ENERGY EFFICINCY TEST

[Eco_Spas]

HI,
So, A friend of mine came across a blog on how to test your "Kilowatt usage" on your spa at home. He told me he tried this "home test" and compared it to his power bill and found it to look accurate, but wasnt 100% positive. Thats when and why he contacted me.
I read the blog and tried this "home test" on one of the spas in my facility. Previously to testing I knew what the kilowatt usage was,(I had tested the spa using my equipment), so I could compare the two results side by side. The results of this "home test" compared to the results of "actual kilowatt usage" are very similar.
They also mention the test at Cal-Poly conducted for the C.E.C. and compare it to thier "home test". I am very aware of the testing procedures and of the 27 manufacturers that attended that test. :-?  
But, as for this "home test" being an acurate and easy way to test your spa kilowatt usage from home? I would say, from the comparison of the two results I gathered, Yes it is. so this is the test address:
mycp1.wordpress.com
I suggest trying the test for yourself and determining if the results compare to your bill.

[Dr. Spa™ Ret.]

Ok, I read it. Took me a while to get to it, as I was laughing so hard at the inaccuracies of the first "article" on spa covers.

Speaking of inaccuracies  

[size=12]"By multiplying the degrees lost, times the kilowatt hours that would have been used in maintaining the 102 degree temperature (1), times the average cost of a kilowatt hour divided by 100 you can estimate the daily cost of running your spa. ( - D x 1.6 x cost of kWh / 100 = daily cost )"[/size]

(1) ummmmmmmmm, where do we come up with "the kilowatt hours that would have been used in maintaining the 102 degree temperature" ? ? ? Additionally, what ever number you come up with will be LESS than the actual cost to maintain the 102 temp. Yes, you might be able to determine, actually rather easily, how much energy the spa lost over a 24 hour period, HOWEVER, as the water cools, it will be losing less energy per measured time unit than it will if maintained at a constant temp (Newtons law of cooling).

gallons of water times 8.33 times degrees of temp loss times 0.01757* = kilowatts of heat loss (this doesn't take into consideration the energy to operate the pump required to move water through the heater)

* I may have chosen the wrong multiplier to convert BTU's to kW

[Chris_H]

Clearly Doc is Einstein.  I have no idea what you wrote.  

[Eco_Spas]

kudos for knowing what "Newtons law of cooling" is.  Unfortunatly, "homeowners" dont have the full resources and equipment to get an "EXACT" usage of kilowatt hours.  So... doing the test in different ambient temperatures(winter then summer) would benefit the consumer more, because the KWH usage will be different. So DR SPA would you say this test is accurate(if you follow the formula given)??

[Chas]

Allowing a tub to cool is a good way to do a comparison, but is not a good way to try to arrive at the amount of energy that a tub consumes. For example, if you and a friend have different types of tubs, set them to the same temperature, and shut them off at the same time. Check the temp 24 hours later and see who's tub stayed the warmest. But to be accurate, you would have to repeat this over and over and take an average, to reduce the effects of wind, contact with the ground (one may be on a deck while the other is on concrete etc.) And, part of what you find out might have to do with the amount of protection the various tubs have from the wind and weather.

To find out how much power any appliance consumes, there is only one method. Connect it to a power meter - independent of any other appliance. Run the test four times in one year (once in each season - or just the one season if you live here in So Cal) and then take the average.

That is the ONLY way to get an accurate idea of what the tub is consuming. Cool-down can be effected by a dozen different things from ambient temperature, the temperature of the water as Andrew mentioned above, to wind, to the security of the cover, to somebody opening the cover during the test, to sun, length of the day (summer vs. winter) to power surges, filter cycles, among other things.

I have just loaned out my meter - the man said he would meter the spa, then his old refrigerator in the garage. Guess what? So far it looks like the tub is not the culprit in his escalating power bill.

 8-)

[Eco_Spas]

You could test your spa each season, yes. OR you could go by the C.E.C. standard and test it on a 60degree day, disregard the wind, sun, and contact with the ground . They are all irrelivent in the (C.E.C Cal-poly test).

[Chas]

You could test your spa each season, yes. OR you could go by the C.E.C. standard and test it on a 60degree day, disregard the wind, sun, and contact with the ground . They are all irrelevant in the (C.E.C Cal-poly test).

They may be irrelevant in the test you cite, but they certainly are not in reality.

If the tub is in contact a slab there can be some heat transfer, depending upon how well the bottom of the tub is insulated. That heat could be going into the tub if the slab was exposed to several hot days just before this test begins. The heat could be leaving the tub if the slab is ice cold from several days of cold weather.


The wind is a huge factor - if there is...

You know what? Skip it. Go ahead.


 8-)

[Shaamus]

Eco_Spas, would you like to tell us exactly what you do as a "green engineer" and what qualifies you as such?

[Eco_Spas]

They may be irrelevant in the test you cite, but they certainly are not in reality.

You know what? Skip it. Go ahead.


 8-)

The test that I cite at Cal-Poly was developed by the APSP

[Eco_Spas]

Has anyone actually tried this test?

[D.P. Roberts]

Clearly Doc is Einstein.  I have no idea what you wrote.  

In summary, what he said was "1.21 gigawatts! Great Scott!"