Getting back to the PV side Getting back to the PV side of the discussion for a second in relation to reducing carbon emmissions. With respect to installing a grid tied PV system, I have never understood clearly whether there is a linear relationship between the amount of kw the PV system produces and the reduction in carbon emmissions that results. For instance, if my local power plant emits 100 units of carbon for each 10kw of energy produced, will a 10kw PV system eliminate the exact same amount (100 units) of emmissions? Another way of saying this is to ask whether a kw of energy produced by a PV unit saves the same amount of emmissions as a reduction in use of a kw of electricity ? Does this depend on many factors such as whether the electricity produced is on/off peak, the capacity of the grid, whether the plants are running on main fuels (e.g., coal), peak load fuels (e.g., gas turbines) etc?
Posted: 04:57 pm on March 31st 2014
Thanks Martin. Since the Thanks Martin. Since the turbines need to run anyway, I always figured that the actual amount of emmissions reduction from a small amount of reduced power (whether from PV replacement or efficiency reduction) was small. But maybe not.
Posted: 06:28 pm on March 31st 2014
with respect to the Manual J, with respect to the Manual J, I thought that one of the advantages of modern mini split heat pumps over most other forms of HVAC equipment is that they are efficient even when oversized-they can scale down efficiently. Thus, you can buy a unit thay is clearly oversized for the space and they will run at lower capacity just as efficiently as a smaller, more appropriately sized unit would run. Given that you are saving thousands of dollars over having a pro install a unit you would just do a back of the envelope calc and buy the larger unit (or several larger units). The real issue here is(i) how efficient are these units (particularly in heat mode) versus the best Fugitsu or Mitsubishi, and (ii) what happens if they break down? Will the company back these with local HVAC delaers who will come out, troubleshoot and fix the problem?
Posted: 02:26 pm on April 14th 2014
In a practical sense, it is In a practical sense, it is very difficult to find an HVAC pro willing to put in a unit purchased online. In New Jersey by the time you pay for labor, a markup and all the ancillary parts, the installation of a high quality mini split like a Fugi ot Mitsu is very expensive, particularly if you choose several high efficiency single units instead of one mulit unit. It is not unusual to find quotes of $15,000+ for a medium sized house around here to do it right. That is the primary reason why they have not caught on as they should have given the great technology.
Posted: 07:40 am on April 16th 2014
I would like to revive this thread for a second. For retrofits, geothermal systems are often too expensive due to the cost of vertical drilling and horizontal trenching. Also, retro fitting radiant systems is expensive, and ductwork is often inefficient. Recently I stumbled upon the web site of Thermomatrix in BC, Canada (www.thermomatrix.net). Not only do they sell a relatively inexpensive Air to Water HP ("Cool Fire"), but they also sell a " fan coil, forced convection ductless air distribution system" called "Comfort Coil" which seems to be a hybrid between a ductless system and hydronic. I am curious if anyone has experience with these products or similar products?
Posted: 09:18 am on April 27th 2014
Multi Splits for "average" houses I see that Mitsubishi now has also extended its Hyper Heat technology (see Dana Dorsett's comment #5 above) to multiple head units . These are the "MZX C" models (such as MXZ-4C 36 NAH). These seem to have very high efficiency at low temperatures (down to -13F like the single head FH models Dana described above), but in multi head configurations. Has anyone tesed these yet in the real world? This seems to be just what those of us with average houses who like to keep our doors shut have been asking for.
Posted: 06:56 pm on February 18th 2015
Re: Are 1 heat pump with 3 multiple indoor unit Hyper Heat minisplits available from Mitsubishi yet?I had the same question so I asked online retailer "Younits" if they had these yet and they said that you could order them but wouldn't receive until later-early spring. If you check their online store, these units don't show in a normal search, but you can search for them using the search function on thetop right hand corner of the site and type in MXZ C. This should bring up the various units and prices for the outdoor unit.
Posted: 02:07 pm on February 20th 2015
Re: Are 1 heat pump with 3 multiple indoor unit Hyper Heat minisplits available from Mitsubishi yet?Dana, , I understand your point of view. Of course, sizing mini splits is tough for those of us who have standard houses like mine with average insulation and multiple bedrooms ( I have two floors of about 1600 ft in northern NJ). As you know, the problem is addressing a combination of sufficient heat, dealing with closed doors and distance down hallways and obtaining sufficient efficiency. In NJ rebates require 18 SEER and 13 EER. Even these new h2 Mitsubishi systems don't meet this criteria with ducted heads. Only some 9000btu single systems meet this criteria when ducted and they are not low temp (this winter we have had 20 days or so where the temp went to 5 F or lower at least some of the day). And when I have had HVAC guys in they all have recommended at least 5tons total. Thus it is hard to resist a multi head system like this. They seem to me designed for retrofitting regular houses. But if I could replace the 800 gals of oil I use to heat with 12000 kW of electricity at 11.5 cents a kw (60 pct natural gas sourced) , that may be a good trade.
Posted: 09:48 pm on February 20th 2015
Jerry, I followed your original post and found it interesting. Did you actually implement your experiment and if so how does it work. If you have not implemented it I note that Mitsubishi now has a multi split h2 system that is rated down to -13F and compatible with ducted systems (see MXZ "C" line). These do pay some price in efficiency for ducted but less so in heating ( according to AHRI, the MXZ 4C36NAHZ has a HSPF of 10.1/ compare that to the Fujitsu 12RLS2H at 9.3). I understand Fujitsu will be coming out with a more efficient low temp multi 24 k system later this year also.
Posted: 08:13 am on February 21st 2015
My two Fujitsu units with the My two Fujitsu units with the pan heaters (AOU RLS2H) have been fine all winter here in North Jersey where we have had 25 days around zero or below at dawn and areasonable amont of snow. I mounted them under an 8 ft high deck so they stay reasonably dry. However you mount them you need to look at the clearance requirements for the unit on all sides-you might be surprised. As someone above said, the next generation Fujitsu and Mitsubishi hyperheat units will likelysolve the issue by having a pan heater that is still very efficient (the AHRI numbers on the new AOURLS3H show an HSFP of 13.8!!!). I understand they are hitting the shelves soon and the online stores are showing them at about the same price as the RLS2H units (e.g., see Younits.com, ACWholesalers.com)
Posted: 02:13 pm on March 2nd 2015