Whole House Cooling

[sargan]

I have a MVHR system (Villavent design) 

The design allowed for the addition of their Comfort Cooling unit ...... not full-blown AC, but would cool incoming air a few degrees to make things more comfortable at night.

 

Unfortunately, they never went into the production of the comfort Cooling unit.

 

Does anybody have or added cooling to their MVHR?

 

[Dan F]

There are multiple suppliers of "heat batteries" for cooling MVHR incluing Zehender and Veab, but cooling via MVHR provides very low cooling output. See: https://www.greenbuildingstore.co.uk/can-an-mvhr-system-be-used-for-cooling/

[Conor]

What's your heating source? I found our ashp was really good at keeping temps down. House was about 25-27c in July and heatpump got it down to 21c in a day.

[LinearPancakes]

We're soon to install an oversized Zehnder CW12 duct cooler in the supply, taking a feed from the reversible ASHP. All supply ducting will be well insulated and has been optimised for low air resistance so we can potentially increase the fan speed if needed without too much extra noise.

 

Not expecting huge cooling power, but if it can discretely drop a few degrees across habitable spaces we'll consider it a win. We've also made sure to have external blinds/solar control glazing on the south elevation, but don't want to risk that alone being enough.

 

I'll report back on how it performs next summer. 😅

[Schoolboy]

9 hours ago, LinearPancakes said:

We're soon to install an oversized Zehnder CW12 duct cooler in the supply, taking a feed from the reversible ASHP. All supply ducting will be well insulated and has been optimised for low air resistance so we can potentially increase the fan speed if needed without too much extra noise.

 

Not expecting huge cooling power, but if it can discretely drop a few degrees across habitable spaces we'll consider it a win. We've also made sure to have external blinds/solar control glazing on the south elevation, but don't want to risk that alone being enough.

 

I'll report back on how it performs next summer. 😅

That sounds well thought through and if next summer is anything like the past one could be a game changer. Do you have a system designer or have you done that yourself?

[LinearPancakes]

9 hours ago, Schoolboy said:

That sounds well thought through and if next summer is anything like the past one could be a game changer. Do you have a system designer or have you done that yourself?

 

Thanks, hopefully it'll do the trick. We've designed it ourselves. It's a radial system but using steel ducting. Using the matching Zehnder manifolds to minimise any crosstalk. The idea is that the thinner duct wall means more space for airflow/insulation. Also lets us increase the diameter where possible. It's a *lot* more work though and definitely the path less trodden!

[Dan F]

@LinearPancakes CW12 is big.  What is you building volume?  Are you planning to hook up the whole house via CW12 or only part? 

[LinearPancakes]

11 hours ago, Dan F said:

@LinearPancakes CW12 is big.  What is you building volume?  Are you planning to hook up the whole house via CW12 or only part? 

It will be on the main supply to the whole house. Our home will only be 144m2, so it's way overspecced. A couple of reasons we decided on this:

• To maximise the cooling output even at lower air volumes. I understand that in the peak of summer, when outside is much hotter than inside, it's generally recommended to keep the MVHR speed lower, since inside will still gradually increase in temperature. I extrapolated, by interpolating the data on the datasheet, that the CW12 should deliver ~3kW cooling even at ~100 m3/h. The CW6 for example could only achieve ~1.6kW. Chart attached.
• The reduce air resistance, both when not actively cooling but also when cooling as the air resistance increases a lot then, presumably due to condensation internally. The CW12 should have a negligible air resistance of ~7Pa when cooling at a boost of 240m3/h. The CW6 comes in at ~33Pa for that.

 

(Caveat, all theory so far!)

 

Edited November 5, 2022 by LinearPancakes

[Dan F]

I maybe be wrong, but I don't think the extrapolation should be linear should it?  Thre is only a maxiumum you can cool with 100m3/h regardless of the size of the comfopost and, while I haven't done the sums, I'm pretty sure it's less than 3kW.

[LinearPancakes]

Yeah, hard to say for sure since the datasheets don't go down that far.

[Dan F]

On 09/11/2022 at 09:08, LinearPancakes said:

Yeah, hard to say for sure since the datasheets don't go down that far.

 

Well, it's constrained by the specific heat capacity of air and 3kW @ 100m3/h just doesn't work.  

 

Using the parameters in the comfopost datasheet the maximum theoretical sensible cooling power at 100m3/h is 0.52kW (1.35kW total @ 80% RH).  A bigger comfopost simply can't improve on this!   You also need to consider that the numbers in the datasheet assume 28C @ 80%RH.  The reality is that on 18th July 2020 (when it was 37C outside) my Comfopost unit was getting around 25C due to MVHR being operational.

 

What MVHR unit are you planning to use and what is your planned maxumum flow rate? 

 

 

[Nick Laslett]

On 03/11/2022 at 23:31, LinearPancakes said:

We're soon to install an oversized Zehnder CW12 duct cooler in the supply, taking a feed from the reversible ASHP. All supply ducting will be well insulated and has been optimised for low air resistance so we can potentially increase the fan speed if needed without too much extra noise.

 

Not expecting huge cooling power, but if it can discretely drop a few degrees across habitable spaces we'll consider it a win. We've also made sure to have external blinds/solar control glazing on the south elevation, but don't want to risk that alone being enough.

 

I'll report back on how it performs next summer. 😅

Hello @LinearPancakes, any update on how effectively the ComfoPost performed?

[LinearPancakes]

Jury's still out @Nick Laslett - the unit is installed in the supply feed, but the water supply is not connected yet. Will report on any real world experiences. In the current cold snap, our upstairs rads seem to struggle a bit with the 45deg flow temp from the ASHP - probably could have done with sizing them up a little. Hoping using the ComfoPost to warm the air will help a little bit too, or at least offset the cooling due to inefficiencies in heat recovery.

Edited November 30, 2023 by LinearPancakes