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  1. #1
    Join Date
    Feb 2013
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    20

    Need advice on converting from oil to natural gas...

    Oil prices are killing me and with all the incentives and rebates out there, it is time to switch to natural gas! I spent the last few week reading a ton of info on the internet. I live in a coastal CT town in a 1960 sq. ft wood shingled raised ranch with a timberline asphalt roof. This week I had an energy audit done. My oil boiler is a 25 year old Utica 122K BTUs which runs at 79% efficiency as per the energy audit. With the blower door test the infiltration was reduced from 4470 to 3830 CFM. The SlantFin heat loss calculated at 41,200 BTUs with a 9 degree design temperature. There are 4 people living in the house and the coil in the oil boiler is inadequate and has been a pita.

    What size gas boiler should I look for? Do i have to size up the boiler for hot water? A couple of contractors have suggested a Navien CH-210 Combi with the tankless HW. After reading comments I am not sure about the reliability and maintenance cost of the Navien. I am thinking of a high efficiency gas boiler AFUE 90%+ for the rebates and operating cost mated with an indirect-fired water heater. What size gas boiler and indirect tank should I get?

    Any suggestions and comments are greatly appreciated and I will be speaking to contractors this week. Thanks.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,736
    I'd probably recommend an Ulta 80 with an indirect water heater. 80 is the smallest size the Ultra comes in. It can modulate down to 16,000 BTUs.
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  3. #3
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,570
    Quote Originally Posted by beenthere View Post
    I'd probably recommend an Ulta 80 with an indirect water heater. 80 is the smallest size the Ultra comes in. It can modulate down to 16,000 BTUs.

    I would recommend the ultra as the best high efficiency option. Either an indirect or separate water heater.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  4. #4
    Join Date
    Feb 2013
    Posts
    20
    Does the 41,200 BTUs heat loss sound correct for my size house? Do I have to increase it for indirect hot water heating? One contractor suggested a 96K BTU ballpark whereas another proposed a 175K BTU Navien CH-210asme Combi. Am I underestimated my heat loss?

  5. #5
    Join Date
    Jan 2007
    Location
    NH
    Posts
    238
    With indirect tank 80,000 btu would be a min. Mod condensing boiler will modulate to your load (with right setup)

  6. #6
    Join Date
    Jan 2012
    Location
    Broomall, PA
    Posts
    382
    As long as you heat loss is done right, go with the smallest boiler. Dont add for domestic hot water.
    Keep in mind youre original oil boiler was 3 times oversized, and very inefficient. You would realize alot of savings with a modern oil boiler w/modern controls.
    You mentioned you read alot on the internet...did you read oil prices expecting to drop next year, and nat gas prices poised to increase (with nat gas approved for export). Also reports published stating, in the last 20 years, oil cheaper then gas 17 out of 20?
    Just food for thought.
    Dont forget, if you can, adding insulation will bring down energy consumption even more, and if you add insulation, dont forget to redo your heat loss. Actually, redo the heat loss like you added the insulation, just to see what it does to your numbers

  7. #7
    Join Date
    Jan 2007
    Location
    NH
    Posts
    238
    Not correct about indirect tank

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,242
    Quote Originally Posted by Edgeman View Post
    1. Does the 41,200 BTUs heat loss sound correct for my size house?
    2. Am I underestimated my heat loss?
    1. What did the Energy Auditor provide?

    _ I'd go with the energy auditor evaluation LONG BEFORE someone trying to sell me a system.
    + I would re-read posts # 2 & # 3 from _ Pros who always Know.

    2. How did You calculate the heat loss or
    . You don't think the auditor did a complete evaluation?

    ... Without knowing anything more than CT [9'F design temp], given infiltration and 1,960 Sq. foot,
    no one here would likely challenge the 41,000 BTU/Hr results because the energy auditor addressed
    the most significant unknown (leakage) in an evaluation.

    Was a duct blaster test also performed? [ 2nd most significant item or most in some people's opinion]
    If yes, any recommendations?
    http://www.buildingperformancebydesi...ctblaster.html

    http://www.habitat.org/lc/env/pdf/blower_door_test.pdf

    x

    http://www.nachi.org/blower-door-test.htm

    x
    I'd select the most Simple Approach and stay away from tankless.
    Last edited by dan sw fl; 02-22-2013 at 12:07 PM.
    Designer Dan
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  9. #9
    Join Date
    Feb 2013
    Posts
    20
    Quote Originally Posted by STEVEusaPA View Post
    As long as you heat loss is done right, go with the smallest boiler. Dont add for domestic hot water.
    Keep in mind youre original oil boiler was 3 times oversized, and very inefficient. You would realize alot of savings with a modern oil boiler w/modern controls.
    You mentioned you read alot on the internet...did you read oil prices expecting to drop next year, and nat gas prices poised to increase (with nat gas approved for export). Also reports published stating, in the last 20 years, oil cheaper then gas 17 out of 20?
    Just food for thought.
    Dont forget, if you can, adding insulation will bring down energy consumption even more, and if you add insulation, dont forget to redo your heat loss. Actually, redo the heat loss like you added the insulation, just to see what it does to your numbers
    I think the supply dynamics are forever changed for oil pricing. It will always be more expensive that natural gas IMO. We import more oil and we as a nation source natural gas which is in abundant supply. Also with all the incentive, rebates and CT state financing, it's currently a no brainer. I will pay less with natural gas even after financial cost in year 1, so there isn't really any up front cost. The fed and the northeast states want houses to be off oil. All these northeast oil companies have a dire future. Maybe the the prices difference will decrease but they will not reverse.

  10. #10
    Join Date
    Feb 2013
    Posts
    20
    Quote Originally Posted by dan sw fl View Post
    1. What did the Energy Auditor provide?

    _ I'd go with the energy auditor evaluation LONG BEFORE someone trying to sell me a system.
    + I would re-read posts # 2 & # 3 from _ Pros who always Know.

    2. How did You calculate the heat loss or
    . You don't think the auditor did a complete evaluation?

    ... Without knowing anything more than CT [9'F design temp], given infiltration and 1,960 Sq. foot,
    no one here would likely challenge the 41,000 BTU/Hr results because the energy auditor addressed
    the most significant unknown (leakage) in an evaluation.

    Was a duct blaster test also performed? [ 2nd most significant item or most in some people's opinion]
    If yes, any recommendations?
    http://www.buildingperformancebydesi...ctblaster.html

    http://www.habitat.org/lc/env/pdf/blower_door_test.pdf

    x

    http://www.nachi.org/blower-door-test.htm

    x
    I'd select the most Simple Approach and stay away from tankless.
    The energy audit doesn't do a heat loss analysis. They do the door blower test and then measure the rooms and add caulking and sealing in the windows, doors, attic where there are leakages. They also swap out all your incandescent lights to CFL dimmable bulbs, aerators in your sinks. I already changed my shower heads to 1.5 gpm from 2.5 gpm so they left those alone. The did the duct blaser test for my A/C ducts and said they were good. They spent 5 hrs or so here in a CT subsidized program for $99 which you have to do if you want CT state financing for energy improvements. If you already has gas heating it cost $75 as CT Natural gas pays into the CT fund to support it. The oil companies don't contribute so it cost $99 for oil heated homes. They basically recommend that everyone gets off oil. With pricing at $4.11 for heating oil, it is an easy sell.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by zibby View Post
    Not correct about indirect tank
    A 60,000 BTU 90% eff mod/con would be able to recover a completely cold(40 degrees to 120 degrees) 40 gallon indirect in 30 minutes. An 80,000 is plenty for his house and a 40 gallon indirect.
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  12. #12
    Join Date
    Feb 2013
    Posts
    20
    One contractor is proposing a Navien 175BTU CH-210 Combi with tankless DHW or for $ more a Weil-McLain GV90+5 140BTU mated with an AquaPlus 55 Indirect. I'm think i can scale it back to a Weil-McLain GV90+4 105BTU with an AquaPlau 45 to cut the cost? He suggested the tankless and I suggested a pricing for an indiret instead.
    Last edited by beenthere; 02-23-2013 at 06:19 AM. Reason: Price difference

  13. #13
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    Jan 2004
    Location
    Lancaster PA
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    67,736
    Prices and price differences are not allowed.
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