Monday, October 31, 2011

Honeywell LG1093AA26 Turbine Flame Sensor From DtiCorp.com


Honeywell LG1093AA26 Turbine Flame Sensor (replaces Honeywell LG1093AA04) - GE Part Number 261A1812P013.



Industrial power generation gas turbine installations demand the superior protection provided by the Honeywell UV Flame Monitoring System. The Honeywell flame monitor system detects the ultraviolet radiation emitted by a hydrocarbon flame and produces an output signal to indicate a flame or no-flame condition. This system has delivered proven performance on General Electric (and GE licensee) gas turbines for more than 35 years. Land-based and off-shore applications include power generation, pumping stations, shipboard power generation among other industrial uses. A variety of sensors types, amplifier types and sensor cable lengths are available.



Flame monitoring of a burner has comprised the use of thermocouples, expansion tubes, and radiation sensors. Due to the extremely high flame temperatures in process boilers, monitoring of boiler flames in large furnaces has been done mainly with remotely located radiation sensors or sonic microphone pickups, which detect the frequency of the flame.


Although the radiation sensor circumvents the problem of placing a sensor in the region of high flame temperature, it has shortcomings such as the inability to differentiate between flame radiation and radiation from the heated boiler or furnace wall regions. Thus, the flame may be extinguished and the flame detector will fail to respond. The fuel supply to the burners will continue to be discharged onto the hot furnace walls. This time lag between loss of flame and shut down of the fuel supply can cause an explosion.


There are specialized radiation sensors which sense ultraviolet radiation and others which generate signals corresponding to the amplitude of the high frequency flicker of the flame monitored. The sensors can distinguish between flame radiation and background radiation since both ultraviolet and flickering radiation find a source of excitation exclusively in the flame. The use of a flickering type radiation sensor produces an output signal that is continuously fluctuating. The fluctuation may be hard to distinguish, and the problem becomes one of accurate detection of this fluctuation.




Sensors are positioned to converge and the radiation magnitude received by the individual sensors is similar. A circuit means subtracts the output signals of the individual sensors of the pair, the steady and slowly varying components of flame radiation from the flame are effectively canceled leaving the rapidly varying difference signal for flame detection. The high frequency flame flickering is due to random pulses or burst of radiation from very localized sources in the flame, and there will always be a residual, varying component from the dual sensor system as long as the flame is present.



Features:


- High sensitivity with fast response time (0.1 sec typical)

- Amplifiers support multiple voltage requirements: 28 Vdc, 20-35 Vdc, and 115 Vac.

- Operating distances up to 1000 feet, sensor to amplifier.

- Available with Factory Mutual approval for explosive atmospheres.

- Available with European Directive CE mark for EMC 89/336/EEC, LVD 73/23/EEC and ATEX Explosive Atmosphere 94/9/EC.

- Qualified component on General Electric turbines.


Specifications:



- Geiger Mueller-type sensor phototube. Detects ultra-violet band and 1800 – 2600 angstroms. “Solar blind” and tolerant to black body radiation.

- Two-year shelf-line, 10,000 hours MTBF with over one billion operating hours.

- Mounting Interface: 3/4 inch internal NPT.

- Control Panel Connection: Teflon shielded cable with one inch external conduit thread.

- Operating Temperature: -40°F to +350°F.


- Window Pressure Rating: 150 psig at 400°F.


- Special Certifications:


- Factory Mutual: Explosion Proof Class I, Divisions 1 and 2, Groups B, C and D

- CE Mark: EMC Directive 89/336/EEC, ATEX Directive 94/9/EC, II 2G, EEx d IIA T3 or EEx d IIC T3 Models

AA34/35/36/44/45/46

- Cable Lengths:

- AA24/AA34: 16ft (4.9m)

- AA25/AA35: 42ft (12.8m)

- AA26/AA36: 61ft (18.6)






Honeywell LG1093AA24 Turbine Flame Sensor From DtiCorp.com


Honeywell LG1093AA24 Turbine Flame Sensor (replaces Honeywell LG1093AA04) - GE Part Number 261A1812P012.



Industrial power generation gas turbine installations demand the superior protection provided by the Honeywell UV Flame Monitoring System. The Honeywell flame monitor system detects the ultraviolet radiation emitted by a hydrocarbon flame and produces an output signal to indicate a flame or no-flame condition. This system has delivered proven performance on General Electric (and GE licensee) gas turbines for more than 35 years. Land-based and off-shore applications include power generation, pumping stations, shipboard power generation among other industrial uses. A variety of sensors types, amplifier types and sensor cable lengths are available.



Flame monitoring of a burner has comprised the use of thermocouples, expansion tubes, and radiation sensors. Due to the extremely high flame temperatures in process boilers, monitoring of boiler flames in large furnaces has been done mainly with remotely located radiation sensors or sonic microphone pickups, which detect the frequency of the flame.



Although the radiation sensor circumvents the problem of placing a sensor in the region of high flame temperature, it has shortcomings such as the inability to differentiate between flame radiation and radiation from the heated boiler or furnace wall regions. Thus, the flame may be extinguished and the flame detector will fail to respond. The fuel supply to the burners will continue to be discharged onto the hot furnace walls. This time lag between loss of flame and shut down of the fuel supply can cause an explosion.


There are specialized radiation sensors which sense ultraviolet radiation and others which generate signals corresponding to the amplitude of the high frequency flicker of the flame monitored. The sensors can distinguish between flame radiation and background radiation since both ultraviolet and flickering radiation find a source of excitation exclusively in the flame. The use of a flickering type radiation sensor produces an output signal that is continuously fluctuating. The fluctuation may be hard to distinguish, and the problem becomes one of accurate detection of this fluctuation.




Sensors are positioned to converge and the radiation magnitude received by the individual sensors is similar. A circuit means subtracts the output signals of the individual sensors of the pair, the steady and slowly varying components of flame radiation from the flame are effectively canceled leaving the rapidly varying difference signal for flame detection. The high frequency flame flickering is due to random pulses or burst of radiation from very localized sources in the flame, and there will always be a residual, varying component from the dual sensor system as long as the flame is present.



Features:


- High sensitivity with fast response time (0.1 sec typical)

- Amplifiers support multiple voltage requirements: 28 Vdc, 20-35 Vdc, and 115 Vac.

- Operating distances up to 1000 feet, sensor to amplifier.

- Available with Factory Mutual approval for explosive atmospheres.

- Available with European Directive CE mark for EMC 89/336/EEC, LVD 73/23/EEC and ATEX Explosive Atmosphere 94/9/EC.

- Qualified component on General Electric turbines.


Specifications:



- Geiger Mueller-type sensor phototube. Detects ultra-violet band and 1800 – 2600 angstroms. “Solar blind” and tolerant to black body radiation.

- Two-year shelf-line, 10,000 hours MTBF with over one billion operating hours.

- Mounting Interface: 3/4 inch internal NPT.

- Control Panel Connection: Teflon shielded cable with one inch external conduit thread.

- Operating Temperature: -40°F to +350°F.


- Window Pressure Rating: 150 psig at 400°F.


- Special Certifications:


- Factory Mutual: Explosion Proof Class I, Divisions 1 and 2, Groups B, C and D

- CE Mark: EMC Directive 89/336/EEC, ATEX Directive 94/9/EC, II 2G, EEx d IIA T3 or EEx d IIC T3 Models

AA34/35/36/44/45/46

- Cable Lengths:

- AA24/AA34: 16ft (4.9m)

- AA25/AA35: 42ft (12.8m)

- AA26/AA36: 61ft (18.6)








HONEYWELL EG1033AC01 Flame Sensor





HONEYWELL EG1033AC01 Flame Sensor.



Industrial power generation gas turbine installations demand the superior protection provided by the Honeywell UV Flame Monitoring System. The Honeywell flame monitor system detects the ultraviolet radiation emitted by a hydrocarbon flame and produces an output signal to indicate a flame or noflame condition. This system has delivered flawless performance on General Electric (and GE licensee) gas turbines for more than 35 years. The Honeywell system is currently used on gas turbines used for land-based and off-shore power generation, pumping stations, shipboard power generation and various other industrial applications. A variety of sensor types, amplifier types and sensor cable lengths are available.




Thursday, October 27, 2011

4 Honeywell R7795 Relay Modules from DtiCorp.com

Fort Lauderdale, FL - Popular Honeywell online retailer DtiCorp.com (http://www.DtiCorp.com)
is introducing 4 brand new Honeywell R7795 Electromechanical Relay
Modules. Provide solid state, electronic flame safeguard protection for
commercial and industrial single or dual fuel burners. Include flame
signal amplifiers that are color-coded: purple for ultraviolet and green
for rectification.

 

Features:


 - Include flame signal amplifiers that are color-coded: purple for ultraviolet and green for rectification.


- Require a plug-in prepurge timer of 1.5, 7, 10, 30, 60, or 90 seconds.

- Mount on a Q795A Wiring subbase with two captive screws.

- Include line voltage airflow switch to prove airflow from the start of prepurge through the run period.


- Prevent start-up with lockout if flame or a flame simulating failure exists.

 

 

 

Specifications:

 

 


- Integral solid state color-coded flame amplifiers: R7795A,C for
ultraviolet detection systems (purple) and R795B,D for rectification
detection systems (green).

- Solid state plug-in ST95A Purge Timers provide prepurge timings of 1.5, 7, 10, 30, 60, or 90 seconds.


- Includes terminals for connection of a line voltage airflow switch to
prove airflow from the start of prepurge through the run period.


- Mounts on a Q795A Subbase with two captive screws. All electrical
connections are automatically provided between the device and subbase.
Wiring terminals are accessible for testing.

- Meter jack on amplifier board for measuring flame signal with system in operation.

- Internal light-emitting diode (LED) indicates presence of flame signal.


- Field selectable ten or four second trial for pilot flame ignition.

- Powered alarm terminal to operate an external line voltage alarm on safety lockout.

- R7795 models are available with either intermittent pilot (interrupted ignition) or interrupted pilot and delayed main valve.


- Run-Test switch on interrupted pilot/delayed main valve models.

- Safe-start feature prevents start-up with lockout if flame or a flame simulating failure exists.

- Recycle or lockout on flame failure is field selectable.


- Safety switch must be manually reset after lockout.

- Meets Underwriters Laboratories, Canadian Standards Association, and Factory Mutual Approved standards.

 

 


Models available:

 

 

- R7795A1001

 

- R7795B1009

 

- R7795C1007

 

- R7795D1005

 

 

 

About Us: DtiCorp.Com (http://www.DtiCorp.com)
carries more than 35,000 HVAC products, including industrial,
commercial and residential parts and equipment from Honeywell, Johnson
Contols, Robertshaw, Jandy, Grundfos, Armstrong and more. Our online
catalog is easy to navigate and search, and all products have a picture
and a description. If a customer has any questions about a product, they
can call 800-757-5999 and speak with one of our product experts. Our
mission is to offer the best prices anywhere to our customers.



Julian Arhire
Manager DtiCorp.com
Phone: 954.484.2929
Fax: 954.484.5155
Web: http://www.DtiCorp.com

 

###

Wednesday, October 19, 2011

DtiCorp.com Is Introducing 8 Honeywell RA890F Electromechanical Relay Modules

Fort Lauderdale, FL – Popular Honeywell online retailer DtiCorp.com (http://www.DtiCorp.com) is introducing 8 brand new  Honeywell RA890F Electromechanical Relay Modules. The RA890F Protectorelay Primary Control is a nonprogramming, amplifying relay that provides solid state electronic flame safeguard protection for industrial and commercial gas, oil, or combination gas-oil burners.


 


 


The flame current check is the best indicator of proper flame detector application. Perform the check at the time of installation, at any time service is done on the system, and at least once a month or more often while the system is in operation. This prevents shutdowns due to poor flame signal. Perform test by connecting a W136 (or equivalent) microammeter in series with the flame detector and reading the flame signal while the burner is operating. Insert a 196146 Meter Connector Plug, wired color-tocolor to the W136A leadwires, into the test jack on the RA890F. This automatically puts the microammeter in series with the flame detector. If a meter connector plug is not available, disconnect the flame detector lead from the F terminal; then connect this lead to the Black lead of the microammeter, and connect the Red lead of the microammeter to the F terminal. When reading the flame current, assure the following criteria are met: 1. The flame current is steady; meter does not vary more than a needle width. 2. The flame current is at least two microamperes for a rectification type detector like used with the RA890F. The normal operating range is 2 to 5 microamperes.


 


 


 



Features:


 


- Uses rectification principle of electronic flame detection.


- Replaces RA890E in most applications and mounts on same Q270A1024 Subbase.


- Recycles if flame signal lost while in Run. Failure to establish pilot results in a lockout.


- Safe-start check prevents start-up if flame-simulating failure occurs in flame detector circuit.


- Includes built-in protection against ignition crossover in flame rod systems.


- Includes SPDT alarm contacts.


- Solid state circuitry.



- Mounts and removes easily through use of captive mounting screws.


- Mounting base is made of strong thermoplastic.


 


 


Specifications:


 


 


- Install the RA890F where the surrounding temperatures remain within the Ambient Operating Temperature Ratings listed in the SPECIFICATIONS section.


- Install the RA890F where the relative humidity never reaches the saturation point. Condensation of moisture on the RA890F may cause enough leakage to short the flame signal to ground and prevent the burner from starting.


- Do not install the RA890F where it could be subject to excessive vibration. Vibration shortens the life of the electronic and mechanical components.


- The RA890F is not designed to be weathertight. If it is installed outdoors, use a suitable weathertight enclosure.



- Locate the subbase where ambient temperature is within the specified rating.


- Mount the subbase so the top and bottom are horizontal and the back is vertical. The subbase can lean backward as much as 45 degrees when necessary.


- When an RA890F replaces an RA890E, there may be installations where ignition interference is not sufficient to destroy the RA890E, but is sufficient to prevent operation of the RA890F due to its arc gap protection.


- UL Listed: 120V models only; File No. MP268, Guide No. MCCZ


- Approved: Report No. 17678,19417,19784


 


 


 


Models available:


 


 



1. RA890F1270


 


2. RA890F1288


 


3. RA890F1296


 


4. RA890F1304


 


5. RA890F1338



 


6. RA890F1346


 


7. RA890F1387


 


8. RA890F1478


 


 


 


About Us: DtiCorp.Com (http://www.DtiCorp.com) carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more. Our online catalog is easy to navigate and search, and all products have a picture and a description. If a customer has any questions about a product, they can call 800-757-5999 and speak with one of our product experts. Our mission is to offer the best prices anywhere to our customers.



Julian Arhire

Manager DtiCorp.com

Phone: 954.484.2929

Fax: 954.4845155

Web: http://www.DtiCorp.com


 


###

Sunday, October 16, 2011

Introducing New Honeywell Software from DtiCorp.com


Fort Lauderdale, FL - Popular Honeywell online retailer DtiCorp.com (http://www.DtiCorp.com)  is introducing brand new HVAC Honeywell Software.

Description

Honeywell Excel LONSPEC is a Windows based software application for the configuration, commissioning, check out, and monitoring of the Light Commercial Building Solution (LCBS). The LCBS includes the Excel 15A Building Manager, Excel 15C Plant Controller, Excel 10 Constant Volume Air Handling Unit (CVAHU), Excel 10 Variable Volume Air Handling Unit (VAV), Remote Input/Output (RIO) device, and Unit Vent (UV), Excel 15 Command Display (CD), the T7300F/Q7300H Series 2000 Commercial Thermostats with Communicating Subbases, and T7350H Communication Thermostat, Q7790A Wireless LonWorks® Receiver with T7790C Wireless Wall Module and Honeywell Variable Frequency Drive.


Features:

• Easy-to-use drag-and-drop setup of LONWORKS® Networks and devices.
• Excel 10 application-specific controllers come pre-configured to the most common settings, yet allow quick modifications of parameters for your application.
• Easy and intuitive configuration of entire control loops.
• No line-by-line programming needed.
• Automatic and customizable data sharing between controllers on a network.
• On-line operation with monitoring and diagnostic and manual functions.
• Convenient right-click floating menus for quick access to LonSpec functions.
• On-line help includes a Quick Start tutorial for system startup.
• Quickly replicates multiple copies of controllers for repetitive applications.
• Remote access allows monitoring and diagnosis of system problems without the inconvenience and expense of service calls.
• Automatic discovery of nodes on a network reduces engineering time.


Product Specifications:

• Description: LonSpec Software
• Application: Software
• Building Management Interface: LonWorks Bus
• Network Communications: LonWorks Bus
• System Requirements: 128 MB RAM, 100 MB disk drive, 500 MHz microprocessor, Microsoft Windows 2000 or XP
• Comments: Excel LonSpec
• Used With: T7350H Thermostat, Excel 10 family of controllers, Excel 15 family of controllers                                                                                                



Models Available:

• ZL7751A1037 Sectra 2.0
• ZL7760A1020 LonSpec Software 5.1.0
• ZL7762A1026 LonStation Software 5.1.0
• ZL7751A1029 RapidZone 3.0
• ZL7300A1009
• ZL7751A1003
• ZL7760A1012
• ZL7762A1000


About Us: DtiCorp.com (http://www.DtiCorp.com) carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more. Our online catalog is easy to navigate and search, and all products have a picture and a description. If a customer has any questions about a product, please call 800-757-5999 and speak with one of our product experts. Our mission is to offer the best prices anywhere to our customers.


Julian Arhire
Manager DtiCorp.com
Phone: 954.298.2515
Fax: 954.206.0767
Web: http://www.DtiCorp.com

Tuesday, October 11, 2011

8 New Honeywell RP920 Pneumatic Temperature Controllers from DtiCorp.com

Fort Lauderdale, FL – Popular Honeywell online retailer DtiCorp.com (http://www.DtiCorp.com) is introducing 8 brand new Honeywell RP920 Pneumatic Temperature Controllers. Proportional, high capacity, single or dual input pneumatic controller used in conjunction with remote sensors to provide proportional (P) or proportional plus integral (P+I) control of temperature, humidity, pressure, or dewpoint for heating and air conditioning systems. Replacement devices are available for Johnson, Powers, Robertshaw, Barber-Colman, and older Honeywell controllers.


 


This comprises a series of dedicated sensors measuring temperature and humidity and transmitting an industry-standard 0.2 to 1 bar (3-15 psi) signal to controllers. The controllers are available with proportional and proportional plus integral control outputs with or without reset and remote control point adjustment (CPA). These outputs are used to control air conditioning and heating plants. Direct indication of the controlled variable can be provided by a gauge calibrated to match the output of the sensor installed in the tubing of any convenient point.


 


The RP920 Pneumatic Controllers provide proportional or proportional  integral control of temperature, humidity/or pressure in heating and air conditioning systems depending upon the controller/sensor combination. The construction is of modular design using modern plastic technology providing a high degree of accuracy and reliability, whilst the compact size and rail mounting saves panel space. Compensation and a remote set point facility are available, with either proportional or proportional plus integral output. Gauges can be fitted to indicate the sensor readings and the output pressure. The control output can be selected as either direct or reverse acting to suit the application. The set point scale is 0 to 100% on set point knob. Separate scales for available sensors supplied with controller. Authority is 20 to 300% of main sensor span. Compensation start point is 0 to 100% of compensation sensor span. Integral reset time is 0.5 to 20 min. Proportional Band is 2.5 to 45% of main sensor span.


 


Features:



 


- Proportional plus integral control option minimizes offset.


- Miniature diaphragm technology provides high degree of accuracy and reliability.


- Direct Acting models can be converted to Reverse Acting (RA) function in field.


- Field adjustable compensation start point.


- Local or remote setpoint field option. Integral action cut-off provides trouble-free automatic startup.


- Transparent cover (optional) provides protection while allowing easy reading of settings and gages.


- Corrosion resistant construction.


 


 



Product Specifications:


 


- Max. safe air pressure: 2bar


- Ambient temperature: 5°C – 55°C


- Air connection: Dual barbs to fit either 6 x 1mm (1/4″ OD) or 4 x 0.75mm(5/32″ OD) PE tubing. Gauge connection 1/8″ NPT.


Supply air pressure: 1,25bar


- Model: P + I controller with CPA


- Pressure: The controller is capable of operating with the MLP (Mainline pressure) as low as 15 psi (100 kPa) or as high as 23 psi (160 kPa), however recalibration may be required.


- Comments: All RP920s can be converted to reverse acting in the field. For additional technical information see literature Form no. 85-0224 and 95-7392EF.



 


 


Models available:


 


1) RP920A1025 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


2) RP920A1033 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


3) RP920B1023 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct



4) RP920B1031 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


5) RP920B1056 Pneumatic Controller, Remote, Action: Reverse, Series 3 changed to eliminate noise


6) RP920C1021 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


7) RP920C1039 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


8) RP920D1029 Pneumatic Controller, Remote, number of pipes: N/S, Action: Direct


 


 


About Us: DtiCorp.Com (http://www.DtiCorp.com) carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more. Our online catalog is easy to navigate and search, and all products have a picture and a description. If a customer has any questions about a product, they can call 800-757-5999 and speak with one of our product experts. Our mission is to offer the best prices anywhere to our customers.


 


 


Julian Arhire

Manager DtiCorp.com

Phone: 954.484.2929

Fax: 954.484.5155

Web: http://www.DtiCorp.com


 


###

Friday, October 7, 2011

Contaminated HVAC Ducts: Fungal Growth And Its Role In Indoor Air Problems

As Indoor Environmental Quality (IEQ) professionals focus increasing attention on fungal growth and its role in indoor air problems, some people are looking at how fungi contaminate duct and duct liner. While most professionals advocate removing contaminated duct liner, recent studies indicate that this isn’t always done — and that contamination is more variable and harder to predict than previously thought.


 


One recent study, which looked at hundreds of duct liner samples taken from “problem buildings,” found that nearly half of the samples were contaminated. This presumably means that contaminated duct liner material was left in place until it either caused or contributed to ongoing IEQ problems — problems severe enough to trigger an investigation. The conventional wisdom is that dirt + moisture = fungal growth. However, another study by a major US environmental laboratory showed that some duct liner supported growth with just moisture. The same study also indicated wide variations in growth among different brands of similar insulation, as well as between many liners of the same brand, making it difficult to tell under what conditions building managers should consider removing the liner.


 


Bare Metal


 


In all fairness, even unlined ducts will support microbial growth if water and nutrients are present, leading some advocates of duct liner — most notably the North American Insulation Manufacturers Association (NAIMA) — to claim that the task is to focus on keeping ducts dry and clean, rather than pointing fingers at the lining material.


 


NAIMA, and others, point out that the insulation provides sufficient benefits to outweigh the dangers. However, this doesn’t mollify others in the indoor air community.


 


 


Growth on Various Liners


 


Another recent study examined the potential for fungal growth on various types of duct liner under different humidity conditions. The researchers looked at how the duct liners performed at what would normally be considered high humidity situations — between 85% and 97% relative humidity (RH). They studied the materials in high humidity, when wetted, soiled, and clean.


 


The materials they studied included:


 



  • Fiberglass duct liner- (FDL) A and FDL-C: >44%-98% fibrous glass, 1%-18% urea polymer of phenol and formaldehyde or urea-extended phenol-melamine-formaldehyde resin, <0.1% formaldehyde;

  • FDL-B: 82%-98% fibrous glass, 2%-18% ureaextended phenol-formaldehyde resin (cured) or urea-extended phenol-melamine-formaldehyde resin (cured), <1% nonwoven, Foil-Skrim-Kraft or vinyl facings or vinyl or latex coatings;

  • Fiberglass duct board: 85%-96% fibrous glass wool, 4%-15% cured binder, <1% formaldehyde; and

  • Fiberglass insulation: 90%-95% refractory ceramic fiber, 0%-10% phenol formaldehyde.


 


New materials were purchased from commercial vendors. The researchers also studied used materials taken from noncomplaint buildings. The used materials were similar in appearance to the new materials, but researchers couldn’t determine their origin. First, the researchers looked at all five samples after placing them in an environmental chamber at 97% humidity and measuring microbial growth. Then, they wetted the samples to see what effect that had on contamination. Finally, they soiled the samples to see how that affected the growth. During the time the new material samples were at 97% RH alone, only FDL-A supported the growth of the test fungus — Penicillium — that had been placed on the samples. FDL-B, which had been manufactured with a “permanent biocide,” actually showed a 1-log decrease. The testing period lasted for six weeks. When the materials were wetted with sterile water, FDL-A exhibited fungal growth similar to what was found during the high RH period alone.


FDL-B showed an even greater decrease in growth. FDL-C, however, underwent a 2-log change over the test period, while the other materials again exhibited no growth. When the materials were moderately soiled, all samples showed significant increases in fungal growth.


 


Effects of RH Alone


 


When the FDL-A was kept in a chamber at various RH levels — 85%, 90%, 94%, and 97% — the samples exhibited a slight drop in fungal growth during the first week. From the second week on, the samples kept at 97% increased steadily throughout the period. However, the sample kept at 94%, while it initially followed the same pattern, began exhibiting growth during the sixth week. When the researchers repeated the experiment on FDL-A samples that had been heavily soiled, using RH levels of 85%, 90%, and 94%, those at the two higher levels began showing growth after the first week. The sample held at 85% initially showed decreased growth, but began showing growth by the fifth week. Used duct materials, from noncomplaint, nonproblem buildings, were all able to support growth immediately when kept at 97% RH.


 


What This Means


 


The research was not intended to cast insulation in a bad light, but rather to provide a screening tool to allow specifiers to select materials with the lowest susceptibility to fungal growth. The research brought up several important points. The first is the tremendous variability among duct liners in their ability to sustain microbial growth. Another finding runs counter to the common wisdom that both dirt and moisture are necessary but some of the duct liner showed growth with just the addition of sterile water. The issue is not so much high humidity as it is areas of the HVAC system where water accumulates, either through water accumulation or because the air stream encounters surfaces that are below the dew point, causing condensation.


 


Recommendations For Acceptable Indoor Air Quality


 



  • Insulation not be used in areas where moisture can be expected;

  • Cold surfaces be insulated to prevent condensation; and

  • Advising against materials that can biodeteriorate or trap dirt and moisture.


 


The standard calls for designers to avoid placing insulation within one and a half feet of the outdoor air intake, as well as the duct area from the coil to the downstream end of the drain pan. The standard also restricts insulation use to within one-half inch of surfaces that may become wet. As to the type of insulation that’s acceptable in areas with cold surfaces, the standard reads: The thickness of insulation shall be as required to prevent condensation on cold surfaces. Insulation that is subject to damage or reduction in thermal resistivity if wetted shall be enclosed with a vapor retarder sealed in accordance with manufacturer’s recommendations to maintain the continuity of the barrier. Special coating that can be shown to inhibit condensation may be used in lieu of insulation if approved by the authority having jurisdiction. In an appendix dealing with microbial growth, the standard further discusses the insulation issue: Microbial growth on HVAC systems’ internal surfaces in or near moisture-producing equipment (e.g., dehumidifying cooling coils, humidifiers,etc.) is an important problem for occupant health and comfort as well as system maintenance. Microbial growth causes damage to biodegradable materials and metal corrosion. Microbial growth is dependent on the presence of both moisture and a nutrient source. Consequently, materials that are used to line the airstream surface near moisture-producing equipment (e.g., dehumidifying coils, humidifiers, etc.) should not contribute to biodeterioration, should minimize the accumulation of dirt, and should not absorb and retain moisture.