Comfort-Aire HEH Series 2 to 5 Tons - Manual (Page 17)

17
Heat Controller, LLC. HEV/H SERIES Installation, Operation & Maintenance
Air Pad or
Extruded
polystyrene
insulation board
Unit Power
Disconnect
Thermostat
Wiring
Pressure
Tank
Shut-Off
Valve
Boiler
Drains
Flow
Regulator
Water In
Water Out
Water
Control
Valve
Optional
Filter
P/T Plugs
Expansion Tank and Pump
Use a closed, bladder-type expansion tank to minimize
mineral formation due to air exposure. The expansion
tank should be sized to provide at least one minute
continuous run time of the pump using its drawdown
capacity rating to prevent pump short cycling. Discharge
water from the unit is not contaminated in any manner
and can be disposed of in various ways, depending on
local building codes (e.g. recharge well, storm sewer,
drain field, adjacent stream or pond, etc.). Most local
codes forbid the use of sanitary sewer for disposal.
Consult your local building and zoning department to
assure compliance in your area.
Water Control Valve
Note the placement of the water control valve in
Figure 14. Always maintain water pressure in the heat
exchanger by placing the water control valve(s) on the
discharge line to prevent mineral precipitation during
the off-cycle. Pilot operated slow closing valves are
recommended to reduce water hammer. If water hammer
persists, a mini-expansion tank can be mounted on the
piping to help absorb the excess hammer shock. Insure
that the total ‘VA’ draw of the valve can be supplied by
the unit transformer. For instance, a slow closing valve
can draw up to 35VA. This can overload smaller 40 or
50 VA transformers depending on the other controls in
the circuit. A typical pilot operated solenoid valve draws
approximately 15VA.
Flow Regulation
Flow regulation can be accomplished by two methods.
One method of flow regulation involves simply adjusting
the ball valve or water control valve on the discharge
line. Measure the pressure drop through the unit heat
exchanger, and determine flow rate from Tables 8. Since
the pressure is constantly varying, two pressure gauges
may be needed. Adjust the valve until the desired flow of
1.5 to 2 gpm per ton [2.0 to 2.6 l/m per kW] is achieved.
A second method of flow control requires a flow control
device mounted on the outlet of the water control valve.
The device is typically a brass fitting with an orifice of
rubber or plastic material that is designed to allow a
specified flow rate. On occasion, flow control devices may
produce velocity noise that can be reduced by applying
some back pressure from the ball valve located on the
discharge line. Slightly closing the valve will spread the
pressure drop over both devices, lessening the velocity
noise. NOTE: When EWT is below 50°F [10°C], 2 gpm
per ton (2.6 l/m per kW) is required.
Water Coil Low Temperature Limit Setting
For all open loop systems the 30°F [-1.1°C] FP1 setting
(factory setting-water) should be used to avoid freeze
damage to the unit. See “Low Water Temperature Cutout
Selection” in this manual for details on the low limit setting.
Figure 13: Typical Open Loop/Well Application
GROUND-WATER HEAT PUMP APPLICATIONS
13.
Table 10C. Since