IVAR UFH Blending Valve stopped working

[Rob99]

On @Nickfromwales recommendation I fitted an IVAR blending valve which has been absolutely faultless (and silent) for over 5 years. This morning the UFH downstairs was cold despite the boiler running with flow temps of 45deg. Further investigation showed the manifold temp was 20deg and, even when I removed the thermostatic head the temperature didn't change.

 

Is it likely the thermostatic valve has failed, or could it be something else?

As an aside, what should the Kv dial be set at? It's been on 0.1 since install so I presume that's fine.

Edited 10 hours ago by Rob99
Missed a bit

[Nickfromwales]

25 minutes ago, Rob99 said:

On @Nickfromwales recommendation I fitted an IVAR blending valve which has been absolutely faultless (and silent) for over 5 years. This morning the UFH downstairs was cold despite the boiler running with flow temps of 45deg. Further investigation showed the manifold temp was 20deg and, even when I removed the thermostatic head the temperature didn't change.

 

Is it likely the thermostatic valve has failed, or could it be something else?

As an aside, what should the Kv dial be set at? It's been on 0.1 since install so I presume that's fine.

When you take the white control (TRV) head off, does the pin push in and release back out freely? 

 

Is there a motorised zone valve feeding the manifold?

 

Also, is is completely bled of air? That will stop it working. 

[Rob99]

14 minutes ago, Nickfromwales said:

When you take the white control (TRV) head off, does the pin push in and release back out freely? 

 

Is there a motorised zone valve feeding the manifold?

 

Also, is is completely bled of air? That will stop it working. 

Thanks @Nickfromwales

Yes, the pin moves freely,

Yes there is and it's working fine (the water inlet to the Ivar valve gets nice and hot)

I checked the UFH manifold and no air trapped

[Nickfromwales]

1 hour ago, Rob99 said:

Thanks @Nickfromwales

Yes, the pin moves freely,

Yes there is and it's working fine (the water inlet to the Ivar valve gets nice and hot)

I checked the UFH manifold and no air trapped

Pump spinning freely?

[Rob99]

26 minutes ago, Nickfromwales said:

Pump spinning freely?

As far as I can tell without stripping it down. When it runs, the flow gauges on the UFH loops all move to their usual positions.

 

I've seen the Ivar youtube video which gives a quick view of the valve block internal mixer arrangement and I've also now removed the valve body itself. As far as I can tell it seems to work exactly as I'd expect and nothing appears broken or missing when I compare it to an online replacement part listing. I assume that it doesn't have any sort of internal wax chamber as the temp control os external to the valve (similar to a TRV)

 

It's the sudden change overnight from working to not-working that's stumped me.

 

Pic of valve attached.

Edited 8 hours ago by Rob99
Pic attached

[Nickfromwales]

36 minutes ago, Rob99 said:

It's the sudden change overnight from working to not-working that's stumped me

Yup. Defo a curious one.

 

37 minutes ago, Rob99 said:

When it runs, the flow gauges on the UFH loops all move to their usual positions.

So boiler fires up, heat gets to the mixing valve (defo on the flow pipe?), manifold pump is pumping, but no heat getting into the pipes.

 

Can you try operating the zone valve manually, when this is running, and push the lever across so see if there's no resistance (eg that the ZV has fully opened, mechanically).

[Rob99]

44 minutes ago, Nickfromwales said:

Yup. Defo a curious one.

 

So boiler fires up, heat gets to the mixing valve (defo on the flow pipe?), manifold pump is pumping, but no heat getting into the pipes.

 

Can you try operating the zone valve manually, when this is running, and push the lever across so see if there's no resistance (eg that the ZV has fully opened, mechanically).

Yes, very weird!!

Boiler fires, upstairs rads get hot and we have hot water (vented hwc)

Zone valve was one of the first things I suspected, all seems to move as it should (only changed it about a year ago)

 

I've now removed the whole pump set. Pump looks ok internally, no sludge or other evidence of potential blockages. All passageways in the mixing valve block also clear. All waterways have a nice smooth finish.

 

As the only moving part within the valve block I have ordered a replacement valve insert as I cannot see what else it could be.

[Nickfromwales]

6 hours ago, Rob99 said:

As the only moving part within the valve block I have ordered a replacement valve insert as I cannot see what else it could be.

Cheap and quick sanity check. Best to start the process of elimination there as it sounds like that’s defo the choke point.