Balancing of radiators after new pump and 2 new mvs why?

[paulp]

Hi
Most excellent site!
Anyway as
mentioned above new grundfos pump with new gate valves, 2 new 2 port mvs fitted Why no downstairs heat in rads ? why did i have to "balance" the rads?
i have a potterton profile and set up above with hot water cylinder and small tank in loft.the reason we replaced mvs one was leaking and change the other parts due to age 17years plus as the plumber was there
also my towel rail is on the HT circuit and now not as hot befor it also used to get hot when CH was on but not now even though towel rail tails are hot
System when drained clear with no black water ,inhibitor added during filling
Why do you think such a changed has happened

 

[ChrisR]

COuld be air stuck in the pipes. Try turning all rads except one off, in sequence.
Can also be sludge, even if you can't see much.

 

[paulp]

thanks for the reply
have done that took out some air yesterday in upstairs bedroom
Plumber replace 15mm ball valve that was blocked and replace it with a new one its just behind the pump i think its a bypass valve its set to just open on the HW side of cylinder
today also took some air out of thumb vent screw behind HW cylinder after a bit of wiggleing!
any ideas
paul

 

[malkie]

What boiler is it and have you vented when its all off,no pump running and also when all full let the h/water run first so it will get the circs all ok then open heating side but have all rads closed bar one then when its hot open next one and so on just open it enough to let heat through use lockshield side to close then open,its not pumping over is it,hot water in header tank

 

[paulp]

its a potterton profile about 10 yrs old pump on speed 2 have bled system cold as suggested
no pump run off into tank in loft thats ok
towel rail not heating when ch is on its a mystery

 

[malkie]

Towel rail rad is off the h/water circs i think so you have a fully pumped system is there a gate valve on circs at the cylinder i reckon the circs are robbing it and needs closing down

 

[paulp]

thanks for reply yes there is a gate valve but why should this be? is it cause of better flow throuh mvs and pump as they are?
thanks

 

[malkie]

Is it on the pipework co,ming off the cylinder were there top and bottom connections just close it a bit,and see if it allows the heat through to rad

 

[paulp]

yes the way you described it is right
there is a gate valve on thr hw cylinder and that is connected to the hw mv
i am not calling for heating so ch mv shut so in theory boiler can concentrate on heating domestic hot water on the ciruit which includes towel rail
as mentioned rail as not as hot as befor

 

[malkie]

Can you close gate valve then as the reason the rad is off the circs is to allow acsess heat somewere to go so the bathroom rad was the one,if you close the gate valve then unless the rad valves are stuck and no air in it it should be roasting

 

[paulp]

i understand what you mean but my problem is related to cold towel rail when central heating is in use when only with hot water turned off
the towel rail gets warm when the hw is on
could i be right in saying if towel rad is plumbed into hw circuit would it also heat up when ch is on is this because ive got 2 mvs both 2 port
or could it be that hw mv was letting by due to age and ware heating towel rad in the process
thanks for your help

 

[malkie]

Did u have gravity circs then get it all to a fully pumped system

 

[paulp]

not sure what you mean can you exspand on it a bit i thought i had a fully pumped system with pump, cylinder etc

 

[malkie]

you do now but did you have it changed to a fully pumped,did you have gravity circs before did u have mzv 3 port or 2 port

 

[paulp]

the new valves fitted are 2 port mvs which replaced old 2 port mvs