Went around last night on Vespa with new camera: Olympus OM-D with Pana/Leica 25mm lens
I wonder how often condensing boilers get installed with their factory settings or wrong settings like mine. If you have a condensing boiler that is sending 180 degree water to your radiators when it’s 60 degrees outside (which is what the old cast iron boilers were designed to do), you aren’t getting any of the efficiencies out of your condensing boiler akin to flooring your Prius at a stoplight while depressing your brake.
Let’s say you send out 150 degree water to your boiler- let’s expect that 10 degrees will dissipate from the radiators to heat your home. That means your return water is 140 degrees and you are right at the edge of getting a benefit from your condensing boiler. Any temperature below that is even better- efficiency for return temperature of 90 degrees is 95%! Compare that to efficiency of 85% for return temp of 170 degrees.
I am one who is quite curious about how new things work. After the installers left, I cranked on the system, waited a few minutes, and then felt the pipes which were way too hot on a warm 60 degree day. Reading the display, it showed it was cranking out 180 degree water. My HVAC contractor performed a manual j heat loss, but I wish they had programmed the boiler with that information as I had requested- I suspect they left the high settings they programmed in to test the boiler.
Determined to re-program the boiler, I geeked out on the installation manual for my Triangle Tube boiler and found out with a mini-computer and display built-in, it is quite easy to check and change the settings.
I used trial and error to program the outdoor reset curve so that I can maximize the time that I’m sending out lower temps to radiators (under 150 degrees) which will get the most benefit out of a condensing boiler. I first looked up the coldest day design temperature for Baltimore which is 17 degrees outdoor and programmed that in with 140 degree water going to the radiators- it automatically adjusts the curve for warmer days based on that info. As the fall season progressed, I found it was having trouble keeping up with heating the house at that setting so I upped the temperature to 150 degrees. 150 degrees is the sweet spot- the boiler kept the house at our desired indoor temp all season.
When the old cast iron radiators were installed when the house was built in 1933, they were sized for receiving 180 degree water from the boiler. Due in part to all the air sealing work, caulking and increased attic and knee wall insulation to R-49, we’ve been able to cut 30 degrees even on the coldest days meaning we don’t have to use near as much energy to heat the water being sent to the radiators. Last season we used 30% less fuel to heat the home after adjusting for outdoor temperature (heating degree days). See future article on how I calculated this.
As you can see, there is a lot more programming involved with the new condensing boilers. They can be installed correctly from a plumbing point of view and pass inspection, but if not programmed to match individual home characteristics and geographic location, will not maximize energy savings.
Side note: one HVAC contractor I met while I was interviewing potential contractors said I would not benefit from a condensing boiler. He said my existing radiators- the old floor standing cast iron ones- are designed to optimally operate at 180 degrees. He went on to state that if I put a condensing boiler in the house, I wouldn’t achieve any energy savings over a non condensing boiler since you can’t condense with return water that is above 140 degrees. He said some large homes with long returns in Roland Park (a community in Baltimore) could dissipate enough heat to send at 180 degrees and return below 140 but in our cape cod, no. I had never heard about this caveat before- so I dug up some information and found that you can operate old cast iron boilers at lower temps. They still put out heat at 70,80,90,100 degree water you just have to adjust the temperature settings on your boiler.
If you’ve ever lived in an older home, one of the first things you realize when you start talking to contractors is that nothing was made to a standard size like newer homes. I suppose this is because everything was crafted on site, including windows and doors. One important aspect that first attracted us to purchase this home is that all of the windows and doors were original except for one hideous circa 1950’s aluminum storm door in the walk out basement. Actually, this door was hidden from view by a “Dorothy door”- the same kind that Dorothy could not open in the big tornado scene- but was still visible from inside the finished basement. I was always a bit apprehensive about opening the “Dorothy door”- you never knew what kind of bug or spider was lurking there. It had to go.
The first contractor quoted a price of $900 for the door itself since it had to be custom made. A couple of years past before I found a woman carpenter who specializes in hanging vintage doors. She came out to the house, measured the opening, and gave me the range of dimensions that I needed. The great thing about wood is you can shave an inch here and there to make it fit. She thought I might have luck hitting one of the architectural salvage companies in town. In Baltimore, we are fortunate to have several architectural salvage companies. For this project, I stopped by Second Chance which is close to Raven’s Stadium.
With the dimensions in hand, I searched row after row of doors looking for one that would allow maximum daylight to enter the basement. Second Chance makes the search easier by listing the dimensions of each door. Then I found it- a true 15 divided light door with thick wavy glass and solid heavy wood- all of this for $125. Saving $775 felt pretty good, plus wavy glass gratis!
The door hanging went off without a hitch so it was time to unhinge “Dorothy” and expose the nice reclaimed vintage door.
For weatherstripping, my energy efficiency auditor installed q-lon. It can be adjusted to match the idiosyncrasies of an older door and is the tightest sealing weatherstripping I have come across. During the final blower door test, I couldn’t feel any air penetrating through it.
Next project- search for vintage exterior shutters to help block the summer heat gain in south and west facing windows. Evidently, the house had many operable shutters once upon a time. I discovered hooks that held the shutters closed when restoring the windows, however, the only shutter left is the one in the front of the house outside the dining room sans hinges. Just the other night I spoke to the former owners’ daughter who had lived in the house in the 50’s and 60’s. She remembers her father closing the dining room shutters.