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Hydro-air

Rob Krawic
Rob Krawic Member Posts: 8
in THE MAIN WALL
We are planning on re-building an old gas fired furnace. We cannot get the heat exchanger anymore it is a 40 year old out of business unit. The furnace put out around 650,000 Btus output heat. We have a customer that cannot afford the total replacement which would be a new 12,000 cfm furnace.

We found we could convert this system to a hydro-air system using a 94.6% eff gas fired Lochinvar and install a 2 pass hot water coil for less money.

My question is: Will this be an improvement in efficiency and will it save the customer money? 

Comments

  • SWEI
    SWEI Member Posts: 7,356
    major improvement

    in efficiency, comfort, noise and more.  Outdoor reset will help a lot.  I'd do it.



    Which Lochinvar?  I'm less than enthusiastic about their older Giannoni-based boilers.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    edited March 2013
    WHN model

    I would do a pair of smaller WHN units and outdoor reset and pair them togeather.

    That way you will get maximum efficiency. It will not be 94 percent unless you can get the water temp down to 120* OR LOWER.

    Could you pair 4 - 95% residential furnaces togeather?
  • icesailor
    icesailor Member Posts: 7,265
    Improvements:

    What are your concerns with Giannoni SS HX's that the other choices? Aluminum seems to be becoming a problem with required nut neglected care.

    Please elaborate.
  • Rob Krawic
    Rob Krawic Member Posts: 8
    Gas Furnace going hydro-air

    Thanks for the great respopnses. The customer has no funding. This means they really can't afford two boilers. The Lockinvar boiler has a heat exchanger that plugs up. It requires around 3 hours to take it apart and clean it so the other brands that were recommended are deffinitely under our consideration. Thanks to SWEI for that.

    The idea that the return water needs to be quite low in order to realize the high 90 + % efficiency is also appreciated. We were told this early on by our supplier. But our question really is whether or not the added pump energy, the stand by losses and having to have a boiler retaining heat during outside temperatures and conditions that might not require any additional heat inside. The old heat Ex probably runs in the 78% to 80% combustion efficiency however it only burns fuel when the control calls for heat.

    Everyone I talked with has felt that with OA reset and a smart control that we would truly save energy.
  • Rob Krawic
    Rob Krawic Member Posts: 8
    Gas Furnace going hydro-air

    Thanks for the great respopnses. The customer has no funding. This means they really can't afford two boilers. The Lockinvar boiler has a heat exchanger that plugs up. It requires around 3 hours to take it apart and clean it so the other brands that were recommended are deffinitely under our consideration. Thanks to SWEI for that.

    The idea that the return water needs to be quite low in order to realize the high 90 + % efficiency is also appreciated. We were told this early on by our supplier. But our question really is whether or not the added pump energy, the stand by losses and having to have a boiler retaining heat during outside temperatures and conditions that might not require any additional heat inside. The old heat Ex probably runs in the 78% to 80% combustion efficiency however it only burns fuel when the control calls for heat.

    Everyone I talked with has felt that with OA reset and a smart control that we would truly save energy.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    edited March 2013
    Boilers only run

    when you call for heat, just like the burner in the heat exchanger. size the hydro coils large for a lower required supply temp to maximize efficiency of the condensing boiler no matter the brand you use.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • SWEI
    SWEI Member Posts: 7,356
    Giannoni concerns

    were sent by email, but happy to share what I sent:



    Does the 650k output match the design load?  I'd size the coil for a design temp of 160 if I could make that work, and also try for a variable speed fan (or fans) on the coil.



    The Knight XL uses the Giannoni HX, so they need to budget for annual maintenance, including HX cleaning (done properly it will take 2-3 hours.)  If you installed a Crest or a TT Keystone, that could probably be reduced to an annual inspection with a PM every 2-3 years.



    Either way, they'll love the results -- and probably save 30% on fuel.





    Best of luck...
  • jumper
    jumper Member Posts: 2,245
    need more info

    duct sizes, square footage, heat loss calculations....

    Hydro air is cheap when you use cheap water heater and cheap coil.

    For efficiency, you need a deeper coil. Use super air filter or it will plug.

    Also a dedicates water heater. Combining recirc with dhw is too cheap.
  • SWEI
    SWEI Member Posts: 7,356
    sizing is critical

    Unless I have access to the original design calcs and the system has not been modified, I always start from scratch when sizing replacements.  First a heat loss calc, then a room-by-room and zone-by-zone evaluation of the existing ductwork, then an evaluation of possible zoning or re-zoning (two smaller coils with smaller fans can sometimes improve operation and efficiency, and may not cost much if anything more depending on fan sizes, boiler sizes, use patterns, etc.)  Multiple fans pulling through a single coil can also work, though they will need backdraft dampers and air mixing can get tricky depending on the return ducting design.
  • heatpro02920
    heatpro02920 Member Posts: 991
    edited March 2013
    Planning...

    This is going to take a bunch of planning, I have done a few similar systems, including a 21K sq ft building which had 2 commercial furnaces originally... I'm not crazy about the lochs and you will still need 12000 cfm and plan on a lot more static pressure {learned this the hard way}.



    But planning is the biggest part...

    Plan on having the proper BTU boiler {heat loss}

    Plan the proper coils {I would shoot for 155-165 area if possible}

    Plan the cfm {pay close attention to the pressures needed}

    Plan on pumps and flows needed for the coils and unit...



    My first system was a learning experience, fans not strong enough and then the mod con I used was the correct BTU per the heat loss but the needed flow was way off and I ended up having to install a tank, now I keep a close eye on these things and always try to use multiple boilers...



    I would say they will save around 25-30% vs a std new gas furnace, but honestly how ever you plan on getting the heat over a half million btu's is expensive...



    IMO what you save on the equipment {which isnt as much as you would think after you consider piping, pumps, valves, safeties, venting, ect} is going to be eaten up by labor, I can change a gas furnace in a few hours, vs the install you are talking about may be a few days... {we just did{had to beat this storm} 2 rooftop heat cool units and an outside unit totaling almost 30 tons in 2 days and most of that time was waiting for the crane}...



    Another note and I will look for the pictures but depending on the furnace, I did a system for Vinagrow farms that had a bad heat exchanger, it was large but not 650K. I pulled the exchanger and installed the water coils in the old unit, used the old units fans and kind of skelontized the original furnace... It worked... and still works... but 200* water and taking it off the bottom of an existing steam boiler..
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