Mitsubishi Ducted Minisplit 30k vs 36k
kramttocs
| Posted in Mechanicals on
Let’s say a zone calls for 30k. Looking at the last two columns in the attachment, what is the benefit of the 30 over going with the 36? I am basing this primarily on the ability for the 36 to idle down past (cooling) or almost to (heating) what the 30 can do. Does that not mean the 36 can do as ‘little’ as the 30 but more if needed?
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Replies
Look at the efficiency numbers
I think you might not get ahead that way
Thanks. So even if the 36 could idle down lower than the 30 it would be less efficient when doing so? I wasn't sure how those numbers and the power input came into play at the bottom end.
It appears it is using more electricity to do the work, even though it is able to output lower. If I read the specs correctly
Sometimes manufacturers use the same equipment with different software for these 1/2 ton size increments. This generally means the "detuned" unit will have the same min capacity but slightly higher efficiency.
The tell tale is if the weight of the two is the same.
Generally means that either will work about as well.
That makes sense especially with the 30 and 36 are limped together everywhere I've looked. I won't say I understand the detuned being more efficient but I am sure that's explained here somewhere already :)
I am trying to get a manual j (harder than I expected) but it dawned on me that I have some pretty good data between my ecobees and my iotawatt units (electricity monitoring). That's got to be a better true-to-my-house-and-patterns than a manual j, right? My concern with the manual j is that I've got downstairs, upstairs, and addition (converted garage/bonus room) heat pumps. Seems like the 3 would skew the manual j but maybe I am not giving the algorithms enough credit?
Guess I never said it but needing to replace the downstairs 3 ton and want to go with the Mitsubishi Ducted Minisplit since I installed a dual head (floor unit and ceiling cassette) in the addition and despite believing I oversized it (due to not realizing just how bad the prior unit was), I've been happy with it.
Going to stick a single day in here to see if it shows anything telltale. This is for a 93 degree day with the 2ton upstairs and 3ton downstairs (again, needing to replace this downstairs one).
House is a Cape Cod so the upstairs (2 beds and a bath) take the brunt in the summer due to the roof (E-W exposure and black shingles). This should actually get a little better as I am in the process of redoing the ductwork insulation and burying it vs it all being well above the attic insulation like it was last Aug. It was bad to say the least. Looks like someone really set the temp down that night which can be blamed for the 9pm to 1am runtime.
Looking at just the downstairs though, assuming the upstairs is doing its share of the work, are those runtimes ok or too long? The fan was set to run some every hour and it looks like there was a drop in wanted temp that accounts for the 8pm run. It also gets some benefit from the Mitsubishi in the addition being on the same floor.
I can't get any helpful heating data since running a pellet stove makes the upstairs never run and the downstairs only once a day or so.
If best to find a similar outdoor temp day with no indoor adjustments, I can post those.