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One flow valve appears to be duff

 
Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls
Last Post by IaAck 11 months ago
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 Walnut-tree-cottage
(@walnut-tree-cottage)
Active Member Member
Joined: 11 months ago
Posts: 6
Topic starter 03/11/2025 10:23 am   [#2568]

One flow valve appears duff.

One of the flow valves on my manifold appears to be duff. I have no flow to that loop.

Is the following a valid strategy please...... If i shut all other valves on the manifold and make a call for heat to try to force flow through the suspect loop is it likely to have a positive effect?

 

I want to avoid draining all or part of the heating if i can help it

 

Thanks in advance



   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5476
03/11/2025 11:08 am  

Posted by: @walnut-tree-cottage
↑

One flow valve appears duff.

One of the flow valves on my manifold appears to be duff. I have no flow to that loop.

Is the following a valid strategy please...... If i shut all other valves on the manifold and make a call for heat to try to force flow through the suspect loop is it likely to have a positive effect?

 

I want to avoid draining all or part of the heating if i can help it

 

Thanks in advance

It may work unless you have a bypass loop.  It puts a lot of pressure on the pump though but probably OK for a short time.  Of course it will only work if they are plumbed the right way round!

TRVs sometimes get stuck if they have been turned off all summer and a solution, which has worked every time I have tried it, is a one or more sharp taps to the side with a hammer, directly opposite the radiator inlet.  There may be a similar treatment for FRVs.

 


This post was modified 11 months ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 IaAck
(@iaack)
Trusted Member Member
Joined: 4 years ago
Posts: 61
03/11/2025 12:07 pm  

Posted by: @walnut-tree-cottage
↑

One flow valve appears duff.

One of the flow valves on my manifold appears to be duff. I have no flow to that loop.

Is the following a valid strategy please...... If i shut all other valves on the manifold and make a call for heat to try to force flow through the suspect loop is it likely to have a positive effect?

 

I want to avoid draining all or part of the heating if i can help it

 

Thanks in advance

You might want to consider the following common faults:

Air in the System/Pipes (Air lock): This is the most common problem. Trapped air prevents water from circulating correctly through the loops.

Solution: The system or specific loops need to be thoroughly bled or purged of air, often using a hose connected to a mains water supply to force the air out of each loop individually.

Stuck Flow Meter Indicator: The internal red marker or float in the flow meter can become stuck due to dirt, debris, or sediment in the system water.

Solution: The flow meter may need to be cleaned or replaced. This involves isolating the manifold, depressurising it, removing the flow meter, cleaning the internal parts, and reinstalling it.

Actuator Problem: The actuator (the control head, often electric, on the return manifold) for that specific loop may not be opening the valve pin underneath it. This can be due to a faulty actuator motor, a wiring issue, or a stuck valve pin.

Solution: Check the actuator is receiving power and try removing it to manually check if the pin valve can be moved freely (it should spring up and down). Free the pin with a silicone spray or pliers if it's stuck.

But try your suggested remedy first as this may be all that is needed.

 


This post was modified 11 months ago by IaAck

   
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