non-wet-rotor circulator pros and cons

[pybyr]

Hello all--

this past weekend I managed to get one other big project off the urgency/obligation list, so, between that and the calendar, am now getting ready to re-dive into the details of my hydronlic layout.

I may need some moderately big circulators such as for the water-to-air heat exchanger that will go over my existing oil furnace and transfer the heat from the wood boiler/ storage into the house's existing ductwork

one circulator that came to my attention as I started to look at the curves of various makes and models is the Bell & Gossett "PL" which looks like it can move substantial amounts of water, and claims to be up to 25% more electrically efficient--
http://www.bellgossett.com/productPages/Parts-SERIES-PL.asp
it's not the "old" type huge Red B&G;with the completely separate motor/pump, like the ones that needed manual oiling every season, but it does have an aircooled motor that does not depend on the system water to lube and cool it. Supposedly this makes it use less electricity and be longer lasting. It looks more expensive than the smaller wet-rotor circulators, but if it really will use substantially less electricity over time, and also have a longer lifespan before failure-- so that it might pay for itself and then start saving money in the long run- I am willing to consider it.

Anyone have any experience or informed opinions on electrical efficiency and lifespan/ durability of these?

Also, anyone happen to know if the motor on this "PL" type B&G;can be speed controlled by some of the speed controllers that are now on the market for circulators, but are "aimed" at the more common modern wet-circulator split capacitor motor pumps?

Thanks, as always, for all the good info around here and peoples' willingness to share knowledge, experience, and ingenuity

 

[heaterman]

I like the Taco 1400 series better than the B&G;version. It's quieter and most models spec out a little better wire to water efficiency.

 

[pybyr]

I like the Taco 1400 series better than the B&G;version. It's quieter and most models spec out a little better wire to water efficiency.

thanks Heaterman- I had not realized that Taco had non-wet-rotor models, and in my limited experience, they definitely seem to have better in-house customer support than B&G;.

Do you have thoughts on my other question about whether these modern-generation non-wet rotor circulators are more electrically efficient and/ or longer-lasting in a way that will, in the long run, offset their extra purchase cost and then start saving $$ back?

or whether they have the same PSC motors as the "wet rotor" ones? and so hopefully could be "throttled back" with a speed controller like the wet rotor ones?

thanks

 

[in hot water]

PLs are fairly noisy circs. With an open frame motor you tend to get more noise. It's worse with the higher rpm models. Never mount a PL to a sheetrock wall in someones house!

One radiant company uses PLs on snowmelt panels and homeowners always complain of noise. Replacing with a wet rotor solves the problem.

If quiet and efficient are the goal, ECM beats them all. The Wilo ECO or Grundfos Magna for larger sizes. 40% less energy consumption and the quietness of a water lubed circ.

hr

 

[heaterman]

Everything you ever wanted to know about Taco performance curves right here.

http://www.taco-hvac.com/en/products.html?view=AllFileList&current_category=18&selected_infotype=5

To state broadly that a wet rotor or an open style circ is more efficient is impossible. The efficiency of any circ is determined by correct sizing to the load it's connected to. That's one of the reasons I get a little torqued when I see people using 1" tube and lashing an 0011 or 26-99 to it trying to jam enough GPM through it to heat their building. A high head circ like those mentioned pushing 8-10 GPM is a waste of energy.

Generally speaking, you'll find the best wire to water efficiency for any circ is in the middle 1/3 of the curve.

 

[Redox]

Ya, such a broad generalization is impossible unless you know where you fall on the pump curve. Similarly, it would be hard to say which is the more efficient motor, unless you look at the pump curve at your specific conditions.

The wet rotor circs are going to be (generally) more trouble free than an open drive pump, but the difference in the long run is probably not significant. I don't think how the motor is cooled will make a difference one way or the other. They both run for years without problem, as long as you keep the bearings oiled on the bracket circ. The PL still has a shaft seal, though.

Those ECM pumps are really neat, but I will wonder out loud if you can replace the pump or the electronics separately? I would hate to have to replace the whole thing if just part of it went south.

Since you are considering such a large circulator, you might consider ordering it as 3 phase and putting it on a speed drive. This will be the most electrically efficient of all. This is basically what an ECM pump is anyway.

Chris

 

[pybyr]

Since you are considering such a large circulator, you might consider ordering it as 3 phase and putting it on a speed drive. This will be the most electrically efficient of all. This is basically what an ECM pump is anyway.

Chris

How small a circulator can I get with a 3 phase motor -- I was trying to look into this a while back, and it seemed as if (from what I could find at the time) as if only really_really big circulators (on the scale that would never be used in a normal person's single family residence) could be sourced with 3 phase motors. The category it seems like I may wind up in, circ-size-wise, is big by residential standards, but still - using the Taco 1400-10 as a possible example of something I might use- only 1/10 HP

By the way, regarding your comment about the higher operating electrical efficiency of a 3 phase motor run by an inverter drive (compared to a single phase motor) what do you & others think about whether I'd pick up some worthwhile long-run electricity savings if I replaced the 1/2 HP 1725 RPM motor that runs the 1600CFM blower in my oil furnace (and which will continue to push air through the fin-coil for my wood system) with a 3 phase motor + variable speed inverter drive? The variable speed on the blower might be a bonus for optimizing the fin-coil's output for the wood system- but I am also wondering whether there might be savings on the electricity if the 3phase+inverter drive might be substantially more efficient than a 10 year old consumer grade 1 phase 1/2 hp motor?

Thanks

 

[BrownianHeatingTech]

By the way, regarding your comment about the higher operating electrical efficiency of a 3 phase motor run by an inverter drive (compared to a single phase motor) what do you & others think about whether I'd pick up some worthwhile long-run electricity savings if I replaced the 1/2 HP 1725 RPM motor that runs the 1600CFM blower in my oil furnace (and which will continue to push air through the fin-coil for my wood system) with a 3 phase motor + variable speed inverter drive? The variable speed on the blower might be a bonus for optimizing the fin-coil's output for the wood system- but I am also wondering whether there might be savings on the electricity if the 3phase+inverter drive might be substantially more efficient than a 10 year old consumer grade 1 phase 1/2 hp motor?

There are electrical savings, as well as comfort increases. I'll get you some information by email...

Joe

 

[Boilerguy]

what makes you think you need a large pump, very few residental applications would needmore than a 007 taco or 15-58 grundfoss. both run at .7 amps and will do a lot of work for that, to much pump =high velocity=water noise

 

[Redox]

An oversized pump slowed down is almost always more efficient than a smaller circ wide open. In addition, it is almost always possible to slow down the circ to take advantage of reduced demand. It would require a controller to do this, but they aren't expensive. Many drives already have PID functions programmed into them. Variable speed systems will have 2 way valves and a differential pressure transducer that provides feedback to the drive/controller. This way, as the valves close, the DP increases and the drive/controller slows down to compensate.

The reason for the energy savings is due to what's called the "affinity law" for pumps (and fans, btw) The law basically states that for a given centrifugal device, the flow is directly related to the RPM, but the power goes up by the cube of the speed. Anyone with a hot tub that has a 2 speed pump will note that the half speed horsepower will be 1/8th that of the full speed number. A 1hp pump that draws maybe 1200 watts on high will be using about 150 watts at half speed and be moving roughly the same amount of water as a 1/2hp pump at 600 watts. You can run the numbers and figure out if it is worth the expense.

I see 3 phase circulators as small as 1/4 hp in catalogs. They aren't cheap, but if you can design your system around a single circulator, it might be possible to save a lot of electricity. The larger and more complicated the system, the more savings are possible. It is going to be hard to justify a $500-1000 pump/drive setup on a residential sized system, but if you don't mind paying for a Cadillac, the savings are there.

For the record, I sell/service drives for large commercial and industrial systems. I have actually installed drives in homes that are too large for a conventional circulator to handle with a single phase motor. In these cases, the drive is acting as a 3 phase inverter powered by single phase to make the required horsepower of the larger pump.

It is possible to retrofit a variable speed fan motor into a furnace or air handler, but it won't be cheap. The newer units have ECM motors that allow for an infinite speed selection rather than the stepped 3 or 4 speed fans of the past. They have a good track record, but need an appropriate controller and are pricy. I have looked into retrofitting one into my furnace, but haven't gone there YET, due to the cost. If you have an older belt driven fan, it is easier as there are a lot of small 3 phase motor manufacturers out there, but only one manufacturer of variable direct drive motors (GE). Someone correct me if this is wrong.

Chris