Just fitted K3 radaitor and the centre front panel won’t heat up

[ShaunCorbs]

Just a thought is the lockshield fully open ?

 

[John.g]

Looks like a circulation problem as the return is only warm, if the water was short circuiting then the return would be very hot, surprising the return isnt hot even with all the other rads shut off, even if it was circulating 7LPM then the 15mm tails should be OK except that they are exceptionally long. I think there may be air trapped in there somewhere interfering with the flowrate except a lockshield throttled or its been inadvertently piped up as a one pipe system.

 

[Benny895]

Just a thought is the lockshield fully open ?

Yes the lock shield is fully open. I have fully opened both valves. I will contact stelrad to see if there is anything they can suggest. Any other ideas I am all ears.

 

[ShaunCorbs]

Yes the lock shield is fully open. I have fully opened both valves. I will contact stelrad to see if there is anything they can suggest. Any other ideas I am all ears.

Try closing it half way (the lockshield)

 

[SimonG]

Check flow out of both sides of radiator, sounds like something is restricting the flow.

 

[John.g]

I think L/S valves have a valve co efficient of 1 so 2 might require a dP of ~ 3.5M at a flowrate of 7LPM ().42m3/hr). A UPS 2 will give a head of 6M at this flowrate so there certainly should be no problem in driving the water through that rad especially with all other rads isolated but the return temperature should only be 4 or 5C lower than the flow temperature, this wasn't happening, the only conceivable reason for this from a pump point of view is that the pump is not running in full speed mode 3 but is on one of the proportional pressure modes which are hopeless on this pump, PP3 will only give a flow of 0.42m3/hr at a 1.6M head but this should have shown up before changing out the rad?.

 

[Benny895]

Looks like a circulation problem as the return is only warm, if the water was short circuiting then the return would be very hot, surprising the return isnt hot even with all the other rads shut off, even if it was circulating 7LPM then the 15mm tails should be OK except that they are exceptionally long. I think there may be air trapped in there somewhere interfering with the flowrate except a lockshield throttled or its been inadvertently piped up as a one pipe system.

Thanks John next weekend. I will try to purge the Radaitor and system of any air. I will attach a hose to the Radaitor bleed valve and then open the shut TRV valve

I think L/S valves have a valve co efficient of 1 so 2 might require a dP of ~ 3.5M at a flowrate of 7LPM ().42m3/hr). A UPS 2 will give a head of 6M at this flowrate so there certainly should be no problem in driving the water through that rad especially with all other rads isolated but the return temperature should only be 4 or 5C lower than the flow temperature, this wasn't happening, the only conceivable reason for this from a pump point of view is that the pump is not running in full speed mode 3 but is on one of the proportional pressure modes which are hopeless on this pump, PP3 will only give a flow of 0.42m3/hr at a 1.6M head but this should have shown up before changing out the rad?.

I have checked the pump and it is working on max power. Tried turning it down and it didn’t do anything obviously. Thanks for confirming

 

[Benny895]

Looks like a circulation problem as the return is only warm, if the water was short circuiting then the return would be very hot, surprising the return isnt hot even with all the other rads shut off, even if it was circulating 7LPM then the 15mm tails should be OK except that they are exceptionally long. I think there may be air trapped in there somewhere interfering with the flowrate except a lockshield throttled or its been inadvertently piped up as a one pipe system.

Hello John
I tried letting some water and air out of the system to clear any airlock. I let some air and water out the front door with a hose pipe. No joy on that front.

On another note we do have 5 cast iron old double panel non convector radaitors on the system. Could this cause any issues? Was thinking about replacing them anyway for smaller height modern radaitiors.

But still don’t get why the K3 won’t heat up when the system is shut down to one radaitor.

Kind regards

Ben

 

[fowlerboi]

How long have you left it on as the only radiator for?

Whats your bypass set to?

Have you shut the motorised valve to the cylinder? If it's a Y plan have you turned the cylinder stat down to close the valve?

Are you on an open vented system or sealed?

Sounds like Air or pipe restriction/damaged. What size was the old rad?

If its air you can shut the TRV/lockshield off, open the air vent and wet vac or towel the water that comes out. Remove the air vent and connect a hose to it using a spare rad valve and some ptfe. Now open one end of the radiator one at a time full bore and run the hose to a bucket or drain, if you hear gurgling that's good news if not then its unlikely to be air.

If its a blockage try removing the rad, fitting a hose to each rad valve then a pressure testing pump as far back on the pipework as you can without going past a tee. pump it up until you're getting a nice flow out the end of the hose then repeat the other side.

 

[Benny895]

I think L/S valves have a valve co efficient of 1 so 2 might require a dP of ~ 3.5M at a flowrate of 7LPM ().42m3/hr). A UPS 2 will give a head of 6M at this flowrate so there certainly should be no problem in driving the water through that rad especially with all other rads isolated but the return temperature should only be 4 or 5C lower than the flow temperature, this wasn't happening, the only conceivable reason for this from a pump point of view is that the pump is not running in full speed mode 3 but is on one of the proportional pressure modes which are hopeless on this pump, PP3 will only give a flow of 0.42m3/hr at a 1.6M head but this should have shown up before changing out the rad?.

I did just check the pump and is it on constant highest setting. The old rad did not have these problems I don’t think. It had Radaitor cover on it so I can’t be 100%.