We woke up after a below zero night to the carbon monoxide alarms in the morning. Even though it was below zero I turned off the boiler function and opened the back door to let in fresh air. The alarms turned off. We were able to keep the hot water function on without the carbon monoxide leak.
Last time this happened I was able to clean out the condensate trap and lower the water pressure and the problem went away for a couple of weeks. That was a spell of below zero weather too. So there seems to be an issue only when the boiler is running close to capacity.
Sometime this season the fan began to whine when the boiler was running to provide heat. So my guess was that the fan is not operating fully to keep up with the exhaust that is created. We checked the flue and that is not blocked and I checked the power to the fan and that was correct. But when I turned the boiler on the #5 error flashed.
This error says the condensate is blocked or the gas pressure is not correct. Since I got it after I cleaned out the condensate trap again and since the gas pressure has no other issues in the house I was even more convinced it was the fan.
I spent a lot of the day trying to decide whether to replace the fan or the entire boiler. The fan costs over $500. The existing boiler cost about $2800 in 11/2012 but I didn’t install it until about 3/2013. I have read that a condensing gas boiler has a service life of about 7-10 years. So we may be close to the end of this one’s operating years. But we don’t run it very hard with the lovely passive solar windows and Trombe wall.
Of course I want the latest clean energy and efficiency for a replacement. I first researched cold weather hydronic heat pumps. The newest technology uses carbon dioxide as the refrigerant. Trane Mitsubishi released a combi CO2 version last year but it is labeled commercial and the smallest version is 150,000 btu. I can’t tell if it is sold anywhere.
I could buy a SanCO2 hot water heater from ECO2 in Michigan that uses CO2 for about $5500. It has a 40 gallon tank with a air to hydronic heat pump hot water heater that can deliver 69 gallons of 145° water in the first hour. But it is rated at 15,000 btu/hr which is pretty undersized for a boiler. Even if I could figure out the heat exchange piping.
My conclusion was that the air to hydronic technology would have to use R410 refrigerant. I didn’t find much that didn’t need an electric heat strip for really cold weather. And these heat pumps don’t operate well for temporary loads. Despite the problems with gas pollution I’m reluctant to switch to electric heat. Maybe I need to do more research.
In the meantime I could purchase one of several other small combi gas boiler/water heaters. There is a Rheem at Home Depot but it is twice the depth of our current Triangle Tube which is no longer made. There are models by Noritz, Weil-MacLain, Lochinvar, and Bosch, Rinaii, and Laars. All available from Supplyhouse where I bought the Challenger. They are all at least 95% efficient.
The Bosch 4000 is 82,000 btu for heat and 150,000 btu for hot water for 4 g/m at 67° rise. Has internal primary pump. The box is 18.1“ x 27.6” x 11.6“.
The Bosch Greenstar 100 is 83,000 btu/hr and 2.6 g/m and advertises 96% efficient up to 98% for low fire although its still rated 95%. About 17“ x 33” x 14”.
The Weil-McClain AB-120 delivers 111,000 btu/hr and 3 gal per minute at 70° rise in temperature. With an internal primary pump, it’s box is x 16.54”x 27.56”x 12.60”.
Laars FT is 129,000 btu/hr and 3.2 g/m at 70° rise. Probably too much heat for us, it’s 17 3/8”x 29” x 15 1/2”.
Lochinvar Noble is 102,000 btu/hr and has two pumps. Delivers 2.6 g/m at 77° rise. It’s big at 17 1/4” x 32.5” x 18”.
Another option is the Noritz 180, 100,000 btu/hr and 4.9 g/m at 70° rise. 18.5”x 27” x 12.8”
There are several Viessman and Rinaii models on back order or out if stock too.
The Rheem at Home Depot is the cheapest at $1800. Rated at 100,000 btu and 4.6 g/m at 70° rise. No internal pump and 17.3”x 28.7”x 14.8”.
The models I’m considering in order of cost are the Rheem, Noritz, Weil-McClain, Bosch 4000 and Bosch Greenstar 100. Our current boiler is 17 1/4” x 25” x 9 3/8”. It is the CC105 model rated at 92,000 btu at 94% efficiency. Hot water production is about 2.7 g/m at 70° rise. It has always been large enough for our use.
I’m concerned about the larger boxes. Although it appears most of these eliminate my primary loop and pump with an internal pump. If I just replace the fan I can put off this decision with so many variables.
I was saved from making this decision by realizing it was the condensate neutralizer filter that was clogged! I disconnected the drain hose and used a bucket to collect the condensate. Although it was not below zero the boiler did not release CO while running. I tested it with an electronic gas detector. I was surprised by how much condensate drained from the heater. The bucket filled to the pipe in just two days during colder weather.
I ordered new filter media from Supplyhouse. I added another project to get the free shipping. I need to isolate the fireplace boiler from the gas boiler because I found that with the gas boiler off the warm water did not circulate through the primary loop and I didn’t have this emergency source of radiant heat although the ambient heat still helped.
Maybe by the time we actually need a replacement for the Triangle Tube Challenger Combi boiler there will be better heat pump options on the market.