H/W and H/W with C/H together but NO C/H ON IT'S OWN - HELP!

[MANDATE]

Don't quite understand your statement 'It appears in CH only mode the boiler is cutting out on the overheat stat due to lack of water flow'

How can this be if you can't get CH only mode?

If you can get CH only and the boiler cuts out shortly after lighting then it's not a actuator head problem. It's more likely due to lack of water flow indicating a pump problem.
I have experienced this type of problem and removed pump for examination. The inlet and outlet orifaces were reduced from about 25mm down to about 8mm with a build up of silt. As pump was 11 years old, opted for new pump and problem cured.

 

[matt1e]

Don't quite understand your statement 'It appears in CH only mode the boiler is cutting out on the overheat stat due to lack of water flow'

I think thats an assumption mandate (it appears)
I still think it appears more like "not cutting in because of the faulty micro switch" read the ops very first post i'm sure you will agree

is the boiler actually going off on overheat op?

matt

 

[matt1e]

Actually I've just read it properly myself
forget I've opened me gob
gonna have a proper read through now

matt

 

[Wildeman]

Matt1e/Mandate,

The actuator is working fine, have tested with the sparky and the correct wires are live when they should be. The sparky has even shorted out the two stats and the programmer in the terminal box to rule them out as being faulty. The actuator and pump were replaced 12 months ago

The problem is only when in CH only mode, the boiler is cutting out on its overheat stat. The stat in the boiler is working fine and the boiler is receiving 240v in HW, HW & CH and CH only modes (boiler only gets a live feed when needed)

It appears to be a flow/air issue, if I turn the boiler to min and then the cylinder stat to 65 degrees and select HW and CH on the programmer I get heat to the radiators but turn off the HW and the valve moves to CH only, boiler overheats and the rads cool off and do not get any hot water to them.

 

[Wildeman]

I can hear air in the system but cannot seem to remove it and when in CH only mode and I turn up the tank stat and select HW as well on the programmer the valve moves to the HW & CH mid position and then there is a hell of a noise and rush of water followed by pipes too hot to touch!!!

 

[doitall]

It's what happens when you loose circulation.

 

[Agile]

I think you are getting closer to the problem!

Its a bit drastic but I would suggest putting it onto heating and setting the boiler to minimum temperature, set the pump to highest setting, "3" usually, then turn the control valve off on all but one of the rads, then move that one "on" rad along one at a time.

My hope is that it may thenforce the air into a rad where it can be bled out!

Tony



Jules Holland's bands are good tonight! Hi def of course!

 

[doitall]

I think you are getting closer to the problem!

Its a bit drastic but I would suggest putting it onto heating and setting the boiler to minimum temperature, set the pump to highest setting, "3" usually, then turn the control valve off on all but one of the rads, then move that one "on" rad along one at a time.

My hope is that it may thenforce the air into a rad where it can be bled out!

Tony



Jules Holland's bands are good tonight! Hi def of course!

Very good Tony, would you care to explain why it works ok when the hot water is on at the same time.

 

[Wildeman]

I will try that Agile, as the only bleeds I can find are on the rads and then one on the return to the boiler just above the boiler itself (see my pics earlier in the thread)

Doitall and Agile does it sound feasible that air is causing no heat when running in HW only mode or I am being too hopeful!!!!

 

[doitall]

Pessimistic.

 

[doitall]

How about an as fitted drawing of the pipework, as we don't have much chance of a wiring diagram.

 

[MANDATE]

So the boiler will light in CH mode only providing boiler/overheat stat does not prevent it.
This is what I understand is happening.
When both circuits are operating together, the HW side (with a much lower resistance than the CH side) allows circulation and prevents a temperture build up.
When HW is no longer operating the CH sides resistance is such to restrict the flow and cause temperture build up. This causes boiler stat to operate as it should.
Turning the valve manually to open the HW port will provide a escape route with minimum resistance. hence the rush of water.
I don't think you have a by-pass pipe with valve. If you have then valve may be closed too much.
The higher than required resistance in the CH side, in my opinion is more likely to be partial blockage of solid matter rather than air.
I would think air would circulate and escape through vent pipe or into raditors.

 

[Wildeman]

Give me a chance doitall !!!

These things take time

Please find attached the wiring diagram for my system



View media item 15734

 

[Wildeman]

doitall/mandate

I do not think I have a by-pass pipe, it would be close to the pump/cylinder wouldn't it?



I have tried to get to the pipes under the landing to draw a diagram but the floorboards are the large boards that would have to be cut with a circular saw and seeing as the electrics and pipes are tight to the underside of the boards I do not fancy slicing through them all.

If I have a blockage how could I tell for sure and is there anyway to pinpoint where it is??

View media item 15438
View media item 15439
View media item 15492

 

[D_Hailsham]

The pipe work is very convoluted. It comes up from the boiler, past the pump, turn horizontal to pick up the feed and vent, and then turn south again to enter the pump.

Could the problem be due to the pump pumping down? This can cause cavitation and air problems, particularly if there is no air valve at the highest point in the system.