Potential electrical power saving by increasing the size of conductors NEC REQUIRED

[Birken Vogt]

Whenever I use larger wire than called for "because I have it laying around" I always seem to regret it.

"If only this #2 was a #3 if would fit right in here!"

They didn't used to carry #3 at the SH but I started ordering it because I like it, now they stock it.

 

[mtnelect]

I was always fascinated how researchers trying to develop a super conductor, dropped the temperature of conductors to extremely low
temperature to achieve a conductor with no resistance. Heat that was a limiting factor on conductivity.
Lowering the temperature by increasing the wire size and decreasing resistance probably reduces electrical usage.
I worked for a large school district, if like the Electrical Inspector for Fort Worth, Texas speculated a single jump in wire size payed
for itself in 5 years and the average of a school is 50+ years, that would be a huge saving in electrical use, which translate into greener
schools. I was never able to catch the attention of the school district, because I had no definitive mathematic calculations to back me
up.
It probably would not be cost effective for all circuits, but probably very effective for services, branch feeders and circuits to large usage
items like like AC units.
Something to think about. It seems like if you have all the variables, a formula or formulas are possible.

The California Energy Commission has been saving Californians energy since 1975. As one example, it requires HVAC contractors to do a "Heat Load Enginering Study" to justify the proper size of unit, instead of the "Rule of Thumb". Many HVAC inspections I perform, the installed unit is oversized because the HVAC contractor used the "Rule of Thumb" instead.

 

[mtnelect]

This is an example of a "Heat Load Engineering Study"

 

[jim dungar]

This is an example of a "Heat Load Engineering Study"

I do not see where these reports include the heat gain due to conductor losses.

 

[mtnelect]

I do not see where these reports include the heat gain due to conductor losses.

Enlarging the wire size to save electricity is "Small Potatoes" compared to oversized HVAC units.

 

[jim dungar]

Enlarging the wire size to save electricity is "Small Potatoes" compared to oversized HVAC units.

my point is: Do heating calculations routinely consider the heat output of conductors and do energy saving recommendations routinely include oversized conductors?

 

[mtnelect]

my point is: Do heating calculations routinely consider the heat output of conductors and do energy saving recommendations routinely include oversized conductors?

No. The "Heat Load Engineering Study" only uses the envelope of the structure and the "Climate Zone" it is in.

 

[wwhitney]

my point is: Do heating calculations routinely consider the heat output of conductors

Routinely? No.

Done by a careful practitioner who has reason to believe that the effect will be significant (e.g. very tight, well insulated residence, or large office building)? Yes.

Cheers, Wayne

 

[mtnelect]

Routinely? No.

Done by a careful practitioner who has reason to believe that the effect will be significant (e.g. very tight, well insulated residence, or large office building)? Yes.

Cheers, Wayne

I was in court a couple of weeks ago, where a Beverly Hills law firm representing the builder of a 24-unit complex. The builder failed to do a "Heat Load Engineering Study" and the Homeowners Association filed a complaint with the state. The homeowner's complaint was that the HVAC system wasn't working properly. The study found that the builder installed a larger system and only one return on four level condominiums.

 

[drcampbell]

To the point where the building has no heating demand in winter. In my youth, I had heard that this was the case for the Twin Towers.

This is actually quite common in larger buildings. They often need year-round cooling because the heat generated internally is less than the heat lost through the building envelope.

Back in the days of magnetic ballasts, it wasn't unusual for there to be no heating equipment installed at all, and the lights used to keep the building warm over the weekend or Christmas break if need be.

Of course, this always provoked a flurry of comments about "wasting energy".

 

[kingpb]

Electrical: Energy Efficiency - One Wire Size Up Means Big Savings

Installing wire only one size larger than has been required by the National Electrical Code increases energy efficiency with dramatic paybacks.

copper.org

Electrical: Energy Efficiency - High-Efficiency Wiring for Energy Savings

Now let's look at upsizing the wiring above code minimum to achieve further energy savings.

copper.org

I'm sure the copper org does want you using more copper. Always consider the source.

 

[kwired]

No. The "Heat Load Engineering Study" only uses the envelope of the structure and the "Climate Zone" it is in.

Why wouldn't it include any naturally occurring gains or losses from within? Usually more internal gain than loss within most places but can go either way.

water heaters, refrigerators, freezers, lighting and more all contribute to heating/cooling loading if they are within the conditioned space.

 

[kwired]

Besides the resistance of the conductors, I have not found a formula or method to accurately calculate electrical use savings by increasing conductor
size beyond the NEC.
Does anyone have a formula or method for these calculations?

For something existing that you are considering upgrading all you need to find out what your current losses are is take amount of voltage dropped times the amps being drawn to find the watts lost.

For single phase circuit say you have 10 amps of load but when you turn this load on the voltage decreases by .5 volts then you have a loss of 5 watts, but it is occurring anywhere from the source, through the service, feeders, and branch circuits or partially occurring in more than one of those. It will take 2000 hours of operation before this particular circuit has a loss of 1 kWHR, and that is presuming the load stays at a constant 10 amps. That loss during that 2000 hours is only going to cost 12 to 20 cents in most parts of the country again assuming the load runs continuously for 2000 hours. It will take longer to have same loss if the load cycles or changes to lower levels at times.

 

[gadfly56]

No. The "Heat Load Engineering Study" only uses the envelope of the structure and the "Climate Zone" it is in.

I had a home that was built in 1929 and heated by oil when I moved in. It had low pressure steam. One of my colleagues had a father connected to Sarco (heat traps) and got me a steamfitter's handbook for residential and light commercial buildings. Tons of great info. One of the first warnings was to guard against the trap of "more is better." It's especially not true for steam heat. You have to carefully match the steam output to the total radiator surface, or you'll wind up with terrible performance.

 

[ggunn]

I had a home that was built in 1929 and heated by oil when I moved in. It had low pressure steam. One of my colleagues had a father connected to Sarco (heat traps) and got me a steamfitter's handbook for residential and light commercial buildings. Tons of great info. One of the first warnings was to guard against the trap of "more is better." It's especially not true for steam heat. You have to carefully match the steam output to the total radiator surface, or you'll wind up with terrible performance.

I have also heard an admonition against installing air conditioning that is too big for the space to be cooled. That makes it cycle on and off more often with more and larger startup (compressor motor inrush) losses.

 

[LarryFine]

I have also heard an admonition against installing air conditioning that is too big for the space to be cooled. That makes it cycle on and off more often with more and larger startup (compressor motor inrush) losses.

Also, short cycles don't give the system enough time to dehumidify well.

 

[hmspe]

I have also heard an admonition against installing air conditioning that is too big for the space to be cooled. That makes it cycle on and off more often with more and larger startup (compressor motor inrush) losses.

I'd like to see an analysis that verifies this. I doubt that utility meters register starting surges, either because they throw out outlier values or because of averaging. Even if surges register a 1 second surge is not too significant compared to a run time of, say, 10 minutes. The required BTUs for cooling should be the same regardless of tonnage.

This is anecdotal, but we changed the heat pump at our house from 3.5 ton to 4 ton and our power bills went down.

 

[winnie]

I rather doubt that the startup surges for a short cycling HVAC system particularly changes the energy consumption.

However an oversized HVAC unit that is short cycling will have much poorer dehumidification performance, and will probably need lower room temperature for comfort if it can get the room comfortable. An oversized HVAC system is not like an oversized resistance heater simply cycling for a shorter period of time.

The change from 3.5 ton to 4 ton probably came with improved technology, and might even have come with a variable speed compressor which allows the system to dial back the compressor power when loads are lower.

Jonathan

 

[kwired]

I have also heard an admonition against installing air conditioning that is too big for the space to be cooled. That makes it cycle on and off more often with more and larger startup (compressor motor inrush) losses.

Also, short cycles don't give the system enough time to dehumidify well.

That is a major benefit of two stage or variable speed units. High stage can remove more heat and humidity when there is demand for it, but low stage or rate will help keep dehumidifying when temp doesn't need to be lowered much - resulting in better overall comfort.

 

[mtnelect]

I welcome the conversations on HVAC systems, since they are one of the most important loads on an electrical service.

1) One of the basic rules of Thermodynamics is that the Latent Heat has to be removed first before the Sensible Heat will drop. So, it is true that oversized units do not run long enough to remove all of the moisture and smaller units never turn off.
2) In today's environment of energy efficiency "Rule of Thumb" is a waste of energy that this country can't tolerate anymore.
3) The "Heat Load Engineering Study" not only determines the size of the HVAC unit, but also the size of the distribution system.