PAYNE-NIST Sprayed Coil Liquid Defrost Air Handler SEQUENCE OF OPERATIONS 210112b.pdf

SPRAYED COIL, GLYCOL SUMP AIR HANDLER SEQUENCE OF OPERATIONS

Abbreviations

AI analog input (VDC, mADC) AO analog output AV analog value (Engineering units normally)

BAS building automation system BI binary input BO binary output BV binary value (ON/OFF, 0/1)

CWV sump cold water supply (fill) valve

DB dry-bulb temperature DP dewpoint temperature

EDH electric duct heater

HWV sump hot water supply (fill) valve

LLMV local loop 3-way mixing valve

NDV sump no-frost drain valve NFV sump no-frost supply (fill) valve NOV sump no-frost overflow valve

SDV sump sanitary sewer drain valve

This environmental chamber is to maintain fine control of dry-bulb (DB) and dew-point (DP) temperatures for room dry-bulbs ranging from 0F to 150F utilizing a sprayed coil air handling unit. The controls for the chamber shall be a modern, BACNet Compliant, digital control system accessible from a NIST network. All modes of operation require ON/OFF control of the chamber chiller and main brine loop pump, and setting/verifying of the chamber chiller system’s main brine loop supply temperature setpoint.

Any non-normal operating condition or equipment failure(s) shall cause an ALARM condition which shall be annunciated at the Building Automation System (BAS). The BAS shall allow the user to program appropriate actions for various alarm conditions that shall shut down the environmental chamber in a controlled manner so as not to damage pumps, electric heaters, or other room/building infrastructure. Further, the BAS shall allow the user to communicate alarms via email, text messages, and/or voice messages to a hierarchical list of recipients. The hierarchical list of recipients shall be notified, in order and repeatedly, until at least one recipient acknowledges the alarm by giving an appropriate response to the emergency shutdown message sent by the chamber BAS.

ALL OPERATIONS of the chamber shall be contingent on TWO SAFETY SYSTEMS:

1) WATCHDOG SAFETY SYSTEM:

A. HARDWARE WATCHDOG: A watchdog timer (physical piece of hardware) shall be periodically reset by the BAS after no more than X minutes (adjustable value, default of 10 minutes). A failure to reset the watchdog timer will KILL OPERATIONS (turn off chamber fan, local loop circulation pump, and EDH; close SDV, NDV, HWV, CWV, NFV).

B. REMOTE CONTROL WATCHDOG: The chamber shall also have a software-based watchdog timer for use with a remote control system (normally a data acquisition and control system for the unit being tested in the chamber). This watchdog shall be optionally enabled through the BAS GUI. The BAS will monitor a dry-contact closure and initiate an automatic SHUTDOWN (turn off local loop circulation pump; close SDV, NDV, HWV, CWV, NFV and turn off EDH and turn off chamber fan after one minute) if the contact is not made after X minutes (adjustable value, default of 10 minutes).

2) REDUNDANT SAFETY SYSTEM: A redundant safety system consisting of a relay(s) that must be closed for normal operation of the chamber shall be installed in a convenient location or with the existing chamber controllers. Upon relay opening a KILL OPERATIONS action is initiated; the relay opens when chamber space temperature is too high, chamber space temperature is too low, sump liquid leak sensor activates, local loop pump liquid leak sensor activates, when a new E-STOP button is pressed (installed at door entering chamber) or when the contractor-provided normally closed dry-contact input is opened (the contractor shall install the contact as closed with a removable jumper). The temperature sensors used shall be separate from the chamber control sensors and adjustable for the high and low temperature cutout. Leak sensors shall also be separate from the normal chamber control system. The leak sensors shall have a time-delay on-break of X minutes (default value 5 minutes) to eliminate nuisance trips. The chamber control system may monitor the safety system sensors, but these safety system sensor signals shall not depend on the BAS controller to initiate a shutdown signal.

The contractor shall provide means for visual indication of what sensor(s) opened the redundant safety system relay. Lamp indicators (red LED lamps located together) shall be provided within the chamber control area (entrance from control room to the chamber) to indicate (solid red glow) which sensor tripped the redundant safety system relay. The contractor shall provide means to reset the redundant safety system in two ways: 1) using the BAS GUI, and 2) manual pushbutton on the control enclosure.

Two modes of operation are to be programmed within the BAS for the control of the environmental chamber dry-bulb (DB) and dewpoint (DP) space temperatures:

1. AUTOMATIC MODE: the automatic mode is set up from a graphical user interface (GUI) residing on the BAS server. The automatic mode of operation allows the user to select CONTINUOUS OPERATION or a SHUTDOWN TIMER RUNMODE. In the shutdown timer runmode, a selected number of minutes (0 to infinity) shall elapse; after this countdown reaches zero, the chamber will automatically shutdown in a safe and predefined manner.

Three modes of DB and DP control shall be programmed in the AUTOMATIC MODE of chamber operation: High DP and DB Chamber Control, No DP Chamber Control and Low DP and DB Chamber Control.

A. HIGH DP and DB Chamber Control Mode: When dewpoint temperatures will be maintained above (40°F), the chamber user shall select the high DP&DB chamber control mode. The BAS chamber control system shall warn the user (prompt them with a message) if this mode of operation is selected and the dewpoint setpoint temperature is at or below 40°F; if dewpoint setpoint is 40°F or below, the user may need to change the mode to Low DP and DB Chamber Control Mode. The sequence of operations is as follows given the chamber user’s input of required DB and DP space temperatures:

1. Chamber chiller is turned ON along with the main brine loop pump (ON) and main brine loop supply temperature setpoint (AV) is updated or verified. User must note (put this in an info click button that will pop up if the user wants more info) that the main brine loop setpoint temperature must be lower than the space dewpoint temperature; a good rule is to set the main brine loop supply temperature at least 10°F lower than the required chamber space dewpoint temperature.

2. Prompt the user “WATER FILL WILL BEGIN, DRAIN NO-FROST or PRESS OK TO CONTINUE”. This prompt hopes to prevent mixing of water and no-frost if possible. User now can place the appropriate drain valve in HAND mode and direct the sump fluid to the appropriate drain: sewer drain if sump fluid is water, storage tank if sump fluid is no-frost. User must press an OK button to continue.

3. Sump water drain valve is CLOSED. Sump no-frost drain valve and no-frost overflow valve are CLOSED.

4. Sump hot water supply (HWV) and cold water supply (CWV) valves are set at 100% OPEN to fill the sump. Sump

HWV and CWV are set at 0% OPEN when sump level sensor indicates 75% (or full sump). If HWV and CWV stay OPEN for more than X minutes (sump fill valve startup timeout (AV)), HWV and CWV set at 0% while prompting the user that the SUMP FILL HAS FAILED. User must press a continue or OK button before startup continues.

5. Sump spray pump is turned ON. Sump spray pump is interlocked with sump level sensor to not operate when sump level is below X% (sump level limit for spray pump (AV)).

6. Supply fan is turned ON (supply fan on/off interlocked with safe duct static pressure). Electric duct heater (EDH) ENABLE is interlocked with supply fan status. EDH begins PID control of the chamber space DB temperature.

7. Local loop mixing valve (LLMV) is set at a X% (LLMV high dewpoint startup setpoint(AV)) at startup. Local loop pump is turned ON.

8. Wait a predetermined number of minutes (default 10 minutes) before LLMV PID control begins. LLMV does PID control of the chamber space dewpoint temperature.

9. If LLMV reaches 10% open and chamber dewpoint is LOW, increase the sump temperature setpoint by 1°F (under PID control of HWV). If LLMV reaches 90% open and chamber dewpoint is HIGH, decrease sump temperature setpoint by 1°F. After any change in sump temperature setpoint wait X minutes (sump temp reset delay time (AV)) before making another automatic adjustment to the sump temperature setpoint. If HWV reaches 0% or 100% for longer than X minutes (HWV limit maximum time (AV)), prompt user that “main brine supply temperature may need adjustment;

0% operating HWV means greater than 90% LLMV and the user should lower main brine supply temperature (suggested decrease 2 °F) while 100% operating HWV means 0% LLMV and the user should increase main brine supply temperature (suggested increase 2 °F)”. Don’t prompt user to adjust main brine setpoint again for 30 minutes;

they should have fixed the problem in this amount of time.

10. Chamber reaches desired DB and DP space temperatures.

11. SAFE Shutdown Sequence: sump spray pump OFF, EDH enable OFF, EDH 0%, NFV 0%, HWV 0%, CWV 0%, delay 1 minute, supply fan OFF, local loop pump OFF, LLMV 0%, and prompt user to “Drain sump or leave liquid in sump. Check that only water is drained to sewer (don’t drain No-Frost to sewer)”. User must press a OK button to close the prompt.

B. No DP Control Mode: If the user selects this mode of operation, the chamber space dewpoint temperature will not be directly controlled.

1. Chamber chiller is turned ON along with the main brine loop pump (ON) and main brine loop supply temperature setpoint (AV) is updated or verified. User must note (put this in an info click button that will pop up if the user wants more info) that the main brine loop setpoint temperature must be lower than the space dry-bulb temperature; a good rule is to set the main brine loop supply temperature at least 10°F lower than the required chamber space dry-bulb temperature.

2. Prompt the user to drain the sump to the appropriate drain; water to sanitary sewer and no-frost to the no-frost drain.

Prompt the user to press a VERIFY SUMP DRAIN STATUS button to continue. User may leave liquid in the sump if they like, or they may want to drain the sump.

3. Supply fan is turned ON (supply fan on/off interlocked with safe duct static pressure). Electric duct heater (EDH) ENABLE is interlocked with supply fan status. EDH begins PID control of the chamber space DB temperature.

4. Local loop mixing valve (LLMV) is set at a predetermined value (0 to 100%) at startup. Local loop pump is turned ON. LLMV does PID control of the coil inlet brine temperature which is automatically set at a predetermined temperature (local loop brine temperature setpoint (AV)) 5°F lower than the chamber space dry-bulb setpoint; this setpoint temperature is user adjustable at any time, but an automatic preset to 5°F lower is preferred.

5. If the LLMV reaches 5% (or below) or 95% (or higher), prompt the user that the main brine loop supply setpoint temperature may need adjustment. Prompt user that “main brine supply temperature may need adjustment; greater than 95% LLMV means the user should lower main brine supply temperature (suggested decrease 2 °F) while 95% LLMV means the user should increase main brine supply temperature (suggested increase 2 °F)”. User must press an OK button to continue; don’t prompt again for 30 minutes. User must press an OK button to continue; don’t prompt again for 30 minutes.

6. Chamber reaches desired DB temperature.

7. SAFE Shutdown Sequence: sump spray pump OFF, EDH enable OFF, EDH 0%, NFV 0%, HWV 0%, CWV 0%, delay 1 minute, supply fan OFF, local loop pump OFF, LLMV 0%, and prompt user to “Drain sump or leave liquid in sump. Check that only water is drained to sewer (don’t drain No-Frost to sewer)”. User must press a OK button to close the prompt.

C. Low DP and DB Chamber Control: If the user selects this mode of operation, the chamber dewpoint temperature setpoint shall be controlled using the no-frost glycol sump spray system to keep the cooling coil frost free. If the user selects this mode and sets the chamber space dewpoint above 40F, the BAS shall warn the user that the High DP and DB Chamber Control Mode should be selected.

1. Chamber chiller is turned ON along with the main brine loop pump (ON) and main brine loop supply temperature setpoint (AV) is updated or verified. User must note (put this in an info click button that will pop up if the user wants more info) that the main brine loop setpoint temperature must be lower than the space dewpoint temperature; a good rule is to set the main brine loop supply temperature at least 15°F lower than the required chamber space dewpoint temperature in this mode.

2. Verify that the sump level sensor is at 0%; if sump level is not at 0%, prompt the user to drain the sump to the appropriate outlet (no-frost or sanitary sewer for water only) or select CONTINUE NO-FROST FILL. Put this in an info popup if the user wants more info, “NOTE: Specific Gravity of the no-frost supply must be at least 30% lower than the specific gravity of the sump mixture at the chamber dewpoint setpoint. The contractor shall integrate the existing no-frost concentration system control into the BAS.

3. Sump water drain valve is CLOSED. Sump no-frost drain valve is CLOSED. Sump no-frost overflow valve is OPENED.

4. Sump no-frost supply valve (NFV) is set at 100% OPEN to fill the sump. Sump NFV set at 0% OPEN when sump level sensor indicates 75% (or full sump).

5. Sump spray pump is turned ON. Sump spray pump is interlocked with sump level sensor to not operate when sump level is below X% (sump level limit for spray pump (AV)).

6. Supply fan is turned ON (supply fan on/off interlocked with safe duct static pressure). Electric duct heater (EDH)

ENABLE is interlocked with supply fan status. EDH begins PID control of the chamber space DB temperature.

7. Local loop mixing valve (LLMV) is set at a predetermined value (local loop mixing valve startup position for low-DP-mode (AV)) at startup. Local loop pump is turned ON. LLMV does PID control of the chamber space dewpoint temperature.

8. Wait a predetermined number of minutes (default 10 minutes) before NFV valve PID control begins. NFV valve does PID control of the sump liquid specific gravity (SG). The NFV OPENS to lower the sump SG and the CWV OPENS to increase the sump SG. The CWV valve only OPENS to increase SG if the NFV valve has remained closed for a predetermined number of minutes (no-frost fill valve 0% low DP time limit (AV)) and the sump SG is LOW. The CWV valve and the NFV valve are never allowed to be open at the same time; when the CWV valve must open to increase the SG, the NFV valve must be 0% open as the CWV valve does PID control to increase the SG to the setpoint. The control of the NFV and CWV must be programmed to prevent oscillations of opening and closing between the NFV and CWV when the SG is near the SG setpoint: this could be done by setting a “SG Deadband %” which would close the NFV and CWV after X min of operation when the SG is within X% of the SG setpoint. As long at the SG is withing the SG deadband %, no PID control by the NFV or CWV should be allowed. Note that normal operation of the system removes moisture from the circulating air and thus the SG will increase during operation.

9. If the NFV valve remains at 100% for more than a predetermined number of minutes (default 10 min) and the SG is still too high, prompt the user with a NO-FROST CONCENTRATION TOO LOW, ADJUST CONCENTRATOR SYSTEM. User must press an OK button to acknowledge this message. NFV set to 0% and wait placed in OFF MODE. Prompt the user with NO-FROST FILL TURNED OFF, TURN BACK TO AUTO WHEN PROBLEM IS

RESOLVED.

10. Chamber reaches desired DB and DP space temperatures.

11. SAFE Shutdown Sequence: sump spray pump OFF, EDH enable OFF, EDH 0%, NFV 0%, HWV 0%, CWV 0%, delay 1 minute, supply fan OFF, local loop pump OFF, LLMV 0%, and prompt user to “Drain sump or leave liquid in sump. Check that only water is drained to sewer (don’t drain No-Frost to sewer)”. User must press a OK button to close the prompt.

All analog values and analog outputs shall have the HOA functionality; if set to the HAND mode, the user may enter a value that remains constant and does not alter due to PID control or programmatic changes. The HOA functionality does not use OFF, the AV or AO should be either HAND or AUTO while in the automatic mode of operation.

2. MANUAL MODE: the manual mode is setup from a graphical user interface (GUI) residing on the BAS server. The manual mode of operation allows the user to place all outputs in a HAND MODE (ON), OFF, or AUTO; HOA function on all outputs. The BAS shall continue to reset the HARDWARE WATCHDOG in the MANUAL MODE. The user may set ALARM values for all inputs.

The user may select ALARM and SHUTDOWN values for all outputs. The GUI should follow some tabular format similar to the format given in Fig. 1, Fig. 2, and Fig. 3. The manual mode GUI should have a SHUTDOWN Button in a conspicuous location at the top of the page. If the shutdown button is ON, all outputs shall be placed in their designated SHUTDOWN positions. If the SHUTDOWN button is OFF, the user should be able to manually manipulate the outputs via the HOA switch functionality and/or by entering a value. If the user toggles from the AUTOMATIC MODE GUI to the MANUAL MODE GUI and turns the SHUTDOWN to ON, the system shall initiate a SAFE Shutdown Sequence. A SHUTDOWN button should also be provided on the AUTOMATIC MODE GUI. If the SHUTDOWN is turned ON, the user shall be prompted with SAFE SHUTDOWN UNDERWAY, PLEASE WAIT FOR SHUTDOWN TO COMPLETE. This notification shall be acknowledged by the user by pressing an OK button.

Figure 1: Air handler air flow in manual mode

Figure 2: Electric duct heater, chamber space dry-bulb temperature control in manual mode

Note – the selection of HIGH, LOW, or NO DP control should be exclusive, e.g. use a radio button that restricts user to just one choice.

Figure 3: Sump liquid control and coil temperature control in manual mode

List of Controlled Points and Programmatic Values (contractor will likely need to add values to this list)

Air Handler Air Flow System AO: supply fan on/off BI: supply fan status

AO: supply air duct damper position (0-100% open) AO: return air duct damper position (0-100% open) AO: mixing air duct damper position (100-Supply % open) AV: damper setting (sets position of all three dampers)

AI: supply air dewpoint temperature AI: sprayed coil exit air dry-bulb temperature

AI: supply fan differential air static pressure AI: supply fan exit air (duct) static pressure AI: filter assembly differential air static pressure

Electric Duct Heater System BO: EDH enable (on/off) AO: EDH value (0-100%)

AV: chamber space air dry-bulb temperature setpoint AI: chamber space air dry-bulb temperature AI: supply air dry-bulb temperature AI: return air dry-bulb temperature

Sprayed Coil and Sump Liquid System AV: chamber space air dewpoint setpoint temperature AI: chamber space air dewpoint temperature AI: return air dewpoint temperature

AV: sump specific gravity setpoint AI: sump specific gravity AI: sump temperature reset delay time (min)

AV: local loop brine temperature setpoint (coil inlet brine setpoint temperature) AI: local loop brine temperature (coil inlet) AO: local loop mixing valve position (0-100%) BO: local loop circulation pump on/off BI: local loop circulation pump status AV: local loop mixing valve startup position for high-DP-mode AV: local loop mixing valve startup position for no-DP-mode AV: local loop mixing valve startup position for low-DP-mode

AI: sump liquid level (0-100% full) AO: sump hot water fill valve (0-100% open) AV: sump hot water fill valve at limits maximum time (min) AO: sump cold water fill valve (0-100% open) AO: sump no-frost glycol solution fill valve (0-100% open) AV: no-frost fill valve 0% low DP time limit (min) AV: sump fill valve startup timeout (min) AV: sump level limit for spray pump (% full)

BO: sump water drain valve on/off BO: sump no-frost drain valve on/off BO: sump no-frost overflow valve on/off

Hardware Specifications LIST

Spring Return (Normally closed), proportional HWV, CWF, and NFV Spring Return (Normally Closed), ON/OFF (two-position) NDV and SDV