Green Mechanical Contractor

Contractor Vince Youndt selected Taco circulators and mixing valves.

UNIQUE HOT WATER SYSTEM

“Usually, when a desuperheater is being used, the geo unit is connected directly to a water heater, pulling water from it, and dumping back into it. That’s not the case with any of the units we install,” says Youndt.

A typical Vertex installation includes two tanks. In this
case, three tanks are used. At the Shaw home, unlimited
hot water was the goal. Two 50-gal. Bradford White indirect
units (acting as buffer tanks) are piped between the desuper-
heaters and an 80-gal. Bradford White, LP-fired water heater.
“We could have used a single 80-gal. buffer tank, but it actu-
ally costs more than two 50-gal. tanks,” says Youndt. “Why
pay more for less capacity?”
Ground water comes into the indirect tanks only, which
the desuperheaters begin to heat by casting off excess Btus.
The LP water heater draws heated domestic water from the
indirect tanks.

This configuration allows for a much higher ΔT for the desuperheater, further decreasing the load on the ground loop. It also lowers the ΔT for the water heater. Additionally, there’s the added benefit of having much more hot water on tap.

“ClimateMaster lists the double (or in this case triple) tank method as one of the recommended configurations,” says Youndt. “It works very well, though I’ve rarely seen anyone else use it quite the way we do.”

WHAT BOILER?

The somewhat uncommon domestic supply has one more secret. It doubles as a boiler, in its ability to provide hot water for a hydronic system.

Off the domestic supply riser, a tee, equipped with a Taco iSeries mixing valve, creates a loop to a small brazed-plate heat exchanger. Using low-temp radiant heat, half-inch PEX loops warm the floor in the master suite, roughly 500-sq.ft.

“The master suite is over the garage, so we wanted something to take the chill out of the walnut flooring in

the bedroom, and the ceramic tile in the master bath,” says Youndt. The plated, staple-up radiant loop’s mix temperature is about 100°F. It’s not meant to heat the room, only warm the floor. An outdoor reset control doesn’t turn the system on until the temperature drops below 50°F. The reset control gently increases circulated system fluid temperatures from 85°F at the beginning of the heating season, to higher fluid temperatures as outdoor temperatures drop.

SIGNATURE EXCHANGE FIELD

With three boreholes, the exchange field is under the home’s front yard. Like every Vertex installation, the HDPE loops are fused together at the wellhead manifold before entering the building’s foundation.

The 7-ton geo-exchange field consists of 8-in. holes drilled to 350-ft. by Sensenig & Weaver Well Drilling, Denver, Pa. Once the 1¼-in. U-bend pipes were dropped, the holes were backfilled with bentonite grout for maximum heat transfer.

“We do something else a little different with our geo instal-
lations,” says Youndt. “Instead of having wells dedicated to a
specific heat pump, the entire exchange field is tied into one
flow center with a switching relay. This allows either of the
units to utilize the entire exchange capacity, maximizing the
efficiency of that unit.”
“You could also say that ‘maximizing efficiency’ is
the theme we used throughout this project,” concludes
Youndt. “We had a big house with the need for a not-so-
big carbon footprint.”