Logging electrical load at small grocery store

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strawburner

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Hi everyone, I have a small town grocery store here that that I service and they would like to reduce their electricity usage. They pay about $5000 a month for electric which owner thinks is outrageously high it is more than their total payroll. They are trying to stay alive and offer groceries for this rural area. The electric service is a 120/208 3 phase. They have multiple refrigeration units. Owner says he did remove half of their fluorescent light bulbs with no difference on electric bill. I do mostly residential work and a little light commercial I dont have meters that would log KW usage over a couple days time, but I am thinking we need to start recording usage on all the different loads and see where KW are going. I am going there next week. I am sure there are electricians out there that have experience or suggestions on how to start. Also they are paying a demand charge that is set during the months of highest usage is there a good way to keep peak demand down during hot weather by some kind of load control timers on the refrigeration units that would stagger run times.
 
strawburner said:
Hi everyone, I have a small town grocery store here that that I service and they would like to reduce their electricity usage. They pay about $5000 a month for electric which owner thinks is outrageously high it is more than their total payroll. They are trying to stay alive and offer groceries for this rural area. The electric service is a 120/208 3 phase. They have multiple refrigeration units. Owner says he did remove half of their fluorescent light bulbs with no difference on electric bill. I do mostly residential work and a little light commercial I dont have meters that would log KW usage over a couple days time, but I am thinking we need to start recording usage on all the different loads and see where KW are going. I am going there next week. I am sure there are electricians out there that have experience or suggestions on how to start. Also they are paying a demand charge that is set during the months of highest usage is there a good way to keep peak demand down during hot weather by some kind of load control timers on the refrigeration units that would stagger run times.
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This is a really complex subject, since so much is at play.


One place I may suggest is a lighting retrofit to LED. You did mention him taking lights out. If he only took the tubes out that will not do anything especially if the ballasts are magnetic. This was actually often done a lot during the 70s energy crisis but latter it was discovered to not help. A LED retrofit would cut lighting costs down over 50%.

The major power user, well over half is in refrigeration equipment. I would start making sure the units aren't defrosting to often, the case and serpentine heaters are turned off during low humidity... and that would be just the surface. Unless your an expert in commercial refrigeration you may need one to check everything out. How old is the equipment btw? If its over 20 years old that's your first excuse to look everything over.



IWIRE will be of help since if Im thinking of the right person has experience in such equipment.
 
Most of the refrigeration equipment is old some of it could be 20 years old also i did not realize a magnetic ballast would still draw power with lamps removed!


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strawburner said:
They pay about $5000 a month for electric which owner thinks is outrageously high it is more than their total payroll.
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Trying to compare electrical useage cost to payroll doesn't get you anywhere.

I think the people you need to talk to is the utility company. They will know if the bill is high for a similar business of that size in that area. Most utility companies offer real energy audits.
 
If their energy supplier is still the power company and if their state had third party energy suppliers, they might check that out.

Sometimes there is a 20% or more difference in the cost of a kWH, but the energy cost is only about half of the total bill around here, so a 20% reduction in the cost of energy is only a 10% reduction in the total bill.
 
Their electrical kW rate is around 12 cents I need to get monthly usage report from them yet but I am sure their demand rate is set in our hot months of june- august. Since they are on a limited budget I need to concentrate on their most inefficient piece of equipment right?

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You could check each leg in the service with a amp-probe and balance them by moving the loads around on the phases.

As far as the lighting and equipment........ There aren't any cheap solutions that I can think of.
Short of replacing all of the lighting and refrigeration equip with newer and more efficient gear.

How is the insulation in the building and the heating and air equip? Lot's of old buildings are very leaking and take a lot of $$$ to heat and cool.
 
I do tons of grocery store work and while you can do things to help save energy electricity is always going to be a huge overhead. 5k a month is actully pretty low.

Removing Flouresent lamps does almost nothing unless you kill the ballasts.

The lions share of the cost is refrigeration and unless they install modern equipment and controls will continue to be costly.


Things we do or see to help recovery or reduce costs.

Replace old lighting with LED (get costs subsidized by power company)

Replace old motors with new high effiancy ones, again you can get subized for that)

Kill lighting that is not needed

Put controls on the case anti condensate heaters so they don't run more than needed offten they run 24/7.

Take the waste heat from refrigeration and use it to heat the store

I may add to this list once I think on it.
 
I am sure that the insulation in this building is probably minimal. I think if we could change out some equipment and save let's say $750 month it would not take long to pay for some upgrades, but I need to figure out and start with the thing that gives the most bang for the buck! Right?

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iwire said:
I do tons of grocery store work and while you can do things to help save energy electricity is always going to be a huge overhead. 5k a month is actully pretty low.

Removing Flouresent lamps does almost nothing unless you kill the ballasts.

The lions share of the cost is refrigeration and unless they install modern equipment and controls will continue to be costly.


Things we do or see to help recovery or reduce costs.

Replace old lighting with LED (get costs subsidized by power company)

Replace old motors with new high effiancy ones, again you can get subized for that)

Kill lighting that is not needed

Put controls on the case anti condensate heaters so they don't run more than needed offten they run 24/7.

Take the waste heat from refrigeration and use it to heat the store

I may add to this list once I think on it.
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All excellent points!:)

Im thinking, on top of that couldn't they add a variable tap changing auto transformer to the ref equipment and do a 5% voltage drop? I know a wild idea. :p

Most motors are sized around the worst case scenario (max rating with a temporary overload sometimes), if the voltage is reduced to the motors when they are lightly loaded, that would yield savings.

I know if this being done on large central chillers and industrial motors were a voltage reduction done when the chillers/pumps/equipment are operating below capacity. Voltage is reduced (-5 to -12%) to the point where the motor has a slight slippage. Full voltage when the motors are back to full torque demand.
 
What types of refrigeration cases do you have? There were older cases that were not all that well designed, and you pump a lot of chilled air into the store - which may help with the general air conditioning, but does require additional heating during heating season. You could fit these units with curtains if necessary to help hold in some of the refrigeration. Iwire mentioned reclaiming heat from refrigeration - why pump it outdoors during heating season - it is heat you already put into the store and your refrigeration system is just taking it outside, again case design not only helps keep cold air in - it also keeps heated air out.

New compressors and refrigeration systems are much more efficient then those that are even 20-25 years old. Lighting in old refrigeration cases also adds heat to the case. LED's not only use less energy but give up less heat.

If you are charged penalty for low power factor then install correction- something you never mentioned but could be on the bill. Correcting power factor if you are not penalized for low power factor does ordinarily not save enough to be worth the investment

Changing peak demand is a little hard as when the demand is the highest - likely mid summer, is when you can least afford to cut back on refrigeration from quality/safety of products point of view.

If demand charges are high enough on site generation could help lower the peak demand, but chances are you are not that large of a user to justify it, your monthy bill would maybe need to be more like 50k per month before that route starts to be feasible.
 
Thanks guys for all the excellent ideas! Power factor is something I have never paid much attention to over the years but I know in the last year or two the poco has started penalizing for low power factor. I am not to experienced with improving power factor though any quick tips on that subject.

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I think the poster who suggested starting with the local electric company probably had the best idea. Usually it is a free audit and they often can tell you if there are any subsidies available that one might take advantage of.

It is not unusual for people who are just hanging on by the skin of their teeth to put off repairs and maintenance hoping to save money. There may be issues with his equipment that need to be dealt with.

Twenty some year old equipment was probably reasonably well designed for energy efficiency, but over time may have just worn out.

Many re-lamping programs are not especially economical unless they are highly subsidized.

It is just hard to say what someone who knows where to look might find.
 
strawburner said:
I am sure that the insulation in this building is probably minimal. I think if we could change out some equipment and save let's say $750 month it would not take long to pay for some upgrades, but I need to figure out and start with the thing that gives the most bang for the buck! Right?
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I assume for building air you heat with gas and cool with electricity. If that is the case any gain made by adding insulation will only show on the electric bl in the summer.

Its hard to say from here what will give the most bang for your buck, a full LED conversion might save 2/3s of the cost of lighting the store, but if lighting the store is only 10% of the electric bill it will not change the bill much.

If they, and you are serious about this there are consulting companies that will go to the store and figure out what can be done. They will know about the rebate programs offered and will come up with a game plan. We work for these types of companies, they generate a lot of work for us.

I have no idea what the fees are but the ones we work with are good at their job working the rebate programs to the fullest they can.
 
mbrooke said:
Im thinking, on top of that couldn't they add a variable tap changing auto transformer to the ref equipment and do a 5% voltage drop? I know a wild idea. :p

Most motors are sized around the worst case scenario (max rating with a temporary overload sometimes), if the voltage is reduced to the motors when they are lightly loaded, that would yield savings.

I know if this being done on large central chillers and industrial motors were a voltage reduction done when the chillers/pumps/equipment are operating below capacity. Voltage is reduced (-5 to -12%) to the point where the motor has a slight slippage. Full voltage when the motors are back to full torque demand.
Click to expand...

I can see that making great sense on large chillers working at partial loads. :)

The stores I work use many small compressors of different sizes on a central common manifold or header. The control systems use the most efficient combination of compressors to maintain the pressure set point. It is a constantly changing volume of gas they need to pump due to different cases going into cooling mode.

They have tried VFDs but they never seem to work out, I always see them bypassed.
 
In Florida a big issue is running refrigeration inside and then using HVAC to move the heat outside meaning you're moving heat twice at less than 100% efficiency each time. Moving compressors outside is the biggest savings. This would give you summertime savings. Ask the man for a year of bills and see when he's spending the money. If his biggest expense is heat you'll want those compressors inside.
 
I kind of like the idea about hiring a energy audit firm but I don't think I can sell the idea to owner if it is too expensive he is just barely keeping his head above water!!

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Kansas gets snow, I hope the compressors are indoors. :)

Around here I typically see them inside but separated from influencing the stores air temp. Typically very well ventilated rooms sealed off from the rest of the building.

Or if its an old store that has not been modernized just a little room filled to brim with compressors, water heaters and transformers with almost no ventilation and all equipment on it's last gasps of life.
 
Most of the refrigeration equipment is in a little room on the roof of the store with two 42" exhaust fans exhausting heat in summer. It does get hot in Kansas we can fry eggs on sidewalks in the summer. Owner had a bright idea of hooking a soaker hose up above the condenser coils to help cool the compressor in the summer.
 
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