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Flow rate keeps dropping


jayc89

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Had our boiler moved yesterday, currently trying to rebalance the UFH as the flow meters were all shut during the move and every 10 minutes or so the flow on each loop keeps dropping to near zero.

 

Is this likely to be air in the loops from the move? 

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Loops will all likely need to be manually purged again, as the flow rates from the UFH manifold are too low to shift stubborn air pockets.

You ( or they ) can sit there and let it run whilst venting / refilling and repeating ( for ages ) or you ( or they ) can just purge with cold mains and be done in an hour.

You just need to put a hose on the return manifold drain off point, remove all actuators temporarily, open the drain and allow that to run freely to outside, then open the filling loop on the boiler to allow masses of cold mains water in / through one loop / out to drain, and repeat for each loop ( doing ONLY one at a time ). You'll need to manually open each loop by pressing down gently on the pin ( that pin that gets depressed by the actuator ) to allow water to flow through.

The installer should be familiar with all this.

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21 minutes ago, PeterW said:

Likely - does it have AAVs..?

 

Unfortunately not.

 

12 minutes ago, Nickfromwales said:

Loops will all likely need to be manually purged again, as the flow rates from the UFH manifold are too low to shift stubborn air pockets.

You ( or they ) can sit there and let it run whilst venting / refilling and repeating ( for ages ) or you ( or they ) can just purge with cold mains and be done in an hour.

You just need to put a hose on the return manifold drain off point, remove all actuators temporarily, open the drain and allow that to run freely to outside, then open the filling loop on the boiler to allow masses of cold mains water in / through one loop / out to drain, and repeat for each loop ( doing ONLY one at a time ). You'll need to manually open each loop by pressing down gently on the pin ( that pin that gets depressed by the actuator ) to allow water to flow through.

The installer should be familiar with all this.

 

It was a PITA the last time I had to do that. There's no drain near the manifold so I ended up running a hose pipe through the house, which SWMBO loved. Is the boiler fill loop still the best place to top up the inhibitor afterwards?

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Can you upload a pic of the manifold etc? You should defo have at least one bottle vent / AAV on this arrangement?!

25 minutes ago, jayc89 said:

It was a PITA the last time I had to do that

Doesn't matter. Likely needs doing again.

Get it done, put this behind you, go to pub. Simples.

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28 minutes ago, Nickfromwales said:

Can you upload a pic of the manifold etc? You should defo have at least one bottle vent / AAV on this arrangement?!

Doesn't matter. Likely needs doing again.

Get it done, put this behind you, go to pub. Simples.

 

Pub sounds good right now.

 

IMG_6290.thumb.jpg.d2b90eb804b44484307b5ea85ec9aa21.jpg

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Thanks. 
You should remove the two manual vents and install automatic ones. 
F2540C83-8CBF-45B0-BD1F-E98A0FC4E211.thumb.jpeg.aa011647712bcd10d835e678379d8dc8.jpeg

 

https://www.heatingcontrolsonline.co.uk/index.php?route=product/product&product_id=821&gclid=CjwKCAiAk--dBhABEiwAchIwkWErcuPQ_EMthpOZ5eBY3VATYjXY3CtsfJKiW2tDL7MfCHybjLhgixoCUXoQAvD_BwE

 

Will be a like for like swap, 5 mins work with an adjustable spanner and an old towel. 
And possibly some wellies, depending on your plumbing skills. 
Just turn off the red and blue taps as per your pic ( they seem to be in the closed position in that pic? ) and then you’ll only lose a pint or so of water when you remove the old vents. 
I’d expect this would solve the problem tbh. Worth trying that first for sure. 

Edited by Nickfromwales
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1 minute ago, Nickfromwales said:

 

An AAV on both the flow and return? I'd seen sets sold where there's an AAV on the flow and pressure gauge on the return. 

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12 minutes ago, jayc89 said:

We do have an AAV in the airing cupboard upstairs, I think it's on the return from the DWH coil.

Noting the gate valve on the connecting pipe, and the positioning of the other pipes, I think it looks more like it's on the cold water inlet.. But that seems an odd place to put on so I might well be wrong! 

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2 minutes ago, MJNewton said:

Noting the gate valve on the connecting pipe, and the positioning of the other pipes, I think it looks more like it's on the cold water inlet.. But that seems an odd place to put on so I might well be wrong! 

 

Pretty sure it's the return, not sure why the gate is there though. The 2 port valve is on the flow and you can just see the nut of the auto-bypass valve, towards the bottom of the picture, between the two. 

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1 minute ago, jayc89 said:

 

Pretty sure it's the return, not sure why the gate is there though. The 2 port valve is on the flow and you can just see the nut of the auto-bypass valve, towards the bottom of the picture, between the two. 

The gate valve is there to balance the flow between the heating and the hot water cylinder coil, eg so the cylinder doesn’t become an accidental bypass reducing flow to the heating if / when both are calling for heat at the same from the one shared boiler pump.

 

Defo not on cold inlet. 

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21 minutes ago, jayc89 said:

We do have an AAV in the airing cupboard upstairs, I think it's on the return from the DWH coil. 

This is nothing to do with the UFH, is on a different circuit, and won’t remove air from the UFH loops. 
The vents need to be on the manifold rails to resolve your issue. 
 

Go buy some. Don’t make me come down there 💪

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Just checked back and the flows across all loops has dropped again. Interestingly, one of the flow valves is half empty - the water stops around 2.5 l/m, whereas all others are pretty much full. I've turned that loop off to see if the other ones continue to lose flow. If they don't I'll flush this loop out tomorrow and see if it helps.

IMG_7965.jpeg

Edited by jayc89
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