AERCO BMK 2000DF - Manual (Page 31)

Benchmark 1500DF - 2000DF Boilers
CHAPTER 2 – INSTALLATION
OMM-0098_0A AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 Page 31 of 196
GF-144 Ph.: 800-526-0288 04/01/2014
• If BST is NOT implemented, the second use is typically in conjunction with the
AUXILIARY RELAY CONTACTS described in section 2.10.14. This interlock circuit
is located in the purge section of the start string. It can be connected to the proving
device (end switch, flow switch etc.) of an auxiliary piece of equipment started by
the unit’s auxiliary relay. If the delayed interlock is connected to a proving device
that requires time to close (make), a time delay (AUX START ON DLY) that holds
the start sequence of the unit long enough for a proving switch to make (close) can
be programmed.
To use this option, you must disconnect the harness from the Delayed Interlock
terminals and connect the proving device in its place.
Should the proving switch not prove within the programmed time frame, the unit will
shut down. The AUX START ON DLY can be programmed from 0 to 120 seconds.
This option is located in the Configuration Menu (Chapter 3).
2.10.13 Fault Relay (NC, COM, & NO)
The fault relay is a single pole double throw (SPDT) relay having a normally open and normally
closed set of relay contacts that are rated for 5 amps at 120 VAC and 5 amps at 30 VDC. The
relay energizes when any fault condition occurs and remains energized until the fault is cleared
and the CLEAR button is depressed. The fault relay connections are shown in Figure 2-12.
2.10.14 Auxiliary Relay Contacts (NC, COM, & NO)
Each unit is equipped with a single pole double throw (SPDT) relay that is energized when there
is a demand for heat and de-energized after the demand for heat is satisfied. The relay is
provided for the control of auxiliary equipment, such as pumps and louvers, or can be used as a
unit status indictor (firing or not firing). Its contacts are rated for 120 VAC @ 5 amps. Refer to
Figure 2-12 to locate the AUXILLIARY RELAY terminals for wiring connections.
2.11 FLUE GAS VENT INSTALLATION
AERCO Gas Fired Venting and Combustion Air Guide, GF-2050 must be consulted before any
flue or combustion air venting is designed or installed. Suitable, U/L approved, positive
pressure, watertight vent materials MUST be used for safety and UL certification. Because the
unit is capable of discharging low temperature exhaust gases, the flue must be pitched back
towards the unit a minimum of 1/4" per foot to avoid any condensate pooling and to allow for
proper drainage.
While there is a positive flue pressure during operation, the combined pressure drop of vent and
combustion air systems must not exceed 140 equivalent feet or 0.8” W.C. Fittings as well as
pipe lengths must be calculated as part of the equivalent length. For a natural draft installation
the draft must not exceed - 0.25” W.C. These factors must be planned into the vent installation.
If the maximum allowable equivalent lengths of piping are exceeded, the unit will not operate
properly or reliably.