No heat coming to first floor radiators from ground floor cylinder

[Rorrim]

Hi,

We have two radiators on the second floor of our two story flat and our Megaflo CL170 unvented cylinder is on the first (ground) floor. For the past few days, we haven't been getting hot water to these radiators, but we have a bathroom on this floor and the sink and shower have been getting hot water fine. Just for kicks, I turned the radiators off and back on again and somehow hot water started coming to them again. Unfortunately, the next day they stopped working. My wife said she's heard some light knocking sounds coming from them on occasion. None of the radiators or taps we have on the ground floor are having any issues receiving hot water.

The Megaflo cylinder pressure is at 0.5 bar which is low, from what I've seen online. Could that be the cause of the second floor radiators not working? If so, should I attempt to repressurize the cylinder or should I have someone that knows what they're doing handle it (clearly, I'm not experienced with all this)? I've seen a video at https://www.redrow.co.uk/tv/videos/howto/how-to-adjust-your-system-pressure on how to do it but since that's not for a Megaflo I wanted to check first. I think I've identified the valves that would need to be turned (in attached picture). I know the radiators have their own pressurized system, too, so I'm not sure if that needs to be bled or adjusted?

I'm not sure if this could be related but the tundish has been leaking very intermittently. We had the combination valve and TPR valve replaced early this year so I'm wondering if it could be a malfunction with that work. I tried replenishing the air gap in the cylinder by turning off the water to the cylinder, opening the lowest sink tap, and turning the TPR valve, but no water came out of the tundish and there were no gurgling sounds from the cylinder, so it seemed as though the air gap wasn't the issue. I'm mentioning the dripping tundish in case that could have some bearing on the upstairs radiators issue.

Thanks in advance for any help and for your time!

 

[terryplumb]

The hot water cylinder does not supply the radiators.
Do the radiators that don't heat up have TRV's (thermostatic radiator valves ) ?
Have you bled them of air ?
What boiler do you have ,and does it have an inbuilt pressure gauge ,if so what is the pressure ?

 

[Rorrim]

Thanks for the info. We have some type of Main heat only boiler (part of the model info on it is scratched off but what I can see says “HE Plus”—can’t seem to find this model online anywhere). It doesn’t appear to have a pressure gauge. I’ve attached a photo of it. The two radiators do each have a TRV—should I bleed them?

 

[Harry Bloomfield]

You could try removing the TRV heads, under which you may find a brass pin. You should be able to press the pin in against a spring and it should pop back out. If not the pins are stuck in preventing any flow - try pulling them gently up/ out with a pair of pliers, but not so hard as to pull them all the way out.

If you can do that, you can also try bleeding them, but the system may be low on water pressure, if no air followed by water comes out.

 

[terryplumb]

Yes bleed the radiators from the vent at the top of each, to release any air ,until a stream of water appears.
Then check the pressure on the radiator systems pressure gauge ,and top up to 1 bar ( if need be )
The TRV's plastic sensor head can be removed to reveal a pin in the centre of the valve body. Press Down on the pin ,it should spring back up. This will indicate that the TRV is not stuck in the closed position ,and is not the reason why the rad is not heating up.
With all above carried out ,if the rads still don't heat up ,turn off ALL other rads TRV's and see if they then heat up.
The unvented hot water cylinders tundish passing water needs investigating ,as a separate issue.

 

[Harry Bloomfield]

Then check the pressure on the radiator systems pressure gauge ,and top up to 1 bar ( if need be )

Via the black plastic tap, nearest the camera in your photo (if you are not sure) - where the flexible pipe is...

 

[Rorrim]

Thanks you both for the help—oddly enough, the upstairs radiators have started working again and I've done nothing. Can they go on and off like this if there's air in the system?

 

[terryplumb]

No. Is your upstairs " zoned" ? ( has it got a thermostat upstairs ,and another downstairs )?

 

[Rorrim]

No, it's not zoned—we only have the one thermostat for the whole flat which is next to the cylinder on the ground floor. The only thing I'd done (which I'd mentioned above) was to try to replenish the air gap in the cylinder, but it was said that shouldn't affect the radiators.