Installation Instructions
Controls
MD
Control Circuit Connections
The Herrtronic MD Series Humidifier has the
capability to utilize one of three types of control
schemes.
1.
On/Off
2.
Proportional
3.
Proportional +Integral
Controls may be supplied
by
the factory or
others. The following information applies to all
controls factory supplied or furnished
by
others. All
external electrical control circuits are to be
connected to the unit using the twelve pole terminal
strip located in the low voltage electrical
compartment. The terminal strip is accessed
through the front door or the side electrical
compartment door. Field wiring from humidistat to
humidifier
and
between safety devices, such as high
limit humidistat
and
air proving switches, should
be
18
AWG
stranded or
20
AWG solid wire.
If
conduit is not used with the controls wiring, install
the black plastic fingered bushing (in accessory
pack)
and
completely seal with
RTV
silicone.
Wall devices should be mounted at a height
similar to that of a typical thermostat and should be
located in an area that will provide good
representation of the overall space being humidified.
Do
not mount wall devices directly in the air stream
of a supply grille or room distribution unit.
Duct control devices should be mounted in a
location where the humidity
and
temperature are
uniform, usually the return duct.
Do
not
mount
in
front of the steam distributor or in a mixing,
turbulent, or isolated area.
Duct high limit devices should be mounted
downstream of the steam
distributors-far
enough
that under normal conditions in the air
stream,
the
steam has been completely absorbed, typically
10
ft.
The device should be located such that it can sense
humidified air as it approaches saturation.
Do
not
mount in dead air spaces such as inside of corners.
Air proving devices should be mounted so that
they sense air flow (or the absence of it). Wire the
device so that it closes
when
air flow is present
and
will open
when
there is no air
flow.
The purpose of
the device
is
to prove that air flow is present before
steam is distributed into the duct.
The following information and diagrams are
shown for each control scheme. Please refer to the
control scheme that your humidifier was set
up
for
and follow the diagram for control circuit
connections. The control type
and
signal are indicated
on a label adjacent to the controls terminal strip.
Control Circuit Connections
1.
Mode
l-On/Off
A. Control Input -Unit will operate with any
two
pOSition device
(See
Fig.
9).
Demand for
humidity will close the contact.
B.
Limit
Input
-Unit will operate with any two
position device (See Fig.
9).
The humidistat
contact will open on humidity rise.
Control Stat
FIGURE 9
II.
Mode
II-Proportional
A. Control Input -Interpreted by the humidifier
as a
demand
of
output
signal. Input device
should be linear. Unit can accept any VDC or
mADC signal within a range of
0-20
VDC
or
mADC
(See
Fig.
10).
Unit may also accept a
resistive signal
0-135
ohms
(See
Fig.
11).
B.
Limit Input -Unit may accept any modulating
input
within the same ranges as the control
inputs listed above.
1.
Proportional VDC or mADC
(See
Fig.
12)
2.
Resistive
(See
Fig.
13)
3.
Two position device
(See
Fig.
9)
Additionally, a P + I sensor may be used as a
limit input.
1.
VDC
(See
Fig. 16A wall,
16B
duct)
2.
mADC
(See
Fig.
17)
FIGURE
10
FIGURE
11
4
5
H--------iO
VDC
or
mADC
H-----+-10
Signal
OUT
W
R
B
+L.:...
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10 Herrtronic
MD
Series Installation and Operation
Manual
o
