Radio Tower Shelter HVAC Preventative Maintenance and Service/Repair

The County Commissioners of Charles County request submissions to identify qualified service contractors to provide preventive maintenance and repair services for radio tower shelters HVAC systems. Following a review of submittals, the County may solicit pricing quotes from selected contractors. The required services are:

1.- Preventive Maintenance and Service/Repair for existing sites (11)

2.- Preventive Maintenance for new sites (7).

3.- Service/Repair for new sites after the 2-year manufacturer’s warranty expires.

Charles County operates eleven (11) remote radio frequency sites which include prefabricated concrete telecommunication shelters of varying sizes from 12x24 to 14x38.Environmental control is provided in these shelters by multiple dual BARD MULTI-TEC 4–5-ton wall-mounted HVAC units. One unit per site is equipped with the mechanical dehumidification option. At least two sites are configured with two zones. All sites have FM200 fire suppression systems which will shut down HVAC operations during a fire alarm condition. All units are equipped with Emerson Soft Start compressor surge suppression devices. See Appendix H.

The County is in the process of adding seven (7) new sites to the radio system. Six (6) of these sites will be equipped with BARD MULTI-TEC units. The Bryans Road site will be equipped with two (2) Mitsubishi mini split unit systems. See Appendix A for the list of new and existing sites.

Sites that are equipped with BARD MULTI-TEC systems are controlled by a BARD LC6000-200 Controller. The Bryans Road mini split systems are controlled by two PAR-41MAAU deluxe MA controllers, paired with a BARD MC4002-BC controller. The controllers provide lead/lag functionality and balanced runtime as well as basic alarming via Dry C contact closures for remote monitoring via the County’s network monitor system. The MULTI-TEC units are equipped with economizers and/or dehumidification. However, the economizer function has been disabled at this time. See Appendix B for HVAC configuration information.

Each site is provisioned with an FM200 fire suppression system which is configured to shut down the operation of the MULTI-TEC Units independently of the LC6000-200 controller, during a fire suppression condition in the shelter. See Appendix D for FM 200 diagram.