Secondary return problems

[Widdzy]

Hi chaps.

something that's really scrambling my head here that I'm hoping someone can help with.
Im connecting a grunfoss comfort onto a secondary return circuit into a megaflo cylinder. Pipe work run is 22mm
from the top of the cylinder for a distance of about 12m in this pipe run there are four outlets in 15 mm to various services before the pipe reduces to 15mm and returns to the cylinder. The pump is adjacent to the cylinder and pumping into the designated inlet approx 2/3 up from the base. Electrically the pump is working fine and I've removed the base of the pump verify the impeller is spinning.... No probls there. I've verified all the pipe work is clear and that all valves are open and. I've ensured there is no air in the pump and the pipe work and that the pump is correctly orientated in the line of flow. When the pump is turned on I can feel it working ok but there is simply no flow. This is derived from the fact that I would expect the pipe work to become wa after a minute or so which it simply does not. I've even tried the pump with a bucket of water to see if there is any flow but no joy again. The pump runs., the impeller spins but no flow.

Any suggestions greatly appreciated

regards

widdzy

 

[SimonG]

Pump valves open?

 

[Ch4 plumbing]

Sounds like the impeller has come away from the spindle, it would still turn but under load it wouldn't pump water.

 

[chris watkins]

If the tapping into the cylinder is clear then it is air. I take it is just a standard Comfort & not an Auto-Adapt ? is it the 1/2" FI con's or the union type ? You have opened the internal valve on the inlet to the pump haven't you ?

 

[Chalked]

Has it got a non return valve fitted? Have seen quite a few with heavily sprung or even double check valves! The pump is not strong enough to open these.

 

[Widdzy]

Hi there

yes the internal valve in the pump body is open and the inlet to the cylinder is clear and free flowing. When used above the sink and sucking all the air out to prime the pump I would expect this to encourage flow but nothing other than the pump spinning around. The impeller spins but nothing flowing .

regards

widdzy

 

[Widdzy]

Hi

yes it does have a check valve. I even went to the extent of removing the valve and spring to confirm this was not the problem.

Regards

widdzy

 

[AlexGas]

Weak pump!? Did you check the pump resistance?

 

[townfanjon]

Is the comfort brand new ?

live and neutral to it are nt reversed ?

 

[chris watkins]

View attachment Secondary return arrangment .pdf
Strongly recommend any one installing secondary return system installs them like this, after years of trying to clear other plumbers ones of air, it is worth the effort & small additional cost.
( Trust me I am a doctor LOL)

Hose on drain off & you can pull water through the system & clear any air locks.

 

[Ermintrude]

You sure your on the right port? Have u tried giving pump body a good smack? Had a big wilo pump where the spring on impeller was ok but the key on shaft was missing so as soon as under load it just span and no water.

You tried t on to the cold inlet for return with a check?