Old issue balancing system

[Dee]

Quick recap....19 rads, sealed system, 4 rads refuse to heat up.

Last year, after much effort to balance all rads unsuccessfully I eventally shut off the 4 (conveniently in one room) rads and shut the door on them!

Now I want to try and bring the 4 back to life. They are all the gtound floor and furthest from the boiler, all column rads with 2 being cast iron.

The remaining 15 are all hot and functioning well. 

Is it simply a case of turning the 4 back on TRV AND LS  and with abit of noodling hope they heat up or do I have to balance the whole system from scratch?

 

[JohnMo]

Turn on your problem radiators and make sure they have no air trapped - so bleed with TRV open.  Can you force the radiator hot by closing off the other radiators via the TRVs?  So the only flow is directed to the cold radiators?  If not your may have bigger issues than simple balancing.  Assuming they get hot, the system isn't blocked up.

 

So now you have two options, pump set at too low a setting and not enough head to get to the issue radiator and/or balancing. dT that is big would indicate too little flow going through a particular radiator, low dT too much flow 

 

I would have a look at all the radiators to see what sort of dT is occurring across the radiators, they should be similar - do this with all TRVs open to get a sound starting point without adjusting anything.

[Dee]

Hi Jo

I did the test last winter of closing all but the 4 and pushed the heat to those and they all heated up well.

Pump is at  highest setting

dT on each rad varied wildly! I used a multimeter on every one trying to achieve 12 degrees ish but couldn't get anywhere close on any rad