Hydro air question

Discussion in 'HVAC Heating & Cooling' started by newguy101, Feb 12, 2020.

  1. newguy101

    newguy101 New Member

    Joined:
    Feb 12, 2020
    Location:
    CT
    I have a 30 year old 2500 sqft colonial in Southeastern CT. The house is currently heated with a combination of electric baseboard (expensive!) and a wood stove, and is cooled with window units.

    I am trying to figure out the best way to upgrade our heating and possibly cooling, since we believe we will be in this house long-term. We care much more about an efficient heating system than we do about cooling, since 1. We are definitely in a heating climate, 2. We have almost complete shade from trees that surround our house, 3. We are pretty tolerant of a warm house. So if we never upgrade our cooling system, that is ok with us.

    We have a very efficient wood stove which is actually able to heat our entire house until it gets really cold. I would like to keep using the stove after we upgrade our heating system, since we enjoy it and it is cost effective (I source wood myself and split it myself). However, I’d like to reduce the amount of wood we’re burning, since it’s a lot of work!

    Since we’d like to keep using the wood stove, I think it’s pretty important that we put in a zoned system. When the wood stove is pumping heat into our first floor, I don’t want the heating system to be doing the same thing.

    I had been looking into putting in a 2 zone furnace, but it seems like a lot of people aren’t happy with them, and they also can require more maintenance. I recently found out about “hydro air”, which is a new concept for me. It seems like it allows for zoning to be done very well.

    Here’s my question – is it possible to run a hydronic loop (not sure if that’s the right word) from the boiler?

    I am thinking that I’d like to put in a ducted hydro air system for heating the first floor (would allow for eventually putting in cooling as well in the future), and then heat the second floor with baseboard radiant heaters. If/when we decided we wanted to do AC, I’d put in a separate ducted system upstairs.

    When I first read about hydro air, I assumed that it can be used either in combination with a ducted system (a loop of hot water from the boiler runs to an air handler, where it heats up the air which is then pushed through ducts), or a radiant system. However, the more I have read about it, it seems like people primarily use it for a ducted system, and sometimes for radiant floor heating, but not for forced water radiators. I am wondering if this is because it seems like hydro air boilers seem to heat water to around 140 degrees, whereas forced water boilers seem to heat water to around 180 degrees?

    If that is the primary reason people don’t use hydro air in combination with radiators, couldn’t I just run the boiler at 160 or something? Or maybe 140 would actually be fine, it’d just take longer to heat up? When it is really really cold out, I will definitely be running the wood stove anyways, so the system shouldn’t have to work too hard.

    I don’t know if I am way way out in left field here, so I’d really appreciate help from the experts!
     
  2. jeremyt

    jeremyt New Member

    Joined:
    Dec 27, 2019
    Location:
    North Central CT
    Funny story. We purchased a home in North Central CT in August 2018, and I am currently working out the details to alleviate the exact same issues. My current plan for the future is to go all electric heat pump, and ducted systems because we are big fans of dehumidification and air conditioning in the summer months. Right now I am looking at Mitsubishi Hyper Heat or Fujitsu Low Temp models. Form my reading, both of these product lines will heat down to -13F. When we purchased the house it came with some sorry excuse for an oil burning furnace. Last winter before I started to make changes we were shelling out $650 a month in heating oil. I installed a used pellet stove, and we have been exclusively on that for heating since. It does ok, but there are cold spots in the house depending on the outside temperature. Last July I installed a heat pump water heater, and shut the boiler off. Haven't turned it on since. Im curious to see what you end up doing.
     
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  4. Sylvan

    Sylvan Still learning

    Joined:
    Sep 23, 2004
    Occupation:
    plumbing - fire suppression - boiler inspector
    Location:
    New York
    I completed a home in Riverdale (Bronx) we installed a new boiler and cast iron base board for heating and a separate unit was installed for AC .

    I dont care for scorched air heating with filters and fans as the more complex a system is the more chance of a failure

    Rule of thumb what is a good conductor of electric is a good conductor of electric so copper (type L) or black piping is proven very cost effective for heating

    The problem with heating "Air" it does not stay warm

    Picture a pot of boiling water turn off the flame and the pot remains hot for a long time and you do not get the wild fluctuations of heat as you would with air

    Air is actually a good insulator but not good for heating
     
    newguy101 likes this.
  5. newguy101

    newguy101 New Member

    Joined:
    Feb 12, 2020
    Location:
    CT
    Thanks for the replies. I understand the advantages of radiant. It would be nice to have radiant on both floors, but putting radiant on the first floor would require more demo than I want to do, since our basement is finished. I am assuming I’d have to tear up either the basement ceiling or the floor on our main level to run the pipes. I know I will have to tear up part of the basement ceiling to run ducting, but I think I can get by with only tearing it up in parts of the basement that I don't care about (trunk line will run through a series of storage rooms that run the length of the basement.

    Since our second floor is carpeted, I was thinking that it’d be much simpler to run radiant up there – all I’d have to do is remove the baseboards and pull up the edges of the carpet.

    Also, we will probably use the hydro air on the first floor only when the temperatures outside are fairly mild (maybe above 40 degrees or so). Otherwise we’d have the wood stove going. With mild weather, my guess is that the fluctuations won’t be that bad since the heat loss shouldn’t be too bad.

    So I’m still wondering – is it possible to mix hydro air with radiant? One boiler that provides the hot water for the hydro air blower on one loop and the upstairs radiators on a second loop? Or is that a bad idea?
     
  6. newguy101

    newguy101 New Member

    Joined:
    Feb 12, 2020
    Location:
    CT
    Glad to hear I'm not the only one with this problem! I looked into heat pumps quite a bit. I came to the conclusion that they are too expensive to operate here in CT, since our electricity prices are through the roof (at least in my area - SE CT). I know several people who put them in recently (both ductless and ducted) and whose bills are much higher than they were lead to expect. Hopefully your experience will be different!
     
  7. newguy101

    newguy101 New Member

    Joined:
    Feb 12, 2020
    Location:
    CT
    Hmm, so the more I think of this, the more you are convincing me, Sylvan.

    Like I mentioned in my first post, we care much more about putting in a good heating system than we care about AC. We have window units which get the job done. So maybe the best way to go is to just put in a purely hydronic system. I would have to cut up the basement ceiling, but I don't think it would be too terrible.

    Then in 5-10 years, I could look into putting in a separate ducted system for AC.
     
  8. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    My house is micro-zoned with 3 zones of cast iron radiator, one hydro air, and one radiant floor. The hydro-air zone is alternately heated with a wood stove, and has a (grotesquely oversized for the load) cooling coil. Any of those zones could work with 180F water, but it would be less comfortable, since the radiation is designed/sized for 125F average water temps. The hydro-air zone originally was set up with a cast iron boiler delivering 180F water, but like the cooling coil that came with the unit was well over 2x oversized for the whole house load.

    Even at a 140F EWT the air handler would be oversized for the whole house- at an EWT of 125F it still delivers that much heat, but going any lower would make the exit air at some of the registers too tepid for comfort.

    There is no such thing as a "hydro-air" boiler, and hydro air handler specifications call out the heat rate at a number of different entering water temps and flow rates.

    Ductless and ducted cold climate mini-split heat pumps are cheaper to operate in CT than condensing propane boilers (when right sized), but not very competitive against condensing natural gas. It's pretty competitive with 82% minimum-legal efficiency gas though. What are the all in $/kwh and $ /therm or $/gallon rates in your neighborhood?

    Whatever the solution, the critical aspect for COMFORT is to right-size the heat emitters for the load. A typical 2500 foot 2x4/R13 colonial with R30 in the attic and clear-glass double pane and NO foundation insulation would have a heat load of around 50,000 BTU/hr @ 0F. ASHRAE recommends no more than 1.4x oversizing for the heat load at the 99th percentile temperature bin as the best compromise of comfort & efficiency. (The 99% outside design temps in CT are north of 0F, in most of SE CT usually north of +5F.) At 1.4x oversizing there is sufficient capacity to cover the load during Polar Vortex disturbance cold snaps, but it runs at a high enough duty cycle to provide both comfort & efficiency.

    With a 1.4x oversize factor the duty cycle at the 99% outside design temp is 1/1.4 = 71%, it's running MOST of the time when it's cold out, which is WAY more comfortable than the typical hot flash followed by the extended chill most people are used to with the typical 3-4x oversized hot air furnaces. Yes, 3x+ oversizing recovers from overnight setbacks more quickly and heats the house, but that's different from providing comfort to the occupants. When right-sized delivering heat with ducted air can be quite comfortable, but when oversized it's too often a comfort disaster.

    Take the time to run a ROOM BY ROOM heat load calculation using either I=B=R methods (using a spreadsheet tool) or a semi-decent ACCA Manual-J-ish freebie online tool such as LoadCalc or CoolCalc. Be aggressive in the assumptions about air tightness, R-values/U-factors, etc, not conservative. Oversizing is the enemy of both comfort & efficiency.

    Also take the time to read/watch Nate Adams' well put together primers on home comfort, and HVAC design/sizing issues.

    With load numbers you will be able to avoid spending a lot of time and money on the HVAC for little gain in comfort, and spend it on what really delivers comfort instead (which in most cases would be air sealing and addressing any insulation deficiencies.)
     
    Last edited: Feb 12, 2020
  9. fitter30

    fitter30 Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
  10. newguy101

    newguy101 New Member

    Joined:
    Feb 12, 2020
    Location:
    CT
    Thanks everyone for the comments. The more I read about radiant baseboard heat, the more I think that's the direction I want to go. I am going to try to get some quotes in the next few weeks. A few questions:

    1. Any tips on what I should look for in a contractor? Lots of HVAC guys around here install ductless systems, so it's easy to get a recommendation from a friend. But I don't know anyone who has had a radiant baseboard system installed, so unfortunately I probably won't be able to get a recommendation from someone who has had this done.

    2. What should I look for in a boiler? Will the contractor give me options, or will he just tell me, "I install this brand"?

    3. Any tips on features of the system that I should ask the contractor to include?
     
  11. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Don't leave it up to the HVAC contractors to spec the equipment. Soliciting a bunch of proposals, 9 out of 10 of which will be ridiculous, is just a waste of your time and theirs. There is no real substitute for doing a proper room by room Manual-J or similar load analysis, and that analysis should be done by a third party whose livelihood & reputation is made on the accuracy of their,= numbers, rather than installing & maintaining equipment. A certified professional engineer, some RESNET raters, and some architects are capable of providing these services.

    The boiler needs to have:

    A: Sufficient capacity to deliver something like 1.4x the design load at the 99th percentile temperature bin in your area (aka "99% outside design temperature")

    B: Has a sufficiently low minimum firing rate to not short cycle on the zones with the least amount of radiation at condensing temperatures. ( See this for an explanation.) Clearly there is interaction between the radiation spec & boiler spec on this front.

    C: Reasonably local distributor or manufacturer support (not just installer support). (For that reason I'm somewhat partial to HTP, whose headquarters are less 2 hours drive from most locations in southern New England, but there is also good support from some of the bigger manufacturers too.)

    D: Reasonable experience of installing the bran & series of boilers by the installer. This is more of an installer feature than a boiler feature, but it's important.

    E: Outdoor reset control (standard on almost all condensing boilers.)

    When you figure out A, you can probably also figure out B as a DIY project. From there do some research on what boilers on the market fills the bill for A & B, then find the local distributor's number and solicit recommendations for contractors who can competently install the equipment you have selected.

    The distributors are in a position to know which contractors are ordering & installing dozens of that series in a year with minimal hand-holding from tech support, and which contractors are tying up the line with questions clearly answered & spelled out in the manuals, and sending in dubious warranty claims on what looks like installer error.

    Contractor warranty support, and at least one or two short visits for tweaking the outdoor reset curves to perfection.
     
    Last edited: Feb 14, 2020
  12. fitter30

    fitter30 Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Properly sized equipment will make the house perform better. Boiler or ac brand doesn't make a good system the contractor and his help do that. Want equipment that the contractor sells and has the training and parts. 30 year old house might need windows, doors and more insulation. Your utility company's might have rebates and offer a energy audit that includes a blower door test ( tell you how air tight the house is). By improving these things their cost would be offset by smaller heating and cooling equipment. My house is has two mini systems three wall unit each. 1900 sq. ft.Advantages efficient, quiet, zoned Disadvantages filters are thin, parts might be 2 days away, and cleaning inside units is labor intensive ( look at utube videos)
     
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