Mabley Isolation VAV work letter.pdf

Three Sixty MEP, PLLC – Saint Charles, IL Illinois Design Firm #184-0008463 Page 1 of 2

September 1, 2022

Paula Price, AIA Batir Architecture, Ltd.

1121 W. Main Street, #220 St. Charles, IL 60174 pprice@batirarch.com

RE: Review and Assessment of Proposed Air Terminal Work Jack Mabley Developmental Center Dixon, IL

Dear Paula, Per your request, Three Sixty MEP has reviewed Mr. Trent Sexton’s proposed HVAC modifications, outlined in an email dated August 4, 2022. Mr. Trent Sexton, Stationary Engineer with the facility, has reported performance issues with the current HVAC system. The issue that has been reported is as follows:

• The kitchen and bathroom/shower space has constant issues maintaining temperature setpoint. This space is labeled as Physio Therapy 38, Toilet 39, & Shower 40 on the referenced set of plans provided.

o Air terminal VAV-6 serves both isolated (negative) and non-isolated (non-negative) areas, while the temperature sensor is located in the non-negative area.

o During winter months, the temperature is too low and in the summer months, the temperature is too high.

Mr. Sexton’s recommendations to remedy the temperature controls issue has been described as follows:

• Install new VAV for Isolation Area Kitchen o Take current zone six that feeds VAV 6 in the Pearson Administration Building and create two separately controlled zones.

o All necessary ductwork connections on supply and return sides, electrical connections and BAS tie-ins, including thermostat to be included.

o Permission to use existing 208V feed for existing electric wall heater in the kitchen is acceptable for new VAV box.

After reviewing the proposed scope of work and the information provided from the recent 2020 renovation, as well as the original 1984 drawings, Three Sixty MEP is in agreement with the proposed solution of adding a new air terminal VAV box. Isolation and non-isolation zones should be separated to provide proper pressure relationships between building areas. Placing a new VAV air terminal will achieve proper pressure relationships and will allow for better temperature control by providing a new thermostat in the area of concern.

mailto:pprice@batirarch.com

Three Sixty MEP, PLLC – Saint Charles, IL Illinois Design Firm #184-0008463 Page 2 of 2

Along with the proposed solution, Three Sixty MEP has the following additional comments, considerations, & recommendations:

• Perform a preliminary balance report to confirm existing airflows, prior to modifications.

• Branch ducts removed from existing VAV-6 shall be removed and capped/sealed.

• Existing VAV-6 shall be rebalanced as necessary to account for airflow removed from zone.

• New VAV box shall be provided with inlet duct connected to existing medium pressure duct main, near VAV-6 connection, if possible.

• New VAV box shall be sized to match existing supply air quantities to the zone, in order to minimize rebalancing area for pressure relationships. However, this review does not include an analysis of internal equipment heat gains (refrigerators, freezers, etc) and whether existing airflows are appropriate for the internal loads.

• Confirm proper negative pressure levels after installation of new VAV box, when at design flow. Design flow of VAV box shall not exceed airflows that would affect minimum negative pressure values required.

VAV box could be set at a constant volume, or allowed to modulate to a minimum position, allowing the room to go more negative. Adjust balance of exhaust fan as necessary.

• Provide reheat coil per scope request. Hot water or electric reheat is acceptable.

• Size reheat coil for approximately 25F temperature rise, or a leaving air temperature of 80-85 deg F.

• The temperature sensor that will be tied to the new VAV box should be placed in the kitchen area away from any potential heat source.

Note: All recommendations are based on old drawings and the best available information provided to us at the time of this report. Some information may not accurately reflect current existing conditions. Contractor shall confirm all existing conditions. In any event, Three Sixty MEP shall not be held liable for the results obtained from any work performed by others as a result of the information contained herein.

In summary, separation of the isolation and non-isolation zones by the means of a new VAV box and new temperature sensor should mitigate the temperature and pressure issues that arise from the current VAV setup.

Overall, this is a cost effective and proper means of resolving the reported issues. Three Sixty MEP will be happy to discuss our recommendations in more detail or address any questions or concerns that may come about.

Respectfully, Michael Wright, P.E.

Three Sixty MEP, PLLC Founder / Principal Engineer MWright@threesixtyMEP.com 630-205-6379 mailto:MWright@threesixtyMEP.com