WattMaster MUA II - Manual (Page 23)

Technical Guide
MUA II Controller
23
Sequence of Operations
Internal Trend Logging
The MUA II Controller continuously maintains an Internal Trend Log
which records a fi xed set of values at an interval programmed by you.
These values can be retrieved only with the Prism graphical front-end
program. If you don’t have the Remote Communications option with a
front-end program, you do not have access to these logs.
There are 120 log positions available. Once the last (120th) position
has been recorded, the log jumps back to the fi rst position and begins
overwriting the old data. This means you are required to retrieve the logs
at an interval that is shorter than the duration of the last 120 logs.
Shown below are some log intervals and the duration of 120 logs.
1-Minute Interval = 2-Hour Duration
15-Minute Interval = 30-Hour Duration
30-Minute Interval = 60-Hour Duration
60-Minute Interval = 120-Hour Duration
The fi xed items in the log are listed below:
Date
Time
Supply Air Temperature
Outside Air Temperature
Supply Air Setpoint
Outdoor Air Humidity
Dewpoint Setpoint
Onboard Relay Status (BIT Pattern)
Expansion Board Relay Status (BIT Pattern)
External Heat (% of Max Heat)
These items and values are explained in greater detail in the Prism
Graphical Communications Interface Technical Guide.
Force Modes or Overrides
The MUA II Controller relay outputs can be user-overridden if the Modu-
lar Service Tool or the Prism graphical front-end program is available.
The modes of operation for the relays are:
0 = Auto (Normal Operation)
1 = Forced ON
2 = Forced OFF
The analog outputs are forced if you specify a value between 0.0 and
10.0 VDC. To cancel the force mode, enter a value less than zero (-1.0
VDC).
When the analog outputs are forced, the display on the Modular Service
Tool or front-end can be interpreted as the actual voltage. During normal
operation, the display indicates the percentage signal applied based on
the user-defi ned voltage limits. For example, if you defi ne a 2.0 VDC to
10.0 VDC range, then 50% would be 6.0 VDC instead of the 5.0 VDC
applied when the range is 0.0 VDC to 10.0 VDC.
As mentioned, force modes can only be activated with an attached remote
communications device described previously. Furthermore, the override
condition can only remain in effect as long as the remote device is con-
nected and communicating with the unit. That means that you cannot set
an override condition and then “walk away” from the equipment with
the override still active. The loss of communications or the removal of
the remote interface will automatically terminate the override within
10 minutes. This is to protect the equipment and to prevent an override
condition from remaining active indefi nitely, resulting in ineffi cient
operation of the equipment.
Caution: No equipment protection is available during the
force mode of operation. That means you could
start a compressor without running the fan or
create other conditions that WILL damage the
HVAC equipment. WattMaster Controls, Inc.
assumes no responsibility or liability for the
misuse of these user overrides that cause
damage to the HVAC equipment!