minisplit ductless heat pump

Highbeam,
I just installed a Fujitsu 18,000 with a 9,000 and a 7,000 inverters. I'm a general contractor so I have all tools and experience for most of the install. I ran the line sets, drain lines and the wiring between outside and inside units. Had my electrician tie into the panel. Had HVAC contractor do the line set connections and start up. Pretty easy to do even the electric and HVAC is easy. I didn't have the tool to vacuum out the line sets. The heating is great and seems pretty economical so far. I put the interior units on inside walls down to the basement to outside. It's very quiet and not so bad looking. I found a site that was helpful. I will pass it on..

This guy is pretty good

http://blog.energysmiths.com/2011/12/a-year-with-a-minisplit-heat-pump.html

And a good video

I bought a Klimaire inverter based unit (from heatandcool.com) for a studio I built for my wife. I partially installed it myself and then had a local hvac company do the final. It's a gimmick because they sell them as complete self install kits but no warranty if you self install them ... they did say that if the HVAC guys did the final hook ups and "approved" the install then it would have full warranty.

It's a really nice unit and came well packaged. The copper lines are a little thin but no worse than the name brand units (according to the HVAC guys). It's supposed to work down to 5 deg F, I haven't tested that but it has worked well into the low teens without issue. It barely runs to heat the space (the inverter tech is pretty nice but I don't know if it's worth the price difference). The space has 3 inches of closed cell foam in the walls, with more in the ceiling and an insulated slab so it really doesn't take much to heat the space.

The Klimaire units are from China and apparently they make some of the Japanese models now. I have family in Montreal, Canada that has used Klimaire for years without issue. I figure if it's good enough for Canadian winters, it's good enough for me

Hope this helps ...

Berardino

Interesting..I wish we would get rebates for stuff like that around here.

To be fair, I am currently spending nothing on my mini split. Both Pen and I burn wood for heat. If Pen was using the mini for full heating then it would of course be higher.

Gotta admit, the cooling would be nice for about a week in the summer.

That is awesome. We had a decent cold snap this year too.

So what is it about mini-splits that makes them so darned efficient when compared to standard central HVAC systems?
The rave reviews here and elsewhere have me considering installing one in our master bed/bath area. We can handle the temp extremes elsewhere in the house.

One thing is the variable speed inverter motors. A regular heat pump is usually one or two speeds so it is generally working too hard where the variable speed can constantly run at the proper output to maintain a temperature. Think of it like city driving vs. freeway driving and the mpg effects on your car.

The other is duct losses. Your central system loses 15-30% of the energy through duct losses.

I think that the manufacturers of the central units should be ashamed of themselves for not making improvements to the evaporator/condensor/blower that fully utilize the improvements that the minisplit market has pioneered. Duct losses are not their fault.

Highbeam is right.....the major thing is variable speed. Duct losses are avoidable with conventional split systems (but often are a problem anyway). The blower on my split ASHP uses 500W...all that ends up as heat in my conditioned space, but it reduces COP by 10% or so.

One other thing is defrost....the mini's don't call a honking big resistive element during defrost, and (I think) many have smarter defrost controls. The way mine (non-mini) was set up, the defrost was killing the COP, from 2.7 to ~1.6 at temps near freezing. I rejiggered the control myself, and got it back to 2.2-2.3.

I think I recall someone reporting that the defrost mode on their mini-split was just the system running in cooling mode for a short time.

How's that ? You mean by obsessively careful attention to sealing with mastic etc ? Even so, the insulation on flexduct ain't that great, plus it seems to be compomised a lot by being compressed in bends and by hanging materials. I think the only way to really minimize the losses is with the encapsulated crawlspace approach - so the temperature on the outside of the ductwork is much higher - and that seems to be one of the most compelling reasons (for closed crawlspace).

You're empirically measuring your COP ?!? Cool-o. How ? I'd love to do that.

Carrier has the Infinity with Greenspeed: http://www.carrier.com/homecomfort/...roducts_of_2012_by_greenbuilder_magazine.aspx

As BG said, with short R-8 flex, thick FG blankets over the trunks, and careful airsealing (a PITA) duct losses (conduction and leakage) can be <=5%. Not a deal breaker.

running geek flag up pole.....

If you know your BTU/h load versus outdoor temp, and log your HP run hours, you can estimate its BTU output per hour at different temps. If you measure its power consumption (e.g. with a home energy monitor), you can compute your COP from (kBTU/kWh)/3.414. Quite tedious, but if you are logging the data anyways, not that hard to sit down and bang out. You need to use a second heater (e.g. resistive aux) with known output to get BTU loads. Switching to aux (emergency mode) for a few selected days to get data costs money.

In practice, I do it the other way.... The module COP, BTU and kW versus outdoor temp are tabulated by the mfr, (using an ASHRAE standard test regimen). You can also check the kW in the table and for the blower while you are at it. The table does NOT include blower power in the kW or those BTUs, as far as I can tell. On a spreadsheet, you can predict HP run hours versus outdoor temp from the tabulated BTU numbers, and the daily run hour log matches the model when defrost is not active. Data is noisy, you need to throw out very windy days, etc, but the model matches.

During typical 'dry' defrost conditions, the unit runs ~18% more than the model prediction, suggesting COP is reduced by 1-1/1.18 = 15%. Under 'heavy frost' or wet snow conditions, it has to run close to 50% more, suggesting a 33% reduction in COP. Before I rejiggered the defrost control, the COP hit was closer to 40% under dry conditions! At 30°F and dry, I would have had COP=1.5 as installed. Now it is 2.1-2.2 or so.

Ah well, I'm going with encapsulated crawlspace, for a variety of reasons. Chief might be moisture, here in this sub-tropical southern climate. I reckon the area of my foundation wall perimeter is about half my floor area, so with half the R-value, it's about break even. But then the obviation of duct losses is a big plus on top of that. Of course, the big unknown is that the crawlspace floor is now part of the insulation envelope. A huge plus in the summer I'm sure; dunno about winter, but summer is a bigger deal here anyhow. Mainly, I like the idea of being able to crawl around down there without fiberglass drooping on me and being able to see all the mechanicals clearly But I guess this is really all for another existing thread ..

Damn, and I thought *I* was a geek. I'd love to try some of this. I like the idea of getting the btu/hr per degreeF empirically with some kind of aux heat. But my aux heat is propane, so pretty hard to measure the consumption of that, over a day'ish-long test period, with necessary accuracy.
You talk about versus outdoor-temp, but shouldn't btu/hr per degreeF be more or less independent of outdoor temp ? I guess you mean HP performance depends on outdoor temp.

Yep.

You could buy a run hour timer, and attach it across blower...

It doesn't apply to me because I have a single stage oil boiler, but, my new thermostat (that I'm still playing with)can apparently track the run times of the different stages of heating and cooling. You can either view it on a built in chart or download the data. The analyzing stuff they call Home IQ resides on the company's server. http://www.ecobee.com/solutions/home/smart-si/

You are tempting me to switch out my nest for the EcoBee. Both multistage control and logging stink on the Nest.