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  1. #1
    Join Date
    Apr 2010
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    18

    Best boiler for hydronic radiant heating

    I am in the process of designing a custom home with my architect/builder. I've decided to do in-floor radiant heating throughout the house (approx 4000sq-ft) as well as finish the basement and heat that as well (additional 1700 sq-ft). The house is in Ontario, Canada so it gets quite cold in the winter.

    I like being an educated consumer but have never dealt with hydronic heating before so I'm a total newb on this stuff. I'd like to know what kind of boiler is best for this application and which brands are good.

    A relative has a slightly smaller home (3500 sq-ft, basement not finished) and uses an NTI Trinity Ti200 for his in floor radiant heating. He claims he has no issues with it. Is this a decent boiler?

    My required criteria are:

    1) High energy efficiency
    2) Low noise
    3) Durability

    Suggestions?

  2. #2
    Join Date
    Mar 2001
    Posts
    1,213
    The Trinity is supposed to be good.. The designer/installer is most important. Someone who will stand behind the equipment installed. Equipment with a good track record & a supplier/mfg. with credentials for long term support. Do your homework, & get some referrals. Don't forget that Ontario is supporting 'green' tech. & solar could be cost effective for you. Hope your architect is aware of that as well.

  3. #3
    Join Date
    Apr 2010
    Posts
    18
    Hmmm solar? Who makes such a system so I can check it out?

    Also one other question, if I wanted to have a heated driveway, what kind of boiler would I need for that?

  4. #4
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    This is a loaded topic bur requires someone with lots of depth of experience to really render facts and not just an opinion.

    The NTH Trinity is a good boiler, so is the Lochinvar Knight, The Buderus GB142, the Triangle Tube Solo and many, many more. The problem with those boilers and a system that is radiant heat is that they have no thermal mass. When you're dealing with radiant, particularly snow melt, you really should have a boiler that has some water volume and some thermal mass. The industry, for almost all other applications, is moving rapidly to low mass boilers. But when it comes to pure radiant, you can't beat the mass of a condensing cast iron boiler and outdoor temperature reset. A low mass boiler will be cycling all day long in moderate weather. A high mass boiler will just cruise. I don't often recommend high mass but for a large radiant job and possibly snow melt, it's the recommended solution.

    Whether straight radiant or snow melt, I'd recommend the same basic solution. For the floors, the Viessmann Vitola, biferral gas boiler has the mass to smooth out the cycles and can run just above room temperature all day. For snow melt you'll need more Btu's and both Viessmann and Buderus have boilers that are up to that task. They also have all the purpose built controls to do the job properly.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  5. #5
    Join Date
    Apr 2010
    Posts
    18
    Hey thanks for the reply!

    Could I do something like this then...?

    Use something like an NTI Trinity for indoor heating (radiant floors) and then get something like a Viessemann Vitola 200 or similar for the outdoor driveway/porch heating system?

    Hopefully I could turn on the outdoor heating only when needed and ofcourse have the indoor stuff running off of a zoned thermostat system.

    Could something like this work?

    Any ideas (very gross) how big each boiler would need to be? The driveway will be for a 3 car garage and porch is about say 80 sq/ft. I want to ballpark how much each boiler will be. Again, no exact numbers needed, just gross and round up if you have to (worst case).

  6. #6
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    When you say indoor heating radiant floors, is that masonry product floors or wooden floors? Either will work but wood needs a higher temperature than masonry. You should understand that the value of radiant is in the constant supply of heat to the room by the mass of the floor. Likewise, the economy of operation is to keep the circulator(s) running constantly so it's a continuous supply of heat and continuous, matching, dissipation of the heat through the floors, into the rooms and then out to the outdoors.

    You can use a low mass boiler whereever you want but it's my experience that a high mass boiler does a better job when it's strictly radiant. However, only radiant is a rare job these days. Most tie in domestic hot water, baseboard in some rooms and/or hydro-air coils, all requiring high temperature water.

    Snow melting systems are no different than any other heating system. When it comes to design there are several parameters that determine how many Btu's you need to do the job. For example, a system in Boston might need 80,000 Btu's for an apron 35 x 24. In Colorado that same space might need 63,000 and in Albany, NY 100,000. Such things come into consideration as pick-up (what is the slab temp at system start up), wind speed, outside design temperature, insulation under the slab and/or edge of the slab, etc. So you need someone to do the load and design just like any other heating project.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  7. #7
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    Quote Originally Posted by skippedover View Post
    This is a loaded topic bur requires someone with lots of depth of experience to really render facts and not just an opinion.

    The NTH Trinity is a good boiler, so is the Lochinvar Knight, The Buderus GB142, the Triangle Tube Solo and many, many more. The problem with those boilers and a system that is radiant heat is that they have no thermal mass. When you're dealing with radiant, particularly snow melt, you really should have a boiler that has some water volume and some thermal mass. The industry, for almost all other applications, is moving rapidly to low mass boilers. But when it comes to pure radiant, you can't beat the mass of a condensing cast iron boiler and outdoor temperature reset. A low mass boiler will be cycling all day long in moderate weather. A high mass boiler will just cruise. I don't often recommend high mass but for a large radiant job and possibly snow melt, it's the recommended solution.

    Whether straight radiant or snow melt, I'd recommend the same basic solution. For the floors, the Viessmann Vitola, biferral gas boiler has the mass to smooth out the cycles and can run just above room temperature all day. For snow melt you'll need more Btu's and both Viessmann and Buderus have boilers that are up to that task. They also have all the purpose built controls to do the job properly.
    I agree with you when zoning and lo mass boilers will short cycle a lot. If the load of the smallest zone is the same or greater than the lowest output of the boiler you won't have this problem. If you have any really small zones you can still use lo mass, you just need a storage/buffer tank to get away from short cycling.

  8. #8
    Join Date
    Apr 2010
    Posts
    18
    The floors will be a mixture of wood, granite and ceramic tiles. The builder says they use pex with a slurry mixture poured over top and then the flooring.

    A similar system they did also uses the Trinity boiler to provide hot water via a storage tank and on-demand system. Can you explain how the need for high temperature water affects any of this? Sorry I am a total moron on this stuff.

  9. #9
    Join Date
    Feb 2010
    Location
    In a boiler room
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    Quote Originally Posted by rgile View Post
    The floors will be a mixture of wood, granite and ceramic tiles. The builder says they use pex with a slurry mixture poured over top and then the flooring.

    In this case you don't need hi temp for anything. BTW if you can run all your floors at a low temp that trinity will be very efficient.

    A similar system they did also uses the Trinity boiler to provide hot water via a storage tank and on-demand system. Can you explain how the need for high temperature water affects any of this? Sorry I am a total moron on this stuff.
    If using the trinity for domestic hot water the boiler will only go to hi temp 180 or so to heat your storage tank. Then on a call for space heating you will be back to the design temp for the floor heat.

  10. #10
    Join Date
    Apr 2010
    Posts
    18
    I think I can get a Viessemann Vitola 200 (100K BTU) for just over $3K. I was wondering if that would be a good unit for the outdoor heated driveway/porch. But I'm not sure how a boiler would work if the water/anti-freeze that's used in the lines is at almost freezing or sub-freezing temperatures?!? Is that allowed or will the boiler not accept that? Also would it be possible to run the system only when it snows and not just whenever it gets sub-freezing? We get a lot of days here where it's cold with no snow so running the system at that time would be a huge waste.

  11. #11
    Join Date
    Mar 2001
    Posts
    1,213
    As said before, a low mass boiler with buffer will work well. For your driveway, a snow sensor will operate the snow-melt system properly. Your designer should know this. Viessman has excellent products, including solar equipment to integrate with your gas/oil primary system. They have in-house design capabilities as well, & training for their installers.

  12. #12
    Join Date
    Jul 2004
    Location
    Massachusetts
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    6,829
    The difference between a low mass boiler and a high mass boiler is less the water content and more the cast iron. Using a low mass boiler to heat a large buffer tank is counter productive from an energy stand point. Yes the burner is energy efficient and probably more efficient than the high mass boiler. However the storage of water at a temperature that's suitable for a design temperture day is not very energy efficient.

    One thing you need to understand about a radiant floor is that it doesn't want to be above 80-82F or you'll experience hot feet!! 80-82 for masonry floors is well below the condensing temperature for a gas or oil flame. Thuse it is necessary to have a condensate tolerable boiler. Now we get to the water temperature. When dealing with a masonry floor, 80-82F is the normal temperature setting. When dealing with wood floors, a somewhat higher temperature is needed. Please note that these are maximum temperatures for coldest days. Temps would be lower on warmer days.

    The two ways to vary the temperature of the system water are to either have hotter water and mix supply water with cooler return water to get a tepid mixture that meets design specs or to just control the temperature of the boiler water directly. So it's either a mixing valve or injection pump or boiler temperature. With a storage tank and low mass boiler, it's almost always an injection pump. When going with a high mass boiler and a single supply water temperature, it's easy. When more than one temperature is needed, the boiler is heated to the higher temperature and injection of valve is used to cool it for those areas needing lower temps.

    Either system will work well and provide comfort. I'm very partial to low mass boilers for high temperature applications but I see much better results for high mass boilers on raidant sytems. The Trinity boiler is a low mass boiler that we've used for dual purpose systems, heat and domestic hot water. I'd still favor a high mass boiler with an indirect water heater a the ideal solution for a lot of radiant heated floors and domestic hot water. JMO.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  13. #13
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    When installing a buffer tank on a lo mass boiler to eliminate short cycling the tank is not kept hot. The boiler only runs on a call for heat but has 20-30 more gallons of water than what is in that small zone that is calling, so the boiler runs longer. Much more economical to install than injection mixing.

    Why heat the water above what you need and then mix it down? Especially on the OP's situation where all zones can use about the same temp water and control floor temp with floor sensors. You will find controlling floor temp is more comfortable than strictly controlling room air temp.

    Again if the smallest zone has a higher BTU load than the boiler output at low fire there is no need for a buffer tank or hi mass boiler.

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