Air or not

[Riley]

Just done a boiler swap and this is killing me. Sealed system was a greenstar ri have put in Glowworm R so no diffference. New pump. Can get all rads hot individually but not all together so no blockage. Out of ideas here any thoughts. Boiler cycling on n off but heat going nowhere else

 

[ShaunCorbs]

Piped correctly?

 

[Riley]

Gone over it and over it. Right pipe on Worcester was return nothing else to get wrong really

 

[ShaunCorbs]

Drain off on boiler ?

if so shut the pump and drain a bit out of it

 

[king of pipes]

New Pump in the right way ??

 

[Riley]

No drain off but AAV above. I’m 99.9% sure pump is right way round as I goes down and under and into centre of three port

 

[Aquarius]

No drain off but AAV above. I’m 99.9% sure pump is right way round as I goes down and under and into centre of three port

I’m guessing you have checked the 3 port?

 

[Riley]

I’m guessing you have checked the 3 port?

As in that it’s opening you mean??

 

[Aquarius]

As in that it’s opening you mean??

Yes mate, and all the way for heating. Also any flow/return valves on boiler?

 

[Riley]

Yeah it works for hw and ch and both. Pipes get red hot coming out

 

[Aquarius]

Yeah it works for hw and ch and both. Pipes get red hot coming out

Andy any flow/return iso valves under boiler?

 

[John.g]

No drain off but AAV above. I’m 99.9% sure pump is right way round as I goes down and under and into centre of three port

What is pump make/model/mode?, if head/flowrate suspect maybe re install old pump temporarily.

 

[Riley]

I’ve tried two. A UPs3 and some Stuart turner one that I had knocking around as a spare

 

[John.g]

A few more thoughts.....maybe stick a pressure gauge in one rad's blank vent to ensure static head is same as filling pressure of 1.5 bar or whatever, allowing for difference in pressure gauge elevations. If OK increase the filling pressure to 2.5 bar temporarily which might collapse/shift any entrained air.
It does point to a head/circulation problem for whatever reason as one rad at the time only circulating, suggest re installing the UPS3 and beg/borrow a energy monitor, put the pump to full speed 3 and measure the power.
27W = 0 circulation, 36W = 0.3 m3/hr, 5 LPM (one rad maybe circulation). 43W = 0.6m3/hr, 10 LPM (minimum, "normal" expected) and 60W = or > 1.1 m3/hr, 18.33 LPM.

 

[Riley]

In case anyone cares it was a non return valve ;-)

 

[ShaunCorbs]

In case anyone cares it was a non return valve ;-)

stuck shut after you drained down ?

 

[Riley]

Partial blockage.

 

[Knappers]

That sucks, well done finding it.
I did a boiler the other week and didn't realise until commissioning that all 5 rads in extension had massive highspots (when I saw the pipes behind the rads I assumed it ran down the wall, not up from the floor and back down to tails!), combined with vented system it was a massive PITA!

 

[John.g]

It can happen not infrequently in systems that have pumped zones which have a (poppet type) NRV on the pump(s) discharge to stop gravity circulation.