Underfloor heating circulation

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24 Jan 2015
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Herefordshire
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United Kingdom
Hi All

I was hoping to get some advice regarding my underfloor heating. Setup is as follows:

6 circuits connected using 1 6 port manifold
Grundfos UPS 25-60 130 pump
Polypipe mixing valve
All controlled as a single zone, no actuators, wire thermostat
Worcester boiler (with a pump inside it)
Pressurised hot water tank

Originally installed as 2 circuits, then extended to 6 zones as part of an extension. Original installation is 8 years old, and extension is 3 years old.

The problem is that the underfloor works, but doesn't seem to get that hot across the floor. I've done some fiddling, and it the circulation doesn't seem to be very fast. The flow meters give barely any reading at all. I've tested them to prove they work by connecting up a hose to the manifold inlets and outlet, turning off each zone with the blue screw cap, and then bring them on one by one. From a normal garden hose I'm able to get around 2-3 litres a minute around each circuit individually. Basically, the hot water just moves very slowly through the circuits, and the return pipe never feels warm. I've tried balancing to see if there's one really short circuit which is 'stealing' all the hot water, but not really much noticeable effect.

Any thoughts? Could it be the pump is underpowered, or has an issue so not driving enough flow? Or could the pump in the boiler be underpowered so cant circulate everything needed. Don't know what that pump is as it's inside the boiler.

Anything else I can try or can give detail on?

Many thanks in advance
 
Thanks for your response. I'm not really sure how to check it's actually working. I get some circulation, which improves when I turn down the temparature of the mixing valve (i.e. have more cold water going in). The pump is definitely energised (it sort of hums a little bit like it's working) but don't know how to check further.
 
Thanks again.

Tried this (not the capacitor bit). I can get the front big metal screw thing open to get inside to check. Is it just a case of brute force?
 
Did you run the pump as in the video and see, hear the shaft spinning?
Now run the system and see how far the flow meters register. The meters can be adjusted to increase the flow or decrease it. Make sure pump isolators are open fully.

If its still not working might be the capacitor or a duff pump.(impellar dislocated from the shaft) Or something else entirely.
 
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