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7 posts

Wannabe Geek


Topic # 166131 3-Mar-2015 18:43
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I've been reading alot about HRV, DVs etc type systems on here. Got a few quotes and they were all around the 3g mark. ended up buy a 2nd system for $500.

Going to install it myself so just got a few questions.

Where should the air ducts be? One of the sales person said that they should be by the doors in the rooms so they push the airs towards the windows, otherwise they will push the damp air from the windows into the room. He also said the system should be in the highest part of the roof.

The system just sucks air from the roof cavity and blows it into the room. Would it hurt to put a air filter on the inlet side as well or will this restrict the air flow too much. The outlet air ducts had a surprising amount of dust in them condescending it runs though a air filter first. 
thanks in advance.

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  Reply # 1250553 3-Mar-2015 20:46
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my DVS vents are by the doors in the bedrooms with shutters to point the air into the room. it should have an air filter on it, should be able to google search the model and pick up a filter for not a lot.



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Wannabe Geek


  Reply # 1250558 3-Mar-2015 21:01
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Hi thanks for the vent help. It does have a filter between the fan and the outlets, but nothing on the inlet side before the fan. 

 
 
 
 


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  Reply # 1250586 3-Mar-2015 21:40
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it should be on the inlet before the fan, well it is with the DVS anyways

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  Reply # 1250646 3-Mar-2015 23:10
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In my house, they are about a half metre in from the bedroom doors and in the centre of the hallway and lounge ceilings. Its a typical granny flat. No high ceilings.
If heating is the goal, i have seen a system that takes hot air from the attic and blows it out at the bottom of the wall near the floor through a vent - i think that would get a much better mixing effect, though when i take the cover off the hrv vents, they work much better

I rug doctored the floor a couple of days ago for the first time since the HRV was installed and usually it takes about 2 or 3 days to dry out but this time it was super fast - only a day and a half and the carpet had already lost that dry-but-is-it-wet? feeling.





Ray Taylor
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  Reply # 1250660 4-Mar-2015 00:33
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I have recently installed a Smartvent system, (last house I had a HRV system installed).
The people at smart vent (NZ) seemed about as clued up as HRV - not so much. More interested in selling than understanding what we wanted.

Anyhoo, the guys that installed the HRV system just asked me where I wanted the vents - thought that was rather odd as they should know where to install the vents more than I should...
I was an alarm installer for 10 years, I would consider myself an idiot if I was asking the client where they wanted to put the sensors and blindly following their requests - which I didn't do...

The difference between the HRV system we had installed in the last house and the Smartvent in the new house is that the HRV was a simple pressurisation system that took the air from the ceiling cavity and pushed it into the house.
It worked well enough, kept the house drier than without.

The new house I decided to go different, I did some research and decided to go for a Smartvent system, this system takes fresh air from outside or in the ceiling space (depending on temp) and then pushes it into the rooms inside the house, but the extra bonus is that it takes a central point in the house and sucks the air out and runs it through a simple heat exchanger that heats the incoming air from outside, keeping 90% of the heat.
Now after 6 months of use and most of a summer I'm looking at getting a core bypass kit for it so we don't keep so much of the heat inside!

The thing is the outlets for the incoming air for this system should be closer to the windows or further away from the doors as the air circulates through the house, unlike the HRV basic system.

I installed this beast myself, it took two days to do and I had the help of my father and it took some work. The hoses were far superior to those used by HRV (insulated and much larger) and the system cost much more even though I did all the work myself, but it was a seven vent system....

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  Reply # 1251364 4-Mar-2015 21:33
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Are the smartvent hoses flexicoil like HRV or solid? as the later has less resistance so should technically use less power to move the same air.

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  Reply # 1253165 8-Mar-2015 09:47
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I have been looking at a smart vent room transfer kit from bunnings, a 3 room kit, it would suck the air from the lounge (fire place, free wood supply) and blow it into 3 bedroom outlets.
Goal is heating the bedrooms in winter.

Anyone done anything similar? It would have to be DIY, as I'm on a budget,

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  Reply # 1253214 8-Mar-2015 10:39
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KennyM: I have been looking at a smart vent room transfer kit from bunnings, a 3 room kit, it would suck the air from the lounge (fire place, free wood supply) and blow it into 3 bedroom outlets.
Goal is heating the bedrooms in winter.

Anyone done anything similar? It would have to be DIY, as I'm on a budget,


Just pay attention to the position of your smoke alarms and also potentially you creating a carbon spreading effect throughout your house  i.e. At the moment you have a Chimney to take out the smoke from fire, but soon you will be sucking that same hot air with the smoke particles and spreading it throughout your house. 

From you post, It sounds like you have an open fire as opposed to a log burner?


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  Reply # 1253381 8-Mar-2015 16:03
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If the fire place has a metal pipe chimney, setup the vent with a shield so that the air is drawn over the pipe and thus pre-heated.  If you just suck warm air out of the area then it will cool down by the time it reaches the bedroom.




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  Reply # 1253407 8-Mar-2015 16:43
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Niel: If the fire place has a metal pipe chimney, setup the vent with a shield so that the air is drawn over the pipe and thus pre-heated.  If you just suck warm air out of the area then it will cool down by the time it reaches the bedroom.


was just going to say this, those flimsy tinfoil ducts they use would shed the heat going through them pretty quickly and just end up blowing out cold air

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  Reply # 1253449 8-Mar-2015 17:05
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Goosey:
KennyM: I have been looking at a smart vent room transfer kit from bunnings, a 3 room kit, it would suck the air from the lounge (fire place, free wood supply) and blow it into 3 bedroom outlets.
Goal is heating the bedrooms in winter.

Anyone done anything similar? It would have to be DIY, as I'm on a budget,


Just pay attention to the position of your smoke alarms and also potentially you creating a carbon spreading effect throughout your house  i.e. At the moment you have a Chimney to take out the smoke from fire, but soon you will be sucking that same hot air with the smoke particles and spreading it throughout your house. 

From you post, It sounds like you have an open fire as opposed to a log burner?



KennyM
An open fire place mainly heats by radiant heat rather than convection. You should have a stove/wood burner/space heater which is primarily heating by convection, ie heating the air. Most of the convective heating from an open fire place is directly heating air that goes up the chimney. That's why open fire places generally do not have quotable heat outputs and most will not produce enough additional heat to heat your three bedrooms. See the Ministry for the Environment review of literature on open fires burning wood.

To heat a whole house you normally want an output above 10kW which your fire place probably does not produce because it much less efficient, i.e. most of the heat goes out the chimney. The result could be that you won't be "heating" the bedrooms so much as "warming" them or "taking the chill off" them. Enclosed burners usually have published heat outputs which makes their suitability easier to determine. They often specify a maximum heatable area (roughly 10 m2 per 1-2 kW) but this is only approximate because it is technically the volume that you will be heating so high ceilings require proportionately more heat.

Heat transfer is dependent upon a temperature difference which has to be large enough to make up for the losses in in the transfer ducts which should ideally be well insulated to reduce such losses.

We looked at doing it ourselves but our heat source was too small (under 10 kW) and the ducting runs too long (8m to the nearest, 20m to the furthest). Even though the living area could get too hot for comfort it would not have coped with the drain heating the bedroom and losing heat through the ducting. The ducting heat losses can be significant because the surface area of the ducting is larger than the volume of air. You can end up pushing more air through to get more heat through but that increasing the fan speed also increases the heat losses so it can be a lose-lose situation unless you have heaps of heat to spare. Anyway there are equations that you can use to determine this.


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  Reply # 1253467 8-Mar-2015 17:21
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http://www.mingfans.co.nz/product/html/?37.html
I can recommend this duct.  The inner foil has holes to trap turbulence.  Insulation rating is something like R1.5 if I remember correctly (don't quote me).  That is very good compared to plain foil ventilation rubbish.




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  Reply # 1253599 8-Mar-2015 22:07
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Thanks for the replies, sorry for tread hijack!

We have a log burner(with wet back), not an open fireplace, we have a large lounge and it gets really really hot if we don't turn the fire down, I have occasionally left doors open to heat the rest of the house, but that means heating the kitchen, dining and hallways before it gets to the bedrooms.

There is definitely extra heat that if diverted to a bedroom or two would mean not having to heat them. Or at least take the chill off as mentioned if that's all the heat I can get.

The chimney goes through a part of the ceiling it's not possible for me to get to due to the second story, so taking the heat from there is not possible, but I can get to the ceiling about 3meters away from the fireplace (still in lounge) from there another 2 or 3meters to the first bedroom, 2meters to the next

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  Reply # 1253616 8-Mar-2015 22:21
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Consider sucking air out of bedrooms and blowing it into the living space so the warm air gets drawn into the bedrooms through the doors.  It produces much less noise in the bedrooms (where air gets sucked out) and it should be acceptable to have some noise near the fireplace (where air gets blown in).  All you need to do is turn the fan around, so it is easy to experiment.




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