mr
.
steam
®
C U S E R I E S
Installation, Operating & Maintenance Manual
29
INSTRUCTIONS FOR ELEMENT REPLACEMENT
R
RE
EA
AD
D IIN
NS
ST
TR
RU
UC
CT
TIIO
ON
NS
S C
CO
OM
MP
PL
LE
ET
TE
EL
LY
Y B
BE
EF
FO
OR
RE
E S
ST
TA
AR
RT
TIIN
NG
G W
WO
OR
RK
K
Before Installing your new elements be sure
McDonnell Miller low water cut-off and aux. low water cutoff (if
supplied) is operating properly. The float chamber and lower
equalizer column of the MM control must be completely clear
of sludge or other foreign matter. Failure to do this may cause
the immediate burn-out of the new elements. If the unit is
probe equipped, check condition of the probes and isolator.
All elements are thoroughly checked before shipment. The
manufacturer cannot be responsible for burn-outs caused by a
faulty low water cut-off.
The lower equalizer column can best be examined by breaking
the unions on either side and then visually and manually examining the piping with
your finger or probes to see if it is clear and clean.
IMPORTANT:
Models CU 360 - CU 1400 use probes for liquid level sensing and
control. Model CU 2000 and higher use McDonnell-Miller MM 150.
1.
Disconnect boiler from electric power supply at main safety switch or fuse panel.
Then turn boiler switch to “OFF" position.
2.
Close water supply valve on incoming water supply line.
Drain boiler completely of water.
3.
Open boiler door to access heating element.
4.
Disconnect wire (electric) leads connecting element to main power
system of boiler. Again, note wire connections to facilitate re-assembly.
Proceed to remove and discard (6) bolts from flange.
IMPORTANT:
Note the wire connections to facilitate re-assembly
(see wiring schematic). Remove and discard six (5/16"-18) bolts from flange.
Do not reuse these bolts.
5.
Thoroughly clean boiler flange of all foreign material. Be certain no part of old
gasket remains on flange.
6.
Apply "Slic-Tite" Gasket Compound (or equal) to both surfaces of new gasket
supplied with replacement element. Proceed to install element flange assembly
with gasket between boiler flange and element flange. In doing this, be careful
to align flange holes so element wire connection terminals on element assembly
are in line with previously disconnected wire leads to facilitate easy connections.
NOTE:
Observe markings on element flange. Install element marking “TOP” on top.
7.
Use only new element flange bolts. Tighten all (6) element flange bolts to a
torque value of 22 lb-ft each (see illustration).
8.
Connect all wires to the terminals. Tighten all element terminals to a torque
value of 20 lb-in each (see illustration). Make sure all wires are clean and
bright to assure good electrical contact.
9.
Check that the wires are correctly connected to the contactor terminals and
are tightened to a torque value of 45 lb-in. (see illustration). Make sure all
wires are clean and bright to assure good electrical contact.
10.
Open water valve to allow water supply to reach boiler feed mechanism.
11.
As boiler automatically refills, observe the new flange assembly for possible
leaks. If water is noticed, the bolts must be re-tightened. Before doing this,
turn the boiler off at the main fuse safety switch.
12.
When boiler reaches working pressure, check flange assembly again for
leaks.
Avoid use of chemical cleaning compounds.
Follow maintenance instructions provided with the boiler.
Torque Values:
Element Flange Bolts: 22 lb-ft
Element Terminals: 20 lb-in
Contactor Terminals: See Torque Chart
For Illustrative Purposes Only.
Power wiring shown in approxi-
mate factory-installed location
Torque
Wrench
Torque Wrench
Torque
Wrench
Boiler with
McDonnell Miller
1
1
⁄
2
”
1” Steam Equalizing Pipe
Pump and Low Water Control
Normal Boiler Water Line
Cut-Off Level is Arrow Mark
Blowdown Valve
1” Water Equalizing Pipe
TORQUE VALUES
Element Flange Bolts
22 lb-ft
Element Terminals
20 lb-in
Contactor Terminals 50 amp 25 lb-in
60 amp 45 lb-in
75 amp 75 lb-in
CAUTION
!
CAUTION
!
