Fault Relay (Nc, Com, & No); Auxiliary Relay Contacts (Nc, Com, & No); Flue Gas Vent Installation - Watts Aerco BENCHMARK 750 User Manual

Benchmark 750 – 1000 Boiler User Manual - INTERNATIONAL
Remote Interlock In (OUT & IN)
2.10.12.1
The remote interlock circuit is provided to remotely start (enable) and stop (disable) the unit if
desired. The circuit is 24 VAC and comes factory pre-wired closed (jumped).
Delayed Interlock In (OUT & IN)
2.10.12.2
The Delayed Interlock terminals can be used in one of two ways:
•
In conjunction with the optional external sequencing valve (see section 2.14 and Chapter
9 – BST), a component of AERCO's on-board Boiler Sequencing Technology (BST)
solution. By default a cable of the unit's wiring harness is connected to these terminals. If
BST is implemented, the other end of that cable is connected to the sequencing valve.
•
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 AUXILIARY RELAY terminals for wiring connections.

2.11 FLUE GAS VENT INSTALLATION

AERCO Gas Fired Venting and Combustion Air Guide, GF-2055 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 (0.64 cm per 0.3 m) 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 (42.7m) or 0.8" W.C. (199 Pa).
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. (-62 Pa). 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.
OMM-0119_0A
GF-130-I
CHAPTER 2 – INSTALLATION
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Ph.: 800-526-0288
Page 29 of 170
11/03/2016