Worcester Greenstar 24i Junior Combi Mark III

[FrankyTheFrog]

New central heating plumbing has been installed to correct the botched job done by WarmFront in Feb 2011. We had an additional radiator installed so now have 9 radiators running off our Worcester Greenstar 24i Junior Combi Mark III. One radiator refuses to work (the living room) - we believe its the last on the "loop".

We've tried bleeding all the radiator's but there is no air in any of them. We tried turning all the TRV's on the other radiator's down to 0 to force the pressure through to the living room - this worked & the radiator heated up but as soon as we turned the TRV's of the other's back on it refuses to heat up again, even the pipes coming up from the floor then don't get warm.

Any suggestions would be greatly appreciated

 

[Gasguru]

Needs balancing see FAQs

 

[FrankyTheFrog]

Needs balancing see FAQs

The balancing act.

Start by switching off the system and letting the water cool down.
The lockshield valve is normally hidden under a push on cover at one end of the radiator and has an adjustment requiring a long narrow spanner. An adjustable spanner closed very small is probably the best adjuster.
Open both the lockshield valve and control valve (normally positioned at the opposite end of the radiator) on ALL radiators.
Fit the radiator thermometers to the INLET and OUTLET pipes of the nearest radiator to the boiler. DO NOT fit them to the main flow and return pipes.
Switch on the central heating system.
Close the lockshield valve on the first radiator to almost closed, as the temperature of the systems comes up, gradually open up the valve until the temperature difference between the two thermometers is about 20°F (12°C).
Move the thermometers to the next radiator away from the boiler. Close down the lockshield valve and adjust it until the temperature difference increases to about 20°F (the temperature difference will probably start at less than 20 degrees as both valves are fully open).
Work along the rest of the radiators until they have all been balanced.


So, do we need to keep turning the CH off so the radiator's cool down every time we go to the next one? And where do you get these radiator thermometers from?

The radiator's were balanced by the plumber which we later found left the porch & living room radiator's not warming up so my Dad then balanced them but we're still left with the living room one not working correctly.

I noticed in the FAQ's post that it recommends against teeing off from another radiator - there is a tee in the system from one of the bedrooms, thru the hall, kitchen & to the porch but the living room radiator isn't on this tee & all the radiator's directly before it are unaffected.

The pipework in the loft is copper which then comes down one copper & one plastic drop down into plastic pipe under the floor & up to copper connected to the radiator's - I think all of it is 15mm......

p.s. we live in a bungalow with bedrooms at the back & living areas at the front.

 

[Gasguru]

I assumed the FAQs on balancing would be sensible...

Ignore it especially the bit about thermometers...use your hands

Assuming you have a 2 pipe system then imagine each rung on a ladder represents an individual radiator. Lets say the LHS upright is the flow pipe from the boiler and the RHS upright is the return pipe to the boiler. The boiler is connected at the base of the ladder.

If all radiator valves were fully open then clearly the water would just take the easiest route and circulate around the radiators towards the base of the "ladder". Since all the radiators are connected in parallel it's simply a case of balancing the flow through each radiator to enable them to all heat up at the same rate with a similar temperature drop across their pipes.

You must have the TRVs or Wheelhead valves fully open on each radiator.
Initially set the Lockshield valves (the ones with the plain caps) with an educated guess based on the size of the radiator and distance from the boiler. For bathroom towel rails and small radiators you are likely to find the lockshield only needs opening a fraction of a turn (often less than a 1/4). Large radiators furthest from the boiler will probably need their lockshield fully open.

As the system comes up to temperature you are aiming to get the same temperature drop across each radiators pipes. A red marker pen to indicate the flow pipe can help. You need to work fast constantly adjusting the lockshields.

It may take several attempts from cold to get it perfect. Once the system gets up to temperature you may not feel the temperature drop so wait until cold again to tweek the valves.

It may sound complicated, but inpractice most small systems can be balanced perfectly in a couple of attempts.

 

[FrankyTheFrog]

Thanks for that! Will give it a go as soon as I get chance & report back