Replaced Radiators now problems

[kevin12345]

Hi,
I replaced two single radiators with Double last year and never had any problems. Now I have just replaced two more, one bedroom and one living room, both the same size but double. Now I;m having problems getting all the radiators in the house to balance and stay hot.
I have read about balancing the system again and have tried to do it as best I can without the thermometers, but still not getting any consistent results.
I have bleed all the rads a few times now but there still sound like a lot of air going around the system.
I used push fit copper fitting soI know I have not blocked the system.
My water is clean so there is no sludge,
Do I have to turn the speed up on the Pump (wilo Gold 50) from 2 to 3 to cope with larger radiators?
Do I have to turn the Boiler temperature up?
The rads that are not getting properly hot do get hot if I turn all the others down but when I put every thing back to correct setting they get cold again.
I have a Glow worm 40FF conventional boiler.
I really feel that I have messed something up, anybody got any ideas.

 

[JohnD]

when you did your balancing, did you close down all the rads in the house? What fraction of a turn open from the "fully closed" position did you use on the lockshields?

were the flow pipes "too hot to hold" and the return pipes "too hot to hold for long" on all the rads?

 

[kevin12345]

I have tried opening them all up the the hottest rads I closed the lock shields down then opened them a quarter of a turn.
The inflow do get very hot but not so hot that you can not touch.
Question, I have TVR on every rad except the one in the hall where the room stat is. The TVRs are bi directional but 3 of the rads have them on the flow end of the rads, may sound like a silly question but closing down the lock shields on the other side, does that do the same as if the lock shields were on the flow??

 

[kevin12345]

Not all return pipes very hot, some just warm

 

[JohnD]

turn down the lockshields of the ones that have a very hot return pipe.

it should not be "very hot"

it doesn't matter for balancing which end the lockshield is on. If the TRV metal body has an arrow, it might matter for noise. Observe if they shut with a clunk when they come up to temp, or chatter.

what about the other questions?

 

[kevin12345]

Hi,
What do you mean did I close all the rads down when doing the balancing?
Should I have all the rads shut and balance one at a time then open the next one up and balance etc?
I read that I should open all the rads full open to start balancing, is that wrong?

 

[JohnD]

start by closing all the lockshields. You can then open them just a tiny bit, enough for the flow pipe to start getting warm. It will then take 10 mins or so for the rads to warm through before you can identify which are warmer and which are cooler. Then you can open the cooler ones just a tiny bit more and wait another ten mins.

If you start with the rads fully open, it will take a long time to cool down enough for you to detect the temperature drop.

You want the flow pipe to be "too hot to hold" and the return pipe to be "too hot to hold for long"

If you can lay your hands on a pipe thermometer, you are looking for a 20C drop in temperature between the two on all rads. If any of them have less drop, the water is flowing through it too fast, so close it down a bit. That will encourage more flow to go through the other rads.

The TRV or wheelhead valve at the other end from the lockshield, you can open fully.

 

[kevin12345]

you for the advice, I will try to get hold of thermometers and try again. I will get back to you once I have tried it.

 

[kevin12345]

One last question, when you say open the lock shields a tiny bit, do you mean a quarter of a turn or even less?
Because not all of my lock sheilds are the same, some are about 3 turns to fully open and some are about 5 turns.
Thanks in advance

 

[JohnD]

yes, just the smallest amount that will allow any water to pass and the flow pipe to start warming.