At the end of last month's column Let's get hitched: boiler to indirect water heater union, I detailed the options available to a retired couple interested in replacing their boiler.
OK, let's review what the issues and concerns were that I picked up by listening to Jean and Wayne: skyrocketing cost for fuel; on a fixed income, but willing to invest in energy saving options — already have by adding insulation and new windows/doors; scalding hot water; poor combustion draft with odor and CO issues expressed; moderately efficient boiler; and objectionable burner and draft-fan noise.
Have you ever wondered why boilers aren't nearly as well insulated as water heaters? Boilers are rated differently than water heaters when it comes to standby and operating heat losses. Heat loss from boilers isn't considered to be lost — it's given up to the interior of the home and, therefore, not deducted. Water heaters are well insulated to minimize heat losses because that energy loss counts against their performance. So, if I'm going to weigh the domestic coil option against the indirect water heater option, I can use this information for a bit of added sales sizzle.
The noise issues go away with many of today's oil-fired boilers. A direct-vent model will remove the venting issue. Here again, it's also easy to address a hidden problem and directly address a stated concern — fuel usage — by reducing the infiltration otherwise needed for combustion air that would have been drawn in, heated and used to support combustion. Up-selling is fun and easy if it fits within the four corners of the customers' concerns.
So, now that we've convinced the customers that these options are a good investment, it's time to determine how to make the components perform to their best efficiency and ability.
Indirect water heaters come in a wide variety of shapes, sizes and models. The literature stating their recovery rates is based on information that often doesn't mirror the real-world conditions where you live.
Sizing the tank: I use design conditions of 40°F incoming and 140°F storage at a 100°F rise. Next, I determine the boiler's net hourly output in Btus. Divide the net output by 833 to determine the hourly gallons of hot water that can be produced and divide that by 60 (minutes) to obtain the GPM rating. During winter's coldest weather, when I'll be seeing 40°F incoming cold water (55°F for well-water systems), I can safely assume 85% of the adjusted bathing temperature will be coming from the indirect hot water tank. Just two things remain to accurately pinpoint the required tank sizing: GPM flow rate from the bathing module(s) and duration of use. It's just that easy!
Sizing the circulator: Properly moving the boiler's energy to the indirect water heater will keep you out of hot water. Match a circulator to meet or exceed the head loss so that you will deliver the required GPM. Screw up this step and you'll have an under-performing indirect, send circulators to an early grave or generate noisy flow. You need to locate the indirect water heater's head loss and the head loss through the boiler at the targeted GPM flow rate. The larger of the two will be the number you use. Today's modulating condensing boilers often have a higher head loss (resistance to flow) than the indirect water heater. Circulator manufacturers' flow charts list head along one side and GPM flow rates along the adjoining side. Drawing lines at 90-degree angles from both points to where they intersect gives you the border you can't fall below or performance will suffer. Given that domestic hot water is required daily, choosing a circulator with a lower wattage rating will save your customer some additional money.
Efficiency matters: Indirect water heaters have very little standby heat loss. A boiler maintaining 180°F (or higher) temperature so that its domestic coil stands ready to deliver hot water, by comparison, wastes great gobs of energy. Add in the dangers related to scalding and limited GPM flow rate and you begin swaying your customers' choice. Price no longer governs the sale. Safety and comfort along with lowered fuel consumption now move to the top of their list.
Although the combined boiler-indirect provides safer hot water temperature regulation, thermal stacking likely will occur. ANSI Z21.10 regulations governing water heaters recognize this phenomenon and permit the stored water temperature to be up to 30°F hotter than the control's setting. So, 140°F can become 170°F and still be in compliance. While scalding can occur at 140°F, it's obvious that 170°F presents a greater danger. Adding an ASSE 1017/1016 listed scald-guard mixing valve set for 120°F will lower the risk (scalding can still occur, but takes longer). Customers will appreciate your taking the time to educate them about this much-needed safety device.
Place yourself in the customers' shoes and imagine you're listening to the feedback you'd give after hearing the customers' concerns. Can't you feel your comfort level rising and the trust developing that will induce you-as-the-customer to invest more wisely — in spite of the added costs? And that, my friends, is exactly how you can up-sell every job, no matter the product. It's our job to provide comfort and protect health. We also must guide consumers toward the products that best fit their needs while (today more than ever before) providing products that conserve energy and last, but certainly not least, price the work properly so that our businesses remain profitable.
Dave Yates owns F.W. Behler, a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at [email protected].
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