Where to install your new mini-split??
 

Want to install a new MSHP and you are thinking about where,
the ODU (outdoor unit) should be located?

AND,
You have a large attic space, that gets really warm during cold winter days,
and would like to harvest some of that heat..
(Maybe you don't have enough south facing windows)..


Here's an idea that I had. Insulated duct work, to pump air down to
the mini-split air-intake, using a standard attic fan.. :D
Just need to control the motor, so it's not running when you don't need it.

http://i46.photobucket.com/albums/f1...lot/hotair.jpg

The sweetest part of this hack, is you are re-cycling some of the heat that was lost via ceiling leakage..
Sorta like a solar space heating + heat recovery system.. :p

Well, since the attic is attached to the house, and the heat loss from the living space in the house to the attic is influenced by the delta-T between the living space and the attic space, and you will be extracting attic heat from the attic (which will lower its temperature) as an input to your heat pump...

Might this just be an electrically-powered heat loss machine?


Here is a similar idea, but a greenhouse is used as a heat capture device (seems like a waste of a perfectly good greenhouse to me) and it's heat is stored in an underground aquifer, but the source greenhouse is completely separate from the sink greenhouse.

-AC_Hacker

Well, hopefully your attic has quite a bit of insulation and heat loss from the house isn't that big of a deal through the attic. If not, I suggest insulating the attic first!

That re-cycled heat is only going to be a small fraction of the heat coming down the duct.

The solar heat 'storage' in my attic is very stratified.
This is caused by solar warmed air flowing upwards and accumulating in the peak.
While the attic floor air temp is sometimes actually colder than it is outdoors.
Because, the attic's thermal mass tends to hold on to that nighttime temp,
and in the morning, it's in the shade, like the north side of the house.

So, if you had outdoor heat sensors and in the peak that would trigger the fan, when it was needed..
A. Mini-Split running in heating mode.
B. Attic air temp a few deg F warmer than outdoor air.

It might even be useful during those early morning Defrost cycles.. :D

I did miss a spot when I was putting down the 3rd layer. (I ran out of insulation)! :o


http://ecorenovator.org/forum/attach...1&d=1323197261

"Might this just be an electrically-powered heat loss machine?"

That's the story of my house!! ;)

I could make it better, but my wife wants to keep the windows!!

I looked at your photo, and I really don't see anything that looks very "massy".

I think that the continual heat loss through you living space ceilings would make it appear that you had a thermal mass up there...

This would be pretty easy to prove or disprove, since you now have that dandy WebControl board, you could put a string of 1-wire sensors at about every foot, from the attic peak to the insulation, and establish a baseline of thermal mass effect. Then you could shut off your heat pumps and open the windows overnight and see what your thermal mass curve looked like then.

It is a pity that the WebControl board doesn't have a built in data logger... It has everything else!

-AC_Hacker

Not too big, the mass is in the structure. Mostly wood and roofing shingles.
You can ask any roofer about the weight of those shingles.. :eek:

I once had a remote La Cross sensor hanging up there about 16" down from the peak,
and I can tell you, it takes a while for the AM sun to heat up the air up there.

Hey! I have not checked that out since we had got the new ridge vent installed. (with the new roof).
It might be interesting to see how effective the mesh type ridge vent is...
And, now we only have one layer of shingles. (versus 2 layers before).

I'm going to go find that sensor..


Yeah, using a dandy WebControl board (with heat sensors etc) should
allow one to tailor the fan motor run time, so it takes out the excess
warm air, without dropping the attic peak's temp down to outdoor levels..
Just harvest the warmest air out of the peak.?.
Yeah, just take the warm air that was going to escape anyways.. :rolleyes:

How much of this heat is going to be lost when feeding outside the house, down from the attic and into the back of the ODU?

My attic peak heat sensor is in place. It's showing 48.8F, my IR pistol shot up there said 47.8F,
my hardwired outdoor sensor (2' off the ground) says 45.1F and the weather guy down the road says 44.3F.?.

It's 70F in the house and it's been raining lightly all day. Yeah, there is some heat leaking up into the attic..

But, I wonder if a lot of it is coming up the basement stairs,
and finding a way into the attic, via the pull-down attic stairs??

The basement & it's stairs are closed off (by a door) from the rest of the house.
So some of the slab heat (50 to 60F) could very well be finding it's way to the attic..


"How much of this heat is going to be lost when feeding outside the house, down from the attic and into the back of the ODU? "


That's going to depend on the insulation around the duct-work.
But, if the air that feeds down is 10, 15 or 40 degrees warmer
than the normal outdoor air, it's going to help efficiency.

During a sunny morning, between about 8AM & 11AM,
the outdoor temperature starts climbing at a good rate.

My guess is, the temperature climb inside the attic is going to lag
behind (outdoor temps) at first, but then the attic will become warmer.
That's the fan ON signal. Warm air forced down to the ODU should
reduce the amount of watts needed to keep the house warm.
(At the same time, sun coming in the windows will be doing the same thing).

I think this scheme would likely work best when the air temp at ground level
was down near the low limit of the ASHP.
If it was around 10 deg F, I'm pretty sure my Sanyo wouldn't mind a shot
of nice 25 deg air coming in..

The Sanyo monitoring system that I'm trying to get running would be very
useful in controlling this kind of attic heat scavenger.

http://ecorenovator.org/forum/applia...ontroller.html

If I can make the CAI board monitor the power (watts) being used by each Sanyo,
factoring in the temperature of the refrigerant, going into and coming out
of the ODU, along with the indoor and outdoor air temps..
It might be possible to come up with some kind of real-time COP data.

I want to use this COP number, to compare the performance of each unit.
Comparing one against the other. If one Sanyo starts working poorly, it should be quickly apparent.

Having a real-time COP displayed on my tablet, might be very useful
for performing little experiments..
Like going outside with a 1200 watt hair drier (4094 BTU) and shooting
some hot air in back of the ODUs..
The effect that hair drier had on the COP display, might tell me if a project
building an attic heat scavenger might be worth the effort...

http://www.nrel.gov/docs/fy11osti/49881.pdf

Check on the duct work in Fig 4 & 6 on pages 16 & 17.
I know it's just for testing, but it's interesting nonetheless.

You're making my head hurt (doesn't take much), but that's an interesting experiment. It would be interesting to see the temperature deltas between the attic peak and ground level throughout the day and we get further into winter.

The average outdoor temp since sunup, has been about 40F
(it's only 42F right now, in the later part of the heat of the day)! ;)

Last 24 Hours Weather: , read this fast, before it changes!

My attic temp right now is 66.4F (overnight min=40.9 max=68.0).

So, 66.4 - 42 = 24.4 deg F of difference (at this second)..


Anyways, since we had Sanyo #1 set for 68F most of the day,
when we were heating, the addition of some warmer air to the intake
would have likely mean less watts would have been used..



Would there be a break-even point within 5 or 10 years??
What does your kW hours cost you? Are you using PV and a GTI? :p
(I've been running this PC on solar all day).

Since I'm using high performance heating machines already,
I would be somewhat reluctant to add-on a hack like this, for a small gain.
Even if it saved 15%! That's not a heck of a lot of money,
when you are only burning 60-70 bucks a month on heating..
(We spend more than $60 on candle-pin bowling)! Prices
Heck, we could cut out bowling and our heat would be "free".. LOL!!

My heating cost is ready way lower than anyone else on this side of town...:D

And, another large duct down the side of our house would not likely be approved by my wife. :eek:

I think it looks pretty darn strange.

In the introduction, it looks like they are trying to establish a methodology for measuring the COP of mini-splits.

But in this photo:


...they are clearly trying to account for ALL of the air that is coming into the mini-split...

And in this picture:


...it is clear that the incoming air duct that is being implemented is MUCH smaller that the opening in the front of the mini-split for air expulsion, so the duct itself is a significant bottle neck to the flow of air, and would significantly diminish the COP of the system.

And this! What the heck is this? It looks like a college freshman's bad-beer nightmare...


I think NREL has some explaining to do.

But the incoming air duct is something for you to keep in mind when you build your attic hear reclaimer duct.

Good luck on this project.

-AC_Hacker

Hey, it's funded by OPM, other people's money.. (Taxpayers), so they don't have to use their
noggins, just hook up a million and one bucks worth of equipment and trash bags..
Presto, another big wad of "study" funding is in the pipeline.. ;)

That duct-work behind the ODU was what I was looking at. BUT, in my goofy brainstorm,
I visualized the warm air output port much smaller. An opening size, about the size of the IDs of wall duct.

When I was reading their paper, it seemed like some of stuff they wanted to
do was a bit out of date for doing a study of modern technology..
It had me wondering if some of their text was recycled from some
older study they did a few years back.?. Before inverter mini-splits.

Looking at what they wanted to start off with, their data collection ideas
are what might be called the "Shot Gun" or Kitchen Sink method.

I half expected to see something like, "Be sure to get the installer's wife's maiden name".. :p

I'm getting ready to install a Mitsubishi 2-zone mini-split and decided to mount the outside unit on a small platform outside the second floor on the north side of the house. Here in South Carolina, the cooling season is longer than the heating season, so having the unit on the north side keeps it out of the hot summer sun. A second reason for having it "upstairs" is to keep it above the approx 8 foot deep cold air drainage flow that flows past the house on clear windless winter nights. This location also requires shorter power and tubing runs than a ground level installation and makes it more difficult for potential copper thieves to make off with the outside unit (not that this is a problem yet in my rural location).

That sounds good, but you want to be sure the unit is mounted so it motor vibration won't be transmitted into your home.

I used some coroplas (stuff used to make signs) to block snow and rain, (gutter over-flow)
and it conducts sound into the house.
http://i46.photobucket.com/albums/f1...0slot/R072.jpg

The top edge is now taped to the siding. Our bathroom is on the other side of the wall.
There are times when the Sanyo is really cranking, the low frequency vibrations are very noticeable.
Especially when you are in the bathroom. Loud enough, so I wouldn't want it near my bedroom..

It's not that Sanyos make a lot of noise, they don't.
But, the motors and their conducted vibrations, can turn the wall into a big speaker-like surface.
Stand next to the Sanyo outdoors, you can hardly hear it.
But in the bathroom it's really drumming on the wall..

This isn't a problem with my other Sanyo, it's case is free standing.
Not connected to a rain roof..

That sheet of coroplas isn't that big of a conductor. It's not rigid, it's very flexible.
But, it's enough to make me want to replace it with a free-standing roof..

I plan to mount the unit using rubber grommets to damp any vibration that might reach the platform.

I've got the rubber shocks on the mounting feet, but they can only do so much.

I've seen a lot pics of wall mounted units, and most of them were on very
solid looking walls. Sometime brick walls.

I live in a 1956 wood frame house and if you hit the outside wall with
a tennis ball, it sounds like baseball @ 600 fps from inside the house..
A 6,000 BTUh window AC vibrates the whole bedroom wall.. :o
That's another reason we like the Sanyos, they are pretty quite..

I like your idea, a few pages back, To have the outdoor unit under a open air Carport or the such,great idea, Worth doing. A simple Structure, With a plywood roof would work well. Keep the snow ,rain and leaf debris from impacting its performance.
Probably 2 sheets of 4x8 plywood would be enough for the roof area.
I have a 10x10 Gazebo that stays dry and snow free easily all but 2 feet in.

A lot of homes have attached decks in the back.
If it's shaded under there and some kind of rain shield can be installed, that might be a good place..
I don't think the specs for over-head obstructions/blockage/snow roof are critical at all.
If there is over a foot of over-head space and good air flow gap (+18") on the sides,
there shouldn't be a problem with intake air flow..

I've had the mini split that I installed running for three winters, so I've had time to think it over.

I've read your considerations, and they are all sound.

I would repeat what has already been said about NOT mounting your outdoor unit to the house. One of the miracles of the mini split is how unobtrusive they are... so any noise that you hear from one will, over time, seem intolerable. The compressor in the mini split is variable frequency, so as it goes through it's various RPMs, any part of the structure of your house that is capable of being resonant with the compressor at that time, will resonate and create an intensified sound... in the long term, you will not be happy. So if you do build an elevated structure for your OD unit, don't even tie it to your house... resonance will be transmitted.


The amount of length permitted in a lineset is fairly long, so if you were able to shave 8 or 10 feet, there's not really a big gain.

The idea of putting the OD unit in a carport type of space is just great, for all the reasons mentioned.

And another thing that might not have been mentioned, is the temperature of the very large quantities of air that get expelled from the OD unit. In cold weather, this air will be much colder than the ambient air temperature, in hot weather, it will be much hotter than ambient air temperature. So, if you like to entertain a lot, you wouldn't want that air being ejected into your outdoor entertainment area... nor in the area near your most frequently accessed entrance to your home.

Best,

-AC

I am going to drift off topic, I am trying to talk myself into buying a mini-split.



Question #1
If Its real cold outside say 2 degrees Below freezing a heat pump may make less heat per watt,compared to electric baseboard heat.

true or false?

Question #2

If I have cold weather should I buy highest BTU heat pump I can afford. The Premise is - I want one sized not for ideal conditions but for my winter heating season conditions.
Who wants a heat pump that only puts out 12000BTU's on a warmish day.
On a cold day it will make what 1/2 that ?

Question #3
How do they rate heat pumps ? as in outside temperature for a Giving BTU output ?

#1. At 30def F, my Sanyos doesn't really see that as being very cold..
Sanyos will perform very well down into much lower temps.
See chart. http://i46.photobucket.com/albums/f1...CL/heatcap.jpg

At around 25F(-3.9C) seems easy for the Sanyos, under 20F(-6.66C)
they start to work harder. But when it's 5F (-15C) they will still
put out more heat than electric baseboard heat (Using the same wattage).
But, when you go lower than -10 or -15C the top-end BTUh falls off.
The chart shows the dead end is around 16,000 BTUh..
So, at that point you might want back-up heat.. (electric baseboard )?
Depending on your load (and insulation/sealing etc).

#2. Wow, that's a good question. I'm using a 36,000 BTUh heater in a smallish Den,
and it's way too large for the room.. But it works great. Because the Sanyo Inverter
allows it to lower the RPMs of the two large motors in the outdoor unit.
That means the BTUh is very adjustable, between 4,400 & 29,000 BTUh..
That uses 290watts to 2.49 kW per the chart,
but it's actually about 420 to 480 watts on the low end (in my house).
I think the 290w might be seen, if you are heating on a very mild day..
http://i46.photobucket.com/albums/f1...L/poweruse.jpg

Because the system is 'too large' for the sq footage it's heating (the load),
it's not working very hard. It might last a few years longer than normal.?.

If it doesn't cost a much more for a larger unit than you really "need",
and the power specs are good.. Why not get the larger unit?
I know a few folks that went larger and are very happy they did..
It allows for fast heating of a cold house and those cooling extra BTUs
BTUs come in real handy on those freak summer days when it's super hot.


#3. Inside and outdoor temps dictate power usage. See chart.

Thanks, that was very helpful.
I found from the chart you posted that A 29,000Btu mini split(with the same components)
would produce 22,420Btu's or 30% less heat (then its rating) on a 23F or -5c day.

It rarely goes below 23F or -5c Where I live, So I could use a unit with about 30% more Capacity then I really need. That should do it.

I could figure out my current use in electricity over the coldest months, convert that to Btu's and size the Mini split accordingly.

And its true rating is for a 43F or 6.1c day @ 29,000Btu's
&
On a warm day 63F or 17.2c it would make 34,000Btu's

Everything points to getting a unit.

I think I can size the heat pump by using my current baseboard heater load.
Also having 3 smaller indoor units hooked to a big outdoor unit would work for me.

So say a 29,000 outdoor unit and 3 12,000btu indoor units.
A 1000 Watt Baseboard Heater is about 3,400Btu's

My living room has 2 1500watt baseboards or 10200 Btu's
Each of the 2 upstairs bedrooms has a 1500 watt heater or a 5100Btu's
My rec room Downstairs Has a 1500w baseboard as well. (don't use it)
So that's 25500Btu. So one 29,000Btu Heat Pump should heat my whole house.

For some reason the manufacturers don't seem to want to give Americans real data about performance. Maybe we are not trained enough to understand it but in Europe that info is front and centre. The standard there is to measure performance at a given air entering temp and water leaving temp.
In the one below they quote the standard of A2W35C and A2W55C to give your COPs.

Other manufacturers I have seen give the data at A-7W35 as well as at 2C. There is a lot more info in that number than we get especially if we have 2 numbers than we can make an output graph.

Sounds like you have the sizing done. :)
Keep in mind, those Sanyo spec is for an older model. You might be able to
get much better performance from newer hardware.

Heat from a source downstairs will flow up the stairs, but cooling upstairs will be a real problem.

If you use a single unit in your living room, think of it as working like
a wood stove in the same location. Will that heat your whole house?
Mine did, but it wasn't really super warm in the back bedrooms..
Nice for sleeping, but I wouldn't want to sit in there to read a book..
I would head for the warmer rooms.. :)

One other thing to consider is the humidity/dewpoint on days when it's between 20&30F.
That will cause(& cost) you some defrost cycles. You might want to find out if anyone
in your area is using ASHPs for heating and find out about their performance.

When the dew point is running at the same temp as the air temp, it will cause defrosts.
http://pauland.net/tempdaycomp.png

Use ahridirectory.org and look up the unit you are looking for in the directory under the Variable-Speed Mini-Split and Multi-Split Heat Pumps section, you can see its 17F rating. Since you don't get that cold you could match your load to that. If you don't have another source of auxiliary heat for the absolute coldest nights, you might want to step up slightly on your load requirement to account for defrost cycles which will cause the unit to temporarily stop producing heat. Also from the AHRI site, higher HSPF numbers are more efficient units. I'm not sure if SEER or EER are terms used in Canada but higher values for those are better for cooling efficiency during the summer.

We use the same system you do and almost all the equipment sold in the US is also sold in Canada. When I am looking for the most efficient product I can find, I go where most of the efficient stuff comes from......typically Germany or Denmark or Austria (sometimes others, including the USA). I find they are more truthful about ratings than we get over here. Take car efficiency for example. If some company says their SUX2000 gets 50mpg, do you believe them? I've never seen a North American vehicle meet the advertised target.

On the other hand, I brought over a 15 year old 1 ton VW truck from Germany. The "passport" (as they call it) states that it gets 9.5L/100km combined fuel consumption. And it did.

In my trade, every advance in heating efficiency comes from Europe. Every company here that makes a similar product, bought parts or technology from Europe.

Anyway, the HSPF numbers are good for comparison with other like products but I think the way I presented it above is more honest and has more real info even though the AHRI has data shown. The home owner has to be smart enough to understand it though, and I don't think the average North American gets taught to understand these things, unfortunately. Just my 2cents.

Finished installing my Mitsubishi heat pump 2 weeks ago and it has been running nicely ever since. The industrial rubber vibration isolation feet I installed on the outdoor unit are very effective and I can't hear or feel any vibration or resonance in the house even when standing inside the house next to the wall with the outdoor unit running 2 feet away on the other side of the wall.

If it's attached to the wall, there is a very good chance sound will conducted.
Almost everything made of solids has a resonance frequency.

There might be sound, but it's at a lower frequency and amplitude than you can hear.
However, you may be able to feel it..

Of course if the resonate freq of the wall, is higher or lower than the range
produced by the heat pump, there won't be a problem.

I've seen pictures of outdoor units mounted on brick walls.
Those might be safe from absorbing acoustic range vibrations.

The energy has to go someplace. Into the Rubber shocks (turned to heat)
or transmitted via air/as sound.
How much energy gets past the shocks, depends on what they are mounted on.
Is the shock mount sitting on a sound conductive medium?

Luckily, not a lot of vibration is emitted by the compressor.
But there is some. If you look at this pic, you can see about six
vibration dampener bags attached to the copper pipes.
The four on the right have brown packing tape around them.
These wrap-around bags contain a putty-like substance.
It absorbs vibrations, keeping the copper from being resonated too much.

http://i46.photobucket.com/albums/f1...r/NCL/R060.jpg

Its mounted on a 4' x 6' plywood deck whose one side is bolted to the wall of the house and whose other side is supported by two 4x4 posts. The vibration isolators are rubber industrial units bought from McMaster-Carr and I can't hear any noise or feel any vibration in the house with the outside unit running wide open or ramping up or down.

I'm glad the rubber insulation feet have worked well for you, and I hope you have no unwanted resonant vibrations.

I posted the message that you quoted because a personal friend of mine had installed an LG unit to an outside wall of his frame house, above head height. He is very thoughtful with his work and his craftsmanship is be best I have ever seen on anything he attempts. To be quite honest, I'm not sure if he used rubber vibration insulators or not. It would be odd for him to overlook such a thing. But his house is very quiet and the noise problem was not easily ignored.

Good that you found a solution.

-AC

Windows are just holes in the wall for energy to flow through . :-(

God bless
Wyr

Speaking of Hole-in-the-wall... There is an old 18k AC in my den wall that needs removal.

The problem is what to do with the 20x25 hole??
Wife don't like a complete seal-up idea. So, besides a window, what cool thing could I install in the hole and not be too lossy.?.

http://i46.photobucket.com/albums/f1...pse3347513.jpg

[QUOTE=Xringer;31975]Speaking of Hole-in-the-wall... There is an old 18k AC in my den wall that needs removal.

The problem is what to do with the 20x25 hole??
Wife don't like a complete seal-up idea. So, besides a window, what cool thing could I install in the hole and not be too lossy.?.

QUOTE]

Window with some kind of planter / flower box ?

Or some kind of whole house vent or fresh air fan , to use when the weather is nice outside ?

God bless
Wyr

I was thinking about planter, but I fear it would be leaky and a security problem.
Busted Burgler - YouTube

The ventilation idea has also occurred to me.
And it would great to use in the summer. But it would have to be sealed
up good in the winter.. :(

Maybe a small ERV? :D

http://residential.fantech.net/wp-co...v-page-top.jpg

Energy Recovery Ventilator ?

I know just about nothing about them ?

God bless
Wyr

Yeah, one of these would allow us to suck in some cold outdoor air,
and heat it up some, by stealing the heat out of the air we are pumping outdoors..
That diamond shaped box in the middle is an air-to-air heat exchanger..

Works the same way in the summer, but does the opposite. Cools off the incoming hot air.

It's a way of getting fresh air in your house, without wasting too much AC or heat..