Pump Curve Help Please

Yes and no. The top graph shows the actual inherent performance curves for the pump operating at three different power levels. That graph shows what the pump — without other controls — will accomplish. The bottom diagram shows the effect of three different electronic control strategies which the "e" version oof the pump can be programmed to do:

There seems to be some confusion. The UPS15-58FC and UPS15-58FRC are the exact same thing but with different flange orientations. The UPSe that you are referring to as a UPS is an ECM motor with pressure sensing controls and a completely different design. The curve is very similar and one will swap for the other unless it's at the very edge of its curve. If the system is zoned and has a magnetic separator and/or minimal ferrous components, the UPSe is a great choice and will likely save a few bucks per month in operating cost. If there is any iron in the system without a mag sep, stuck with the standard UPS

There are two versions of the high efficiency 15-58 Grundfos pump, recently introduces.

In addition to the Alpha 2 15-55 model still around.

The UPSe 15-58 is the basic model, around $220 online

The Alpha 15-58 has more features, $285

In the basic operating mode they consume about 1/2 the power of the standard 15-58, while moving the same gpm flow rate.

Shown below, under blue Grundfos, the standard 15-58 non electronic (ECM) model shows 60, 80 or 87W depending on speed.

The Alpha, green chart can run down as low as 7W, max. 38W

Using the variable speed function on zoned system they can reduce power consumption by 80%

There are energy efficiency rebates available for upgrading to these SCH, electronic, high efficiency circulators in many areas, if you do plan on upgrading.

Most important is selecting the correct pump for the application.

when you say 15-58 ups are you referring to the UPSe 15-58? that letter e is very important to include. both pump models will start with UPS

@Jamie Hall false. The UPS compared to the UPSe are entirely 100% different. Nothing will interchange from one to the other.

My bad. I would have though that at least the impellor and volute would be the same. But nyou certainly seem to be right — the pump characteristic curves seem to be quite different. One is obliged to wonder what, if anything the 15-58 designation stands for.

you can tell a lot about a circulator by looking at the impeller.

Generally a small diameter wide impeller will be a low head high gpm circ

The green Taco if it is an 007 is at 23 gpm, max. head 10’

The Grundfos with a large diameter, thin impeller is 17 gpm, max. 19’ head

They are not really an exact swap circulator.

if you do have a zoned system the ECM does have several distinct advantages. Think of it as a cruise control on your vehicle. The engine output, rpm constantly changes with road conditions.

With any fixed speed pump, it is sized for max load all zones calling. As zones close off you start over pumping the remaining zones. The Taco handles that better than the 15-58 due to the low head flat curve.

But better yet is a pump like the Alpha that adjusts speed (cruise control) as zones close. So power could drop as low a 7W with one small zone calling. Possibly an 80% reduction in energy consumption over the standard pumps.

Adjusting speed down also reduces flow velocity, noise, piping wear, prevents grossly over pumping the zones

Some graphs to demonstrate the pumps performance, starting with a fixed speed. Notice with only one zone open you at at the top of the curve, the worse spot on the curve to be running.

a flat curve would be the ideal operating condition.

, head remains constant as gpm changes.

today’s ECM variable speed circs get very close to the ideal operating (flat) curve. Withing seconds of a zone opening or closing the pump reacts and adjusts it flow rate.

the rpm also comes into play. The B&G series 100 a classic low head high flow circ was a 1750 rpm. wet rotors tend to be higher rpm, 2450 on a 15-58, so impeller design, involves shape, size, and rpm

Although I have swapped various 15 series among different volutes, 42s, 55s, 58 and not noticed a big difference. Probably not an option with higher efficiency circs nowadays

Back in the day pump dealers would shave the impellers to dial in larger circ, now the variable speed does the adjusting, and the electronics make the decisions.

Saving electricity with an ECM circulator is nice, but no one will care about the savings if the last room on the loop is cold. Most monoflow systems of that era used a B&G Series 100 circulator. A direct replacement would be a Taco 010. What circulator are you using currently and how does it perform?

My first house had a 1960 monoflow system that worked well for many years, until a tech replaced the B&G Series 100 with a Taco 007. It pays to do the math and see what is needed.

I think @EdTheHeaterMan made a pump curve sheet showing the 007 and 15-58 on the same sheet to easier see the performance difference. The 15-58 is a higher head circ which would have been more than the series 100 or 007 would have provided.

At mid curve of 8 gpm the 007 is 8', the 15-58 is 11', for example.

Monoflo have all the heat emitters in series, so last take off see lower supply temperature= lower output.

When monoflo systems are modified from the original design, assuming the original design was correct, things can get wonky.

Over-pumping can get you out of a under-heating situation.

If the system is noisey, (rushing water sound) the pump running way off curve, it may not be the best solution :) You may have traded a bad situation for a worse one.