Flow rate through UFH too low

[OopNorf]

Does anyone have any ideas why we cannot achieve more than 1 lpm through our underfloor heating 

11 loops

grundfoss UPM 3 auto pump 

 

it used to work…. Now it doesn’t. Cannot pinpoint in my mind the point at which it changed. 

 

the house doesn’t feel warm enough as we cannot get the flow high enough

 

 

[Originaltwist]

I don't suppose this is the answer but I had a similar problem on one of my systems... terrible flow remained after checking everything.... in the end it was the return and flow plumbed back to front on the pump so it was trying to flow backwards ....dooooh

[JohnMo]

Air?

[Conor]

Is it just me or do the pipes and the flow indicator tubes look a bit brown? Is there inhibitor in the system? Could be crud built up somewhere.

[OopNorf]

3 hours ago, Conor said:

Is it just me or do the pipes and the flow indicator tubes look a bit brown? Is there inhibitor in the system? Could be crud built up somewhere.

Yes they are, we’ve drained it down twice and put inhibitor in it both times. Both times it was full of crap, which I can’t understand in a closed loop system ??? 

 

It’s not plumbed up back to front but we’ve had the mixer valve off tonight and there was a loose oring and another “chewed” oring inside the mixer.

no idea where the loose one has come from, nothing of similar size where it could sit so we’ve take that out and put the chewed one back in until we can get a replacement.

since refitting the mixer the flow seems better but still doesn’t seem 100%.

Going to have to drain it down tomorrow and get the air out 🙄 but will see if the improved flow improves the room temps overnight.
 

-4 here tonight so I hope it can limp along for a few days 🥶

[OopNorf]

3 hours ago, JohnMo said:

Air?

There wasn’t but now there is! 

[Conor]

What's the heat source and are there any radiators on the system? Sounds like there's corrosion going on somewhere or contamination.

[OopNorf]

15 minutes ago, Conor said:

What's the heat source and are there any radiators on the system? Sounds like there's corrosion going on somewhere or contamination.

Electric boiler and no radiators