Mechanical contractor solves office building’s heating problems during hydronic retrofit

Dec. 6, 2013
“As soon as the installation was complete, you could feel the air coming out of the vent on top of the separator,” said Hansen. “The following Monday, there were no heat complaints. We didn’t know where the air was coming from, and we weren’t losing water, so we thought we had the problem fixed. “But we were wrong..."

LAKE SUCCESS, N.Y. — Ahhh… Lake Success. Sounds like a pristine mountain resort or a remote and shimmering water sport destination. And if it was a body of water, eliminating bubbles would deal a blow to the system’s ecology. But it’s not. Lake Success is, however, a village of about 3,000 folks just east of Queens, N.Y.

(Left to right) Guy Basso, site supervisor for We’re Associates, Ray “The Rev” Schmitt, HVAC department manager at Wales-Darby, and Bob Barbour, new business development manager at Taco.

Marching onward with the mystery of unique names and word-plays, you’ll learn about two companies, C Me 4 Pipe and We’re Associates. 

We’re Associates is a privately owned developing and building operating company. For more than 50 years, designing, building and operating suburban office buildings has been their focus.  Today, the company holds more than 3 million square feet of commercial space on Long Island.

We’re Associate’s 130,000-sq.ft., three-story “H Building” in Lake Success was built in the 1960s with a two-pipe hydronic heating and cooling system. Around the perimeter of the building, fan coil units supplied hot or cold air, depending on the time of year.

The steel supply and return lines for the first floor units were buried beneath the building’s slab; portions of it failed a few years ago. Since then, they’ve embarked on a four-phase plan to abandon and replace the old steel pipe.

New copper piping was installed to supply the numerous fan coils throughout the first floor. The retrofit pipe wasn’t easy to thread through the building.

The circuitous distribution piping left plenty of areas for air to become trapped, making consistent flow to the fan coils nearly impossible. Usually, with coin vents installed on the top of the fan coils, maintenance crews could have the air bled off within a day or two.   

But recently, at the completion of the third phase of pipe replacement, trapped air pockets were too resistant, unwilling to be coaxed into air elimination devices.

Occupants were complaining that they received little or no heat, even though maintenance was spending three or more hours a day bleeding lines at each tenant location. Yet, as the lines were bled, water was lost, only making matters worse. Regardless of what they did, the air in the pipes stubbornly held its ground. 

Half the equation

“We spent hundreds of hours bleeding coin vents,” said Herb Hansen, PE, engineering manager for We’re Associates. “We even installed risers and small air vents on many of the fan coil supply lines.”

“Our efforts were like trying to bail out the ocean with a teaspoon,” added Hansen. “I hadn’t seen a problem like this in the 30 years I’ve been with the company. So I contacted an old friend who I thought might have some ideas.”

“Hansen called me hoping I might have a solution,” said Ray Schmitt, HVAC department manager at manufacturer’s representative firm, Wales-Darby. “The coin vents were obviously not cutting it, and were costing a lot of man hours, too.” Schmitt — nicknamed “The Rev” because of his sermon-like hydronic explanations — knew that what the “H Building” needed was an automatic means to efficiently flush air from the system. He suggested a Taco 4900 high velocity air and dirt separator.

We’re Associates hired the mechanical contracting firm, “C Me 4 Pipe” based in Holtsville, N.Y., to install the strainer in the mechanical room. Heat for the building comes from two, 175 HP Scotch Marine steam boilers.

Installation is complete of the eight-inch inlet, 4900 Series high velocity air and dirt separator.

A massive steam-to-water heat exchanger moves energy to the big hydronic loop. The 8-in. inlet 4900 was piped into the main loop on the return side of the supply pumps.

Initially, the thought was to put in-line separators in the supply piping just upstream of the fan coils to get the water as free of air as possible, but Ray was adamant that it go on the return side, where the pressure is the lowest and the temperature at its highest.

“Ray is a real asset for those he works with,” said Hansen. “He’s very knowledgeable; we’ve put his insights to work on many occasions.” 

Schmitt also insisted that an air and dirt model be used, as opposed to just an air separator.  The likelihood of shaking dirt loose in fan coils, or introducing new dirt in the remaining retrofit phase warranted the upgrade.

On a Saturday in mid-January, C Me 4 Pipe had the 4900 installed and in service. With building occupation near capacity, taking the system off-line during a week day wasn’t an option.

Once the air and dirt separator was installed, KLM Insulation Wrapped the unit to match the rest of the building’s hydronic piping.

 In less than eight hours, technicians had the big air separator installed, even though it required rigging the unit down through an access door in the building’s courtyard.

“As soon as the installation was complete, you could feel the air coming out of the vent on top of the separator,” said Hansen.

“The following Monday, there were no heat complaints. We didn’t know where the air was coming from, and we weren’t losing water, so we thought we had the problem fixed.”

Persistent problem

“But we were wrong,” continued Hansen. “Two weeks later, the heat complaints started again, and the air from the vent on the 4900 was literally blowing out like an air hose. We thought of every possible explanation. Even if we had reversed or double-crossed the piping somewhere, it wouldn’t have created a problem like what we had on our hands.”

“Then — one time while I was holding my hand over the vent — it hit me like a ton of bricks,” continued Hansen. “The hydronic system uses hi-pressure, pneumatic actuators.”

The two-pipe hydronic system handles both the heating and cooling loads. In the mechanical room, two large double-acting pneumatic valves switch the system from heating to cooling by directing fluid to the steam-to-hot-water exchangers or to a large Carrier absorption chiller. 

When the 80 pounds of air pressure to the actuators was shut off, the 4900 stopped pushing air out the vent almost instantly. When the air was turned back on, it took only 10 seconds for the air to pour out of the vent again. 

Ghost buster

“An O-ring was leaking in one of the actuators,” explained Hansen. “The separator was so effective at eliminating the entrained air, that it completely hid the problem for two weeks. The O-ring on the actuator deteriorated further, until the air leak overwhelmed the ability of the separator to combat it. This particular actuator is directly connected to the valve body, so the compressed air could travel unheard and unseen, right into the hydronic loop.

As a temporary quick-fix, Hansen taped an adjustable wrench to the top of the valve to keep it in the open position.

“The valve manufacturer’s representative told me he never heard of such an instance,” added Hansen. “With the 4900 in place, and having a centralized point of air release, it was easy to confirm the culprit.”

According to Hansen, he currently has two 6- and 8-in. electric actuators on order to replace the pneumatic models. In the meantime, there’s a adjustable wrench holding the valve open, and the separator isn’t pushing any air.

From here forward, when the loop needs to be opened for any reason, maintenance crews won’t need to chase air around the building, trying to pull it out of the water by opening coin vents.

The air separator in the basement handles the task automatically.

“Back at in our headquarters building, in Jericho, N.Y., we have a similar issue,” said Hansen.  “Twice each year, when we switch from the heat pump to the chiller operation or vice versa, we lose water in the two-pipe system. We’d spend a full day bleeding air out at the fan coils. Not this year. We’re about to install two, five-inch Taco 4900 air and dirt separators. It’ll be a relief to know the problem is solved for good.”

They found success in Lake Success, so why not duplicate it?

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