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Gas + Electric Condo VS All electric condo

cbut8995 | Posted in General Questions on

Hi I’m doing a development in Brooklyn between 2 houses and wanted opinions on whether or not a minisplit heating and cooling system would be enough to heat each apt. NYC does get cold but since its a multifamily building we are only exposed on the right and left sides. 

Originally we were going to have a minisplit system that has heating and cooling AND baseboard heating for all the units but after talking with the GC and architect, I can save somewhere between 100-125k in project cost alone if we completely remove the baseboard heating, and make the entire building electric and it will quicker to build without having to wait for national grid for gas hookup. Instead of the combi gas units we would then use an electric Tank HWH which is significantly cheaper and have less penetrations on the roof for exhaust from the HWH so less possibility of roof leaks.

Anyone have opinions of having each apt use only the minisplit heating and cooling? We are using 9K BTU wall mounts from Mitsubishi for the bedrooms and living rooms (2 per apt, each apt is 1 bedroom/1 bathroom) total 550 sqft. These will be rentals so we need something reliable. For the larger apt, we are using the ducted minisplit and using 9K BTU for the bedroom which is about 150 sqft, 9K BTU for the Living room 350 sqft, and 9K BTU for the 400 sqft basement. All apt ceiling heights are around 10 feet and all these units will be hyperheat and placed on the roof so I am hoping it wont get cold than -13F since that is the coldest operating temp for the Mitsubishi hyper heat minisplit models. Just looking to see if anything uses this only for the entire home and if they think it is sufficient for Heating and Cooling.

Thanks.

-Cody

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Replies

  1. jkonst | | #1

    For what it’s worth, I’m actually condo shopping in Brooklyn (Boerum Hill/downtown) right now, and all the new construction is mini-split only - mostly ducted, some ductless. Some have radiant heat in bathrooms, as a luxury rather than a need. I’ve seen a bunch of brownstones running only mini-splits as well.

    Now if only more developers offered induction instead of gas stoves...

    1. cbut8995 | | #4

      Hi Jkonst,

      I hear you haha. A lot of the new developments I am seeing are swaying away from gas in the buildings and just doing all electric so induction is a possibility but most of the developments will do electric cooktops/stovetops but induction cost so much more and requires A LOT more power so thats probably why new construction doesnt sway towards it too much.

      1. Expert Member
        BILL WICHERS | | #6

        Induction shouldn't use more power. Most induction cooktops I've seen use the same size supply circuit as a similar size "regular" electric cooktop.

        The biggest downside for induction right now is the relatively short life of the typical induction cooktop. This is entirely a manufacturing issue that should be easy to solve, manufacturers just need to do better engineering and maybe use a few beefier components.

        Bill

        1. cbut8995 | | #8

          Thats bad news for me. I was planning on using electric cooktops from bertazonni paired with wall ovens for the smaller 1 bedrooms:
          https://www.ajmadison.com/cgi-bin/ajmadison/NEM5466UC.html
          https://www.ajmadison.com/cgi-bin/ajmadison/PROF24FSEXV.html

          But for the apt I was going to live in, I was going to use induction for myself since it heats the fastest. I was either going with Miele or Wolf induction cook top but now you are making me rethink this for my own apt. Even the high end brands like Wolf or Miele are bad?

          1. Expert Member
            BILL WICHERS | | #9

            It's not that they're "bad", it's just that a lot of people find induction cooktops often have issues as they age. Many have said they get about 5 years out of their induction cooktops.

            Some of this is due to improper installation. The Kitchenaid induction cooktops, for example, require a small ventilation slot in the front of the cabinet. Many people don't put this vent slot in, so the cooktop runs too hot. Heat is bad for anything electronic, and the result is those cooktops would have control issues in a few years due to the excessive heat. This isn't the fault of the cooktop itself, but it shows that people don't always install things correctly.

            My own opinion is that induction cooktops are more susceptible to power problems too. A whole-home TVSS (surge protector) installed on the electric panel will help with this.

            Some of the issues I've seen or read about look to me (I'm an electrical engineer) as components having been operated too near their limits. It's a good idea to leave some extra headroom in power electronics to ensure long life, but that means using slightly more expensive parts. This is why I think at least part of the logevity issue is related to the way the manufacturers are designing these cooktops.

            My recommendation to you would be to buy an extended warranty with your induction cooktop. They are VERY nice to use, just know where the issues can be and with this particular appliance, the extended warranty is more likely to be a good investment for you. The whole-home TVSS unit has other advantages too since it will help to protect ALL of the electronics in your home, not just the cooktop.

            Bill

          2. cbut8995 | | #10

            Hi Bill,

            I will def have the electrical contractor do that then. When you mean TVSS is it something you add to the electrical panel or each individual high electrical output device. Our minisplits are high in power as well as the electrical ovens we plan on using.

            Im assuming that this TVSS should be used in the units with regular electrical cooktops as well too since this is a rental building.

            I think Ill stick with wolf induction and get the longer warranty like you said!

          3. jkonst | | #11

            I didn't realize that - very helpful information. In these parts, it seems the biggest obstacle to adoption is awareness, and the market demanding a "luxury" 36" gas cooktop. I have a feeling that will change in the next few years, as large all-electric buildings are starting to be announced here.

            Anyway, sorry for the tangent on your thread, though this has been very enlightening for me :)

          4. Expert Member
            BILL WICHERS | | #12

            A TVSS is a relatively small device that goes on the main electric panel where service enters a building. I recommend the little ~$50 units made by Ditek for most residential services since they're inexpensive and effective.

            In a larger commercial building, it's a little more involved. What I would do for your development is to put a big TVSS on the main service, which I'm guessing is probably three phase, either 120/208Y or 277/480Y. You need a TVSS specific to the voltage and phase configuration you have. I like the larger units made by Liebert, which is Emerson Network Power now. I use these extensively for my commerical work in critical facilities, but they are NOT cheap. Eaton's "IT Protector" line is cheaper and still pretty good. Use one of those type units on your main service panel ahead of everything in the building. This unit will handle the big transients from outside the building (like lightning, power glitches, etc.).

            Use a small Ditek unit on each tenant's service panel. These will get smaller gltiches from stuff inside the building (mainly switching transients from maintenance work elevator motors, etc.).

            With a first and second line protection scheme like that, you're pretty safe. The units are cheap enough to just install everywhere. You can market it to tenants as an extra layer of protection for their sensitive electronics. Your cost for the big main unit will be around $1,000 or so max, the Ditek units would be about $50 per unit, so pretty minimal.

            Note that if you're installing a generator for anything (sometimes these go in for emergency lights and one of the elevators in commercial properties), you really want a TVSS on BOTH sides of the ATS (Automatic Transfer Switch). In your case, if you have a generator, the big main unit serves as the protector ahead of the ATS. A smaller protected on the "output" side of the ATS would handle switching transients when swtching between utility and generator power and back. This is how we design all the big telecom facilities I normally work with.

            Bill

  2. Expert Member
    BILL WICHERS | | #2

    You'll probably be OK, especially if the building is such that there is a large ratio of interior to exterior walls for the individual units. More interior walls compared to exterior walls means less overall heat loss per unit. Corner units would have the worst-case heat loss, especially if they have a lot of windows.

    I don't think you'll have a problem with hyperheat minisplits here. I'm assuming you don't have any other options (like city steam). Steam tends to be very cheap if you have access to it, and in many areas it's green too, since it's usually sourced from combined cycle plants to boost overall plant efficiency in what are primarily electric power plants. You can air condition with steam too with absorption chillers, which are nearly always the cheapest way to air condition if you have steam available.

    For the water heater, be careful with tankless electrics in a multi-unit property. You could have VERY high peak electric loads if everyone takes a shower around the same time and every unit has their own heater. The most overall efficient option is probably a large, central tank-type electric water heater in a larger development, but that will make it difficult to meter energy use to each unit. If you do go with tankless units, I would try to use three phase units (I'm assuming you probably have three phase electric service to the building), or at least rotate the tankless units through the phases so that you have load spread out as much as possible.

    The issue you have with tankless water heaters in a multi unit development is that while code allows for deman factors for service sizing, some things can be a problem. In this particular case, everyone is likely to take showers around similar times in the morning due to the typical work schedule, so demand factors don't always work out as you'd expect and you can have problems. If you can get 480v tankless water heaters (I've never looked), and have 480v service to the building, try to run all the tankless heaters directly off of the 480v system for maximum efficiency since that will eliminate one level of transformer losses, and will also save you money on wiring due to much smaller feeder cables needed for the same amount of water heater wattage.

    Bill

    1. cbut8995 | | #3

      Thanks for the great insight Bill. This is very helpful. I am hoping the 9K BTU mitsubishi would be enough since I have read all over GBA that its already probably oversized. I am just worried as I dont want to have any complaints of it being cold. We have large 3 foot x 8 foot tall windows in each apt (6 per apt) and two 9K BTU units in each apt which should be enough.

      As for the water heaters, we were actually going to go with either Rheem or AO smith tank electric water heaters so not tankless. I think that should work for this building. Each 1 bedroom will probably get the 40 gallon electric tank and the larger apt will probably get the 55 or 80 gallon electric tank.

  3. ohioandy | | #5

    Of course you would do well to run proper heat loss calculations, but I'll give you some real world comfort feedback on those splits. In my tight SIP house, I'm running two 9k units for 900 sq.ft. total on 1.5 levels. The upstairs unit is ducted to two small bedrooms, and it cycles to the point of disturbing our sleep with both noise and wind. Way oversized, as you'll hear all over GBA--don't put a single head in a small area. The downstairs unit, a ceiling cassette, seems to be just right for this volume, as it runs constantly at a very low level.

    Another problem might come up with your large windows. My wife gets cold in our house, even at 72 degrees. The minisplits are really good at maintaining setpoints, but I think the radiant cooling effect of our large windows with no curtains have a sneaky way of creating discomfort. I guess the lesson is either go with the better windows than you can afford, add curtains, or both.

    You sure don't need any backup heat source, and having two 1:1 units is great redundancy if one goes down.

    1. cbut8995 | | #7

      Thanks Andy!

      So the 9K Concealed Duct unit with hyperheat and a basepan heater from Mitsubishi for a small 150 sqft bedroom is overkill then? I cant find a smaller concealed duct unit because it seems they all have a min BTU for heating and cooling around 4000-5000 BTU which is unfortunate. I dont want to necessarily have it used in both the bedroom and living room because like you said 1 to 1 is best and when we are sleeping in the bedroom I dont imagine we would have the living room or basement units on at all.

      The attached mech plan shpws the basement accessory (400sqft) space to have its own 9K BTU concealed duct, the Living room (450 sqft) space to have its own 9K BTU concealed duct. Bedroom (150 sqft) to have its on 9K BTU concealed duct unit all 1 to 1 configuration.

      The other 1 bedroom/1bath apts in 2nd,3rd,4th floor each bedroom is about 100 sqft will have a 9K BTU wall mount (min BTU cool/heat: 1700/1600) and same unit in the Living room 350 sqft and also 1 to 1 configuration.

      Its unfortunate concealed duct doesnt go as low as the wall mounts but I want the concealed duct look for the 1st floor apt since I will probably live in there and I like the modern slim slot diffuser look.

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