Roberts Gorden Corayvac CRV-B Series, Installation, Operation & Service Manual

Page: 61 / 96

SECTION 12: C
ONTROL
M
ETHODS
53 of 85
temperat u re. The mod u lating controls offer many
feat u res like 7 day programmability, fo u r time periods
per day (2 occ u pied, 2 u nocc u pied), temporary
temperat u re setpoint o v erride, keypad locko u t
sec u rity and more.
Remote sensors or o u tdoor sensors are optional, not
req u ired. Remote sensors w ill allo w for zone
temperat u re a v eraging, if req u ired.
12.3.1 Analo g Si g nal Modulatin g Thermostat
A programmable, 7-day programming, mod u lating
thermostat can be installed to s u pply an analog (4-
20mA) or (2-10Vdc w ith 500 Ohm resistor) control
signal to dictate the speed of the p u mp. For
thermostat w iring, See Page 60, Figure 44 . Optional
room sensors (P/N 10081520) and o u tdoor air
sensors (P/N 10081521) are a v ailable.
Room temperat u re a v eraging net w orks can be
created w ith u p to nine room sensors (P/N
10081520). Refer to thermostat installation
instr
u ctions for w iring.
12.3.2 Cable Re q uirement
Table 3 , on on Page 53 lists w iring types, sizes and
distances for mod u lating thermostat comm u nication.
Power Re q uirement
Programmable thermostats req u ires 24 v olt, AC
po w er.
12.3.3 Se q uence of Operation
Depending on the space temperat u re, the thermostat
w ill control the heat o u tp u t based on demand signal
comm u nicated from the thermostat program. The
thermostat w ill close contact on the transformer relay
(P/N 90436300). The VFD r u n command is
energized by the transformer relay. When the VFD
energizes the p
u mp and the v ac uu m has been
established, the press u re s w itch w ill close and
energize the b u rners. At high heat, a demand signal
w ill t u rn the p u mp speed to a maxim u m freq u ency
and b u rner(s) ON at maxim u m firing rate. As the
space temperat u re gets closer to the set point, the
thermostat program w ill slo w the p u mp speed and
b u rner(s) firing rate do w n u ntil the room temperat u re
reaches the thermostat set point.
NOTE:
To obtain Analog 0-10VDC signal, connect as sho w n
on Page 69, Section 15.2 and set standard speed
so u rce (parameter 05 inside VFD men u ) to 03.
12.4 DPDT Transformer Relay (P/N 90436300)
The transformer relay w iring diagram is sho w n on
Page 56, Figure 39 . The transformer relay can be
u sed to control an EP-100 or EP-201 p u mp
CORAYVAC ® system. The do u ble pole relay can be
u sed to control one or t w o zones of b u rners. The
electrical circ u it is a 120 V AC (20 A) s u pply. The
transformer 24 V AC o u tp u t for the thermostat is
rated at 40 VA. Thermostats u sed w ith the
transformer m u st not exceed this po w er req u irement.
A transformer relay operated system w ill not gi v e any
post p u rge p u mp operation to completely exha u st
prod u cts of comb u stion from the system or pro v ide
indication of operating conditions.
Table 3: Modulatin g Thermostat Cable Re q uirements
Wire Function Recommended Wire Size
(Minimum)
Specification or
Re q uirement
Distance (Maximum)
Digital O u tp u ts 18 AWG (0.75 sq mm) Standard thermostat w ire 1000 ft (304 m)
Mod u lating O u tp u ts 18 AWG (0.75 sq mm) 1 pair 500 ft (152 m)
O u tdoor Air Temperat u re Sensor 18 AWG (0.75 sq mm) 1 pair 500 ft (152 m)
Remote Sensor 18 to 22 AWG
(0.75 to 0.34 sq mm) T w isted pair w ire 1000 ft (304 m)
Po w er Wiring 18 to 14 AWG
( 0.75to 2.0 sq mm) NEC Class II 140ºF (60°C ) Limited by line-loss effects on po w er
cons u mption.
LonWorks
®
(P/N 90424104 only) 18 AWG
(0.75 sq mm) nonshielded
1 pair Refer to E-b u s Wiring G u ide 74-2865
for maxim u m length and generic cable
specifications.