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HI everyone

I am working in hotel industry in Qatar. We have 3 HRUs (Heat Recovery Units) on rooftop for 3 different buildings. The HRU consists of 1 extract fan, 1 supply air ,1 Heat recovery wheel, chilled water cooling coil supplied with chilled water and flow controlled by an actuator. We are facing a issue with one of our HRU. Recently we noticed that there is huge amount of water gets collected inside the HRU unit base and the condensate drain line can't drain the water while the unit is running although there is U trap on the condensate drain line as well as there gravity slows downwards. When the HRU is in running condition with supply, extract and HRW motor is ON , we noticed inwards suction towards inside of the unit through the condensate drain line and as soon as the HRU is switched OFF condensate water flows out of the unit through gravity force but as soon as the unit is started condensate line water flow stops. 

Im afraid this huge amount of water collected inside the HRU might create moisture in motor windings which again might result in motor winding ground.

Kindly suggest me any corrective action on this.

Hi Carlos,

 Google " Condensate Drain Configuration"  that should send you down the right road.

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David Summers
Maintenance Engineer at NASA Glenn Research
Peraton
Brook Park OH
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Condensate accumulation can be caused by negative pressure due to restricted airflow through the coils, or through the filter(s) upstream from the coils.  If you have a way of checking the pressure drop across the coils and filters you can verify this.  If not, you may need to clean the coils and/or replace the filter(s) and see if the problem is corrected.

I sincerely hope this helps.

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Daniel K Corman, CMRP
Houston, Texas, USA
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