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-   -   Mini split heat pump for us? (http://www.diychatroom.com/f17/mini-split-heat-pump-us-97336/)

Cedrus 03-05-2011 03:05 PM

Mini split heat pump for us?
 
We are in Southern Oregon and have a 1993 York 3.5 ton all electric split system. 2100 sq.ft., single level. Have had various heat pump licensed contractors here as our system is producing high electricity bills. Got some bids in the $7500 to $9000 range depending on do I want the very best rated unit or drop down one grade and get merely a fine unit. None did a Manual J or Manual D calc.

Yesterday a contractor came and had different views: He said our air handler and associated air lines/vents were not tight and causing outside air to come inside via cracks, holes, etc. He did measure windows, room size and will get back to me later with more info/recommendations. He said our single 20x25 inch air return was very inadequate (so did the other contractors) and our air flow was poor and no wonder it is $$$ to run.

He wants to seal everything it is possible to seal in the garage where the air handler is located, up in the attic and the ducts under the house (as they were taped.) He thinks (without going under) that they need sealing with a liquid product.

If he does this and installs one more 20x25 inch, he says we do not need a new heat pump. At least for a while. :thumbup: Sound right?

As an alternative, he wants us to consider sealing off our air handler and ductwork and install a ductless mini split system by Mitsubishi. He left some brochures and I went to their website and am still a bit confused. Apparently you can use only 4 wall mounted vents per heat pump. Might not be enough for our 6 rooms, two of which are large. It seems you can install two units and get 8 wall vents. Is this correct? Also see that Fijitsu and Sanyo make these, among others. Apparently they work well down to 17 degrees and even below. If I read correctly there are no heat strips or emergency heat?

Any comments please. We moved here 5 years ago and this is our first heat pump. Thank you

hvacguytn615 03-05-2011 03:29 PM

there ary no heat strips on the mini splits the room unit is not a vent it is an air hndler with its on fan an evaparator coil and hand held t-stat if the 6 rooms are all like bed rooms air flow could be a problem but if they are acouplr areas that are open like dinning or living areas your probly ok also check out emmersons web site they are producing mini splits now

beenthere 03-05-2011 03:42 PM

Sealing the duct work is a good first step.

A 18 year old heat pump may last you years yet, or just another few months, no one can tell that for sure.

Problem with thos mini split systems. is that you could end up being tied into that one contractor for years to come. If no one else works on them in your area. And if your contractor goes out of business, your stuck with a white elephant.

Cedrus 03-05-2011 06:24 PM

Thanks B.There:

Yeah, that why I'm checking out contractors and getting my bids now. In case I need a complete replacement......I have a head start.

I did check other Mitsu dealers. There are another 4 within 30 miles. :thumbsup:

Poppyloppy 03-06-2011 01:13 PM

Problem with the mini splits is they can be pricey...you'll have to get refrigerant lines run from evry wall unit to the outside unit (how's that going to look on th ouside of the house)..now you've got 6-8 wall units and 2 outside units that can break down, etc. and usually, not as long
a warranty.

Assuming your return is a direct 16"> duct to the ceiling the 20x25 grille will only allow some 1000 cfm (2.5 tons) of return air and more return can be a big bang for your buck, increasing airflow and efficiency by up to 35%.

Duct sealing is somewhat iffy (except at the end connections) and be be very time consuming and expensive. Make sure your duct ending connections are sealed and get some airflow studies done; if your blowing the same cfm of air that you are returning, then the ducts' integrety is basically fine.

BRO931 03-08-2011 09:47 AM

I've had three mini-split heat pumps over 5 years. I had trouble with one of the three. The controller board was damaged by a shorted expansion valve. It seems mice got into the outdoor unit. These mini-splits all have very similar construction and use R-410A refrigerant. And they are VERY energy efficient and they can extract heat from very cold air (down to -13 F on some units). But they do have their disadvantages. As mentioned already, you have to run two refrigerant lines between the outdoor unit and each of the indoor units they service. I think back-up heat strips are an option on some mini-splits, but I don't have any.

If good air handling is possible (ducts, vents, etc), I'd opt for the traditional system. But when adequate air ducting is not an option, mini-splits are great.


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