Normal Running speed for MHRV

Mrs Doyle

Hiya, I have agreed to go with a supplier for MHRV. I got a call from a competitor wondering how/ why he had lost out no it, and after talking things through, he said my supplier had undersized the unit, and the unit would be very noisy running. I queries this with my supplier and he said the normal running speed would be 65% (0.5 ach) and at night running at 30%. [The house volume is approx 640m3, and the supplier has removed 10% for fixtures and fittings. The unit is a Kenetic Plus B].
He also went on to say if I prefer a 2 unit system I could do it, but thats up to me....what do people think, is the above sufficient? Is the competitor spouting for the sake of it?

cullym

The specs for that unit state:

Airflow

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Maximum, FID, 500 m3/h
Low default 20%
Normal default 30%
Boost default 50%
Purge 100%

Sound levels (@ 3 m)

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24 dB(A) (normal), 34 dB(A) (boost)

So running flat out it can shift 500m3/h.
Running at 65% as your supplier intends would indicate to me that it will be in boost mode normally. If running at 65% of max then it would be up around 34db(A) which is noisy enough. You can listen to audio of various computer fans running here http://www.sidewindercomputers.com/tecar.html

Not exactly the same but gives you an idea of the sound level involved.

I think normal or low is where you would normally want it to be. If it is running in normal mode 30% of 500m3/h = 150m3/h then it would not be sufficent to give you the 0.5ach of 640m3 (320m3/h).

Now I may be completely off with all of this. It's just my understanding based on looking into MVHR for my refurb project.

Mrs Doyle

Thanks Cullym, thats exactly what I needed. hmmm, what to do...he has already carried out some of the ducting work....