McQuay TGZ 040A User Manual

OMM TGZ-1 TGZ 040A through TGZ 190A 47
Compressor Start/Stop Timing
This section determines when to start or stop a compressor. There are two separate
functions used, one for staging up and one for staging down.
Stage Up Now
The Stage Up Now flag is set based on the following tests:
If Unit mode = Cool AND
no compressors are running AND
LWT error > Start delta + 0.5 * Control Band AND
Motor Protect Timer expired AND
Stage up timer expired THEN
Stage Up Now = True
If Unit Mode = Cool AND
At least one compressor is running AND
LWT error > 0.5 * Control band AND
Pulldown rate <= Max pulldown rate AND
Compressors running < unit capacity limit AND
Stage up timer expired THEN
Stage Up Now = True
If Unit mode = Heat AND
no compressors are running AND
LWT error > Start delta + 0.5 * Control Band AND
Motor Protect Timer expired AND
Stage up timer expired THEN
Stage Up Now = True
If Unit Mode = Heat AND
At least one compressor is running AND
LWT error > 0.5 * Control band AND
Pulldown rate <= Max pulldown rate AND
Compressors running < unit capacity limit AND
Stage up timer expired THEN
Stage Up Now = True
Stage Down Now
The Stage Down Now flag is set based on the following tests:
If Unit Mode = Cool AND
LWT error < -0.5 * Control band AND
More than one compressor running AND
Stage down timer expired THEN
Stage Down Now = True
If Unit Mode = Cool AND
LWT error < (-0.5 * Control band - stop delta) AND
One compressor running AND
Stage down timer expired THEN
Stage Down Now = True

McQuay TGZ 040A Specifications

General

Brand	McQuay
Model	TGZ 040A
Category	Water Heater
Language	English