Development of Active Micro Climate Controls

The search for an active system commenced in February 1978, when the Royal Ontario Museum held a workshop to explore practical ways to make this happen.

The purpose of this workshop was to explore practical ways of producing micro climates for displaying museum materials which cannot withstand exposure to fluctuations of ambient gallery conditions. Existing solutions to the problems of creating and sustaining micro climates include documented pieces of research and some successful but very specialized applications. In the hope of consolidating the existing information into a more coherent whole and possibly discovering new solutions, it was decided to hold this workshop. The aim was to assemble experienced people in all of the fields involved – conservation, design, and mechanical engineering- and to analyze the present state of the art as well as determine whether there might be viable new ways to approach micro climates. All this would be discussed in the workshop in a concentrated study by a group which had experts on all facets of the problem. The emphasis was to be on the production of practical solutions, not merely the exploration of abstract ideas. The workshop explored a variety of questions throughout the three days. Most generally they focused on the following problems areas:
Which artifacts do not require micro climates?
Which artifacts need micro climates which can be provided using existing solutions?
Which artifacts require new solutions?
What are appropriate solutions to the problem of case design?
Which buffers are appropriate?
Which mechanical solutions are appropriate?
What are the requirements for new mechanical solutions, including product parameters?

The workshop covered four main areas of discussion:

  1. The physical and environmental conditions in the present ROM building, and those proposed for the expanded and renovated museum
  2. Sensitivities of museum artifacts to temperature, relative humidity, light, dust, and pollutants
  3. The form of display units, such as cases and period names which are to enclose micro climates. They were examined with respect to the needs of the artifacts from the viewpoint of designers, curators, and conservators
  4. The nature and use of micro climates themselves. They were discussed in terms of energy savings, the appropriateness of their use to the ROM’s collections and environmental conditions, the advisability of using sealed or “leaking” cases, construction materials, and lighting methods


General
This specification describes the performance criteria for a family of temperature and relative humidity conditioning equipment. The units are to be used with moderately well-sealed exhibition cases in three size ranges. The units will be designed to fit within a space below the exhibition case and will be capable of being powered by standard electrical inputs and will interface with the case in an unobstructed manner.

Scope
This specification is intended as a means of defining the required micro climate end products necessary for the conservation of certain objects. These end results are capable of being produced by a variety of mechanical, electrical and chemical techniques. The specification makes no attempt to fix those techniques applicable to each micro climate.

Classification
The units shall be classified into two types and will be provided in three size configurations.

Type A Humidifiers
Units in this category shall be capable of increasing the relative humidity (RH) within the conditioned space. They shall also have the ability to heat or cool air to maintain a fixed temperature-humidity condition.

Type B Dehumidifier
Units in this category shall be capable of decreasing the RH within the condition space. They shall also have the ability to heat or cool air to maintain a fixed temperature-humidity condition.

Type C Dehumidifier
Units in this category shall be capable of decreasing the RH within the conditioned space. They shall also have the ability to heat or cool air to maintain a fixed temperature-humidity condition.

Load Range Type A or B Units
A1-A3: Humidifier for space of 10-1000 cubic feet
B1-B3: Dehumidifier for space of 10-1000 cubic feet

Applicable Specifications
Shall comply with national and regional electrical code requirements.

Output Characteristics
Relative Humidity
All type A units (humidifiers) shall be capable of producing a constant RH within the conditioned space of 50% -/+ 2%. This output shall be maintained within the all range of all input conditions. All type B units (dehumidifiers) shall be capable of producing a constant RH within the conditioned space of 20% -/+ 2%. This output shall be maintained within the full range of all input conditions.

Temperature: Type A or B Units
Both type A and B units of all sizes shall be capable of maintaining the conditioned space at a temperature between 21ºC and 23.5º C (70ºC and 76º F -/+2ºF).

Temperature: Type C Units
Type C units shall be capable of maintaining the conditioned space at a temperature of 4ºC +1º (40ºF +2º)

Make-Up Air
Units of all types will supply air in quantities shown here (see airflow rates) in order to make up for air leakage from the cases. This make-up air shall be re-filtered for particulate matter to a level of 99% efficiency to 10 microns and 95% efficiency to 1 micron and for sulfur dioxide, ozone, and nitrous oxide by the use of charcoal or equivalent filtration.

Airflow Rates
Type A1,2 and B1,2 units shall have the capability to supplying a minimum of 2.0-8.5 cubic feet per hour (CFH). Type A3 and B3 units shall have the capacity of supplying a minimum of 45 CFH.

Cooling and/or Heating Capacity
Units shall have the capacity of modifying the case interior temperature to within the limits specified in the paragraph on Temperature: Type A or B Units. The unit shall be capable of cooling and/or heating the supply air to achieve this result. Heating or cooling loads will be dependent upon the process used for humidity control and for case surface heat load. A case surface heat load of 7 watts per square foot, from lighting shall be used for computations. Affected surface area for A1 and B1 units shall be considered to be 25 square feet; for A2 and B2 units the area shall be considered to be 50 square feet; for A3 and B3 units the area shall be considered to be 125 square feet.

Sound Level
The equipment for the micro climate units shall operate at a sound level not exceeding NC-35 of the noise criteria curves recommended by the American Society of Hearing, Refrigerating and Air Conditioning engineers. This criterion may be exceeded during hours when the Museum is not open to the public if significant savings in efficiency, cost or ease of operations can be realized.

Vibration
The equipment for the micro climate units shall be designed and isolated such that the transmitted vibration from the equipment to the exhibition case and the exhibits shall be negligible.

Input Characteristics
All micro climate units will be subject to the following conditions.

Environmental Conditions
Temperature and Humidity
Air temperature surrounding the exterior of the exhibition cases and air available for make-up shall be provided at a temperature between 21º and 23.5ºC (70º and 75ºF -/+2%) and at a relative humidity ranging from 25% to 50% -/+ 10%.

Air Quality
The surrounding ambient (building) air shall be filtered for particulate matter to 99% to 10 microns and 90% to 95% to 1 micron. It shall also have been passed through a charcoal or equivalent filter to remove SO2, O3 and NOx

Electrical
Each unit shall be capable of operation when supplied with electrical power with the following characteristics: 120 VAC, 1 phase, 60 Hz, 15 Amperes.

Other
Specific designs may require input water lines, drain or exhaust ports. Each of these , if required, shall be coordinated with the proper Museum personnel for size, location and availability.

Physical Considerations
Size and Weight
The equipment to be utilized in the micro climate controllers shall fit within a space to be provided below the exhibition case and shall not exceed 4 cubic feet in volume for size 1 and 2 units, and 8 cubic feet in volume for size 3 units, exclusive of storage containers (such as water tanks) which may be required. Available space for storage containers shall be identified by and coordinated with Museum personnel where such containers are necessary for a specific design. Wherever possible designs should limit equipment weight such that installation and removal may be easily accomplished without the need for special lifting or handling equipment.

Materials and Workmanship
Materials selected for use in the units shall be such that they do not introduce contaminants into the micro climate. Materials shall also be selected for minimal maintenance and a long life. Workmanship shall be provided on a level to best commercial quality.

Life, Reliable and Maintainability
Each micro climate unit shall be designed and constructed such that it will be capable of 24-hour-per-day, 365-day-per-year operation with a minimum of repairs, replacements or downtime. A design goal for equipment life should be such that a minimum of five years of operation be attained without major overhaul or replacement of any major components. Redundant components will be necessary to achieve the required life of reliable, trouble free equipment.

Museum maintenance must be considered when designing the unit for access doors, plug-in modules, quick connect circuits, and similar techniques for improving maintainability and shall be provided wherever applicable.

Instrumentation and Controls
Controls
Each unit shall have, as a minimum, a switch for energizing the equipment, a light indicating that the equipment has been energized, and a setting for the control of relative humidity. Humidifiers (type A) shall be adjustable from 30% to 70% RH. Dehumidifiers shall be adjustable from 5% to 40% RH. Controls shall be easily accessible to operating personnel but shall be protected from inadvertent disturbance.

Instrumentation
Each micro climate unit shall be provided with a signal device such as an indicating light which will signal an out-of-tolerance condition. This light shall be visible on the exterior of the exhibition case so that a guard or personnel assigned to micro climate checking may see the signal readily. In addition, the specific out-of-tolerance condition, (ex. high humidity, low humidity, high temperature) shall be indicated on the equipment control panel and shall be visible when the unit is checked at the exhibition case. In addition, the units shall be equipped with plug-in read-out ports such that the actual RH and temperature may be indicated or recorded near the exhibition case by plugging in a specific indicator or recorder for relative humidity or temperature. The selection of type of instrumentation shall be coordinated with cognisant Museum personnel. The intention is to have each micro climate controlled case equipped with the ability for read-out (sensors) and to have several portable read-out devices, both indicating and recording types which will be utilized on specific cases as deemed necessary.