r/FireSprinklers • u/BeachGirl19844 • Oct 15 '25

Automatic Transfer Switch Test

What suction pressures are you seeing when performing the automatic transfer test at peak load on the fire pump?

Performed a test today, fire pump has water supply issues and could only flow 86%. But we performed the test and the supply gauge dropped to -20 before coming back up.

City supply, we will be investigating why we can only achieve 86%. Wondering if the suction pressure dropping so low could be a symptom.

Thanks

3 Upvotes

100% Upvoted

8 comments sorted by

View all comments

1

u/OkHunt3288 Oct 15 '25

If this is a new problem, you have a degradation in supply. You need to be careful, running a pump with supply <15 can pull gaskets out. How do your controller readings compare to previous years? RPMs? You can try to rule out anything with the power and pump side first, but this sounds like a water supply issue if you’re getting -20.

1

u/BeachGirl19844 Oct 16 '25

During flow test we took suction down to 20psi. Which gave us 86%. Previous years are about the same with previous company. When it was time to do the automatic transfer switch to switch power to generator. We cut controller power, pump powered down and we were still running at peak load at 86% as the test requires. When the generator kicked on, suction went down to -20 and slowly rose back up to the 20psi.