Questions about DIY Install of Mini-Splits

[Xringer]

My units are 220v. The larger BTUh units all have to use 220v, due to their higher power usage.
Units rated for 12,000 BTU or less can run on 120vac, but some use 220, so they can have
common parts with the larger BTU units in the same product line.

Plus, people in other parts of the world use nothing but 220..
And it's easier to build them with just one type of power supply..

If the 18,000 has good specs, you could use it. If your living space ever needed a full
12,000 BTUh to keep it comfy, that extra 6,000 BTU would be good to have,
just in case..

My den never gets real cold when we BBQ and we are in and outdoors 20 times..
That 36,0000 BTUh can handle it easily..

Here's some basic ASHP info.. A mini-split has some small differences, but the theory is the same..

http://youtu.be/14MmsNPtn6U
Here's how they say it in the UK.. http://youtu.be/g39nM7GbSJA

[AC_Hacker]

Originally Posted by woody

Anyone....
Can someone point me to info on how these systems work?
Like for example.... does the heat pump actually heat up the R104A refrigerant and then move it to the conditioner in side? If so then I would think the length of tubing will make a difference of efficiency. shorter the run the better?

The charts you are reading are for some "average" situation, what ever that is.

There is a calculated value that you can find for heating and cooling in your area. For heating it is called Heating Degree Days (HDD), and for cooling it is called Cooling Degree Days (CDD).

You can go HERE and enter your zip code and answer a few other obvious questions and find out what the HDD and CDD is for your area. I can tell you for sure that the HDD and CDD for Xringer's location is higher than yours.

Also to consider is the level of insulation in your house... this means ceiling, walls, windows & floors.

If you don't know that, you really don't really know how much heat you're going to need, because what your heater does is pump heat in as fast as your house looses it.

I know that Xringer has pretty good insulation in his attic, but the walls might not be so good.

And in the summer, Xringer's house is out in full sun in the summer, so there's no shade at all to help with his cooling.

I wish everybody on this Forum published their HDD & CDD info on their posts, it would go a long way to understanding where advice was coming from.

The bottom line is that you want your Mini-Split to be sized just big enough to do the job. That will be the most economical situation.

Bigger than that is not better.

In fact some people (like me) think that your heat pump should be just a little bit smaller than 'big enough'... and that axillary heat should be used on those minority days.

-AC

HDD @68F = 5293
CDD @78F = 198

[woody]

well hec.... the link does't work

[nokiasixteth]

I like the 220v because less amp in the wire . Still around same watts but less amp less amp means less heavy of guage wire few cents is a few dollars after while.
Accordin to Xringers chart 550 sq ft would be 1 ton. Thats along what my figures has been. My house used to not have a drop of insulation until this year. I put in around r38. Plan on doing the walls . Just havent had a money tree sprout yet. And one day do the floors.
13 seer ant the greatest but im guessin even 13 seer would be more efficient in 30 degree temps than a oil filled electric radiator heater even on a bad day.

[pinballlooking]

Originally Posted by AC_Hacker

The charts you are reading are for some "average" situation, what ever that is.

There is a calculated value that you can find for heating and cooling in your area. For heating it is called Heating Degree Days (HDD), and for cooling it is called Cooling Degree Days (CDD).

You can go HERE and enter your zip code and answer a few other obvious questions and find out what the HDD and CDD is for your area. I can tell you for sure that the HDD and CDD for Xringer's location is higher than yours.

Also to consider is the level of insulation in your house... this means ceiling, walls, windows & floors.

If you don't know that, you really don't really know how much heat you're going to need, because what your heater does is pump heat in as fast as your house looses it.

I know that Xringer has pretty good insulation in his attic, but the walls might not be so good.

And in the summer, Xringer's house is out in full sun in the summer, so there's no shade at all to help with his cooling.

I wish everybody on this Forum published their HDD & CDD info on their posts, it would go a long way to understanding where advice was coming from.

The bottom line is that you want your Mini-Split to be sized just big enough to do the job. That will be the most economical situation.

Bigger than that is not better.

In fact some people (like me) think that your heat pump should be just a little bit smaller than 'big enough'... and that axillary heat should be used on those minority days.

-AC

HDD @68F = 5293
CDD @78F = 198

Heating & Cooling Degree Days - Free Worldwide Data Calculation
OK I did it for a year then added it but what does this tell me.
HDD @73F = 4979
CDD @78F = 226

[AC_Hacker]

Originally Posted by pinballlooking

Heating & Cooling Degree Days - Free Worldwide Data Calculation
OK I did it for a year then added it but what does this tell me.
HDD @73F = 4979
CDD @78F = 226

HDD is defined as the number of degrees that are below the temperature at which you want your house, time the number of days. I happen to like 68F, you might like 65F, so for the exact same location, we would have somewhat different degree days.

But if someone from Miami, Florida says that insulating your house is a waste of money, the degree days comparison between your location and his would tell you why his advice might not be relevant to you.

Miami
HDD @73 857
CDD @78 854


And if someone from Minot, North Dakota tells you that you'd be a fool to not build with 12" thick walls, to get you through the winter, their advice should be cautiously considered, too. (* I would agree with the guy from ND, but I am an insulation extremist, and proud of it. *)

Minot, North Dakota
HDD @73 11676
CDD @78 97


And so it would go for someone in San Diego, CA

San Diego, CA
HDD @73 3713
CDD @78 26


So, knowing HDD and CDD for where you live and also for where various people in this Forum live, can give you a clue as to how relevant their experiences might be to your situation.

...and now you know how to make that comparison.

-AC

[pinballlooking]

I would say it shows heating is more important here that I thought.
HDD @73F = 4979
CDD @78F = 226

[AC_Hacker]

Originally Posted by pinballlooking

I would say it shows heating is more important here that I thought.
HDD @73F = 4979
CDD @78F = 226

Just out of curiosity, do you actually keep your house at 73F in the winter time?

I usually keep mine at 68F.

-AC

[AC_Hacker]

This Climate Zone Map gives you similar information, but it's less specific.

-AC

[pinballlooking]

Originally Posted by AC_Hacker

Just out of curiosity, do you actually keep your house at 73F in the winter time?

I usually keep mine at 68F.

-AC

The mini split where I work is 70-72 day time 68-69 night time.
the living room kitchen area 75-76 late night 72-74.