Heating furnace blower shutdown interlock
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Dear sea friends: The heating furnace is equipped with two blowers, and there are no quick-opening dampers. During normal operation, both blowers run simultaneously; if one fails and stops working, the other takes on an increased load. At this point, the air pressure at the outlet of the blower will drop instantly to the interlock value. Has anyone used this type of design, or encountered similar problems?
Why set two to run simultaneously? Is one unit not enough? On my end, it’s one in use and one as a backup
The interlock is set for air volume and fan shutdown, with no outlet pressure setting
One unit is sufficient; his design philosophy is to avoid using quick-opening dampers. If one unit stops working, the other unit that is still operating can quickly increase its frequency to raise the air pressure, thereby preventing accidents caused by low oxygen levels in the heating furnace.
Do you confirm that \"when one fan stops operating due to a fault, the other fan increases its load via interlock – will this cause the outlet air pressure to drop instantly to the interlock value?\\"
When blower A stops, the flow at the outlet of blower B will shift to blower A, resulting in a sudden drop in furnace air pressure and thus triggering the low pressure interlock.
The rate at which load is increased isn’t that fast; when one unit stops operating, the load on the other unit certainly can’t increase that quickly, so the pressure will definitely be low. I don’t understand why a quick-opening damper isn’t installed – is the cost of adding such a damper higher than that of installing an additional blower?
Thanks for sharing, I’ve learned something! Can the interlock trigger time be delayed by three to five seconds? Additionally, in my opinion: this design is only aimed at mechanical failures of a single fan; if there is a power fluctuation but all other equipment is functioning normally, then what if both blowers stop working at the same time? Wouldn’t that result in a complete shutdown as well?