circulation

[Mike Smith]

A large open vented system with 28 radiators 38kilowatt boiler (new) new pump, finding difficulties to get all radiators to heat up. Tried balancing, if you turn 3 off at one end of the house all the rest will run, but they won't all run at the same time.

If you turn all the radiators on it's always the same 3 that won't heat up unless you turn some others off.

I'm stumped....do you think it could be that the pump is the wrong size?

 

[doitall]

Pipe size and pump too small

More info wanted

 

[Mike Smith]

perhaps the runs are a bit long on some of the pipework but I don't think it's the pipe size, but I'm not sure, you might be onto something.

 

[doitall]

Would need a complete breakdown of the system to work it out.

Radiator sizes/outputs and pipes sizes/lengths.

What pump is installed as well

 

[Mike Smith]

It's difficult to do that as you can't see a lot of the pipework as it's under the floorboards and buried in the walls. I do know it's a mix, some microbore and some 15mm

 

[doitall]

But what is the main run and any MVs

 

[Mike Smith]

22mm main run. MVs?

 

[doitall]

22mm is too small.

MV = motorised valves, 2 or 3 port.

You haven't said what pump yet.

 

[Mike Smith]

1 x 3 port valve, the pump is a Grunfos 1560 variable speed.

 

[giblets]

Have you had any extensions added to the house?

 

[Mike Smith]

yes, the house has been extensivly extended (not mine I might add).

 

[doitall]

I would have expected to see at least 28mm pipe upto a 28mm 3port valve and a 25/55 or even a 25/80 pump for a system that size.

As I said it needs breaking down and sizing properly or we can only guess from experience.