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Community and Q&A

Best Turn Down Ratio Cold Climate Mini Splits – Recommendations for 2021

mattbrennan4 | Posted in Green Products and Materials on

This weeks task has been reviewing  cold climate heat pumps as part of my own Deep Energy Retrofit (or at least shallow…).

Again, this has been a painful task as there seems to a lot of poor information out there, particularly among some HVAC websites. I get why, you need to support the product you’re selling. I found lots of blanket statements, little comparison, and in some cases straight up mis-information. 

The resources I’ve found so far to be most useful are:

– NEEP Cold Climate Heat Pump List – https://ashp.neep.org/#!/product_list/

– Load Calc – https://www.loadcalc.net

– I’ve also used the attached excel file that someone had posted on another thread (sorry I’m not sure who to credit here). On this file I’ve highlighted my most likely product selections at this point AND I’ve added a turn down ratio column (AU) based on Dana Dorsett’s definition from this article – https://www.greenbuildingadvisor.com/article/getting-the-right-minisplit .

For air-source heat pumps, the usual definition of the turndown ratio is the maximum heat output capacity at 5°F divided by the minimum heat output capacity at 47°F

I’ve one issue I’ve noticed is that most of this data is a few years out of date. At the last conference I attended, Pre Covid, I heard a lot about how new advancements are really improving cold climate heat pumps in terms of efficiency and cycle time (turn down ratio?). It’s now 2021 and I am asking the question what is the best option today….?

The models I am looking at now are:

Mitsubishi M-Series MUZ-FH15NA
Mitsubishi M-Series MUZ-FH18NA2
Daikin Aurora Series RXL15QMVJU
Fujitsu Halcyon Single-room Mini-Split Systems Wall Mounted RLS3HY Series AOU15RLS3H
Fujitsu Halcyon Single-room Mini-Split Systems Wall Mounted RLS3HY Series AOU15RLS3H

All range at approx 18,000BTU. My heating load for the whole home is approx 35,000BTU though this unit is just for main floor heating, electric baseboard is in the upstairs bedrooms. House is 1600 sq ft, 800 per floor + a basement that is mildly finished. House is in Halifax NS, CAN – climate zone 7 for those in the US.

Manual S:

Manual J:


Currently I am leaning towards the Diakin as they seem to have the most reputable contractors in my area, but for those most familiar with these units what would you recommend? Is there any tech that I should be looking for now that will be best suited for cold climate?

Thank you and I hope the group finds this useful.

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Replies

  1. [email protected] | | #1

    Quick question which I just asked on another thread: how do you search heat pumps by turn down ratio?

    by the way: I'll be watching replies to this thread as well.

    Thanks,
    Adam

  2. paul_wiedefeld | | #2

    Turndown ratio is misleading - minimum capacity at 47 is a bit more useful. For example if your true heat loss is 13kbtu, an 18k unit with a 6:1 ration is not any better than a 15k with a 5:1. Many boilers mislead even worse by advertising a 10:1 turndown ratios but a minimum output of 8kbtu.

    You’re definitely approaching diminishing returns here due to the efficiency of these units and the small load you’re serving - get a well installed, well supported unit and you’ll be fine!

  3. Expert Member
    Akos | | #3

    I think the brand selection really comes down to local availability and support. Doesn't matter which unit you pick, they will all be much more efficient than your current resistance baseboards.

    Some of the larger units do have so-so turndown, I have a Midea 18k and notice it cycling in warmer weather.

    On thing to watch is the NEEP data isn't always accurate, always check the manufacturer's data.

  4. jwasilko | | #4

    Have you looked at NEEP's "sizing for heating" data in the cold climate HP database? It has a column for 'Percent Annual Load Modulating'

    https://ashp-production.s3.amazonaws.com/NEEP_ccASHP+Heating+Visualization+User+Guide_v2.2_TRC_04.01.22.pdf

    It draws a graph showing potential for low-load cycling...

  5. tkzz | | #5

    Hey just jumping on this thread because I've been trying to find manufacturer's data for the Trane XV19 horizontal discharge heat pump. The neep site shows that its turndown ratio is actually below 1. Is that true I wonder?

  6. frankcrawford | | #6

    We are using the Daiken products in Alberta for new high performance builds and Deep Energy retrofits. 70% of rated capacity at -25 C depending on the product line, good turn down ratios and a 12 year warranty with option to purchase a 12 year labour warranty as well.

    I agree with Akos in that the installer support is equally important to the equipment. Others were using Mitsubishi, but the service was poor so we switched to Daiken.

    I installed a Daiken Aurora two head ductless ccASHP in my passive house in the spring of 2022, so far this winter it has performed well. Below -27 C the performance dopped significantly, so plan for supplementary electric heaters if your design temp is below -25 C. I have only got one or two winter electricity bills so far but my overall consumption is down about 50% from last year. No accounting for weather differences yet, I will do that after a years worth of data.

    Going a bit off topic.
    Check the cost of a two head unit compared to a one head unit and then you can meet the entire load of your home with a head on each floor, or get three heads to qualify for the full $5000 greener homes grant rebate.

    2.5 tones (35,000 BTU) for a 16,000 sq ft house is a bit high for a post Deep Energy Retrofit (DER) heating demand. Do you have a plan that gets you to Net Zero on site Energy after you put solar panels on the roof? Start with the building envelope, maybe go through a winter after the envelope upgrades and then you can best size your mechanical equipment. On some of the DERs done recently the Hot2000 predicted heat load was off from the actual heat load.

    some references for you.
    https://www.retrofitcanada.com/
    https://4egreenhomes.medium.com/
    https://www.ecosynergy.ca/

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