Musty smell in chapel

[sstaycoolmlh]

I work in a nursing home as a maintenance tech. We have several additions to our buildings, the last addition in 1977.
Last year we started noticing a musty damp smell in the chapel. It is heated and cooled by an air handler across the hall. Last year I found the water in the drain pan not draining while the a/h was running.We repiped the drain to assure clean drain lines, regularly check/replace filters, 2in. pleated w/sock filters. The coil was pressure washed last year.What may have changed that we are getting this musty smell/dampness in the chapel? What steps should we take to get this corrected? I assume that with the water staying in the drain pan that has a carry-over affect, but why in the last 2-3 years would this start? Any ideas would greatly appreciated.

[DocHVAC]

Same answer as the last question you had some air exchange see http://www.lifebreath.com for commercial units.

[teddy bear]

Situations that grow mold may depend on damp outdoor weather. If a little mold grows in the wall under occasional outdoor weather conditions like very high outdoor dewpoints, it takes years to become noticealbe. Check the indoor relative humidity, it should be less than <50%RH. The indoor temperature should be as warm as possible to avoid condensation in the walls. Condensation in the exterior walls and under carpeting causes a musty odor. Water leakage around windows will cause musty odors. Vinyl wall paper on exterior walls traps condensation on the back side of the drywall. During extreme outdoor high humidity/low indoor temperatures, condensation accumulates behind the drywall growing mold. Make-up air ventilation helps this problem by pressurizing the space to force dry indoor air into the wall cavity. Caution, more fresh air ventilation introduces more moisture raising the indoor relative humidity. 100 cfm of outdoor air @ 70^F dew point is 100 pints of moisture load. Additional dehumidification is required to maintain <50% RH during the cool wet outside conditions. To maintain <50%RH, 2,000 sq.ft. with make-up air may require 200 pints of dehumidification per day. Start by following you nose to the musty smell and monitoring the %RH.

[tony williams]

I don't know if this will help any but I have gone through similiar situations and have noticed that a lot of churches/chapels hvac do not have a tendency to run as long as areas next to them. The units do not have the chance to remove moisture. Humdistats can help keep the room at desired RH levels. Also in one instance we noticed moisture building up and causing stagnant smells on the partitions adjacent to the chapel and causing condensation.

[killeen-heatair]

Could very well be a MOLD issue. Consider upgrading to a Carrier variable speed type unit and have the place tested.

[Steve Wiggins]

loose belts & outdoor air blocked off.

[airman1]

smells are humidity period...reduce humidity and smell will go away...get to 45%..for three months..inside humidity