Positive Pressure Ventilation Systems 2022

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#2943196 17-Jul-2022 16:43

to add:

reading a bit more i see they recommend turning auto summer feature off in winter (having to turn it on/off is not my idea of automatic) but i think i see why.

what happens if you set the heat pump above the ventilation system set point (or the kids do), or crank up the fire place. it trips the summer feature which then tries to cool down the house. the heater is trying to heat the place, ventilation system is trying to cool it. $$$$. to add insult to injury if your not heating the other rooms, it will be making those rather cold. so you waste a lot of energy in the lounge and then jump into a rather cold bed.

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Handle9

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#2943228 17-Jul-2022 19:38

mattenz:

I've never read a convincing argument that PPV roofspace air is better than a heat exchanger for older homes.

It's not better, it's cheaper.

tweake

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#2943314 18-Jul-2022 10:07

FineWine:

And apparently that is how this system is designed to work: DVS® Premium Connect - Summer Ventilation system

3 temperature sensors: main control panel, roof space & at the outside vent.

i had a look through some of the older model manuals and it looks like they used to have it setup to change over due to roof temp. i guess they have changed it in the later ones. pity.

FineWine

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Nurse (R)

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#2944381 20-Jul-2022 17:04

tweake:

FineWine:

FineWine reply: correct - HRV is 0.3ach and SV is 0.35 whilst DVS 10.5 changes I read in the small print

it won't be 10.5. that would cause damage to any half decent house.

any link to the small print?

Oh dear my boo boo, that figure, along with the typo (1 change/1.5hr) is for their balanced system.

I can not find the figure for my system but according to a BRANZ 2019 document the DVS systems work as such:

The DVS Home Ventilation System is designed to deliver various air changes per hour, depending
on the particular system installed. The ventilation rates, and hence the number of air changes is
determined during the set-up phase of the system and will vary for each particular site. Final set-
up must be determined by the owner and Installer by monitoring the functioning of the system over a period of
time and its ability to control moisture to required acceptable levels. Once established, the most
effective ventilation rate can be controlled by the owner

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

FineWine

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Nurse (R)

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#2944382 20-Jul-2022 17:09

OK - we have gone with the DVS® Premium Connect with Summer Ventilation system and one optional CO2 sensor.

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

tweake

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#2944391 20-Jul-2022 17:33

ok, DVS is doing a bit of customer confusion with the nomenclature. generally they should use ACH not one air change per time. quick math i think thats 0.6 ach, which is roughly right. 0.5ach is a common number but you can set it to whatever you like. as all homes are different sized, you need to match flow to the house size.

balanced ventilation means you can run a lot more ventilation and constant flow in all weather because you don't have the temperature penalty as with positive pressure. positive pressure they slow it down to avoid bringing in to much cold air and then counter that by speeding up during the warmer part of the day. but it also can turn off if the roof space gets to hot. so the amount of ventilation can be somewhat variable. thats why i like the summer kit, especially a proper auto one which keeps the ventilation going.

but balanced ventilation needs a fairly air tight house for it to be worth it.

these companies using BS marketing, not given out any real detail, making it confusing for the customer, is why i get pissed off with them.

tweake

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#2944424 20-Jul-2022 19:17

FineWine:

OK - we have gone with the DVS® Premium Connect with Summer Ventilation system and one optional CO2 sensor.

i hope they can set the summer kit to work properly rather than tryin to cool the house with it.

co2 sensors, i would think you want them where you would have guests, eg lounge. normal ventilation should keep normal co2 down just fine, its when you have a lot of guests inside is when you get elevated levels, especially if its cold and ventilation has slowed down. don't get to fussy on the settings, those sensor won't be highly accurate.

FineWine

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Nurse (R)

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#2960477 28-Aug-2022 15:02

Well it has been 3 weeks now with our new DVS Positive Pressure Ventilation system with Summer Vent add-on.

3½ hours to install. All very tidy work. One tiny mistake on our part - we had the light switch sized control panel installed at the same height as the two other switches in the hallway. This ended up being a light switch height too low. We have to slightly bend/crouch down to read or adjust the system.

From the first morning post install - NO crying windows. Warmer house. 50% less run time of heat pump. Way less to near nil damp atmosphere.

Very happy owners.

Only criticism would be, is that for what the system is in actual hardware (4 plastic out-vents, one plastic in-vent, approx 15m insul ducting, 'Y' duct junction, fan & assembly, filter, 2m cat6 cable, control panel) is all this worth $5300 including 3.5hr labour of 2 persons (electrician plus electrician assistant) & ECoC & ESC ??

Oh well 🤷‍♂️

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

tweake

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#2960483 28-Aug-2022 15:21

Yeah they know how to charge for those systems. I have a similar setup and it was ~$1500 without labor and that is with insulated ducting.

What mode of action is the summer kit? It will be interesting to see how that functions as we roll into summer.

FineWine

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#2960486 28-Aug-2022 15:55

tweake:

What mode of action is the summer kit? It will be interesting to see how that functions as we roll into summer.

Quote from brochure:

DVS® Automatic Summer Ventilation. A continuous supply of fresh, filtered air is drawn from outside of the roof space when the roof space itself becomes too hot. This allows you to make better use of your DVS® during summer, ventilating with fresh air when you’re not home to open the windows.

So when our Tin Roof roof space temp goes above the default or our set temp, then it shuts off and opens up the outside vent to drawn in cooler air from summer shadiest side of our house.

As you say, it will be interesting to see how that will go. At the moment we have left it at the default setting for kick-in and fan speed. This we can change though. The overall master system temp is set at 21º which is our comfortable winter temp. During summer we will lower that to 19º.

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

tweake

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#2960488 28-Aug-2022 16:20

FineWine:

tweake:

What mode of action is the summer kit? It will be interesting to see how that functions as we roll into summer.

Quote from brochure:

DVS® Automatic Summer Ventilation. A continuous supply of fresh, filtered air is drawn from outside of the roof space when the roof space itself becomes too hot. This allows you to make better use of your DVS® during summer, ventilating with fresh air when you’re not home to open the windows.

So when our Tin Roof roof space temp goes above the default or our set temp, then it shuts off and opens up the outside vent to drawn in cooler air from summer shadiest side of our house.

As you say, it will be interesting to see how that will go. At the moment we have left it at the default setting for kick-in and fan speed. This we can change though. The overall master system temp is set at 21º which is our comfortable winter temp. During summer we will lower that to 19º.

If you get some good sunny days this week, i would check it does that. one of the more common setups is to switch to outside air when room temp goes above the set temp, which is not good.

I would not bother changing temps for summer etc. i would leave it at 21 and forget about it. Its a ventilation system, not a house heating/cooling system.

Handle9

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#2960497 28-Aug-2022 16:44

tweake:
If you get some good sunny days this week, i would check it does that. one of the more common setups is to switch to outside air when room temp goes above the set temp, which is not good.

There’s nothing wrong with utilising free cooling if it’s controlled correctly. If there’s no mechanical cooling utilising outside air below a setpoint (not necessarily below room temp) will work pretty well.

If you have mechanical cooling it’s much more complex and ideally you’d have enthalpy control.

tweake

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#2960498 28-Aug-2022 16:55

Handle9:
tweake:

If you get some good sunny days this week, i would check it does that. one of the more common setups is to switch to outside air when room temp goes above the set temp, which is not good.

There’s nothing wrong with utilising free cooling if it’s controlled correctly. If there’s no mechanical cooling utilising outside air below a setpoint (not necessarily below room temp) will work pretty well.

If you have mechanical cooling it’s much more complex and ideally you’d have enthalpy control.

Of course the issue there is ventilation airflow is not large. it also depends on if the outside air is cooler (which its not during summer), so it also can fight against your mechanical cooling (ie aircon). the control setup becomes messy, especially as many systems do not have enough temp sensors to even read all the required temps. A lot of the ventilation "cool the house" setups are hack jobs.

The whole point of ventilation system is ventilation. Use the summer kit to keep the ventilation going, ie doesn't stop due to the high roof space temps.

Handle9

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#2960500 28-Aug-2022 17:06

Outside air is very frequently cooler than inside air and/or has lower enthalpy during summer. Economy dampers don’t close during summer, they are at least partially open for most of the day.

tweake

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#2960503 28-Aug-2022 17:15

Handle9: Outside air is very frequently cooler than inside air and/or has lower enthalpy during summer. Economy dampers don’t close during summer, they are at least partially open for most of the day.

what country are you in?

its certainly hotter outside in summer than the temp i want inside (even at night), plus the higher humidity.

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