Energy Efficient Motors

[doodoo]

In the HVAC industry (heating, ventilating, and air-conditioning) there has been a lot of work done in developping and installing DC variable speed motors (also known as DC Brushless motors, or ECM which has been trademarked by GE).  

In short, the most costly element to heating a home where forced air is the system and most common in today's housing industry, is not the fuel to heat but rather the electricity required to distribute that heat throughout the home. Ie the blower in the furnace. This is proven by converting the consumption into gigajoules or kilowatts so that one can compare. The savings typically come out at about 60% less in consumption of the electrical load otherwise required. Naturally this will vary based on the size of the house and a plethora of other reasons. But on average this is what is known

That being said. Although they are still a little bit pricy within the HVAC, these motors are now being found more often given the rising costs of electricity. More often than not the incremental costs are saved within the first 18 months of operation adn after that it's money in the bank.

My question is this, has any work been done to incorporate this technology in the pool and spa industry. A tremendous boost to the industry if they could incorporate a known technology in a piece of equipment that works primarily on electrical consumption heating but most importantly for motors.

[Chas]

Nope - I haven't seen any of this technology show up in spas yet. But you can bet that it will one day, most likely after other industries - such as HVAC and houshold appliances - embrace it fully, and bring the price down a bit.

HotSpring has been using "energy efficient" motors for years, not that this is the same as the ECM or Brushless DC technology, but it is a step in that direction. These motors do cost more, but return a savings on energy use.

[Shut_Down_Stranger]

Most AC electrical motors are resonably efficient. Somewhere between 91 and 94 percent for 1 to 5 hp range. Premium AC efficiency motors are avaliable, as Chas has indicated.  Some of the DC drive are more efficient, but cost more as you have to convert AC to DC and there is an nominal loss there (97%) or so.

Pump efficiency is another issue. Most horizontal end suction centrifugal pumps are somewhere between 75 to 80 percent efficient. The lost energy is "unfortunately" conveted to heat. Heat is released  in two ways, work input into the fluid, or heat generated by the motor.   Keeping the motor cool is important.

overall pump HP (continuous) is determined by the following equation.

HP = flow * gpm * pressure (psi)
           ------------------------------------
            1714 * pump eff * motor eff.  

and energy consumption in kW/hr is the HP * 0.745 * $/kW/hr

Bottom line is that the biggest culprits is the pump efficiency, not the motor efficiency.

In addition, those spas that use 2 speed motors or small recirculation motors are generally a pretty good idea. HP increases to the cube of the rpm so the draw at low speed is minimal.

[Chas]

Good info. Cal spa tried to push that envelope with it's double-ended pump, but it didn't tend to last very long.

I wonder how much the overall cost is affected by the pump shroud that recycles hot air from the jet pump motor into the water?

I know it makes a big difference on the cooling of the water while running jets....

[Shut_Down_Stranger]

Good info. Cal spa tried to push that envelope with it's double-ended pump, but it didn't tend to last very long.

I wonder how much the overall cost is affected by the pump shroud that recycles hot air from the jet pump motor into the water?

I know it makes a big difference on the cooling of the water while running jets....

I saw that, Sticking two pump ends on the same motor does not make a lot of sense. One larger pump will do, and it is one less seal to replace.

The fan running over the motor is desinged to cool the motor, the are has to be dischaged somewhere, Venting, as Hot Springs does, is a good idea to keep the motor cool.  Remember you are in an insulated envoronment so getting rid of unwanted heat from the motor is just as important as keeping wanted heat.

[doodoo]

Thanks for the info on this to both of you. SDS I'll do the math on my optima and see what I get out of it. I know that a recirc pump is always a good idea what with low amp draw (1/10th of a regular pump) which is what is on my Optima and most other reputable brand.

But what I am very surprised at is the difference in motor efficiency and pump efficiency. I had not realised that they would be calculated seperately. I just assumed that they were one and the same. Does make sense though.

Perhaps in a few years this technology will find its way into spas.