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Air handler with DX A/Cz and hydronic heat.

StentyStenty Member Posts: 74
I have a property with two apartments that each have very small heating and cooling loads. I plan to heat with a central boiler and cool with separate systems.

My first thought was ducted mini splits for cooling and baseboard heat. That's a lot of equipment.

A new thought is an air handler with an a coil for cooling and a hydronic coil for heat. That's less piping and equipment.

My cooling load is 9k and heat is 14k. I have zero interest in any resistance backup for heat. Heating design temp is 10 degrees

Any suggestions?

I'm finding traditional condensers no smaller than 1.5 ton. That's too big. And a mini split heat pump looses output below 45F and would need to be way oversized (especially for cooling) to compensate. Plus the COP drops to 2-3.


  • SnowmeltSnowmelt Member Posts: 751

    I would go with the fugitsu ductless with heat pump. With a boiler back up.

    2 boilers that way you charge them for heat also. Don't be so cheap. It's called biting the bullet. All landlords hate it. That's the nice way of saying it.
  • SWEISWEI Member Posts: 7,356
    Small through the wall heat pumps

    usually called a PTAC even though they are bidirectional.  They've gotten quite a bit quieter and more efficient during the past decade.  A COP of 2 is rarely a problem if it's just for a few weeks.

    One of my suppliers imports a 9k 13 SEER unit that installs through two 8" holes in the wall.  Ping me and I'll send you a PDF.
  • StentyStenty Member Posts: 74
    What did you call me?

    You don't know me.

    And you're being nice?

    What exactly am I being cheap about?

    Wanting, and putting in the effort to get, a practical, sensible, well planned, designed, and executed HVAC system is being cheap?

    Wanting that system to be efficient is being cheap?

    Taking the time to ask questions and get professional help is being a "typical" landlord?

    And really, two boilers? One each for the 7k load of each unit? Where do I find 7k boilers?

    Did you even read the post?

    Don't reply to my posts anymore.
  • StentyStenty Member Posts: 74
    Thank you SWEI

    Thank you for taking the time to read my posting and offering a viable solution.

    I will look into PTAC units and ping you for the .pdf.

    Its great getting professional responses to my post.

    I appreciate your time and effort.
  • SnowmeltSnowmelt Member Posts: 751

    The Navien Ncb unit goes down to 14,000 btu

    The takagi goes down to 11,000 btu

    The Navien is a combo so you get domestic hot water at same time.

    Use a buffer tank and you will never short cycle

    With the takagi you put bigger baseboard ( more btu per linear feet ) use a flat plat heat exchanger and you will be able to lower the water temperature to 140 , use a 3 way mixing valve and you will have both domestic and heat off same boiler.

    For ac, can use ductless.
  • SpenceSpence Member Posts: 316

    Do the homes have separate electric meters now, or do you have to split them?
  • John MillsJohn Mills Member Posts: 767

    Some heat pumps, especially Mitsubishi, have amazing capability at heating even below zero. They don't fall off like you'd think. But they are pricey. PTAC or PTHP can be DIY if you can cut a hole in the wall and run electric to it. 
  • StentyStenty Member Posts: 74

    The apts. do have separate gas and electric meters now but they will be combined into one meter each for both apts.

    I will be taking over the utilities.
  • StentyStenty Member Posts: 74
    J. Mills

    Yes, the Mitsu mini split single zone is available in a "Hyper Heat H2i" model that can provide 100% output down to -5F.

    But the COP does drop.

    And those Hyper Heat H2i models are only available in the wall hung units. I'm planning to use a concealed ducted unit.

    The concealed ducted unit provides 100% down to 45F-ish and  by the time temps hit 10F, they're down to 60%.

    I'd have to seriously oversize it to make the heat I need for only a small part of the year.

    Cooling would be supersized at that point.
  • SpenceSpence Member Posts: 316

    OK, so now we need to think about this, since you're the one with the checkbook. We have three immediate goals: comfortable residents stay longer, making sure your first costs are in line with your budget, and ensuring an acceptable ROI and life cycle. You gave us a total cooling load; what is the sensible portion?
  • StentyStenty Member Posts: 74
    You hit it on the nail

    Yes, comfortable tenants stay longer, are willing to pay more, and I get to select from a better pool of renters. That's how I run my business. I have 36 tenants with very very low turnover.

    The total cooling load is currently a moving target. I tried my hand at Taco's Load Calc, plus an online retailer worked up some numbers, plus I hired an online residential HVAC designer.

    I got 9k sensible for each floor.

    The retailer has sensible at 6.5k for each floor

    The designer has it at 7.5k for each floor.

    I carefully looked over the designer's Wrightsoft results and have found that a few adjustments need to be made. I bought Andersen windows with SmartSun so the SHGC is much better than his default. So is my U value. Also, the party walls of the apartments (its a row house) showed a full load. He and I are working out those details.

    So....I don't have an exact answer yet. I will soon and it will likely be below 7.5k per apartment.
  • StentyStenty Member Posts: 74
    I have the sensible loads

    1st floor is 4,906btu sensible

    2nd floor is 5,830btu sensible
  • SpenceSpence Member Posts: 316
    Cooling Load

    We now need the total load. My error for not asking earlier; I assumed the numbers you gave us were total loads. If we have total and sensible we then know your latent load.
  • TechmanTechman Member Posts: 2,144

    1fl units are sensitive to snow and snowdrifts.
  • SnowmeltSnowmelt Member Posts: 751
    2 different apartments?

    You have 2 post going

    One where you poured a lot of money into it, what you got back is an undersized unit,

    Here's what I would do if I was you, decide who your going to go with.

    Navien, weil mclain, Mitsubishi, fijitsu, takagi. First company, goodman.

    Have one of there reps come down and do a heat loss. If your smart you will give a rep $100.00 to show you how they came up with the numbers he gave you.
  • StentyStenty Member Posts: 74
    Latent loads

    1st floor 2,235

    2nd floor 2,517

    Total loads

    1st floor  7,141   (4,906 + 2,235)

    2nd floor  8,347   (5,830 + 2,517)
  • RobGRobG Member Posts: 1,850

    What! I have never paid a manufactures representative anything to help me with ANYTHING! The name says it all. They are paid by the manufacturer to represent / promote their products. I have dealt with them directly by purchasing products and bypassing the wholesaler, but that is rare and usually for specialty items or replacement / warranty items. 

    Stenty, it sounds like you have some products in mind? Please post your ideas and you will get great feedback. (for the most part)

    After all, you're a cheap landlord. :)

  • StentyStenty Member Posts: 74
    edited June 2014
    Two in mind

    And they are probably the only two as far as I know.

    They are the Mitsubishi SUZ/SEZ KA09 and the Fujitsu 9RLFCD. (.pdf attatched)

    Despite the issues that I've had with other Mitsu products (poor install by the contractor, see my other posts) I have a strong sense that the Mitsu is the better product.

    But, the Fujitsu has a higher rated SEER...21.5 vs. 15.

    It has a higher rated peak cooling...12k vs. 11k.

    Has a lower rated power draw...620W vs. 670W.

    Notice that I've used the word "rated". That brings me to my next question. How true and how reliable are rated specs?

    The hand power tool industry is/was full of claims of torque and hp that the manufacturers were allowed to claim w/o any standards of measurement.

    A 5hp shop vac with a motor that's 1/5 the size of the 5hp motor on my table saw.

    If I put the Mitsu in one apartment and the Fujitsu in the other and all else being equal, would the Fujitsu consume less power over the course of a season?

    Then again, I'm not smart and too cheap to pick one over the other for any reason other than what it cost for the units themselves.
  • SnowmeltSnowmelt Member Posts: 751
    620 vs 670

    How many watts in therm. What are you paying per therm. What was last years cooling usage of ac for the year.

    If you figure it out then you figure that out. Then you have the difference you pay for electric.

    As far as one cooling better then the other in MO there equal.
  • SpenceSpence Member Posts: 316

    Your latent loads are quite a surprise; rather high for the property as you have described so far. Yet we can't select equipment until we have this in the bag. Latent loads come from two "Ls": leaks and lifestyle. You seem to be leak-savvy if you've insulated and weather-sealed. Do the residents have 1,000 orchids or have large cooking vessels in extreme use? If not, I would double-check the Wrightsoft (a program sanctioned by ACCA-fantastic!) weather station, ventilation, and people load inputs. If all OK can we do more to the envelope? I'd like to see your sensible heat ratio in the 90s instead of the .68 you now have.
  • StentyStenty Member Posts: 74

    I hired a designer to do the calcs.

    On the report, is the sensible/latent ratio calculated or the % plugged in. I see 0.69 and 0.70 listed on the report.

    The location is correct, Philadelphia.

    I've attached a .pdf of the report for the 1st floor that shows some info.

    People load is 2 x 230 = 460

    Appliances at 1,200.

    No orchids, saunas, or whirlpools in these
  • StentyStenty Member Posts: 74

    I hired a designer to do the calcs.

    On the report, is the sensible/latent ratio calculated or the % plugged in. I see 0.69 and 0.70 listed on the report.

    The location is correct, Philadelphia.

    I've attached a .pdf of the report for the 1st floor that shows some info.

    People load is 2 x 230 = 460

    Appliances at 1,200.

    No orchids, saunas, or whirlpools in these 700sf apts.

    If the sensible loads are correct, and I believe

    that they are, and those latents are a worse case at 68%, then we have a

    maximum load, no?

    Since 9k is the smallest units available, do we already have an equipment size?
  • SnowmeltSnowmelt Member Posts: 751

    The calcs show almost 5,000 btu and the smallest unit is 9,000 btu, it seems like an open and shut case. Don't worry I'm sure your going to by the " more expensive unit" (sorry had to say it.) the machine will mudulate down to what the room is calling for. It does that by what I think are some type of thermistors that give info to the computer board and tell the machine to ramp up or down. I hope this was an educational poet for you & rob.

    I just wanted to point out that you did have a heat loss done and he did pay some money for that, I try to think of it as a tip, it all works out even because when I get a job the sales rep for that company who did the heat losss & gain calcs brings a pizza for lunch. I'm also talking bigger jobs.

    Did you figure out your degree days of ac? And how many watts you use last summer then convert that to therms, and then go to your electric company and see how much you pay per therm. Then the difference between 620 & 670 watts
  • SpenceSpence Member Posts: 316

    It sounds as if you have chosen a machine, and that you're using a mini-split. You have an interesting issue to overcome. With your high LL, you'll need a lower fan speed to neutralize it. At the same time, you have one indoor unit that has to wash cooling around 570 ft2, which would dictate a higher speed. With this contradiction in mind, indoor unit placement becomes tantamount, plus you'll need at least 10' of throw to keep the unit happy.

    Since you're covering the bills, at least you can choose an OD unit that will accept multiple heads. Now we need to find out the heating capacities of the model you like.

    By the way, you can determine the operating cost comparison in this manner: divide the BTUH capacity by the SEER (watts); then divide watts by 1,000 to get Kw. Electric is measured in Kw, not therms. Multiply your answer by your local cost per Kw. The answer is cost per KwH to compare different SEERs.
  • StentyStenty Member Posts: 74
    I have chosen the Fujitsu

    90% positive.

    Its a concealed unit that can be ducted. I plan to place it in the middle of the floor plan and duct the supply and return for each room from there

    I'm not sure what you mean by 10' throw. Do you mean registers that are 10' from the exterior walls and aimed at those walls?

    I've included the floor plans to give a sense of the space and the Fujitsu cut sheet.

    A multi indoor system is both pricey and probably way over sized to serve each little room.

    If the LL seems oddly out of sorts, then it probably is. There is nothing extraordinary about these apts.
  • SnowmeltSnowmelt Member Posts: 751
    edited June 2014

    I think your thinking yo hard , the slim duct what you want to install I don't think is your best choice , why add duct work if you don't have to. I'd rather use the ceiling cassette, you can add fresh air duct to it, or just use a wall hung unit.

    I don't know why you wouldn't want to go with a flex zone unit to do up to 8 units per condenser.
  • SpenceSpence Member Posts: 316

    My fault; I missed that you were using a ceiling cassette rather than a wall unit, which requires a 10' path for the blower to circulate properly.
  • Harvey RamerHarvey Ramer Member Posts: 1,929
    edited June 2014
    Slim Duct

    I'm not really familiar with Fujistu but, if their slim duct unit is anything like Daikin's slim duct, it operates at a very low external static pressure. Best suited for short, straight runs of duct. Such as ceiling soffits.

    I looked up the 9kbtu that you posted. On high fan speed, 353 cfm, you have .35" available esp. That's not a lot so proceed with caution. You have to figure in filters, grills, turns, takeoffs, ducting, ect....

    Ramer Mechanical
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • StentyStenty Member Posts: 74
    I am concerned about the static pressure

    Is the low static pressure negated by larger ducting? Or by another method?

    Its very close to purchase time and I need to be confident that I'm going in the right direction. I can reply later with an approximate of duct lengths.

    The designer who calculated the loads also provided a duct layout and knew of the choice of equipment but I'm not certain that the ducting allows for the low pressure.

    The Fujitsu 0.35" is quite higher than the Mitsu's 0.20.
  • Harvey RamerHarvey Ramer Member Posts: 1,929
    Manual D

    You need to perform a Manual D duct design @ the slim duct's capabilities.

    Ramer Mechanical
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • SnowmeltSnowmelt Member Posts: 751
    edited June 2014
    Call fijitsu

    Why don't you call them, from the class I took it was like 3 years ago, I just remember them saying it's not desighned to do multiple rooms, just really ment for one room at a time and not really ment to be splitted into two large rooms. (Slim duct)

    At the most a bedroom then the walk in closet or a bathroom. ( never put a return in bathroom or kitchen). I personally think your better with the wall mount units.

    I recommend you call fijitsu and ask for there dealer in your area.

    On another note: this post has 30 threads, and the first reply was from me saying fijitsu ductless, this is the simplest way to heat & cool a home. I would get multi- zone or the flex zone, with yearly p.m. But that's my opinion.
  • StentyStenty Member Posts: 74
    A new thread

    I'm starting a new thread for the ductwork.
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