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Considering ductless for a small Cape Cod home

Monte Kravat | Posted in Energy Efficiency and Durability on

hello people, I have a question on some possible scenarios for ductless unit to be put into our home.We have had some estimates and are quite confused. The prices are very similar BUT the brands are different and the BTU’s are different and being complete novices we are baffled. So here goes.
One contractor has the following–
1)Fujitsu 12,000 BTU heat Pump system for our Living room/Kitchen area.- Now the size of my small living room width wise I would say is as follows- When you walk in the front door – consider the wall to your right that wall and going across to the other wall to the left is 240″(20 feet) then if when you walk in to the home from that front door- you can see straight back into the kitchen thru an archway- so that whole length from the from the front wall to the end of the kitchen is 285 “(about 24 feet). Now once you enter the kitchen its width is only 155″(about 13 feet) Remembering that the kitchen leads into Living room but is blocked by a wall except for the archway opening. So there I hope you see the proper outlay for the 2 rooms.
Now each contractor said the exact BTU units for our basement which was 12000 BTU so that is not a question on BTU. But for our 2 small rooms on the main level are also different BTU’s- so here goes with those 2 rooms.
2)the contractor wants to put in a 7000 BTU blower in our bedroom which is as follows-it is 12 feet by 12 feet (simple) and also a 7000 BTU blower in the small den room which is as follows- 132″(11 feet) by 112″(about 9 plus feet). very small rooms. Now as the configuration goes- the small rooms and the basement are to be put on what he is calling a TRI-ZONE Heat Pump system that is 24000 BTU. and he is giving us a 1 year parts and labor warranty. and a 5 year parts only warranty and a 7 year compressor part only warranty.
So there you have one of the contractors proposal.
Now for the other contractor-
Very similar price as mentioned earlier- he wants for the Living room/kitchen-the BRAND is CARRIER-
so for the living room/kitchen- he mentioned a 38MFQ17-what he calls a 17000BTU OUTDOOR unit- and a 40MFQ17- a 17000 BTU Indoor unit?? See our question- the other contractor did not mention the BTU of the outdoor unit but the blower was only going to be 12000 that is big difference to a novice like me- 17000 compared tom a 12000??? The contractor who wants to use the 17000 explains it to us this way- he says that when the temperature outside reaches the 100 degree feel temperature you want that extra power and he says that we can raise or lower the temperature we want it at to adjust to the outside temp and he used the word RAMPS down- that the unit would ramp down when it foes not need to do that much cooling?? Is this true- and you people knowing the size of the connected rooms and its configuration- what is the right BTU?? is 12000 too little and is 17000 overkill?? Oh boy??who to believe??
Next is for the 2 small rooms– the contractor who only wants 12000 for the living room/kitchen wants only 7000 BTU blower for each small room and remember those are the units connected to the TRI-ZONE system- and the contractor who wants 17000 for the large area wants to put in the following- 2 units one in each room-40MAQB09 – 9000 BTU units and a 12000 40MAQB12 in the basement(but forget the basement since both contractors have the same BTU for that area. BUT as you can see one contractor wants 7000 BTU for the small rooms and one wants 9000 BTU???
As for the warranty the contractor with the 9000 BTU units and the 17000 BTU unit has the following- 10 year compressor warranty ,10 years parts and labor and 2 years labor guarantee- which is much better than the other contractors warranty ans stated above?

So to sum it up I hope- one contractor wants for the large area- a 12000 BTU blower and two 7000 BTU blowers with 1 year parts and labor and 5 year part only and 7 year compressor warranties.

The other contractor wants – for the large area a 17000 BTU blower(and a 17000 outdoor compressor) and two 9000 BTU blowers on the tri-zone system with 2 year labor ,10 year parts and 10 year compressor warranties.
remember the triz-zone system is because they are adding the basement to the 2 small rooms on that one outdoor compressor.
So there you have it- we are really confused. First – not sure which is the better unit FUJITSU or CARRIER – I am sure both are equally as good?? And also why is there such a discrepancy between the power of the units. Please explain if you think we should go with the stronger units or the lower BTU units and why. This is a big project for us and we need to do it right.. So please in your answer please try to explain in as simple word as possible- since we really do not know anything about this and once it is done that is it. We thank you for your time and effort and await someones reply.

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Replies

  1. D Dorsett | | #1

    It's impossible to properly assess what is appropriate without a room-by-room, zone-by-zone heating & cooling load calculation. The gold-standard approach is ACCA Manual-J methods for calculating the loads, performed by a qualified engineer or energy nerd (RESNET raters, etc), and specifically NOT an HVAC contractor.

    The cooling BTU ratings are not an indication of how much heating capacity the unit has at your 99% outdoor design temperature, or even the maximum cooling capacity of the mini-split (which is often higher than the "rated" BTUs, which is the modulation level at which it's SEER efficiency is tested.)

    In my neighborhood a competent third party Manual-J costs between $500-800 (though I've been verbally quoted higher numbers in gold-plated suburban areas.) YMMV. Getting the load numbers correct and optimally sizing the equipment will usually result in smaller equipment with a lower up front cost (saving more than the cost of the Manual-J), and higher efficiency/higher comfort down the road.

    It is my impression (no hard data), that Carrier's mini-splits are either re-branded Gree units or manufactured to Carrier specification in China by Gree (the largest manufacture of air conditioning equipment in China.). As I understand it, Gree uses component parts from lower cost manufacturing locations all over southeast Asia. Fujitsu units are largely manufactured in Japan, and are a first-tier vendor. It's not clear to me what the relevant failure rates or support issues are for Carrier relative to Fujitsu, but mini-splits are a secondary line of their HVAC business for Carrier, but the primary focus for the HVAC portion of Fujitsu. A handful of years ago Fujitsu was a supplier of sub-components to other Japanese vendors' ductless systems, but I'm not sure if that is still the case today.

    Your location (got a ZIP code?), construction type/age, the total square footage you are heating & cooling, and any fuel-use history would be useful for taking a WAG at the likely heating & cooling loads, but would still not be a substitute for a Manual-J.

    When the units are sized correctly, they run nearly constantly and "ramp" , modulating the blower & compressor speeds to where it just covers the cooling or heating load. At part-load when they are just cruising a long at low to mid speed the efficiency is very high- much higher than the SEER or HSPF numbers indicate. But modulation range is not infinite- if you oversize it to the point that it cycles on/off most of the time rather than modulating, the efficiency (and comfort) is lower.

  2. Monte Kravat | | #2

    Holy Moly-- we thank you for your help- but as stated - wow- you really know your stuff and are quite technical- that is why the consumer has to be so leary -I mean we had two VERY reputable installers come over and they are both highly recommended so to have an engineer now come over adds so much more to the picture. We were hoping that like buying an A?C for the window or wall that when you go online or go into the store and give them the dimensions of the room they tell you what size BTU is needed. We were hoping it is or would be that easy and as mentioned all the estimates we had all did simple measurements to get to those numbers. Our only 2 concerns is why was one installer so much different than the other(one contractor said because Fujitsu does not make a 9000 BTU unit whereas Carrier does) so that is one explanation as to why he was only putting in the 7000 BTU units in the small room??? And as for reliability- most sites say that Carrier has a great reputation and better servicing of their units??? As for my zip code- it is 11572 Oceanside NY. we again thank you for your answer but not really sure if we have been pushed either way as to what to do and to whom we should believe with both contractors- as mentioned we were hoping that with just vague measurements we would be able to have someone say which strength unit would be more appropriate? Sorry...

  3. Stephen Sheehy | | #3

    Monte- The problem is that we don't know how airtight your house is. We also don't know how well insulated it is. A tight, well insulated house needs less heat than a leaky, poorly insulated house. A manual J analysis looks at each room, considers insulation, air leakage, windows, etc. You then get a realistic estimate of how much heat you'll need to stay warm.
    Just knowing the room sizes doesn't help much.

  4. GBA Editor
    Martin Holladay | | #4

    Monte,
    Q. "Our only 2 concerns is why was one installer so much different than the other (one contractor said because Fujitsu does not make a 9000 BTU unit whereas Carrier does)?"

    A. That's impossible to answer. There are good contractors and bad contractors. As far as I know, Fujitsu does make a 9,000 BTU/h unit. To learn more, read this article: How To Buy a Ductless Minisplit.

    In that article, I wrote, "The small [Fujitsu] indoor unit is the ASU9RLS3. The “9” in the middle of the model number is a hint at the unit’s cooling capacity rating, which is 9,000 Btu/h. Its SEER rating for cooling is 33. This indoor unit is paired with the AOU9RLS3 outdoor unit in mild climates, or the AOU9RLS3H in cold climates."

    Q. "Why was he only putting in the 7,000 BTU units in the small room?"

    A. I don't know. You can't design a system without performing a heating load calculation and a cooling load calculation.

    Q. "And as for reliability- most sites say that Carrier has a great reputation and better servicing of their units."

    A. I agree with Dana Dorsett -- I would go for the Fujitsu instead of the Carrier if you are concerned with reliability.

    Q. "We were hoping that with just vague measurements we would be able to have someone say which strength unit would be more appropriate?"

    A. Calculations are better than vague measurements.

  5. Monte Kravat | | #5

    AIR LEAKAGE RESULTS
    Your building Shell Leakage was determined to be 3088 cfm50.
    Current industry standards indicate that your Building Air
    Tightness Limit is 1044 cfm50.
    Shell Leakage indicates how much air is leaking into your home.
    If a Blower Door test was performed, the leakage was calculated
    from measurements taken during this test. If no test was
    performed, the leakage was estimated based on your building
    volume and the age and overall condition of your home.
    The Building Air Tightness limit indicates how much air should
    be leaking so you have fresh air even when the windows and
    doors are closed.
    Given that your leakage is 196% greater than the limit, it is
    recommended that airsealing be performed to improved the
    comfort of your home and reduce unnecessary leakage.
    ATTIC RESULTS
    Existing Proposal
    One of your attic flats with an
    area of 189 sq.ft. has 2" of single
    fiberglass batting insulation in
    poor condition. The effective
    R-Value for this surface is 4.
    By installing 10" of cellulose on
    top of the existing insulation, the
    resulting effective R-Value will be
    43.6.
    One of your kneewall floors with
    an area of 216 sq.ft. has 2" of
    single fiberglass batting
    insulation in poor condition. The
    effective R-Value for this surface
    is 4.
    By installing 10" of cellulose on
    top of the existing insulation, the
    resulting effective R-Value will be
    43.6.
    One of your kneewall s with an
    area of 216 sq.ft. has no
    insulation. The effective R-Value
    for this surface is 4.
    By installing 3" fiberglass batting,
    the resulting effective R-Value will
    be 13.4.
    Ventilation in all attic areas is at or above required levels.
    WALL AND FLOOR INSULATION RESULTS
    Existing Proposal
    FLOOR INSULATION
    One of your rim joist surfaces
    with an area of 114 sq.ft. has
    no insulation. The effective
    R-Value for this surface is 4.5.
    By installing 2" of high density
    foam, the resulting effective
    R-Value will be 15.2.
    Existing Proposal
    WALL INSULATION
    One of your exterior wall
    surfaces with an area of 976
    sq.ft. has 2" of single
    fiberglass batting insulation.
    The effective R-Value for this
    surface is 5.3.
    By installing 4" of dense pack
    cellulose on top of the existing
    insulation, the resulting
    effective R-Value will be 12.8.
    HEATING AND COOLING SYSTEM RESULTS
    Existing System Specifications:
    * Location: Basement
    * System: Pilot & damper
    * Fuel: Natural Gas
    * Manufactured: 1985
    * Distribution: Steam single pipe
    * Estimated AFUE: 70%
    * Overall Efficiency: 64%
    It is recommended that you:
    * Do not replace the system at this
    time, but always look for ENERGY
    STAR qualified models if
    replacing this system in the futureWATER HEATER RESULTS
    Existing Proposal
    Your natural gas tank - standard
    water heater located in the
    basement was manufactured in
    1986.
    No recommendation is being
    made at this time, but please
    look for ENERGY STAR rated
    products if you replace this unit
    in the future.
    Heating System
    Water Heater
    Oven
    Range
    Gas Oven
    Appliance CO Readings (PPM)
    100 PPM
    100 PPM
    300 PPM
    CO LimitRecommended Measures
    Measure
    Estimated
    Annual Savings
    Estimated Payback
    Installed Cost (years) SIR
    Basement Insulation $114.00 $39.99 2.9 6.35
    Attic Insulation, Airsealing $4,623.00 $522.70 8.8 2.05
    Wall Insulation $3,416.00 $241.93 14.1 1.28
    Totals:
    Please see your contract for details on the specific recommended products for any of these measures.
    $8,153.00 $804.62 10.1 1.79
    C

    the above was fro an energy audit done about 1 year ago-- for a cost of about $7000-- we are not doing that- but I hope this info helps---bottom line is we are getting a few more estimates and hopefully one of them will give us the same numbers twice (like scientific evidence) when the numbers come out the same more than once- that is usually the right answer. So if we hear either the 7000 BTU or the 9000 BTU number again that will confirm for us which is the right size to get for our home.

  6. GBA Editor
    Martin Holladay | | #6

    Monte,
    Getting an energy audit is usually a good idea, and I hope that you have been able to implement the recommendations provided in your report.

    However, an energy audit is not the same as a room-by-room heating and cooling load calculation. The purpose of the energy audit is to suggest insulation and air sealing improvements to your building's thermal envelope.

    A room-by-room heating and cooling load calculation is the first step to designing a heating or cooling system.

  7. Expert Member
    Dana Dorsett | | #7

    The 99% outside design temp for almost all Long Island locations is +15F, with 1% outside design temps in the 87-89F range, none of which presents much of an issue. Nearly all mini-splits have a specified output at +15F, though the heating capacity will vary from model to model at a given rated cooling BTUs, even within a single vendor's line-up. A temp of +15F is just low enough that the actual model matters. But it's actually close enough to the HSPF efficiency testing of +17F, that the "nominal" or "rated" heating capacity quoted in the submittal sheets will be good enough to know whether it will actually heat the place. For instance, take a peek at the venerable Fujitsu -9RL2's submittal sheet:

    https://www.master.ca/documents/regroupements/19RLS2_Submittal3_1_.pdf

    Even though it's rated cooling capacity is 9000 BTU/hr it's rated heating capacity is 12,000 BTU/hr (quite a bit more than 9000 BTU/hr). To rate it at 12K "nominal" for heating it has to be able to deliver at least that much at +17F.

    The newer 9RLS3 has comparable output capacity ratings, but higher efficiency ratings:

    https://www.master.ca/documents/regroupements/1fujitsu_submittal_9RLS31.pdf

    On the other end of the scale, a Gree Neo 09HP is also rated 9000 BTU (cooling), but only has a rated +17F heating capacity of 5600 BTU/hr (the modulated output at which it's efficiency was tested), and only 8516 BTU/hr running full-out, which is LESS than 9000 BTU/hr, and only about 70% of the "rated" heating capacity of any 9000 BTU Fujitsu.

    http://17uo7e27w1attiybs22of10v.wpengine.netdna-cdn.com/wp-content/uploads/2014/11/Neo-Submittal-NEO09HP115V1A-V2.pdf

    But they are both described as 9000 BTU mini-splits. In short, the actual model numbers really matter, and their rated capacity at +17F needs to be compared against the calculated heating & cooling load numbers at +15F.

    Most of the air sealing and insulation recommendations really are "must do", no matter what you're going to be heating with, and the load calculations should be based on the "after" picture of any intended upgrades. The fact that it's 2" econobatts and single pipe steam indicates it was perhaps built in the early 1950s? Is it full-dimension rough 2x4s, or is it milled 2x4s (1.5" x 3.5" nominal dimensions)? At the very least dense-packing the wall cavities and air sealing the attic & basement will prove highly cost-effective,improving wintertime comfort by quite a bit, and is probably eligible for for rebates through NYSERDA. (I haven't stayed on top of current subsidy offerings in NY state.) Oversized mechanical systems cost more up front, and cost more to operate, and while they keep up with the load, don't provide nearly the comfort of a tighter better-insulated house. You're probably looking at more than $7K (for even right-sized) ductless heating & cooling, but in terms of both operating cost and comfort you'd be better off insulating the place, and cooling with right-sized window-shakers.

    The steam system is most likely ridiculously oversized for the heating loads now, and will be even more so after you tighten up the place, dropping it's as-used efficiency to the 55% range (from the energy auditor's estimated 64%) but it'll still use less fuel since you will have cut the heating load by more than 1/3, and lowered the heating/cooling balance point from 65-67F down to something closer to 60F, which means it will run far less often.

    How many square feet of conditioned space upstairs, and how many on the first floor? Based on the blower door CFM limits presented in the audit I'm guessing this is a fairly modestly sized house, under 1000 square feet total, perhaps a ~500 square foot cape?

    In the aggregate as-is I would expect the heat load @ +15F outdoors to average 25 BTU/hr per square foot of living space (not counting the basement, or the attic spaces behind the kneewalls), but after air sealing and insulating it'll be around 15 BTU/hr per square foot, maybe less, depending on how well they can air seal the kneewalls and any thermal bypasses between the floor joists up stairs. Using fuel use against heating degree-days using exact meter reading dates and a nearby weather station it's possible to verify the heat load of the "before" picture, at least for the whole-house load. The room by room load numbers won't be exactly proportional, but if the temperatures seem reasonably balanced room-to-room we might be able to estimated the relative loads by the radiator sizes. This will all change a bit after insulating, but at least we'd be able to tell if the equipment recommendations by the HVAC contractor resembles anything like "reasonable" even for the "before improvements" picture.

  8. Monte Kravat | | #8

    I really appreciate all the answers BUT they are completely over our heads-- we just had some estimates on ductless units and 2 of the estimates varied as I mentioned earlier- as well as the brand of the units being sold-- I simply wanted to know if with no other factors involved- if given the size of the rooms mentioned what would you people recommend as the BTU used for ductless. As mentioned I now have a 5000 BTU in window A/C that works great - so why is one contractor offering 7000 and the other 9000 in ductless and which would you recommend. Also for the living room we have an 11000 thru the wall A/C and one man wants to put in a 12000 and the other a 17000-- that is truly my only concerns- with as I mentioned NO other factors involved. Again we appreciate your answers but they are a different language to us.

  9. Monte Kravat | | #9

    We actually are having another estimate tomorrow- from Sears- we are going to see what they recommend and hopefully will have a better idea.

  10. GBA Editor
    Martin Holladay | | #10

    Monte,
    You wrote, "The answers are completely over our heads."

    I'll try to give you some simple, straightforward advice.

    1. If you have a 5,000 BTU/h air conditioner that "works great," then a minisplit rated at 7,000 BTU/h of cooling capacity should also "work great." You don't need a 9,000 BTU/h unit in that location, although a 9,000 BTU/h unit would work (because these units can ramp down when necessary).

    2. You can't expect us to explain why two contractors give different advice.

    3. Fujitsu is a very reputable brand with a good reputation for reliability.

    4. You can't use the number of square feet in a room to size a heating or cooling system. You have to take into account window size, window direction (N, S, E, or W), and room insulation levels. However, many contractors aren't aware of this fact.

    5. If you don't want to get into the nitty-gritty details of sizing equipment, that's OK. Choose a contractor with a good reputation and one who provides good warranty service.

  11. Expert Member
    Dana Dorsett | | #11

    A 7000 BTU ASU7RLF Fujitsu mini-split head would more than cover your room currently cooled by a 5000 BTU window shaker. But it only modulates down to 3100 BTU/hr. If you found a Mitsubishi contractor, their 6000 BTU head, the MSZ-FH06NA will modulate much lower, to about 1700 BTU/hr, which will be more comfortable and more efficient in a low-load room.

    If the 11,000 BTU window shaker works fine, that zone doesn't even need a 12,000 BTU/hr head if going with Fujitsu or Mitsubishi. The 9000 BTU rated Fujitsu ASU9RLF Fujitsu will modulate between 3100-12,000 BTU/hr in cooling mode , and the 9000 BTU Mitsubishi MSZ-FH09NA ramps between 1700-12,000 BTU/hr in cooling mode. The 12,000 BTU maximum is more than 11,000 BTU your window shaker puts out, and your real load is clearly less than 11,000 BTU, possibly much less.

    It may not even need a 9000 BTU mini-split head, but without calculating the load numbers or measuring the duty-cycle on your window shaker there's no way to really tell. It's entirely possible that the bigger zone could also manage just fine with a 7000 BTU rated ASU7RLF or a 6000 BTU rated MSZ-FH06NA, either of which can ramp up to about 9000 BTU/hr at max speed.

    The lower the minimum output is, the more it will run continuously at maximal efficiency, and the more stable the room temperatures will be. Since you're shooting from the hip here, see if you can't find a Mitsubishi contractor to quote it, since in the smaller head sizes they modulate down to about half the minimum output of the nearest equivalent Fujitsu, giving them quite a bit more modulation range at the low-load end. Most of the time it's a lot cooler than at the peak outdoor temperature, and with more low-end range it can spend a lot more time modulating, which is more efficient and comfortable than cycling on/off. http://www.mitsubishicomfort.com/contractors

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