How does low RAT kill a heat exchanger? It cools the heat exchanger, causing the flue gas temperature to drop below its dew point.
Sound familiar yet?
The moisture mixes with the flue gas and forms acid, and the acid causes corrosion. Yup, you got it; it’s just like the oversized unit from the first post.
So, what causes of low RAT? I’m glad you asked!
- Leaking curb gasket (drawing in outside air)
- Economizer open (too much ventilation air?)
- Space temperature set-point too low (warehouse, unoccupied?)
In the end, if you don’t have a corrosion resistant heat exchanger (stainless steel), keep return air temperatures above 65 degrees during extended run times.
Stay tuned for part three.