| YR-RYR "YEAR ROUND"
MAKE-UP AIR SYSTEMS The need to replace air exhausted from
buildings with 100% outside air is a year around requirement. Outside air must be
heated in the winter and, in many applications, cooled in the he summer.
Model YR_RYR "year-round" make-up air systems incorporate
cooling with the traditional Hastings 100% outside air indirect gas-fired units. The
same concept of modulated discharge air temperature control found in Hastings RMU and IMU
units is applied to the all season or "year-round" systems. As an added
feature, YR-RYR systems include space over-riding heating and cooling temperature controls
like those with Hastings RHV and IHV heating and ventilating units.
Conventional equipment is limited in the choice of heat-to-cool
ratios and control systems. Standard cooling/heating units are designed for comfort
air conditioning with a minimum of outside air. They are unable to provide comfortable
discharge air conditions with the temperature extremes of 100% outside air entering the
units.
YR-RYR "year round" make-up air systems are available in a
wide range of cooling and heating combinations to meet any climatic condition and
application.
YR-RYR Operating Sequence
The "On" position of the "On-off" system switch
energizes the unit and provides continuous blower. the summer-winter sequencer
monitors the temperature of the entering outdoor air to provide fully automatic operation.
With the sequencer in the winter mode, the unit operates as a RHV or
IHV heating and ventilating system. On call for additional heat in the space, the
room thermostat opens the by-pass gas valve to provide full gas input to the burner.
If room thermostat is satisfied, the modulating non-electric gas valve (and
discharge air controller on the 400 MBH furnaces) maintains a constant discharge air
temperature.
When the summer-winter sequencer switches to the summer position,
the air cooled condensing unit is energized and the liquid line solenoid valve opens
allowing refrigerant to flow to the DX cooling coil. The furnace(s) remains in
operation and the discharge air controller maintains a constant leaving air temperature.
If the thermostat in the space calls for additional cooling, the
reheat function is shut-off. this allows the cooler air directly off the DX coil to
discharge into the space. When the summer-winter sequencer switches out of the
summer position, the liquid line solenoid valve closes and the condensing unit pumps down,
shutting off on low head pressure.
Equipment Selection - Air handling and
heating Section.
| 1. Check the exhaust specifications or equipment to
determine the total SCFM of fresh air required. 2. Increase
the total SCFM by approximately 10% if building needs too be slightly pressurized.
3. Determine air temperature rise, usually 70 deg F minus winter
outside design temperature. |
4. Select model and motor size to deliver
desired air temperature rise and SCFM against required TSP. Total Static Pressure (TSP) is
the sum of all system component pressure drops external of the Mb blower including
plenums, intake hood, dampers, filters, DX coil, transitions, furnaces, system ductwork
and registers. See Bulletin RD-1 or SD-1 for pressure drops thru duct furnaces. |
|
|
