Some cold rads but not always same ones!

[urfolomeus]

I've been trying to track down the reason that some of my rads are cold but not others. At first it was the same two so I assumed it was the TRVs but I fixed them yesterday and in the process found that it's not always those two.

Basically ...

1) Bled rads, no effect
2) Emptied and refilled problem rads, no effect
3) Fixed one TRV and replaced another, little effect (the rad with the broken TRV got a bit warmer but not much)
4) Turned off other three rads on circuit, now the ones which weren't working are! If I turn others back on, the original two stop working again.

Is it possible that not enough hot water is getting round system? I think the two that aren't working are probably last in the circuit. Could it be a problem with the divertor?

Any help much appreciated.

Thanks, Alan

 

[chrishutt]

You need to balance the system, which is covered in the FAQs.

 

[urfolomeus]

You need to balance the system, which is covered in the FAQs.

Thanks, Chris. Much appreciated.

 

[D_Hailsham]

You need to balance the system, which is covered in the FAQs.

Thanks, Chris. Much appreciated.

If you have TRVs on your rads, balancing is a bit trickier as you have to prevent the TRV operating while doing the balancing.

There is a good guide to the procedure at: Balancing systems with TRVs

Although it is written with Drayton TRVs in mind, the principles still apply; i.e. You need to fix the position of the pin while balancing. Some people do this by removing the head, Drayton advocate the use of the decorators cap to hold the pin in the 2 position.

 

[zimmers]

are you sure when your venting a rad your not just robbing another ones water is the header tank filling or is it full and when you vent does it start to filll up can you the water going in the tank

 

[urfolomeus]

are you sure when your venting a rad your not just robbing another ones water is the header tank filling or is it full and when you vent does it start to filll up can you the water going in the tank

We've got a combi boiler so there's no tank but thanks for the reply.

 

[urfolomeus]

If you have TRVs on your rads, balancing is a bit trickier as you have to prevent the TRV operating while doing the balancing.

There is a good guide to the procedure at: Balancing systems with TRVs

Although it is written with Drayton TRVs in mind, the principles still apply; i.e. You need to fix the position of the pin while balancing. Some people do this by removing the head, Drayton advocate the use of the decorators cap to hold the pin in the 2 position.

Thanks, I'll give that a shot. I've got four out of five fine now. This is like a Rubiks cube!

 

[D_Hailsham]

are you sure when your venting a rad your not just robbing another ones water is the header tank filling or is it full and when you vent does it start to filll up can you the water going in the tank

We've got a combi boiler so there's no tank but thanks for the reply.

If you have a combi you will not have a hot water cylinder but you will still have a header tank aka Feed and Expansion Tank. This is the smaller of the two tanks in the loft. The purpose of this is to keep the heating system topped up. The water level should be about on third up. Check that the float valve works. When you bleed a rad, the lost water is replaced from this tank.

The only time you do not have a F&E Tank is when you have a sealed system; but, as you have not mentioned this, I assume you do not.

 

[urfolomeus]

The only time you do not have a F&E Tank is when you have a sealed system; but, as you have not mentioned this, I assume you do not.

I think I must have a sealed system then because I can't see a tank anywhere. Sorry for not mentioning, I'm a bit new to this.

As far as I'm aware I have the following: -

1) An Ideal Europa combi boiler that switches heat from CH to HW using a 3 junction diverter
2) A series of four rads and a heated towel rail in a sealed circuit