ECM circulator payback formula

Mark Custis

retscreen. If you get it let us know we are still working with it. The potential is there, we may need our grad school nerd to make it go.

singh

Formula

I seem to recall a thread giving the method for figuring cost to operate a circulator. I'm looking to justify the 4x cost difference for a ECM pump and how long to recoup ROI.

New construction seems like the best way to go for these circs as cost can be rolled into mortgage.

I would like to replace my two circs in my own home, but I must admit, price was more than I expected.

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tim smith

The ideal and most efficient way to do this is one ECM pump and

2 zone valves instead of 2 pumps. This provides for the most energy savings but still quite pricey to do. Tim

Paul B_5

Hi DS: in the industrial world ( high speed manufacturing)there are not too many fixed speed motors(non-ECM) left out there. Of course here they have good payback due to 24 X 7 operation. What we are looking for is precise digital/computor control and variable start / stop curves based on loads and of course then theres the robot applications..Lots of them. Reliability is unbelievably GOOD. Manufacturers data does state that the smaller horsepower motors may not have the payback of the larger ones though. if you want the link to the article I'll see if I can find it and post it. ( Mark can you still track me down a training CD ???) Paul This all being said, YES go for the ECM circulator, Energy is not going to get cheaper EVER!!!!!!

Bob McKenzie

Paul

E-mail me your address and I will mail you one personally.

A contractor that lurks on this site (never posts) that did a complete over-haul of a mechanical room in an elementary school located on the Isle of Long.

Original pump on the job was 7.5 H.P, 3Ph. He checked the amp draw on the pump before he did his removals. 17 amps average between the three.

The pump was controlled by the maintenance crew. The pump was turned on on October 1st and turned off on April 30th. It ran 24/7 during this time period.

Every room in the school had a T-stat connected to a zone valve. NO communication back to the boiler room though.

He installed a Stratos 3x3-40. First number being flange connection size and the next two are minimum/maximum head. 230v, single phase.

He dialed the head set point to 25 feet on the Stratos, meaning that the circulator would only produce up to 25 feet of head and modulate on an incline from 25 down to 12.5 feet of head. Pump affinity law.

I visited this job in December of 2007 after the new system had been up and running for months. Using our infra-red device to collect data from the pump, we found the Stratos was drawing 360 watts. 1.5 amps.

We are also able to pull an operating history from the pump and this history revealed that the Stratos never once even attempted to hit 25 feet of head. In fact, the pump spent 90% of it's time spinning at MUCH lower speeds indicating that the circulator's head setting could be lowered.

The contractor turned the head set point to the lowest setting possible on that particular model (13 feet) and waited for the "insufficient heat" call. Never came. The Stratos was now drawing 240 watts.

The original spec called for a 7.5 HP circ that would produce 250 GPM @ 70 feet of head. The circ used was chosen to meet this criteria some where in the middle third of it's performance curve. Meaning that the circ had the capacity to produce well in excess of 70 feet of head.

I interviewed the head of maintenance for this school and he told me that last winter was the first time in his 20+ years of being at the school that NO WINDOWS were opened during the heating season. Why would windows need to be opened? Because those zone valves could not stop the flow @ the head being produced. The water blew right past and the only way the teachers could control the temp in their rooms was to open what I call "the window valve". Lets BTU's OUT.

We can calculate the electrical savings very easily. What is impossible to calculate is how much energy was saved by keeping the windows shut.

I get more stories like this all the time now.

I asked John Siegenthaler if he knew of any program that could calculate the energy savings of a modulating piece of equipment compared to a fixed performance unit. He did not know of any at the time and neither do I.

Over pumping wastes more than just electricity. Higher return water temps due to low DT decrease thermal efficiencies of the heat generators we use.

The Wilo Brain Box and I will be back on the road in a couple weeks. Seeing is believing.

Mark H

Chris M

High Efficiency Pumps

Mark, can you contact me after the Thanksgiving Holiday. I have several projects that could use the ECM technology. I especially like the idea of lowering operating cost.

Mark Hunt_6

You got it!


Dan Foley copied me in an e-mail he sent to you.

I will talk to you soon.

Have a Happy Thanksgiving!

Mark H