91e Controller
2
MC10 – 1-3
1
D
ESCRIPTION
1.1
Early Versions of 91e Controller
The early version of the 91/91e was fitted between 1990 and early 1995. It did not have a ramp-
to-setpoint feature, but in other respects is similar to the later version described below.
1.2
Later Versions of 91e Controller
The later version of model 91e was brought into use in early 1995. It is a digital instrument with
PID control algorithms, made by Eurotherm. It is supplied as an integrated part of the control
section of the furnace.
The 91e features:
- Easy use as a simple temperature controller, where on setting the required temperature the
controller immediately attempts to reach and maintain it.
-
A ramp-to-setpoint feature, which may be used to limit the heating (or cooling).
Model 91eHL also contains a “power limit” feature, enabling it to be used on furnaces that
require a maximum setting to the supplied power.
The controller does not contain a real-time calendar, and is not subject to century-end date
problems.
2
O
PERATING
I
NSTRUCTIONS
2.1
Controls
Most Carbolite products are fitted with an “Instrument Switch” which cuts off power to the
controller and other parts of the control circuit. See the instruction manual for the furnace for the
overall operating instructions.
To operate the 91e there must be power to the furnace, and the Instrument switch must be on. If a
time switch is included in the furnace circuit, this must be in an On period.
