T8 vs T12 lighting savings

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dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
I work in a old plant where we are replacing about 300 t12 ballasts and 34w lamps with t8 retrofit ballasts and 32w t8 bulbs.

Is there any substancial energy savings in doing this? Especially since this involves buying new ballasts and bulbs and discarding and paying for removal of the old equipment.

What if any consequence is there in putting a t8 bulb in a t12 ballast and vice versa?
 
If replacing one T12 for one T8 I don't know that payback is all that great.

If replacing a 4 lamp T 12 troffer with a 3 lamp T8 troffer if will make more difference, but you have cost of entire fixture factored in there vs just a ballast and lamps.

3 lamp T8 puts out about same light as 4 lamp T 12
 
We are not using any less lamps, whether it is a 2 or 4 lamp fixture same amount of lamps just ballast and bulb replacement
 
dm9289 said:
We are not using any less lamps, whether it is a 2 or 4 lamp fixture same amount of lamps just ballast and bulb replacement
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I have nothing to back it up but often wondered if that kind of install is worthwhile. You are going from 34 to 32 watt lamps. You will have more light output than you originally had.
 
maybe i will amp clamp it tomorow before and after to see what results I get.
 
I have noticed recently that the cost of (1) T12 lamp is more than the cost of (1) T8 lamp.
As the T12 are going to phase out of market the cost will go up more or you would not be able to get them anymore.
 
good point on the lamps we are even having some problems getting incandescent flood lamps
 
dm9289 said:
maybe i will amp clamp it tomorow before and after to see what results I get.
Click to expand...

That may not be enough information to figure energy savings. Power factor needs consideration also. You need to know what actual watts is before and after.
 
I would consider T12 lamps being near obsolete in the near fixture, making the switch to T8's worthwhile. If buying in bulk, that shouldn't be much of an issue for a very long time though.

The question I would want to know is what kind of ballasts are currently used? If they are magnetic, a cost effective bandaid would be to switch the ballasts to new electronic ballasts. As far as actual savings in this process, you aren't looking at a considerable amount, nowhere near the cost of an entire retrofit. However, the price of T12's will start to rise, and eventually far surpass that of the T8. The "bandaid" would not be a consideration by myself, only suggested if requested.

If you decide to go T8 with the specs you stated, you are going to produce significantly more light at an insignificant amount of savings that will most likely never catch up with the cost of the retrofit.

It would be a much wiser decision, efficiency wise, to purchase the T8 retrofit and delamp from there for the facility.

If you go to T8's, you may also increase the CRI (not sure how important that is anyway).
 
Fixture Watts

Fixture Watts

A t12 1 lamp strip uses:

Room_Ex_Fixture_ID
1X4-1L-34W
Room_Ex_Fixture_Watts
43

Where a t8 on a low power ballast uses:

Room_Ret_Fixture_ID
1X4-1L-T8-LO
Room_Ret_Fixture_Watts
24

That's a 44 percent reduction in energy use.
2 lamps go from 78 to 45 watts, a 42% reduction.

3 lamps goes from 120 to 69 watts. 42% and so on and so forth. You have to look at fixture wattage with ballast installed not just the rated lamp wattage.
When compare fixtures to get an accurate comparesion you have compare new lamps to new lamps because the wattage consumed is reduced as light output goes down with older lamps.
 
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kwired said:
Where do you find wattage? Only thing marked on ballast is line amps. Power factor needs consideration and is not marked on them.
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My numbers came from a spreadsheet given us by one of the Texas utilities to calculate rebates for a lighting retrofit project. Ballast and power factors are considered. The data for line amps on the ballast label should be after power factor, it is a property of the ballast and can't be ignored when they calculate power consumption of the ballast and lamps.
 
BullsnPyrs said:
My numbers came from a spreadsheet given us by one of the Texas utilities to calculate rebates for a lighting retrofit project. Ballast and power factors are considered. The data for line amps on the ballast label should be after power factor, it is a property of the ballast and can't be ignored when they calculate power consumption of the ballast and lamps.
Click to expand...

Data on label that says line amps is exactly that - line amps at whatever the power factor is. If you have power factor other than 1.0 you can not simply multiply by voltage to get watts, you need to know what the power factor is and then you can determine watts.

The energy savings will depend on what watts is not line amps as you are billed for (kilo)watt hours and not amps.

Clamping an amp meter around the old then the new does not tell you the difference in energy used unless you know what power factor of each is and figure out the actual watts.
 
A/C bill reduction

A/C bill reduction

Do not forget the heat/cool factor

Electronic t-8 ballast put out much less heat.
A/C cooling bills will decrease also.
 
You also need to consider running time of the luminaires.

One that is used 8 hours or less per day will have a longer ROI than one that runs 24/7. Sometimes you run into ones that only run certain days of the week also.
 
WHOA! Before you do anything else you need, absolutely need, to find out about incentive programs in your area. Stop what you are doing because many utilities will not give you a rebate if you proceed and then seek incentives. It's not uncommon for utilities to pay for 50% - 70% of the total cost of installation. I know PA offers incentives and you need to tap into them. Whatever you are doing I advise you to stop if you have any regard for your wallet.

If you have questions about energy savings I'd be glad to help you. If you want me to calculate savings for you I can do so in less than five minutes. You can shoot me an email if you like, TNBaer@Gmail.com . (I'm in Oregon so this is not a solicitation)
 
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