Thank you for your time,
    I have a B&D flow center that my installer left the pump on high. My loop temps seemed like they should be better. My thought was that the flow was to high. There was no flow restriction placed in the system.  My delta T on the water side was 3 ish deg. I turned it down to low and got it to 5 ish deg. And my loop temps went up, this is in heat mode.My head pressure from the pump pack is 3-1/2 feet. Looks like I might be running around 16ish GPM. The pump pack has a ball valve on the outlet side. I throttled it down and got much better delta T  6.9 deg on low and 8.3 deg on high load. On a Water Furnace 5 Series 2 ton unit. First off do you guys throttle your water down? And where do you do it? Should I add a ball or globe valve on the water outlet side? My installer thinks that it needs to be on high. That would get me around  30ish GPM. He tells me that they tested it with pressure gauges. I don't see how there would be a pressure drop with no back pressure on the non pressure system. I read that it needs to be around 8-9 GPM on this unit.

Thank you for your help!!!
John

Rule of thumb says you would only need 5-6 GPM with a 2 ton unit. 3 GPM per ton.

Thank you Chris,
    So lowering the GPM, I'm better off right?

To a point, yes. Don't think it's necessary to have a 9* deltaT. Keep an eye on LWT. If it was me I would just leave it on low speed.

Any noise when you throttled it down?

Chris, there is very little noise with the valve throttled. It's no louder then the compressor. With lower GPM the water will be able to work longer in the loop filed. And I see temp gains from it.

Why would you pay for the cost of pumping, just to throttle it back down? Keep in mind that heat transfer is flow x delta T x 485. In other words if you reduce your flow, your delta T goes up, but the heat transfer stay pretty much the same. With the only difference that you now pay for pumping power you don't need.
Set it to "low" and open all the valves...geo needs flow, let it flow....