# Ductwork and Geyser question



## hemlock (Nov 27, 2012)

Hello,
I am thinking of ducting my Geyser outside to eject the cold air out of the house.  My question is this - there is already existing 6" flex duct going outside, so can I reduce from the 8" duct I would need to come of of the Geyser outlet air side with no adverse effects from any back pressure I may create?  Thanks.


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## GaryGary (Nov 27, 2012)

Hi,
I don't know, but that cold air that you push outside has to be made up from somewhere -- is the makeup air going to be coming from outside?

On this house, they have summer and winter ducting for the HP water heater: http://www.builditsolar.com/Projects/WaterHeating/TC47paperAug05-1-1.pdf
In the summer, the HP intake air comes from around the fridge, and the cool HP outlet air goes into the kitchen for cooling.  In the winter they pull semi conditioned air from the crawl space and then exhaust the HP air outside.

Gary


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## Redbarn (Nov 27, 2012)

hemlock said:


> Hello,
> I am thinking of ducting my Geyser outside to eject the cold air out of the house.  My question is this - there is already existing 6" flex duct going outside, so can I reduce from the 8" duct I would need to come of of the Geyser outlet air side with no adverse effects from any back pressure I may create?  Thanks.



In summer mode, I "Y" the cooler, dry air from 8" outlet of my Geyser into 2 x 6" dia pipes. 
These are insulated and transfer the cool air from the Geyser (in the basement) to the outlet registers (on the 1st floor) which are "round to rectangular". 
These outlets are certainly more restrictive than a 6" dia pipe, probably more like a 4" dia pipe. 
I have run for 2 summer periods of 7 months like this with no problems.

This is obviously not your exact situation but in my opinion, the Geyser is darn rugged and provided the air passages are smooth without kinks or tight turns, you should be fine.

If you are thinking of dumping a steady 6" flow of air outside, where is the replacement air coming from ?


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## semipro (Nov 27, 2012)

GaryGary said:


> Hi,
> I don't know, but that cold air that you push outside has to be made up from somewhere -- is the makeup air going to be coming from outside?
> 
> On this house, they have summer and winter ducting for the HP water heater: http://www.builditsolar.com/Projects/WaterHeating/TC47paperAug05-1-1.pdf
> ...


Thanks for posting this Gary. We have a HP water heater in the basement and I've considered venting warm air from the bottom of the fridge through the floor to room where the HPWH is located. I hadn't seen this article on your site despite many hours spent there.

I've also considered venting air from our HPWH outside or elsewhere but shared Gary's concern about makeup air. I've since decided to instead try and direct all waste heat in my house to the room where the HPWH is. This includes placing electronics like routers there, and redirecting hot air from the fridge and possibly the dryer (if I can figure out how to sufficiently dry the exhaust first).


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## hemlock (Nov 28, 2012)

Hello,
Thanks for the replies.  The make up air would come from the HRV with the duct for outside exhaust air removed.  The Geyser would play the part of the exhaust.  I realize that this is a bit of a cobbled up system, but if I could pump the cold air out, it may make for a bit easier heating, and make the room a bit warmer.


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## woodgeek (Nov 28, 2012)

Not to be a negative nellie, but I don't get how this would work at all.  Sounds like a big waste of time.


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## semipro (Nov 29, 2012)

hemlock said:


> Hello,
> Thanks for the replies. The make up air would come from the HRV with the duct for outside exhaust air removed. The Geyser would play the part of the exhaust. I realize that this is a bit of a cobbled up system, but if I could pump the cold air out, it may make for a bit easier heating, and make the room a bit warmer.


It seems you could only possibly gain heat if the Geyser exhaust is at a lower temp than the outside ambient temp.   Under those conditions I think it would work.. at least during the heating season.


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## hemlock (Nov 29, 2012)

woodgeek said:


> Not to be a negative nellie, but I don't get how this would work at all. Sounds like a big waste of time.


 
Just sending the cold air outside, rather than back into the house and having to reheat it.

Semipro - thats just it.  I'd only do this during the heating season.  During the warmer months, I would simply put the colder, dry air back into the house.  The ducting is essentially already there.  It would be  fairly easy project.


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## woodgeek (Nov 29, 2012)

semipro nailed it.  If the exhaust of the geyser is cooler than the interior (which it is) but warmer than the outside, then exhausting it only costs you energy (since you are sucking in even colder air somewhere else as makeup).  So, it would only pay to do this a few hours per year when the outside temp was only slightly cooler than the indoor temp.


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## semipro (Nov 30, 2012)

semipro said:


> It seems you could only possibly gain heat if the Geyser exhaust is at a lower temp than the outside ambient temp. Under those conditions I think it would work.. at least during the heating season.


Edit: Actually, heat flow in this case is also dependent upon the amount of heat the air can hold, which in this case is dependent upon water content.  It is possible to "lose" heat from the house even if you're exhausting air colder than that outside if the air you're exhausting contains more water than that returning to your house via the HRV.


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