Multi-Unit System On/Off Conditions - A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual

12-9. Multi-unit system ON/OFF conditions

In an Easy-Link system, the amount of 520 Indoors or 520 Outdoors called on to activate depends on the
FLOW RATE SET TEMPERATURE.
and the
1. Condition required to activate an additional 520 Indoors or 520 Outdoors:
Flow rate required to activate additional 520 Indoors or 520 Outdoors= A × n
Where
and
2. Condition required to reduce the number of activated 520 Indoors or 520 Outdoors:
A. In the case of reducing down from two unit of 520 Indoors or 520 Outdoors to one units
of 520 Indoor or 520 Outdoor: Flow rate = A / 1.7
B. All other cases: Flow rate = A × (n - 2)
3. Example: Set temperature = 120˚F in a four unit system and priority unit is No. 1
To activate additional
520 Indoors or 520 Outdoors
Unit No.
No.1 ON
No.2 ON
No.3 ON
No.4 ON
n
= number of currently activated 520 Indoors or 520 Outdoors
A
is dependent factor of the set temperature. See table below:
Set temperature
˚F
100 – 120
125,130
140
145,150
155 – 185
Flow rate
GPM L/min
0.5 2.0
3.4 12.9
6.8 25.7
10.2 38.6
520 Indoor / 520 Outdoor Service Manual
Factor "A"
˚C GPM
38 - 49 3.4
52 - 54 3.2
60 2.9
63 - 65 2.6
68 - 85 2.4
To reduce number of activated
520 Indoors or 520 Outdoors
Unit No.
No.4 OFF
No.3 OFF
No.2 OFF
No.1 OFF
72
CONFIDENTIAL
Ver. 1.00
L/min
13
12
11
10
9
Flow rate
GPM L/min
6.8 25.7
3.4 12.9
2.0 7.6
0.4 1.4