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Hi all,

 

I've been trying to balance the system today, and am struggling.

 

House is approx. 95m2, on 1 level only.  5 supply, 3 extract valves.  MHRV unit is a Vent Axia Sentinel Kinetic BH.

 

Supply (1 75mm pipe to each plenum)

I can get this to balance at 60% boost easily.

 

Extract (2x 75mm supply pipes to kitchen and bathroom, 1 to Utility.  Pipe runs are all very short, no more than 4m) 

Won't balance.  When I get the system to 65% boost I can get the total required airflow, but I cannot reduce the bathroom and utility plenums to their required values, and cannot increase the kitchen to it's required value.  At 100%, there is plenty of flow everywhere.

 

Do you think I need some sort of restrictor inside the plenum to reduce the output?  I am using these plenums: https://www.bpcventilation.com/90-plenum-round-pipe-airflex

 

Also, for a house of this size, should I need boost levels so high?  The unit is spec'd to be good for up to 150m2 of floor area.

 

Feeling a little deflated, as all if the installation wen't very well generally.  I have also ensured there are no air leaks and foil taped up every join on the 5" side.

 

Any tips or guidance much appreciated as ever.

 

Tim

 

 

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got this to do so interested in the replies here - hope ours goes OK, I'm pretty sure you will get an answer here. 

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I assume everyone has gone outside to enjoy the weather, but hopeful that one of the resident experts will be about again soon.

 

I'll try BPC again tomorrow, but whenever I've called the person who deals with these things isn't there 🤔 

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Still not had much luck with this.... I don't feel the unit should need to run at 80% on boost for a house the size of mine.

 

BPC looked at the rates they provided, and said they were wrong and re-did them, requiring a slightly higher overall rate!  They also said I needed to set the Cooker Hood ''Normal' and 'Boost@ settings to 100%, even without a hood fitted - maybe a useful note for others with a Vent Axia unit.

 

Hopefully at the weekend, I will try and balance it up at 90%, or 80% of BR requirements and see how I go.  Reality seems to be nobody wants to run their systems at BR rates anyway!

 

Tim

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Things are looking a bit more positive now!

 

I can get the system roughly balanced, with the system at 60% boost extract, and at 90% of BPC's recommended flow rates.

 

I've asked BPC to supply me with a proper restrictor for the utility plenum, as this is the one I was struggling to get to a low enough rate, to get the others to a high enough rate.

 

Tim

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good news for you - bet you're relieved.

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