Slant/Fin EH - Manual (Page 3)

2. Service Connections and Electrical Ratings
A. All circuit breakers ahead of and at boiler must be
OFF. Remove the Service Connection Panel (right hand
front). Cover by removing 5 screws from the top, bottom
and side flanges (see wiring diagram on back of the
Service Connection Panel and Figure 5).
B. Draw power feeder cable (75°C minimum) and conduit
through service K.O. provided on side, top and bottom.
C. Connect hot lines to main lugs on breaker base or to black
and red or to black, red and blue leads provided in service
compartment. A ground lead should be drawn and wired
to the ground lug in the service compartment. If rating
plate indicates boiler is a single phase 3-wire or 3-phase
4-wire model, draw a neutral wire #12 AWG maximum,
75˚C. minimum and connect to neutral lug or white wire
lead provided in service compartment. See Tables 1 and 2
for lug sizes and current ratings.
Main * Lug Grounding Lug Wire Size
Wire Size Small Holes Large Holes
Model Phase CU-AL† CU-AL† CU AL†
EH-40 1 2-250 MCM CU DO NOT USE 6-2/0
EH-28 thru 32 1 2-250 MCM DO NOT USE 14-4 6-4
EH-8 thru 24 1 6-2/0 14-8 14-4 6-4
EH-8 thru 40 3 6-2/0 14-8 14-4 6-4
Neutral Lug Wire Size: For 3-wire single phase and 4-wire 3 phase models
equipped with circuit breakers
Small Holes: #14-12 Solid CU or AL † and #12 stranded CU or AL†
Large Holes: #14-8 Solid CU, #10-4 Stranded CU and #6-4 AL †
The neutral tap is for the circulator and control transformer. The maximum wire size of
the neutral should not exceed 12 AWG in that 2" conduit accommodate 2 incoming
power feeders plus a neutral wire and a ground conductor for the large size models.
Table 1. Lug Sizes
* For models with circuit breakers only.
† ALUMINUM conductors may be used, lug size, conduit size, ampacity and all applicable
codes permitting. However, aluminum conductors may NOT be used for model EH-40 single phase.
SINGLE PHASE 3 WIRE THREE PHASE, 4 WIRE
120/208V, 120/240V‡ 120/208V-WYE
CIRCUIT ONLY‡
Basic Heater Basic Heater
Model Amperes* Model Amperes†
No. @240V No. @208V
EH-8 33
EH-10 42
EH-12 50 EH-12 25
EH-16 67 EH-16 38†
EH-20 83 EH-20 48†
EH-24 100 EH-24 60†
EH-28 117 EH-28 60†
EH-32 133 EH-32 73†
EH-40 167 EH-40 95†
Table 2. Current Ratings
* For current values @ 208V, multiply current @ 240V by 0.867.
† Leg with the highest value of line current of an unbalanced 3-phase load.
‡ 125 VAC maximum rating of all hot conductors.
Flow Switch Minimum
Model McDonnell Pipe Length of
No. & Miller No. Size Flow Switch*
EH-40 FS8V 1-1/4” 8-1/2”
EH-8 thru EH-32 FS4-3T3-1 1” 6-1/2”
Table 3. Flow Switch Size Selection
* Straight pipe upstream and downstream
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