Metal Halide to T-5, how many do we need?

[brewchief]

When we setup a friends shop ten years or so ago we used some 400 watt metal halide high bay lights, we would like to replace them with T-5 fluorescent fixtures, how many t-5 bulbs will we need to get the same amount of light?

A little backstory, the highbay lights were free and are 277v running on 240v so I doubt that they are producing even the amount of light that they would be rated at. My friend works in a warehouse that decided to upgrade from T-5 to led fixtures so he was able to buy the used T-5 fixtures for cheap, if we didn't have a couple of pallets of nice T-5 fixtures then we would consider LED.

The main shop lights might go a couple of weeks at a time without being turned on, we have a few 105w CFLs that we use to provide enough light to move around and only turn on the big lights as needed.

Shop area that we need to light up good is aprox 50'x75' with 16' ceilings, steel building with the white faced insulation. The highbays we have put out a decent amount of uneven light and the buzz they make is pretty annoying.

Any thoughts or advice?

 

[cybrdyke]

I assume you mean T5HO, not T5. Tell us a little more about those fixtures. How many lamps are in them?
CD

 

[brewchief]

I assume you mean T5HO, not T5. Tell us a little more about those fixtures. How many lamps are in them?
CD

Yeah probably T5HO, 4' fixtures with 4 or 6 lamps, might be a couple with 2 buried in there as well, they all have a clear plastic flip down lens. IIRC they were in the cooler or freezer section and wouldn't turn on quick enough( many were on motion sensors). All are multi volt so we can keep on 240v.

 

[cybrdyke]

Can I also assume that the 400MH highbays are aluminum domes? If so, at 16' they're barely high enough to get a full beam spread and will put hot spots on the ground. If they're old, you've lost over half their potential output and the fixture itself is grossly inefficient.
From that height, the 4 lamp fixtures would probably be fine if you put them in the same locations as the highbays. Normally, the 4 lamp ballast will have a mysterious extra wire in it. That wire is a switch wire that will allow you to turn off two of the lamps. Look for it and use it to reduce your load with bi-level switching.
The T5HO's should give you more even light, better wall bounce, better color & CRI and about 1/2 the energy. One downside is that you'll have 4 times as many lamps to do maintenance on.
To further reduce energy, you could consider T5 LED tubes. They'll be about 24 watts instead of 54. They go right into the sockets without any re-wiring or bypassing. Should cost around $15 each. Depending on your annual burn hours, they may make sense. YMMV.
Good luck,
CD

 

[American Locomotive]

It depends on how efficient optically the T5HO fixtures are. However, single, efficient, 6-bulb T5HO fixture should easily put far more light to the ground than a single 400 W MH fixture.

Especially since you're not running the MH fixtures at their rated voltage.

 

[brewchief]

While I don't have exact specs on the lights we have these are close https://relightdepot.com/light-fixt...o-enclosed-body-high-bay-with-door-frame.html

I think all the lights we have have a clear plastic lens.

The old highbays are the aluminum domed ones and the light output is pretty spotty.

We were looking at placement a week or two ago and I think we will end up with two of the 6 lamp fixtures for every one of the old high bays with a few extras added in a few areas where it's needed. If one of the 6 lamp fixtures is about equal to one of the old lights then I think we will be in pretty good shape.


Converting to LED doesn't make sense as these lights might only be on one or two days a month on average.

 

[86turbodsl]

I went from 400W metal halide low bays to T5HO earlier this year. I pulled out 6 MH and put in 18 T5HO. I feel the shop is better lit now though. Shop is 40x64x14.

 

[brewchief]

Well some after some research I found that the light output from one of the old 400 watt metal halide fixtures and one of the 6 bulb T5ho fixtures is roughly the same.

So far we have taken 7 of the old fixtures down and put up 13 of the 6 bulb T5ho fixtures, a 50x50 section is done at this point. We have FAR better light with none of the shadows or buzzing that we had before.

It would have gone faster but despite all the lights coming from the same warehouse and being installed at the same time there are like 4 or 5 different styles of fixture that are all slightly different, some white, some stainless, some have a lens and some don't, it makes it tough when you are trying to decide where to use each style so it doesn't look out of place. Working out of a man basket on a forklift doesn't help either.