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Ultra Gas S3 CT Gas Boiler

  • Gas fired water boiler with cast aluminum heat exchanger
  • Venturi mixing body mixes air and gas providing higher efficiency
  • Designed to operate in low temperature condensing applications
  • Outdoor reset and domestic hot water priority standard
  • Negative regulated gas valve precisely delivers gas to the boiler
  • U-Control gives you the power for easy set-up and maintenance
  • Modulates with 5 to 1 turn-down ratio
  • Variable speed motor matches combustion output to heating needs
  • High grade stainless steel burner features quiet operation, high efficiency, and cleaner combustion for low NOx applications

Technical Data

Model AFUE (%) CSA Input (GPH) DOE Heating Cap. (MBH) Net AHRI (MBH) Vent Size (in.)
UG-80 93.5 80 71 62 2 or 3
UG-105 94 105 94 82 2 or 3
UG-155 94 155 139 121 3
UG-230 94.1 230 207 180 3 or 4
UG-299 92.5 299 270 235 4
UG-399 91.7* 399 364* 317 4

Ratings & Reviews

Rated 1 out of 5 by from Not a very good boiler This boiler is incapable of keeping the house warm when the temps outside reach 10 above or lower. In order for it to be comfortable in the house, the kitchen oven needs to be turned on and the door left open in order to heat the house to a comfortable temp. An earlier review was rejected supposedly because of language. I think it was because it wasn't a good review. I had a contractor just do a rebuild on this furnace. Hopefully that will help. Yes, I get more warmth from my cats when they cuddle then what this furnace puts out. Nothing that should be considered offensive here.
Date published: 2017-03-09
Rated 5 out of 5 by from Excellent Experience in high altitude living This boiler was installed almost 5 years ago. I have it maintained and it delivers. We live at 8000ft. of elevation in the Colorado Mountains. We get some nasty cold nights and high winds with regularity in the winter. My home is well insulated and I have not yet paid $100 for a gas bill. My bills for my full time residence averaged in the $80 range this winter. Our temps are kept at 68-69F during the day time and 66F at night. Home is 3400+ square feet on two levels. Raised ranch so most of our lower level is exposed. Love this furnace.
Date published: 2017-03-15
Rated 5 out of 5 by from Well McLain boiler's right now Well McLain boiler is excellent boilersinstall 20 never had a problem
Date published: 2017-01-30
Rated 1 out of 5 by from disappointed More service calls because it keeps shutting down. Do not recommend this unit.
Date published: 2017-01-04
Rated 1 out of 5 by from VERY UNRELIABLE Purchased Ultra 105 series 3, 8 years ago. For the first 7 years it was pretty good but for the last year it has been terrible. Within the last 5 months I have received error message 'SUPPLY TOO FAST' over 100 times. I had several heating contractors, on your list, look at the unit but they haven't been able to fix the problem. I have call your customer service at least 5 times, and the contractors have also called many times, but they have been of no help. The question is now what do I do?????
Date published: 2017-04-30
Rated 5 out of 5 by from GREAT BOILER I BOUGHT THIS BOILER IN 2010 FOR MY HOME AND I VERY GLAD I DID . I LIVE IN NEW JERSEY, MY HOME IS ABOUT 2300 SF. / W 4 HEATING ZONES. BOILER IS SUPPER EFFICIENT AND LOWER MY HEATING BILLS DURING WINTER . SINCE I INSTALLED IT ,NEVER HAD ANY PROBLEMS WITH IT.JUST LOVE IT .IF I HAVE TO BUY AGAIN I WOULD CHOOSE THE SAME BOILER,AND BELIEVE ME I DID MY HOMEWORK BEFORE I BOUGHT THIS BOILER.
Date published: 2017-01-14
Rated 2 out of 5 by from Shuts down in cold weather, does not reset Does not work well below 35 degrees. Shuts down and does not reset. House is cold in low temperatures Fourth year, problems continue.
Date published: 2017-03-18
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  • REVIEWS, PRODUCT
Ultra Gas S3 CT Gas Boiler is rated 2.9 out of 5 by 7.
Rated 1 out of 5 by from Not a very good boiler This boiler is incapable of keeping the house warm when the temps outside reach 10 above or lower. In order for it to be comfortable in the house, the kitchen oven needs to be turned on and the door left open in order to heat the house to a comfortable temp. An earlier review was rejected supposedly because of language. I think it was because it wasn't a good review. I had a contractor just do a rebuild on this furnace. Hopefully that will help. Yes, I get more warmth from my cats when they cuddle then what this furnace puts out. Nothing that should be considered offensive here.
Date published: 2017-03-09
Rated 5 out of 5 by from Excellent Experience in high altitude living This boiler was installed almost 5 years ago. I have it maintained and it delivers. We live at 8000ft. of elevation in the Colorado Mountains. We get some nasty cold nights and high winds with regularity in the winter. My home is well insulated and I have not yet paid $100 for a gas bill. My bills for my full time residence averaged in the $80 range this winter. Our temps are kept at 68-69F during the day time and 66F at night. Home is 3400+ square feet on two levels. Raised ranch so most of our lower level is exposed. Love this furnace.
Date published: 2017-03-15
Rated 5 out of 5 by from Well McLain boiler's right now Well McLain boiler is excellent boilersinstall 20 never had a problem
Date published: 2017-01-30
Rated 1 out of 5 by from disappointed More service calls because it keeps shutting down. Do not recommend this unit.
Date published: 2017-01-04
Rated 1 out of 5 by from VERY UNRELIABLE Purchased Ultra 105 series 3, 8 years ago. For the first 7 years it was pretty good but for the last year it has been terrible. Within the last 5 months I have received error message 'SUPPLY TOO FAST' over 100 times. I had several heating contractors, on your list, look at the unit but they haven't been able to fix the problem. I have call your customer service at least 5 times, and the contractors have also called many times, but they have been of no help. The question is now what do I do?????
Date published: 2017-04-30
Rated 5 out of 5 by from GREAT BOILER I BOUGHT THIS BOILER IN 2010 FOR MY HOME AND I VERY GLAD I DID . I LIVE IN NEW JERSEY, MY HOME IS ABOUT 2300 SF. / W 4 HEATING ZONES. BOILER IS SUPPER EFFICIENT AND LOWER MY HEATING BILLS DURING WINTER . SINCE I INSTALLED IT ,NEVER HAD ANY PROBLEMS WITH IT.JUST LOVE IT .IF I HAVE TO BUY AGAIN I WOULD CHOOSE THE SAME BOILER,AND BELIEVE ME I DID MY HOMEWORK BEFORE I BOUGHT THIS BOILER.
Date published: 2017-01-14
Rated 2 out of 5 by from Shuts down in cold weather, does not reset Does not work well below 35 degrees. Shuts down and does not reset. House is cold in low temperatures Fourth year, problems continue.
Date published: 2017-03-18
  • y_2017, m_5, d_23, h_4
  • bvseo_bulk, prod_bvrr, vn_bulk_1.0.0-hotfix-1
  • cp_1, bvpage1
  • co_hasreviews, tv_0, tr_7
  • loc_en_US, sid_ultra-gas-s3-ct-gas-boiler, prod, sort_[SortEntry(order=RELEVANCE, direction=DESCENDING)]
  • clientName_weil-mclain
  • bvseo_sdk, p_sdk, 3.2.0
  • CLOUD, getContent, 94.47ms
  • REVIEWS, PRODUCT