1 or 2 mvhr units?

[lizzieuk1]

So, PaulHeat have calculated as below, I think that means we need a unit(s) to do 438 m3/hr max. 

They suggest either 2 x zehender 450 or 1 x 600 - I'm not sure why if we need 438m3/hr, we can't have 1 x 450, is it to do with the l/s do you think? 

Anyway, if we need one or other of those options any opinions on 1 or 2 units? (We may go for the Ventaxia units but undecided, same Q re 1 or 2 units though)

Initially I thought is it easier to have 2 units so that we have less logistical issues ducting from 2nd floor plant room to gf (we could put the 2nd unit in the utility room on the gf) but, I'm not sure if that's reason enough to buy 2 units! 

Any thoughts?

 

 

[JohnMo]

You're flow rate is determined via building regs, however you will most likely to reduce through put to meet passivhaus standards, otherwise a big house equals very low humidity levels.

 

1 or 2 units, I did two for ease of duct routes and reduced duct length. So location is in very different places for best routes of duct. But you have twice the maintenance bill. So a balance for you to make.

[Mike]

1 hour ago, lizzieuk1 said:

I'm not sure why if we need 438m3/hr, we can't have 1 x 450, is it to do with the l/s do you think?

Because if you run MVHR flat out the noise can be intrusive. Ideally run it at no more than 2/3 capacity, but maximum ¾ capacity.

 

1 hour ago, lizzieuk1 said:

We may go for the Ventaxia units

Preferably choose units from the Passivhaus database, which lists units have been independently tested to into account both the heat recovery rate (for which the standard way of measuring it is inadequate) and the electrical consumption of the fans (which will be running 24/7 for many years). Efficiency Ratio = overall performance (heat recovery & electrical consumption).

 

[Thorfun]

We were told we needed two units but I pushed back as I didn’t want to pay for two units and to pay to install two units and to maintain 2 units with filter changes etc. So the M&E company calculated that if we upped the duct size to 92mm we could use one Zehnder 600 which is what we did and I have no complaints at all. 

[Nickfromwales]

3 hours ago, Thorfun said:

We were told we needed two units but I pushed back as I didn’t want to pay for two units and to pay to install two units and to maintain 2 units with filter changes etc. So the M&E company calculated that if we upped the duct size to 92mm we could use one Zehnder 600 which is what we did and I have no complaints at all. 

I never fit lesser than 92mm. Always great results tbh.

 

10 hours ago, lizzieuk1 said:

They suggest either 2 x zehender 450 or 1 x 600

The Brink 600 out-performs the Z'r and is less money  Just fitted one, last week, and about to fit a 2x 600 install in a weeks time.

[Nickfromwales]

9 hours ago, JohnMo said:

But you have twice the maintenance bill

Which is? 

[Oz07]

The units are very expensive for what they are aren't they? I'd be trying to keep it to 1. 

[JohnMo]

8 hours ago, Nickfromwales said:

Which is? 

2x filters, and paying for someone to it if you can't.