Good results from an 8 Star house on a nice hot day

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Re: Good results from an 8 Star house on a nice hot day

Postby munrre » Sat Jan 07, 2012 10:30 pm

Very impressive staying that low on a 41 degree day. I'm sure the concrete slab helps.

I couldn't find mention of the overnight temp? Our place is fine if the overnight temp is below 20 degrees but the recent mini heatwave in Adelaide didn't get lower than 29 overnight. So the AC was on for about 10 hours this week.

I'm very interested in the fridge cooling project. Our fridge/freezer (auto defrost grrrr) averages 1.3kw per day at ambient 18 degrees. As it has the condenser in the walls I am unable to super insulate it so I am planning to vent it at the sub-floor and ceiling. I intend to enclose the vented part and insulate the cabinet it will sit in, mainly to stop the cold during Winter entering the house via the walls.

It may sound like a bit of overkill but our house is averaging between 5 and 7 kw/day usage at the moment and the fridge is taking a disproportionate amount for my liking.

Rod
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Re: Good results from an 8 Star house on a nice hot day

Postby PeterReefman » Sun Jan 08, 2012 3:36 pm

Hi Rod - we're lucky here with nights. Small country town on the coast of Vic means things cool off well at night even on hot days. It dropped to about 25c over night which was the same inside the house (windows opened up).

Funny you should mention about fridge venting. We did pretty much that with our 5 Star 413l fridge. The following is a description of it that was printed (in part) in the second edition of Michael Mobbs "Sustainable House" book.
The fridge duct has been very good. The main thing was it was quite easy to install during construction, and of course would be all but impossible to retrofit for a concrete slab.

There is an exhaust fan in the duct to help draw cool air. This fan is hard wired to the fridge so that it's only on when the compressor is running.

In actual figures we moved in with an old(ish) fridge that I knew wasn't very efficient, and didn't have the duct hooked up at all. It shocked me to learn it was chewing through 3.5kWh per day! This made it the biggest user of energy in the house by a long way. I then hooked up the ducting and the consumption dropped by almost a full kWh, which was much better but still very high in relation to the rest of the house.

So I bought one of the mid-sized 5-star Electrolux fridges which are rated at 355kWh per year. That figure was pretty accurate as the fridge without ducting (in early Spring) was using about 1kWh per day. I then sealed the fridge into the cabinets and hooked up the ducting. The consumption went down to 650wh per day, which is an AMAZING improvement over the original old fridge. At that time the average outdoor temp was approx 10c, and the average indoor temp was approx 20c.

Since then the very cold outdoor weather is behind us meaning the outdoor temp is similar to inside, and the fridge is using the rated consumption of around 1kWh per day. That makes perfect sense of course, but all in all the savings over Winter are more than enough to justify what the duct cost me to install.

The big picture as I can see it is that the upgrade to the fridge cost $1,500, and to for a consumer to get a builder to install a ducting system like this in a new house would probably also cost around the same amount. If we ignore the embodied energy of getting a new fridge, there's around 900kWh per year saving in the fridge upgrade and around 100kWh for the ducting which would make the money better off being spent on making sure the fridge is as good as possible first of all.

But taking the embodied energy of the new fridge does change this a little. From my understanding the embodied energy in mid sized fridges is around 1.5t of carbon or equal to about 2,500kWh. The ducting would require a fraction of this. So for the first three or more years the new fridge would be only paying back its carbon debt, but eventually that fridge would actually be better economically and environmentally. But doing both is even better of course!

The other factor for me was that the energy saved was equal to about $8,000 worth of PV panels (at that time) to create that 3kWh per day difference in consumption (not to mention the embodied energy of the extra panels...), so saving energy with the better fridge and ducting was certainly the best and cheapest way to go.


Here's some pics
http://www.flickr.com/photos/30247641@N04/4309363077/in/photostream/

Cheers,
Peter
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Re: Good results from an 8 Star house on a nice hot day

Postby bpratt » Sun Jan 08, 2012 4:35 pm

Interesting read.

I guess if you have an inefficient fridge, this ventilation system would be very handy to have, but its value lessens as the replacement fridge is a new very efficient model.

I'm wondering if any form of venting a fridge 'hole in the wall' (as a lot of places seems to want to seal the fridge in to the cabinetry), via at least a cavity that opens in to the ceiling above it would be a worthwhile activity ?
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Re: Good results from an 8 Star house on a nice hot day

Postby Smurf1976 » Sun Jan 08, 2012 5:14 pm

A lot of this will depend on climate. In a cooler climate such as Tasmania, it gets a bit more complex.

A - Improve the efficiency of the fridge itself by keeping it cooler through venting. That's the good bit.

B - Increase the need to heat the house due to loss of the heat otherwise released from the fridge. That's the bad bit.

Obviously it's more clear cut if you're in a warmer climate with less need for heating.
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Re: Good results from an 8 Star house on a nice hot day

Postby Tracker » Sun Jan 08, 2012 5:15 pm

bpratt wrote:I'm wondering if any form of venting a fridge 'hole in the wall' .......via at least a cavity that opens in to the ceiling above it would be a worthwhile activity ?

One could only speculate that ANYTHING cooler than INSIDE the house, has to be better. In addition, NOT having to remove that condenser-heat from the kitchen, via Air-Cond.., would also help.

BUT - I have to declare that I would hate to be the Fridge'-Mechanic, trying to work on appliances sealed into walls/cabinets..
It's like these dumb F'ing Paykel fridges and their integration kits.
Just so much work to pull it all apart , it would not be worth the effort, and the customer would not be happy to PAY the extra labour costs , just to get at it..

IF -- you do attempt to build-it-in, be sure that the GPO is OUTSIDE the sealed area. 80% of fridge repairs do not need access to the rear.

By way of complete confirmation of the issue of getting rid of the heat, and the efficiency of that fridge..
Many fridges have forced cooling, where cool air is drawn in and blow out the front, cooling a wire (heat-Exchanger) grill, or scroll-cage..
Please be certain, if you have one of these, that you vacuum it at least yearly.
I have seen fridges completely stop cooling, because this wire-heat-exchanger (condenser) was blocked with dust. Their owners had been prepared to go and buy a new fridge, and were astoundered when their Dysan, fixed the fridge.
..
.
M.Mobbs wrote:At that time the average outdoor temp was approx 10c, and the average indoor temp was approx 20c.

I thought MM lived at inner Sydney (Chippendale or Darlo.. or ??) -- I can't imagine the AVERAGE daily temp ever being 10C..

The actual suggestion that there was an efficiency benefit from using the colder air, is the basis for my earlier wondering (about multiple fridges) and if the energy cost of using a RAC was warranted.
BUT - I suspect that GORDON is completely right, and that whilst it would be marginally better for the fridges, there would be a NETT increase in the heat to be disposed of.. via the RAC..
..
.
PS - now you can understand why you MUST have a good space around the "In-Wall" condenser cabinets. ..
I have seen MANY that are a snug fit into their space, and God-Only knows how the Efficiency suffers.
It's like the dust in the Scroll-Condensers, going from WORKING to Finally-DEAD, and back to working, according to the DUST content. :mrgreen:

PPS - An exceptional design, would be to get a Forced-Cooling fridge and just seal up the Air=Flow path, such that you draw air from under the house, and exhaust it into the roof, leaving the entire cabinet, otherwise standing in the Room-Air.. AND - if you can work it, allow for the use of an REAL Air-Cond Filter, so that there is never any Dust-Build-Up in the Condenser.
Yearly replacement of the filter would save so much..
..
.
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Re: Good results from an 8 Star house on a nice hot day

Postby bpratt » Sun Jan 08, 2012 5:48 pm

Tracker wrote:
bpratt wrote:I'm wondering if any form of venting a fridge 'hole in the wall' .......via at least a cavity that opens in to the ceiling above it would be a worthwhile activity ?

One could only speculate that ANYTHING cooler than INSIDE the house, has to be better. In addition, NOT having to remove that condenser-heat from the kitchen, via Air-Cond.., would also help.

BUT - I have to declare that I would hate to be the Fridge'-Mechanic, trying to work on appliances sealed into walls/cabinets..
It's like these dumb F'ing Paykel fridges and their integration kits.
Just so much work to pull it all apart , it would not be worth the effort, and the customer would not be happy to PAY the extra labour costs , just to get at it..

IF -- you do attempt to build-it-in, be sure that the GPO is OUTSIDE the sealed area. 80% of fridge repairs do not need access to the rear.


This is the sort of thing I was wondering about, as I've been seeing a few places these days with appliances built right in to them. Surely some of those fridges must be working hard without the ventilation that they are expecting to have there.
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Re: Good results from an 8 Star house on a nice hot day

Postby Tracker » Sun Jan 08, 2012 5:57 pm

PeterReefman wrote:Funny you should mention about fridge venting. We did pretty much that with our 5 Star 413l fridge.


Peter, as a curiosity... Ref
http://www.flickr.com/photos/30247641@N04/4309359327/in/photostream/

What are we looking at here.. Is this a PIT with a cover sheet and BUG-vent.. .. If it is, then my thought would be that the egress is far to forward, and should be roughly UNDER the compressor bay, allowing maximum cooling of the compressor and then the external fridge-walls.. IMHO.. :ugeek:

Have you arranged some kind of seal material, under the kick-plate, because they are designed to let a deal of room-air in, under the fridge.... Otherwise, you will be likely SUCKING more Room-Air out than what enters from the Sub-Floor Vent.

Were I attempting it, I think that I would have done it differently, by having the FAN blowing air into the base, and hence creating a POSITIVE pressure area around the fridge, and not a negative one.. sucking away room air also.

You can buy special timer/relays called "Run-On" timers..
I would also be considering one of them, such that the fan runs a few minutes longer than the fridge..
These are used for coolers etc, so that the motor cooling process continues, after the motor has shut down..
This is the sort of thing I was wondering about, as I've been seeing a few places these days with appliances built right in to them. Surely some of those fridges must be working hard without the ventilation that they are expecting to have there.

If done correctly, the sealed "Fridge Cupboard" is open to the roof, and vented at the base, to the room.
UNFORTUNATELY, many are added during a Kitchen-Make-Over, and the Brain-Dead, just leave a big space ABOVE, to act as a heat resevoir. ... :lol: ... NO VENTILLATION.. :roll: ..
.
.
..
.
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Re: Good results from an 8 Star house on a nice hot day

Postby Smurf1976 » Sun Jan 08, 2012 8:03 pm

What you really need is a split system fridge...
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Re: Good results from an 8 Star house on a nice hot day

Postby PeterReefman » Sun Jan 08, 2012 8:15 pm

No worries - thanks for the Qs
What are we looking at here.. Is this a PIT with a cover sheet and BUG-vent.. .. If it is, then my thought would be that the egress is far to forward, and should be roughly UNDER the compressor bay, allowing maximum cooling of the compressor and then the external fridge-walls.. IMHO.. :ugeek:
Yes it's a pit cut into the concrete. Originally the duct came up at the back of the fridge, but the new (better) fridge has it's coils directly underneath, so after discussing with my heat pump installer, decided to get the feed as far forward as possible, so that the cool air could be dragged across the coils rather than just go straight up the back. And yep there's a copper mesh on both the entry and exit point of the duct. LOTs of mice, insects, etc around...

Have you arranged some kind of seal material, under the kick-plate, because they are designed to let a deal of room-air in, under the fridge.... Otherwise, you will be likely SUCKING more Room-Air out than what enters from the Sub-Floor Vent.
And yes there's a tightly fitted foam/rubber seal around the front of the fridge, which very much stops any 'inside' air getting into the sealed system. The seal is mostly just good quality plumbing lagging, so it's actually quite cheap and easy to source.

Were I attempting it, I think that I would have done it differently, by having the FAN blowing air into the base, and hence creating a POSITIVE pressure area around the fridge, and not a negative one.. sucking away room air also.
Fair enough - At the end of the day there really is lots of ways to do this (and everything else). And while it works relatively well, it's certainly not perfect. I was very much balancing doing it as well as possible at the time, and also trying to finish the house (and still am - paving at the moment)

You can buy special timer/relays called "Run-On" timers..
I would also be considering one of them, such that the fan runs a few minutes longer than the fridge..
These are used for coolers etc, so that the motor cooling process continues, after the motor has shut down..
Yes we looked at this, and other options too, but because the fan is directly hard wired to the compressor itself (the power for the fan comes THROUGH the fridge), it was just a bridge a little too far for the resources we had.

This is the sort of thing I was wondering about, as I've been seeing a few places these days with appliances built right in to them. Surely some of those fridges must be working hard without the ventilation that they are expecting to have there.

If done correctly, the sealed "Fridge Cupboard" is open to the roof, and vented at the base, to the room.
UNFORTUNATELY, many are added during a Kitchen-Make-Over, and the Brain-Dead, just leave a big space ABOVE, to act as a heat resevoir. ... :lol: ... NO VENTILLATION.. :roll: ..
Yep - agree entirely. I personally think it's RIDICULOUS that houses have ovens, dishwashers, etc built in (that all have relatively common sizes), while we feel we need to carry our fridges with us from house to house... crazy in many respects. I'm looking forward to much smarter design across MANY fronts - basic house passive design for a start! Again - crazy.
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Re: Good results from an 8 Star house on a nice hot day

Postby munrre » Sun Jan 08, 2012 8:38 pm

Thanks for the additional information on the fridge project Peter.

Just the sort of confirmation I was after that this is a worthwhile project. I was intending to use natural air movement but the hard wired fan coming on only when the compressor is on is a great idea.

Our kitchen is adjacent to our Northern glass room (which heats our living areas) so the the kitchen gets pretty warm in Winter/Autumn. I've never measured the air temp under the floor but I expect it would be about 10 degrees cooler than indoors most of the year round.
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