Best Internal Pump Speed

smithfan

I have an oversized Triangle Tube boiler with 3 zones. It's piped primary/secondary. Just wondering what the best pump speed for the internal pump should be? Right now it's set on medium and I'm wondering if it should be on low instead. Both of my pumps for my fintube zones are set on low.

SWEI

Is the boiler running on an outdoor reset curve? What kind of ΔT does the boiler run at, and does that difference change much with swings in outdoor air temperature?

smithfan

SWEI said:

Is the boiler running on an outdoor reset curve? What kind of ΔT does the boiler run at, and does that difference change much with swings in outdoor air temperature?

Yes it is, and I program it twice a year. Once for the shoulder seasons and the other for the middle of winter. The Delta-T is never great. So what I've been doing is running all 3 of my zones simultaneously so that I'm adding as much volume to the system as I can. That's when I get "okay" Delta T's. Like maybe 10 degrees. When I'm running just 1 zone at a time I get some pretty short burn times and crappy delta-t's. My idea is that if I slowed down the pump for the primary loop it would lower my return water temp slightly. But yeah, it just seems like a losing battle with an oversized boiler. My reset curve in the shoulder season is set pretty high so I'm reaching setpoint quickly and not short cycling. But in a perfect world, with the right sized boiler I'd be doing the opposite.

SWEI

smithfan said:

The Delta-T is never great.

Slow down the pump. See what happens.