Heat Transfer System - best inlet location

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FishinKiwi

2 posts

Wannabe Geek

#174936 11-Jun-2015 13:20

Hi folks, I have recently brought a Heat Trans 3 room system which I will fit myself (apart from a sparky for the wiring). The manufacturer’s instruction is to locate the inlet on the opposite side of the room from the heat source, and I understand the logic of this. However there is a 2 deg C difference in ceiling air temp at this location compared to closer to the fire (32 deg C at 2 meters from wood burner, 30 deg C on opposite side of the room). The length of ducting from either location is the same, about 8 meters to the bedroom and I’m conscious of the heat loss over that distance.

Am I better to fit the inlet as per instructions (opposite side of the room and about 4 meters from the woodburner) to ensure warm air is drawn right across the lounge (i.e. no cold area on the far side), or put the inlet in the center of the room about 2 meters from the burner and have 2 deg C hotter air going to the bedrooms? Other relevant info, the wood burner is on the side wall of the lounge at one end of a 1970’s two story house (heavy insulation in ceiling and underfloor insulation, but nothing in walls and original glazing). I’m intending to locate the 3 outlets, 2 in bedrooms and 1 in the hallway outside the toilet and bathroom which are located off to one side from the bedrooms. Any help would be much appreciated – thanks

Jaxson

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#1322802 11-Jun-2015 14:02

That inlet area will warm up once you start drawing air towards it, so the cold area concept doesn't really apply if it's not turned on yet.

Honestly the return air path is more important. You can't suck air out of a room without air getting into the room to replace it.
And you can't blow air into a room without some air leaving the room to make way for it.

These systems work by creating a flow through the house, so having the doors open makes a big difference, to allow the air to circulate.

Niel

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#1322930 11-Jun-2015 16:59

With a door closed, keep in mind that the air at floor level (gap under door) will be cooler so cool air will be transferred to the next room and warm air retained. Unless you leave the window open (or have large gaps) in which case the whole system is useless.

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ben28

190 posts

Master Geek

#1322945 11-Jun-2015 18:00

Good luck with this. If possible try to minimise the length of ducting from inlet to outlets I read that you lose 1 degree every metre (or was it 3m).
I've done this and the results weren't as spectacular as I would have hoped. In Auckland seemed to add a couple of degrees to the bedrooms even when I had the lounge hot as. But 2 degrees is better than nothing.

timmmay

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#1322984 11-Jun-2015 19:40

Can you insulate ducts? Put batts around them or something?

Niel

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#1323064 11-Jun-2015 22:25

You can insulate over rectangular ducting as it has flat sides, but it is hard to insulate over round ducting. Better to go for larger diameter so the pressure is lower and the air moves down the centre, but it gets expensive. A company in Auckland called Ming Fans sells an acoustic insulated ducting that works well. It is perforated foil on the inside, covered by insulation, covered by plastic, covered by foil. The perforation allows sound to enter the insulation to be absorbed, the (thin) plastic helps contain the heat so it does not leak out through the foil. At peak Winter (near zero degrees) I loose a few degrees over 6-12 meter, but it is like 2 or 3.

You can never have enough Volvos!

Aredwood

3885 posts

Uber Geek

#1323079 11-Jun-2015 23:37

Why are you putting an outlet in the hallway? Is your house 2 bedrooms, yet you have a 3 bedroom system? For the return air - Shorten the bedroom doors so they have a 20mm to 30mm gap at the bottom. And if there is a door between the lounge and hall do the same to it as well. This is so the bedrooms will "fill up" with warm air. Instead of it spilling out into the hallway.

FishinKiwi

2 posts

Wannabe Geek

#1323900 13-Jun-2015 11:15

Thanks for all the info, I'm now in the process of installing this system. While I intend to keep the ducting length as short as possible, to some degree the inlet location will be determined by practicalities of working in the roof (my first choice location is too far out towards the eaves and impossibly cramped to do a good job of connecting the ducting to the inlet).

Reducing the total length of ducting from the inlet to the bedrooms, I find the amount of ducting in the kit is about 1 meter more than I need. My understanding is the flexible ducting needs to be kept taunt to keep the inside as smooth as possible to maximise airflow, so logically I should cut the ducting to the required length. So the next decision is do I shorten the 200mm ducting to the 3 way branch or shorten the 3 individual 150mm pieces of ducting to the bedrooms? Any thoughts much appreciated.

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timmmay

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#1323964 13-Jun-2015 12:25

I'd reduce the total piping required, whichever way that works best. Probably keep the section to the junction long, then shorter after. Consider wrapping the ducting, or if it's laying on something put pink batts over it, or some kind of wrap.