Why is my HRV heat transfer not working?

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mynx

3 posts

Wannabe Geek

#319425 23-Apr-2025 21:21

Hi, we have recently moved into a new home which has hrv. We have figured it out...for the most part. One thing I can not figure out is the heat transfer. We have 3 bedrooms. When the heat transfer is working it will send warm air out of the vents in two of the bedrooms...the third there is nothing. However, when sending cold air through the system all three bedrooms receive cold air. Why is it just one bedroom not receiving warm air? Would love to sort it before winter. Any ideas? Thanks!

Linux

11413 posts

Uber Geek

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Lifetime subscriber

#3366970 24-Apr-2025 08:24

You would have to inspect the ducting in the roof would be impossible to tell from your post

tweake

2391 posts

Uber Geek

#3366987 24-Apr-2025 09:49

pics of the system please. also pics of the returns from each room.

odds are its been built like that. probably got a damper in one leg to shut it off (it may have been a storage room etc). should be able to tell from photos of the system.

mynx

3 posts

Wannabe Geek

#3367569 25-Apr-2025 20:52

Sorry for the delay in replying. I looked at the system but tbh I don't know what I am looking at lol I have attached a couple of pics of the panel. In picture one there is hot air being blown into all bedrooms (including the one that didn't seem to get heat) however in pic 2 (which is how our system normally looks) again warm air in two of the bedrooms but not the third.

https://cdn.geekzone.co.nz/imagessubs/26982306142e47ee609d4c4456e0ab11.jpg

https://cdn.geekzone.co.nz/imagessubs/7a91e3aabf346ef28fa042b9476c2c83.jpg

Hopefully that works!

tweake

2391 posts

Uber Geek

#3367573 25-Apr-2025 21:32

need to see whats in the roof. many pics as you can please.

also how many grills in the bedroom? if only one how much gap is under the door? this is rather important as there is potential for death.

mynx

3 posts

Wannabe Geek

#3367575 25-Apr-2025 21:53

Grill? The vent? There is one in each bedroom and 2 in them lounge. Why could having the door shut cause death? From what I have read it is only if there is something that produces carbon monoxide in the room that it could cause iasues

tweake

2391 posts

Uber Geek

#3367625 26-Apr-2025 11:16

mynx:

Grill? The vent? There is one in each bedroom and 2 in them lounge. Why could having the door shut cause death? From what I have read it is only if there is something that produces carbon monoxide in the room that it could cause iasues

i'll try to keep a long story short.

i assume you have a fireplace in the lounge as heat transfer systems only work well with fireplaces. thats the source of carbon monoxide.

a lot of these systems get installed with no return path (no undercut doors in the bedroom and lounge or jumper ducts). that makes it very inefficient as it blows your bedroom warm air outside. all hvac systems need a return back to the heat source. but what it also does is removes air from the lounge creating a slight vacuum in the lounge. combine that with a fireplace that dies down at night, it can (and it does, its happened more than a few times) cause the fireplace to back draft. ie pull air back down the chimney. this means the smoldering fireplace exhausts into the lounge and that is transferred to the bedrooms. that results in a house full of smoke and carbon monoxide. fortunately the smoke sets off the fire alarms and no one has died yet.

this has been in the media a few times. it gets incorrectly diagnosed by fire brigade as they assume its a ventilation system not a heat transfer system. most manufactures ignore this, i have only seen one that has it written in their instructions. i've heard of installers telling customers to leave the doors open. its cheaper to install when you don't install the return side.

tweake

2391 posts

Uber Geek

#3367626 26-Apr-2025 11:20

the system will have a damper which changes the system over from ventilation to heat transfer. its probably on the leg that goes to the two rooms. all that would need doing is to move the 3rd outlet connection to the other side of the damper where the two other outlets are.