Thermolec Application &Technical Notes - Manual (Page 34)

STEP 3 - (continued)
Summary of Temperature Control
1- Electric ON / OFF thermostats are available up to three stages for room or duct control and up to four
stages for duct control only. Three and four stage thermostats are not recommended for FINE or
MEDIUM temperature control because of their large differentials. However, they are suitable for
COARSE control.
2- P.E. Switches with a pneumatic thermostat are recommended for up to four stages only and can be
used for FINE as well as MEDIUM or COARSE control.
3- FULL SCRs are compatible with electronic or pneumatic signal. They are recommended where FINE
temperature control and energy conservation is required. As a general guideline, it is economical to
use Full SCR on heaters up to 70 Amps total load. Between 70 and 120 Amps, the cost is slightly
more expensive and beyond 120 Amps Hybrid controllers are the best choice.
4- Hybrid controllers are compatible with electronic or pneumatic signal. They are recommended where
FINE temperature control is required and where the heater capacity is too large to be controlled
economically by a FULL SCR (over 120 Amps).
5- Thermolec is engaged in a countinuous effort of product development, hence, the following information
is presented as a general overview of existing products and can be modified without further notice.
Notes:
a- Although ON/OFF stages can offer some economy, in most multi-stage (2 stages and over)
applications up to 40 KW, SCR proportional control can be obtained at almost the same price.
Please see selection of most economical KW / voltage combination on page 7.
b- In order to manage the energy resources properly and provide the best comfort,
Thermolec recommends specifying a proportional control at all times.
ON/OFF Room Thermostats
24 volts wall thermostat, ON-OFF type with built-in thermometer and adjustable heat anticipator.
1 stage 2 stages
1 and 2 stages
T874 Honeywell
1F30W-301 (1 stage) and 1F37-408 (2 stages) - White-Rodgers
THREE EASY STEPS
T86 Honeywell