Do I need a bigger pump?

[newnhambolton]

Just had an extension done with a new condensor Worcester 24Ri boiler put in, as well as a further 6 radiators using 10mm plastic piping. Most have TRVs. (The existing 7 radiators were connected using 22mm/15mm copper piping). The existing pump is a Grundfos 15-50. The furthest two new radiators are 2m high designer radiators and they are only luke warm. The plumber says that we need a bigger pump. Do we really?

 

[Agile]

I think you have a nupty plumber!

It all depends on how it has been piped!

You cannot expect to feed six rads through a single 10 mm pipe, that will feed just ONE rad !

15mm will feed about three rads.

I hope you have not paid him?

Tony

 

[mickyg]

problem with system design/pipework layout or balancing not pump size.

 

[doitall]

Ah come on guy's no-one would be that stupid to connect 6 rads off a single 10mm pipe.

Would they

 

[newnhambolton]

The 10mm piping are spurred off the original 22mm copper piping (I think). Is that okay?

 

[doitall]

The 10mm piping are spurred off the original 22mm copper piping (I think). Is that okay?

Two 10mm to each radiator ??

 

[Agile]

If its two 10 mm to each rad and originating from 22 mm then thats OK if the 10 mm TOTAL length ( to/from each rad ) is no more than about 10m.

In that case its just balancing! You can demonstrate that by turning off all your existing rads on the old system. That should make the new ones work.

Then turn each old rad on until water JUST starts to flow.

Tony

 

[billy bob]

You need to find the index circuit of the heating system, from this you can determine the pump size.

 

[newnhambolton]

I think the total length to and from the furtheest radiator is around 10-11m. What is a heating index? Where can I find it?

 

[billy bob]

The index circuit is the circuit with the most resistance, this will not necessarily be the furthest radiator away from the pump location.

 

[bhm1712]

i had similar problems with my CH after moving in last year

upstairs my rads are on 15mm spurrs from 22mm, downstairs are on 8mm microbore from 22mm main.

if the upstairs rads LSV were open to much, this starved the downstairs rads. the difference in resistance between the 15mm and 8mm is huge, so the pump would circulate the water easily to the upstairs rads and not downstairs.

i sorted it by re balancing the system, with the upstairs rads balanced right down low, i gradually opened the LSV on each upstairs rad until they all warmed up nicely, along with downstairs. However, due to the pressure/resistance difference, having the upstairs rads LSV opened only slightly, there is more noise in the system.

to have both 8mm and 15mm spurrs from the same main is always going to cause issues with balancing,

 

[kevindgas]

as previously said the pump should be adequate for 13 rads but not if 6 are fed on 1 pipe out and 1 pipe back!
as a rough guide i wouldn't run more than 15 rads over 2 floors on a 15/50 if 3 floors then i would use a 15/60 as a norm
large houses with lots of rads then i would be looking at possibly using a 25/80

 

[D_Hailsham]

I know it's a bit late now, but who said you needed a 24kW boiler?
Did they do a calculation, or was it just guesswork based on "experience"?