Positive Pressure Ventilation Systems 2022

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Handle9

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#2960507 28-Aug-2022 17:30

tweake:
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.

A lot of the time it’s hotter inside than outside, especially if the space has high solar gain and reasonable heat loads. You can easily exceed 40 degrees inside.

I’m currently in the Middle East but worked with building automation for more than 10 years in NZ.

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tweake

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#2960511 28-Aug-2022 17:46

Handle9:

A lot of the time it’s hotter inside than outside, especially if the space has high solar gain and reasonable heat loads. You can easily exceed 40 degrees inside.

I’m currently in the Middle East but worked with building automation for more than 10 years in NZ.

i think your forgetting that we are cooling to low 20's inside and outside is 25-35 range in summer. of course your also talking commercial setups not domestic.

however, spring/autumn nice fine days warm house but cool air temps. yes if you pump in enough air flow you can get cooling. however thats not really the purpose of the system, its setup for a lot less airflow than an air handler. nice if it helps but not really made for it.

Handle9

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#2960632 29-Aug-2022 07:01

It’s the same air and the same laws of physics in commercial and domestic applications.

The majority of spaces in the vast majority of NZ homes have zero mechanical cooling so you are not trying to cool to “low 20s”, you are trying to reduce the temperature of the space. Typically that’s via a fan and open windows. That’s pretty much what a summer kit does. It’s not high volume so it’s not going to make a huge difference but it does help.

For most of summer in the upper north island (I believe OP is in the Bay of Plenty) the temperature isn’t particularly high. 22-24 is pretty typical. You do get hotter days but the number of days that fresh outside air will be helpful is more than you are suggesting.

Summer kits are not perfect, or a substitute for air conditioning, but they aren’t a complete waste of time either.

tweake

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#2960829 29-Aug-2022 17:17

Handle9: It’s the same air and the same laws of physics in commercial and domestic applications.

The majority of spaces in the vast majority of NZ homes have zero mechanical cooling

thats changed a lot especially in the last 10 years or so.

of course we are dealing with domestic gear, not commercial aircon with economisers. a lot of the "summer kits" are a hack especially compared to commercial equipment.

But of course the answer is "it depends". which is why i ask to check the way it works.

Many of these systems are sold on the idea that the ventilation will heat the house in winter and the summer kit will cool the house in summer. neither of those things are really true tho it can help in the right circumstances. The catch is, does your house have the right circumstances?

neb

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#2960844 29-Aug-2022 17:51

Handle9: It’s the same air and the same laws of physics in commercial and domestic applications.

Speaking of laws of physics, if you are putting in ducted ventilation and have multiple exit points, make sure the ducting is the same length, or has the same flow resistance, for each outlet otherwise you'll get most of the flow out of one and very little out of the others.

If you're in a house where this is already happening, then that's why.

tweake

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#2960912 29-Aug-2022 19:28

neb:
Handle9: It’s the same air and the same laws of physics in commercial and domestic applications.
Speaking of laws of physics, if you are putting in ducted ventilation and have multiple exit points, make sure the ducting is the same length, or has the same flow resistance, for each outlet otherwise you'll get most of the flow out of one and very little out of the others. If you're in a house where this is already happening, then that's why.

or you add restriction with dampers or adjust the outlet itself. the flows should be different due to the different sized rooms, as the flow should match the room. you may need to do unequal length or different diameter ducts depending on flow and distance.

insane

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#2960978 29-Aug-2022 20:56

I'd honestly put the money into whole home airconditioning.

I wasted around $4000 on a HRV PPV system with drops into 6 areas/rooms. It really was just two cheap plastic boxes and cheap ducting - guessing cost price of $300 tops.

1970 house with tin roof means the roof space is too cold to bring in air in colder months (or for me to want it), and roof space goes to 50+ in summer, so similar problem there too.

The salesperson flatout lied about their installers too - Stressed that they were 100% employed by them and not contractors, but techs just put a HRV tshirt on when they showed up in the private company vehicle and said they get paid per job and install units for many different companies.

Putting in multiple aircon units later was game changing, just wish I hadn't wasted $4000 to start with.

Maybe an HRV would work better in another part of the country, but for me, total waste. I nearly went with Sayr, but they were even more expensive and got really unprofessional once they learned I took a cheaper offer from a competitor.

tweake

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#2960987 29-Aug-2022 21:44

insane: I'd honestly put the money into whole home airconditioning.

I wasted around $4000 on a HRV PPV system with drops into 6 areas/rooms. It really was just two cheap plastic boxes and cheap ducting - guessing cost price of $300 tops.

1970 house with tin roof means the roof space is too cold to bring in air in colder months (or for me to want it), and roof space goes to 50+ in summer, so similar problem there too.

The salesperson flatout lied about their installers too - Stressed that they were 100% employed by them and not contractors, but techs just put a HRV tshirt on when they showed up in the private company vehicle and said they get paid per job and install units for many different companies.

Putting in multiple aircon units later was game changing, just wish I hadn't wasted $4000 to start with.

Maybe an HRV would work better in another part of the country, but for me, total waste. I nearly went with Sayr, but they were even more expensive and got really unprofessional once they learned I took a cheaper offer from a competitor.

imho most of them are a complete rip off. very expensive for what you get.

However i disagree a tiny bit because you really need both, but i would still go heat pump first. ventilation can always be done the old fashion way, however i found ventilation systems worked better in providing more consistent ventilation. Hence really need both.

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