant is to move on from mid position and this can only be verified if HW is OFF or if it is on then HW must be satisfied.
If for any reason grey wire is not live, then motor cannot move on from mid position so will not open valve to CH and will not trigger microswitch.
I would have thought the quadrant would need to move about 40 degrees for each section making a total of 80 or maybe a little less.
On the valve I examined the spindle was free to rotate a full 360 degrees but the quadrant movement was around 30 to 35 degrees for each section. This something you can check if you operate it while it's off the spindle.
If the spindle only moves a total of 30 degrees by hand, I'm thinking! the valve may not reach the CH only position.
I suppose you could have system on 'HW only' while head is off the spindle and turn spindle by hand to CH only positon and see if radiators start to warm up. If not problem with spindle and if they do get hot it would suggest quadrant not moving valve far enough.

 

[PaddyBourne]

Just to complete the thread. Problem now fixed.

1. Replaced three -port valve with new one (with detachable motor etc).
found that this seemed to work fine but no water going through radiators still (even when only one was turned on)

2. Checked the pump connections - power provided at the corect times but could not see spindle moving. Removed the pump and seemed to have water leakage into the "windings" - might explain why the pump got so hot.

New pump has corrected the problem. Either the pump was the fault all along or I have busted it during my experiments.

Still, only cost me about £140 all told and I now know much more about the heating system (and am less afraid of plumbing) so thanks for everyones help.

Paddy