Weil-McLain PER 550-141-396/0801 - Manual (Page 5)

Part number 550-141-396/0801 5
PER Series 3 Electric-Hydronic Boilers Installation Instructions
Sequence of operation
Call for heat
1. The thermostat contacts close, energizing the first contactor (2K), the circulator relay
(1K), and the heater in the first thermal time delay (H1).
2. Approximately 15 seconds later, the thermal delay contacts (1C) close energizing the
electronic circuit inside the first electronic time delay (ED1).
3. After approximately 2.5 minutes, the first electronic time delay energizes the second
contactor (3K) and the second thermal time delay heater (H2).
4. This sequence continues until all contactors are energized or until the call for heat ends.
Call for heat satisfied
5. The thermostat contacts open, de-energizing the first contactor (2K), the circulator relay
(1K), and the heater in the first thermal time delay (H1).
6. After a minimum of 10 seconds, the contacts in the first thermal delay (1C) open, instantly
de-energizing the electronic time delay (ED1), the second contactor (3K), and the second
thermal delay heater (H2).
7. This sequence continues until all elements are de-energized.
Limit control operation
8. If the high limit setting is exceeded, the transformer secondary circuit is opened and all
contactors are de-energized instantly. It is recommended that the “high” side of the control
be set at 220
° F. The “low” side should be set according to the design requirements of the
structure to be heated but never less than 20 ° F below the “high” setting. The differential
control should be set at a minimum of 20 ° F.