Is Hyper Heat necessary for 7F design temperature?
ranson
| Posted in Mechanicals on
I’m comparing the MUZ-GL and the MUZ-FH lines of Mitsubishi mini-splits. My 99% design temperature in Brockport, NY is 7F. Both units have good performance ratings down to 5F. Do I actually need a hyperheat unit? I’m aware the FH line has better SEER.
–John
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Replies
Nope.
There are quite a few mini-splits out there that have a specified output at -15C/+5F- it doesn't have to be Hyper Heating (or other cold-climate specific mini-split) to work.
But it's still a good idea to go with a cold-climate mini-split for reasons other than just efficiency- it's also about capacity. (HSPF is what you care about,- you don't much care about it's SEER in your climate.)
Mitsubishi will void the warranty for ice damage to the outdoor unit unless it has a pan heater to clear defrost ice during extended cold weather. In Brockport it'll get above freezing for at least a few hours on most winter days, but not all days, and if it stays below freezing for a week or more the potential for ice damage is real.
If using a mini-split without a pan heater, pay attention- check up on whether and how much defrost melt water is accumulating as ice on the bottom of the pan, and figure out how to apply enough heat to melt it out before it's deep enough to interfere with the blower. (I know of someone in MA who rigged up a DIY pan heater for his Daikin to deal with this problem.)
The -GL series Mitsubishis all have a rated output at +5F, so it should be pretty easy to size it for your +7F design temp, but the minimum operating temp is -4F, as indicated in the submittal sheets:
http://meus1.mylinkdrive.com/files/MSZ-GL09NA-U1_MUZ-GL09NA-U8_Submittal.pdf
http://meus1.mylinkdrive.com/files/MSZ-GL12NA-U1-MUZ-GL12NA-U1_ProductDataSheet.pdf
http://meus1.mylinkdrive.com/files/MSZ-GL15NA-U1-MUZ-GL15NA-U1_ProductDataSheet.pdf
The 3/4 ton FH09 has 10% more capacity at +5F than even the 1-ton GL12, and also delivers a slightly higher HSPF efficiency:
http://meus1.mylinkdrive.com/files/MSZ-FH09NA_MUZ-FH09NA_Submittal.pdf
Similarly, the FH12 delivers about the same heat @+5F as the 1-1/4 ton GL15, also at a slightly higher HSPF:
http://meus1.mylinkdrive.com/files/MSZ-FH12NA~MUZ-FH12NA_Submittal.pdf
The difference in price between a GL15 and an FH12 of equivalent heating capacity @ +5F is less than $250.
A MAC-640BH-U pan heater designed to work with the FH, GE, FE, GL and SUZ-KA series) is another $150-170 at internet pricing, so you COULD use the difference in price to pay for the pan heater, then a little bit every year thereafter in higher power bills.