Bryant 50YEW Design Manual page 47

Part III: Source Side Design / Closed Loop Installation Guidelines
Inside Piping - Polyethylene pipe provides an excellent no leak
piping material inside the building. Inside piping fi ttings and elbows
should be limited to prevent excessive pressure drop. Hose kits
employing 1" rubber hose should be limited in length to 10-15 feet
[3 to 4.5 meters] per run to reduce pressure drop problems. In
general 2 feet of head [6 kPa] pressure drop is allowed for all earth
loop fi ttings which would include 10-12 elbows for inside piping to
the Flow Controller. This allows a generous amount of maneuvering
to the Flow Controller with the inside piping. Closed cell insulation
(3/8" to 1/2" [9.5 to 12.7 mm] wall thickness) should be used on
all inside piping where loop temperatures below 50°F [10°C] are
anticipated. All barbed connections should be double clamped.
Flow Controller Selection - The pressure drop of the entire
ground loop should be calculated for the selection of the Flow
Controller (a pressure drop spreadsheet is downloadable from
the web site). In general, if basic loop design rules are followed,
units of 3 tons [10.6 kW] or less will require only 1 circulating
pump (UP26-99). Units from 3.5 to 6 tons [12.3 to 21.1 kW]
will require a two pump system (2 - UP26-99)*. Larger capacity
units with propylene glycol as antifreeze may require 2 - UP26-
116 pumps. However, the UP26-116 should be avoided where
possible, as power consumption of the 26-116 is signifi cantly
higher than the 26-99, which will affect heating and cooling
operating costs. In many cases, where pressure drop calcuations
may call for 3 - UP26-99 pumps, try substituting 2 - UP26-116
pumps. This makes the installation much easier and reduces cost.
Chart 3-1 shows the various pump combinations. Pumps for 50Hz
units will have similar characteristics, but different model numbers.
Figure 3-6: Typical Ground-Loop Application
Unit Power
Disconnect
Thermostat
Wiring
ASP30 Air Pad or
Extruded polystyrene
insulation board
Bryant Geothermal Heat Pump Systems
Loop pressure drop calculation should be performed for accurate
fl ow estimation in any system including unit, hose kit, inside piping,
supply/return headers, circuit piping, and fi ttings. Use Tables 3-3A
through 3-3E for pressure drop calculations using antifreeze and
PE/rubber hose piping materials.
Prior to installation, locate and mark all existing underground
utilities, piping, etc. Install loops for new construction before
sidewalks, patios, driveways and other construction has begun.
During construction, accurately mark all ground loop piping on
the plot plan as an aid in avoiding potential future damage to the
installation (see Site Survey Sheet). This should be done before and
after loop installation. Final installation should be plotted from two
fi xed points to triangulate the header/manifold location.
Loop Piping Installation
The typical closed loop ground source system is shown in Figure
3-6. All earth loop piping materials should be limited to only
polyethylene fusion in below ground (buried) sections of the loop.
Galvanized or steel fi ttings should not be used at any time due
to the tendency to corrode by galvanic action. All plastic to metal
threaded fi ttings should be avoided as well due to the potential
to leak in earth coupled applications; a fl anged fi tting should be
substituted. P/T plugs should be used so that fl ow can be measured
using the pressure drop of the unit heat exchanger in lieu of
other fl ow measurement means (e.g. fl ow meter, which adds
additional fi ttings and potential leaks). Earth loop temperatures
can range between 25-110°F [-4 to 43°C]. Flow rates of 2.25 to
3 gpm per ton [2.41 to 3.23 l/m per kW] of cooling capacity are
recommended for all earth loop applications. **
Flow
Controller
Insulated
Hose Kit
P/T Plugs
Do not install bricks or
blocks under air pad.
Water-to-Water System Design Guide
* For water-to-air units. 50YEW010
water-to-water units need two pumps.
** This note is for water-to-air
units, which are rated for cooling
capacities. 50YEW series residential
water-to-water units are rated for
heating capacities at 32°F [0°C]
entering source temperature.
Consult unit performance data for
open loop minimum fl ow rates.
Closed Loop Systems
Rev.: 06/10/05D
45