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Keep the old boiler vs. all split system

My wife and I are renovating an old (ca. 1910) 2500 sq. ft. town home in Brooklyn, NY. It's 2 stories plus a basement that we plan on finishing. We currently have what I've been told is likely an early 90's Crown boiler in the home. Please see the photo below.



The problem is this: My wife and I hate window AC units... so I've been looking at the split-system units offered by the likes of Sanyo (see here: <a href="http://us.sanyo.com:80/HVAC-Multi-Split-Systems">http://us.sanyo.com:80/HVAC-Multi-Split-Systems</a>) that offer both heating and cooling.



My question is: Would I be crazy to think I could heat and cool the home using split system units? Will it cost me a grillion dollars a month in electric bills?



Any thoughts/ideas/opinions would be greatly appreciated.



Thanks very much

Comments

  • Bklyntownhome
    Bklyntownhome Member Posts: 7
    photo

    sorry the photo didn't attach the first time...
  • Bklyntownhome
    Bklyntownhome Member Posts: 7
    photo

    boiler
  • Jack
    Jack Member Posts: 1,047
    Both

    Add the MS. You all ready own the boiler. Keep it. You will find the inverter 410a minisplits will heat effectively. I've run mine down to 5 f. Now, do i run it when temps are very low? No! As i still have the boiler I can determine my "balance point", the temp at which I run the boiler over the mini. Your decision will largely be predicated upon the choice of mini-splits, size and lay-out of the equipment.



    There are now 4 ton units you can run up to 8 evaporators (indoor heads). In my house I ran a dual indoor evap system upstairs and the highest efficiency 25 seer/12HSPF) down stairs.



    The way to make oil more efficient is to burn less of it. You'll like the combination system.
  • Bklyntownhome
    Bklyntownhome Member Posts: 7
    Thanks

    Hi Jack,



    Thanks so much. That's very helpful. Did you install Fujitsu brand units? I wanted to get an opinion on which brands are good as well.
  • Ross_7
    Ross_7 Member Posts: 577
    edited January 2011
    Reduced heat output for the mini-split

    Hello Jack,

    How much difference of heat output have you noticed when running you mini-split heat pump at 5F outside?  

    To BrklynTownhome,

    I have a straight cooling Fujitsu unit, that I installed at my house. Runs very well, and whisper quiet. Kept us nice & cool on 90+ days last summer. Just make sure it's sized correctly.
  • World Plumber
    World Plumber Member Posts: 389
    Balance point

    I would keep the boiler. With the proper controls you could set the system up so the mini split runs down to the balance point. I usually set them up to run down to 30 degrees then the fossil fuel system kicks in. If you choose to go with the mini split as you primary heat be sure that they are sized for the heating not the AC or you will be cold in the low temps. I'm dealing with a system now that the out door units are not large enough for temperatures below 20.

         I have customers who use them as primary heat and they work fine. Most manufactures recommend a switching to another form of heat below 20 degrees.

           The systems I have in, where the heat pump runs above 30 then the boiler have achieved a large saving in their heating costs. Plus they have air conditioning in the summer.

    MC
  • Bklyntownhome
    Bklyntownhome Member Posts: 7
    Cost of split system

    Thanks to both of you for the advice. It sounds like the split-system may be good for about 75% of the year in NYC... maybe more.



    The cost of buying and installing the split system should be far cheaper than central air, right?
  • Jack
    Jack Member Posts: 1,047
    Yes, I installed Fujitsu, but...

    I represent them in New England. I always, except in this post, provide a disclaimer to that effect, but did not do so in my initial response to you. My apologies.



    You need to look at how you live in the house. For instance, in my home here in MA, it is my wife and I in a 4br. We basically "live" in about 1/4 of the house. That is the area i have Fujitsu's in here. I was going to add more, but we have sold the house and are moving next month...yeah! As well, I have a whole house fan which does and excellent job upstairs. YMMV, but I like the fan. I'm moving next summer and in that house I have the dual upstairs and the 25 seer unit downstairs.



    Some of the questions you need to answer are, do you want to do the entire house? Mini-splits are the ultimate in zone control, so you can start with a total plan and add them year by year, or go for the whole enchilada at once. I believe you will find that you will exceed 75% of your heat load with the MS'. The previous post about sizing is correct. Careful heat loss/gain calculations should be run FOR MINI-SPITS, meaning no duct losses, as there are no ducts. Keep your boiler serviced and ready. Again, you select your balance point for comfort. My recommendation is to not oversize the system. It will then give you the best comfort in cooling and dehu and help a great deal in the heat side. Go to www.miniheat.com and run some numbers. The information I use mostly there are the BIN numbers. That is a compilation of weather statistics upon which Maual J heat loss calcs are based. Check out the total number of hours that the temperatures is in each temp range. You will see that the vast majority of your heat load is above 30F



    The problem with a complete central ducted system is that in order to add duct work to a home you basically have to tear the place down and loose a lot of closet space along the way, to get it done. On my house I added the couple systems to there was a ducted system installed 5 yrs ago with ductwork/cooling/gas heating. Lots of air in some areas, none in others, LOUD. Just a terrible system. I pulled the entire system out and added the Fujitsu's and a Rinnai Energysaver (which I also represent). My point is that, yes, you can add ductwork to a building, but to do it well, is incredibly difficult. the other issue is that no central system is going to give you the inverter control (modulating heating and cooling as in true variable speed) and efficiencies you can achieve with mini-splits.



    Hark! she calls me to dinner! You can call me many things, but you cannot call me late for dinner!
  • Tranberg
    Tranberg Member Posts: 4
    edited January 2011
    Not a fan of multisplits

    My experience with multi-splits in heating mode vs 1:1 split systems is that the former have smaller outdoor unit heat exchanger surface/capacity ratio than the latter, resulting in more frequent de-icing.



    If you keep your boiler, you can just turn it on when the de-icing becomes to frequent.,



    If you have both systems, you get the most savings by picking the low hanging fruit, ie. using the splits when it's not so cold outside but you still need heat, especially int the evening and morning. You can save a bunch of idle loss from the boiler, and the splits are very effective. They also react quicker.
  • Bklyntownhome
    Bklyntownhome Member Posts: 7
    Thanks

    Thanks to all of you for the helpful info. I really appreciate it.
  • World Plumber
    World Plumber Member Posts: 389
    Cool Mornings

    The mini splits are nice on cool mornings you have instant heat. Where you are on your way to work by the time the boiler gets hot, so you just wasted that fuel.
  • alotlikeearl
    alotlikeearl Member Posts: 68
    Agree With Most

    While I agree with most of Jack's points I would note that Nordyne makes central systems that have inverter compressors and variable speed outdoor and indoor motors.  They call it IQ Drive and the condensers can achieve up to 24.5 SEER and the heat pumps up to 22 SEER. 
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