Energy Detective: The Case of the Busted Boiler
Inside a boiler with a serious internal leak.
Feb. 2, 2015 — My friend Octavia was in a quandary. "I need a new boiler," she informed me, "but I don't know how big it should be."
"If I had to surmise, I'd say probably a lot smaller than what it is now," I offered somewhat drily. "How big is the existing one, and by the way, how do you know you need a new one?"
Before replying directly, Octavia reminded me of the facts concerning her 25-unit building. The heating plant, which provided both heat and domestic hot water (DHW), was 50 boiler horsepower (BHP). It was now leaking water out of the back end. The heating season was a month away, and she had two fairly old bids in hand: one for another 50-horse unit, and the other for a 60-horse unit!
A wistful sigh escaped my lips, unfortunately loud enough for her to hear. "Did I say something wrong?" she asked, a hint of annoyance in her voice.
"To be candid, Tave, yes," I admitted. "Several things. And I think you know what they are."
"Let me guess," she replied with a winsome smile. "I should not have waited so long to get bids; I should have called you before I got the bids; I should have had someone put specs together so everyone bid on the same thing; and I should've, uh, should've..." She paused, and then finished with a bit of irritation creeping into her voice, "Well, okay, I give up. What else should I have done?"
Three out of four was not bad, even if she didn't actually do them, and at least she was calling me now instead of not at all. "You realize you are going to get hammered for the cost of temporary heat, right?" I said with exasperation. "Why is it that everyone pleads poverty when it comes to making energy-efficiency investments — which will actually pay back over time — but then are more than willing to defer maintenance and then pay for needless stuff like temporary heat, which doesn't pay back at all?"
"Hey, I called you for help, not a lecture," she admonished. "Do you have any concrete suggestions for me?"
Somewhat abashed, I laid out what I thought she should do.
- Step 1: Survey the radiators in as many apartments as possible.
- Step 2: Find someone to develop specifications for the job. Even if the specs are bare bones, they are a lot better than having nothing at all.
- Step 3: Find someone — maybe the same person, maybe not — to oversee the contractor's work. "You need someone knowledgeable in your corner," I explained. "A lot of important details are frequently given short shrift, especially on a rush job during the heating season."
"I don't suppose you could survey the radiators for me, could you?" she asked in her sweetest voice, knowing full well that I was way too busy but would nevertheless come over immediately to help her out. "Nothing like a busman's holiday to liven up a midweek evening or two," I said to myself.
Sometimes radiator surveys are a challenge because apartment access is so difficult, but fortunately Tave smoothed the way considerably, and I was able to acquire enough information in just two evenings of detective work to solve the problem. To my surprise, after making the calculations, it turned out that the space heating load in her building was only 13 BHP. Of course I still needed to figure out the DHW load, which can be very tricky.
In this case, however, even if I used some very conservative numbers, the total for both space heat and DHW was only 27 BHP. So much for that 60-horse bid!
Those of you with long memories will recall that I advocate sizing the boiler for the larger of the two loads. If, as in this case, the space heating load is 13 BHP and the DHW load is 14 BHP, I'd spec out a 14 BHP boiler (okay, maybe 18 or 20 BHP, but no more than that). The idea is that a residential boiler rarely, if ever, sees peak space heating and DHW loads at the same time, and when it does, the building can "coast" without discomfiting the occupants.
Advocating something and persuading people to do it, however, are two very different matters, and I knew that, with the heating season upon us, it would be difficult to find contractors to bid on a boiler that was the same size, let alone one that was much smaller. So I chickened out and recommended a 32 BHP boiler.
Still a lot smaller, but not as small as it could have been. If only these decisions had been made in April or May instead of October or November…
But Octavia was happy again, and my job was done.
Tom Sahagian is Senior Program Director, Technical Services, at Enterprise Community Partners.
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