20deg temp diff on new install

[chrisey]

Hi guys, it always seems to be a bit of a pig trying to get this 20deg temp differential with condensing boilers. On a new install old house how many of you guys are still using the old 15mm copper or are you religously working out your pipework resistance to obtain the correct differential. Or are we just running a bit of 10 mm the last couple of meters to the rads. Would be interested to hear Honestly what you do? Cheers chrisey
Or is there a bit of softwear that will work it out for us?

 

[Agile]

I hope that they use the lockshield on each rad to regulate the flow!

Many installers dont seem to know how to balance rads though. Some even think that you dont need to balance rads when a TRV is fitted.

Its interesting that few even think that its necessary to do anything much apart from connecting the pipes up.

Tony

 

[chrisey]

Hi Tony, It is quite tricky to balance the system and get the correct differential across the rads especially using 15mm throughout the system accept for the index circuit, because you seem to need smaller pipes to give more resistance at certain points in the system, With the old convensional boilers to get 11deg with 15mm pipe wasnt to bad proply balanced, but 20 degs always seems to be more tricky unless using microbore 8 or 10mm the last couple of meters. and its a pain constantly changing pipe sizes regards chrisey

 

[Agile]

Much of the problem is that a combi on minimum power on CH is often far too much heat.

A 32 kW will only mod down to about 10-11 kW and thats the whole house heat requirement when its -1°C outside.

Use a heat only boiler rated for the actual heating load and its much better.

Tony