Service Manual

1Service

Table 1-1(continued from previous page) Sequence of Operation

 

 

OPERATION

 

 

DISPLAY

 

 

8. If the space heating call for heat is active, and the tank

 

thermostat or sensor starts a DHW call for heat, the boiler will

 

switch to the DHW mode. If programmed for normal DHW

 

operation (not as a zone), the DHW pump will turn on first, then

 

the

boiler

pump

will

turn

off 2

seconds later.

 

This will divert the boiler’s outlet water from the heating system

 

and

send

it

to

the

tank

coil

instead.

 

The control will then modulate to maintain the outlet

 

temperature to the DHW boiler set point.

 

 

 

 

 

9. If the boiler is not part of a Cascade, and both the space heating

 

and DHW calls for heat remain active long enough, the boiler will

 

switch back and forth between the two heating modes until one

 

of them is satisfied.

 

 

 

 

 

 

 

 

10. Once both calls for heat are satisfied, the control will turn off the

 

burner. The blower will continue to run during a 10 second

 

postpurge.

 

 

 

 

 

 

 

 

 

11. Any pumps that are running will continue to run for their

 

respective pump delay times before turning off, unless

 

programmed

to

 

remain

on

continuously.

 

A 60 second anti-cycle period will start, which will delay any

 

new call for heat until it times out.

 

 

 

 

 

 

 

 

12. In Standby, ready to start a new cycle.

 

 

 

 

 

 

 

 

 

 

 

 

12

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Lochinvar 400 - 801 service manual From previous page Sequence of Operation