Church picks options that conserve resources, increase comfort and eliminate CO risk in retrofit.
BY DAVE YATES
SPECIAL TO CONTRACTOR
Commercial and residential heating/cooling applications have one thing in common today: the advent of ultra-high-efficiency products that incorporate smart logic to squeeze energy dollars and reduce parasitic energy losses to a bare minimum. Boilers, water heaters, A/C and heat pumps are no longer a slouch where efficiency ratings are concerned. Sales opportunities for upgrading to high-efficiency equipment make perfect sense — if presented to customers as a sound investment, rather than focusing on a payback period of time, which is typically years.
The call from the York County (Pa.) Council of Churches expressed concern about a carbon monoxide incident that had required a building-wide evacuation. CO is something we take seriously; that's the main reason why we switched from our old dumb-bell chemical combustion analyzers to precise electronic combustion analyzers.
Rita Hewitt, the director of YCCoC, left no doubt that the CO incident was the driving force in the request for bids. Besides the CO incident, and the need to know what happened and why, her other issues were high fuel bills, the need for a firm quote, a small budget and a firm start date.
The sprawling church complex is comprised of a sanctuary with high vaulted ceiling and large single-pane leaded stained-glass windows, youth hall and large office under the sanctuary, multiple double-door entryways, classroom building and an office complex. I wanted to get a feel for how the occupants felt about overall comfort. Hewitt's office was a sauna-like sweat-box; several areas were cooler than staff liked; and the pastor's office complex was hotter than H.E.-double-hockey-sticks!
Convectors were the primary heat emitters, but a heat pump served several-offices, and Hewitt's happened to have a wall-to-wall convector and a ceiling supply register — a double-dose of heat! No wonder the tropical plants were flourishing while she wilted.
Smedley Craig, a YCCoC board member, introduced me to the mechanical room. He opened the door to reveal the most horrendous mechanical nightmare I'd laid eyes on for many years! Immediately to the right was a hot water boiler with its supply riser run to the ceiling where it wrapped around the mechanical room and dropped into a rat's nest of circulators and what appeared to be a failed attempt at outdoor reset via a modulating three-way mixing valve — its wires disconnected and hanging askew while its shaft had been locked in one set position. A quick glance back at the boiler revealed that it had no circulator of its own.
A hydro-air unit stood sentry to the left with its piping running back to a large steam boiler. A modulating zone valve regulating flow was perched in its supply line.
Next to the hydro-air unit sat a forlorn-looking condensate feed-water tank with a twisted piping arrangement that incorporated a condensate pump-tank (missing its pump) and on the floor sat a centrifugal pump — no doubt wired to the steam boiler's low-water-cut-off. The overflow pipe terminated adjacent to a floor drain and a large wet spot surrounded the area. The feed-water tank was actively weeping condensate in more than a few spots.
The steam boiler had numerous soot streaks at every opening in its jacket and was, no doubt, the source of the CO leak. The technician who responded to the distress call had slathered refractory cement around the burner-and chamber-doors in an attempt to halt any CO from escaping.
Gas boiler + soot-streaks = bad combustion, and there was no evidence of anyone using a combustion analyzer on this unit.
I had carved out a 90-minute spot in my schedule for surveying this job, and it was clear that I needed much more time if I was going to adequately assess what was needed. Here's what I discovered during my return visit.
The steam system
Steam systems must be sized to produce-enough steam to completely fill inside void of all radiators and piping connected to the boiler, which is to as the "connected load." I measured each individual section of radiation (convectors, radiators and bare piping used as a heat source in the basement youth center) and that information was then used to determine volume in square feet for each emitting device. Then I added a pick-up factor, which represents energy required to bring the interconnecting distribution piping up to temperature. Together, the connected load and pick-up factor equaled 196,248 Btuh.
I found the following conditions related to the CO incident and high fuel bills: Refractory cement smeared around the access door to the boiler's combustion chamber and soot streaks at various openings in the boiler's exterior jacket, which indicated combustion gases had been escaping the combustion chamber at any point they could find. This is a tell-tale sign that other problems exist.
The boiler's rating plate indicated a maximum firing rate of 470,000 Btuh. When I timed the gas meter (with only the steam boiler operating), I discovered it was being fed in excess of 1.2 million Btuh! That explained the CO production issue, and over-stuffing any heating appliance with excess fuel reduces its operating efficiency.
Here's the formula for timing a gas meter: 3,600 x the test dial size x Btu content for 1 cu. ft. of gas ÷ the number of seconds per revolution. In our area, natural gas is rated at 1,050 Btu per cu. ft. and the 5-ft. dial completed its revolution in just 15 seconds.
The connected load survey revealed that this steam boiler was grossly oversized. Over-sized heating systems suffer a parasitic loss of efficiency. The farther apart the size required vs. the size in place, the worse the overall efficiency becomes.
This was originally a one-pipe vapor system and designed to operate on ounces, not pounds, of pressure. The pressure controls governing this steam boiler's operation were set to maintain 9 to 12 PSI. Boyle's Law tells us that if you double the pressure you will halve the volume of a gas, which is steam in this instance. When you reduce the volume of steam produced, you still need to fill the radiators and connected load, which means the boiler is required to produce more steam. The higher the pressure, the more steam required to fill the same volume.
I discovered an antique condensate return pump at the far reaches of the steam system. Judging by its looks and the debris that was concealing it from plain sight, it hadn't been serviced for decades.
The feed-water tank in the boiler room was riddled with pin-hole leaks. Its purpose is to act as a reservoir for returning condensate until the boiler's low-water-cut-off senses a need for water, closes its end switch and energizes the centrifugal pump connected to the feed-water tank.
I witnessed this cycle and saw that the pump couldn't overcome the high pressure in the boiler. This, in turn, caused the pump's impeller to cavitate and the heated condensate to overflow from the feed-water tank. This heated water is rejected to the adjacent floor drain where the energy disappears down the sewer line. Energy dollars were literally running down the drain.
Lost condensate must be replaced with fresh water, which contains free oxygen and that contributes to accelerated corrosion of all ferrous components, which encompasses just about everything in the steam system. Corrosion leads to sludge. Sludge blanketed the boiler's interior surfaces, robbing its efficiency. Eventually, a sludge build-up will cause a premature failure of the boiler.
To the rear of the boiler and at the floor level, a return pipe was severely corroded on its exterior. Directly above this spot an open pipe connected into the chimney. Very old steam systems often saw their relief valves connected into the base of the chimney. It was not uncommon for those old relief valves (not nearly as reliable as today's relief valves) to leak steam, and letting them blow off steam to the chimney was an accepted practice.
Energy dollars were literally running down the drain.
Evidently, the hot flue gases were, to a limited degree, escaping from the chimney through this steel pipe. For every 100,000 Btu of energy burned in combustion, 1 gal. of moisture is generated if the temperature falls below 350°F. No doubt condensate from flue gases, which is corrosive, had been dripping onto this return line.
The hydro-air unit connected to the steam boiler serves a 40-by-65-ft. recreation hall (the adjoining kitchen is served by the hot water boiler via a Modine unit heater mounted at the ceiling). In order to operate the church sanctuary and recreation hall separately, modulating steam zone valves were installed. Should either of these zone valves require service/repairs/ replacement, they are very expensive, as are their various components. The hydro-air system and its connected load represent a tiny fractional load for your grossly over-sized steam boiler. Even with a new and properly sized steam boiler (for the sanctuary's connected load), the basement recreation hall would be a fractional load. Why this unit was added to the steam boiler is a mystery that baffled me; it should have been added to the hot water boiler instead! Given the 12 - PSI s team pressure its coil had been seeing , i t wa s already up to snuff for pressures seen in hot water systems — but was its coil adequately sized to accommodate the heating-load at a reduced Btu outlet?
No wonder their fuel bills were driving them to distraction.
Hot water heating system
Unlike the connected load required to properly size steam boilers, hot water systems are properly sized by calculating the actual heat loss of the structure. While heat emitters such as baseboard, convectors or radiators need to be large enough to adequately meet or exceed the heat loss on a design day, they no longer dictate the boiler's sizing. I found the following issues to exist during my survey and subsequent Manual-J heat loss/gain calculations:
One issue surfaced when I timed the gas meter for the hot water boiler.
The issue, however, was exactly the opposite seen with the steam system — the hot water boiler was grossly under-fired! Under-firing a boiler can lead to sustained flue gas condensation in the boiler, metal flue piping and the masonry chimney. As noted, flue gas condensation is corrosive and will lead to accelerated deterioration of system components. Excessive CO production is likely and loss of efficiency can occur under these conditions.
If my Manual-J calculations were correct, this boiler was also over-sized and, here again, over-sizing kills operating efficiency. A significant reduction in fuel usage would be seen if the new boiler were properly sized and installed. And yes, the hydro-air coil was more than adequate to meet the calculated heat load.
The distribution piping within the boiler room was not installed for optimal performance. The weather-responsive controls, which failed miserably, had been eviscerated and left for dead.
A circulator was missing from one zone with its flanges now joined with a pipe-nipple. As a result, this zone would see circulation whenever any other zone pump was activated.
The automatic water-feed valve was not connected at the point of no pressure change, and, consequently, had the potential-to overfill the system.
The boiler had no circulator of its own. One is needed to move the proper gallon-per-minute flow rate required for matching the boiler's net output rating and may be one reason why this boiler's firing rate was reduced. The burner's operation was governed by a flow switch, which acted as the on/off switch whenever one of the zone circulators was activated. Given that three circulators were active, the potential existed for varying flow rates through this boiler, which was potentially detrimental. It was maintaining temperature, which wastes fuel and a steam pressure switch had been added to act as a low-water-cut-off.
A number of imbalance issues were reported within the occupied spaces: Overheating occupied spaces = wasting energy and contributes to higher fuel bills.
An antique gas-fired water heater manufactured in 1953 was, as you would expect for a product of that vintage, very inefficient. I felt sorry for recommending its demise, as it was just one year younger than I am, but such is life, my friend! With an overall efficiency that likely was less than 50%, it was long overdue for the recycle heap.
The YCCoC board picked from our good/better/best options for installation of the following:
- Install a new Burnham steam boiler properly sized to match the connected load;
- Eliminate the steam zone valves and move the hydro-air unit's energy input from the steam boiler to the hot water boiler;
- Reduce system operating pressure;
- Test combustion utilizing a digital certified analyzer and print out the results to establish a benchmark and verify operating efficiency;
- Replace the feed-water tank and verify the remote condensate pump's operation;
- Clean up all items, pieces and parts that have been casually discarded over many years and, unless otherwise requested, remove all components replaced by our service technicians;
- Install a Laars Mascot high-efficiency modulating condensing boiler with outdoor reset to automatically adjust its output to match the building's heat loss;
- Install a Watts Hydronex pump panel;
- Install a Bradford White indirect water heater;
- Install several Grundfos three-speed SuperBrute circulators, including one of the high-head pumps; and
- Install a Caleffi HydroSeparator.
A standard issue chimney-vented boiler might, at first glance, seem like a better choice than a condensing modulating boiler for what's typically run as a high-temperature system. I'd have argued that same point a few years ago, but who says we have to run convectors at higher-than-condensing temperatures? The fact is, they work quite well when matched to outdoor reset temperatures and we utilize a modified reset curve so that the lowest temperature will be able to produce enough convection to offset the heat loss on those milder days/nights.
We've seen the lowered fuel consumption granted by mod-con boilers in this type of application and the fuel savings have been nothing short of remarkable. Given the fact that on any given year, we only see true design conditions for about 10% of the heating season, which means we'll be in a condensing mode for more than 70% of the run time, this is an option you may want to add to your sales arsenal.
A job like the YCCoC is rare in that it had so many opportunities to pick "low-hanging fruit" from the options tree, but we often visit opportunities where we can offer our customers extremely good choices for conserving energy, fossil-fuel resources and the ability to lower their global-warming carbon foot-print.
And — don't forget to get the ongoing service contract!
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]. Visit www.yccchurches.org for more on the York County Council of Churches.