Install Instructions
6 EH-M2-40 Boiler Operation and Installation Instructions
Table 1. Lug Sizes
Table 3. Current Ratings
Table 2. Flow Switch Size Selection
† Leg with the highest value of line current of an unbalanced 3-phase load.
‡ 125 VAC maximum rating of all hot conductors.
* Size must be based on installation requirements of National Electric code (NEC), Canadian Electric Code,
and local codes (where applicable).
Model
Phase
Distribution
Block Wire Size
CU
Ground Lug
Wire Size
CU
Neutral Din
Rail Mount
CU
EH-40-M2
EH-8-M2 thru 32-M2
EH-12-M2 thru 40-M2
1
1
3
2-3/0 MCM CU
6-2/0
6-2/0
6-2/0
6-2/0
6-2/0
14 Min.
14 Min.
14 Min.
The neutral tap is for the circulator and control transformer.
† Aluminum conductors may be used, lug size, conduit size, ampacity and all applicable codes permit-
ting. However, aluminum conductors may not be used for models over 32kw.
Model
Flow Switch
McDonnell
& Miller No.
Pipe
Size
Pipe Length
of Flow
Switch**
EH-40-M2
EH-8-M2 thru 32-M2
FS8W
FS4-3T3-1
1-1/4"
1"
8-1/2"
6-1/2"
SINGLE PHASE 3 WIRE, 120/208V
‡
Basic Model
No.
Heater Amperes
@ 208V
FLA
@ 208V
Circuit
Breaker Size*
EH8-135-M2
EH10-135-M2
EH12-135-M2
EH16-135-M2
EH20-135-M2
EH24-135-M2
EH28-135-M2
EH32-135-M2
EH40-135-M2
29
36
43.4
58
72
87
101
116
145
32
39
46
61
75
90
104
119
148
40
50
60
80
100
125
150
150
200
SINGLE PHASE 3 WIRE, 120/240V
‡
Basic Model
No.
Heater Amperes
@ 240V
FLA
@ 240V
Circuit
Breaker Size*
EH8-135-M2
EH10-135-M2
EH12-135-M2
EH16-135-M2
EH20-135-M2
EH24-135-M2
EH28-135-M2
EH32-135-M2
EH40-135-M2
33
42
50
67
83
100
117
133
167
36
45
53
70
86
103
120
136
170
50
60
70
90
110
150
150
175
225
THREE PHASE 4 WIRE, 120/208V WYE CIRCUIT ONLY
‡
Basic Model
No.
Heater Amperes †
@ 208V
FLA
†
@ 208V
Circuit
Breaker Size*
–
–
EH12-345-M2
EH16-345-M2
EH20-345-M2
EH24-345-M2
EH28-345-M2
EH32-345-M2
EH40-345-M2
–
–
43
58 †
72 †
69 †
69 †
83 †
108 †
–
–
46
61 †
75 †
72 †
72 †
86 †
111 †
–
–
60
80 †
100 †
90 †
90 †
110 †
150 †
THREE PHASE 4 WIRE, 120/240V DELTA CIRCUIT ONLY
‡
Basic Model
No.
Heater Amperes †
@ 240V
FLA
†
@ 240V
Circuit
Breaker Size*
–
–
EH12-345-M2
EH16-345-M2
EH20-345-M2
EH24-345-M2
EH28-345-M2
EH32-345-M2
EH40-345-M2
–
–
50
67 †
83 †
79 †
79 †
96 †
125 †
–
–
53
70 †
86 †
82 †
82 †
99 †
128 †
–
–
70
90 †
110 †
110 †
110 †
125 †
175 †
** Straight pipe upstream and downstream.