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#217611 - 09/15/16 10:59 PM Replacing 70W HPS with 18W LED
Potseal Offline
Member

Registered: 02/23/13
Posts: 187
Loc: Saskatchewan
A homeowner asked me to take a look at a Lithonia wall pack (TWS) that wasn't working. This light, mounted at the back of the house, is used as a security light for a rather dark and hidden area of the backyard. Even before I attempted to determine the reason the light no longer worked the homeowner made it obvious they would prefer a LED light instead of the 70W HPS. When I asked why the owner replied that they felt it ran too hot which caused the lens to warp (I didn't see the lens since they had it removed before I arrived). After looking at the way the fixture was installed, horizontally instead of vertically due to variations in the siding and conduit running out the bottom KO to a remote photo eye, I thought the simplest fix would be to retrofit the fixture with a suitable LED bulb. I called a local supplier with the details and was a little surprised when they quoted me $125 CDN for a 18W LED (2160 Lumen and 4000K). Another option was to buy a Lithonia TWS LED wall pack for a few dollars more although it is only rated for a 1000 Lumen. I then inquired about a $25 18W LED (Cree brand, 2160 Lumen, and 4000K) and what the difference was between it and the $125 model. The sales rep said it had to do with "optics" and that in the right fixture it would have more "punch"...? I do not know what brand the $125 LED bulb was but I do know that it is meant to replace a Metal Halide or HPS and that physically it is different in appearance than the cheaper incandescent looking LED. Other than that does anybody know if there is a significant difference in light output and light quality between these equally rated but substantially different in price LED bulbs?
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#217612 - 09/16/16 06:22 AM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
sparky Offline
Member

Registered: 10/18/00
Posts: 5542
There may be no "optical" difference at all Potseal .

You're talking the 'corn cob' led retrofits that operate at any voltage, we just gut the original HID

>>>


Perhaps it is really a listing difference ?

Our NEC had to 'openly address' this , not sure of your CEC

>>>
410.6 Listing Required. All luminaires, lampholders, and
retrofit kits shall be listed.

~S~


Edited by sparky (09/16/16 06:24 AM)
Edit Reason: computer challenged

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#217613 - 09/16/16 08:27 AM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 187
Loc: Saskatchewan
Sparky, I wonder if that lamp would even fit in the old Lithonia wall pack fixture? The sales rep I spoke with brought the subject up that it may be a little tight and asked me if the original HPS had a good amount of open space around it. Tough call without ever seeing the LED up close.

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A malfunction at the junction

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#217614 - 09/16/16 08:49 AM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 187
Loc: Saskatchewan
Here's the LED I plan on using after I bypass the transformer:



Just by appearances alone I can see why the LED in Sparky's post would be more expensive plus the fact it can tolerate different voltages. But does it perform any better?
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A malfunction at the junction

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#217616 - 09/16/16 12:52 PM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
Just from the gut...

sparkys nice retro more than likely will not fit in the existing wallpack.

The 18/100 Cree may not provide the illumination of the area in the clients 'eye', even though it's 'white light' as opposed to the yellow/orange of the HPS. That is unless they had the 'white HPS' that is pricey.

As you mentioned, the lens is 'warped', per the client; I would strongly suggest they buy a new complete fixture.
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John

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#217617 - 09/16/16 05:47 PM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
twh Offline
Member

Registered: 03/11/04
Posts: 892
Loc: Regina, Sask.
I think your 18 watt LED bulb in a HPS (or MH) fixture will produce a lot less light.

HPS and LED produce about the same number of lumens per watt. To get the same amount of light from an LED as a 70 watt HPS, the same amount of heat is created. An LED can't survive that in an enclosed fixture.

The LED is different because it's very directional. This allows you to use a fixture that puts all the light where it's needed and almost none where it isn't needed. The reduction in waste means fewer lumens and watts are needed.

A fixture made for an LED will have heat sinks and might aim the light produced in one direction. Depending on how much light spread you need, you might choose an LED or HPS.

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#217618 - 09/16/16 10:35 PM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 187
Loc: Saskatchewan
Went to the house today and removed the ballast from the Lithonia wall pack. I went ahead and installed the Cree 18W LED. The lens was not warped as I thought I had been told. It had a dark spot on the side of the lens that was facing up (remember, it was installed on the horizontal).

twh, concerning your comment about the heat affecting the LED in an enclosed fixture - I was talking to another electrician today about that very subject. Likely another reason the other LED bulb recommended for this type of retrofit is so much more expensive. It likely has some built in heat dissipation when used in an older fixture. Although the Lithonia wall pack has a gasket around the edge of the lens it doesn't close tight around the KO. The lens isn't damaged so it's just the way it's designed. The way the fixture was mounted this opening is on one side and may allow for some heat to escape. The fixture faces south but sits in a corner of the house with tall trees in front so I doubt it sees much direct sun. Definitely not a perfect solution but if it lasts a good number of years then it will be the most economical.

BTW, the Cree 18W LED just fit in this fixture. Length wasn't a problem but it sits right against the reflector. I didn't have to force it in but there's no room to spare on that side.
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A malfunction at the junction

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#217619 - 09/17/16 08:52 PM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 187
Loc: Saskatchewan
Went out for supper this evening and ended up not far from the house where I did the work. Drove by on the way home to take a look at how bright the light was. Even though it wasn't fully dark outside that light seemed really bright and my wife and I were looking from a fair distance away. If the main goal was to attempt to deter thieves from breaking into the house by entering the basement window in that corner then this retro-fit was a success. Other than discovering that the LED has a short lifespan in that fixture I would not hesitate to retro a fixture in the same manner again.
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A malfunction at the junction

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#217621 - 09/18/16 09:36 AM Re: Replacing 70W HPS with 18W LED [Re: Potseal]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5299
Loc: Blue Collar Country
I can't speak for ALL such replacements, but ....

The one time I used a 'corncob' replacement, it fit only because the fixture had an open bottom - it was the more square bottom of the bulb that got in the way.

ALSO, just as important, the LED bulb actually produced a 'warm' white light. That yellow you see in the LEDs is simply the circuit board, and NOT the color of the light emitted.

(Personally, I detest the color of the light produced by HPS
fixtures).

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#217622 - 09/18/16 06:41 PM Re: Replacing 70W HPS with 18W LED [Re: renosteinke]
sparky Offline
Member

Registered: 10/18/00
Posts: 5542
Potseal, i hope you're making out on this retro deal here

On you're sales rep query, i gotta say i've spent a LOT of phone time with them in my ear

When it comes to retrofits, they slice,dice, make julian fries, have somehow evolved to be seated at the right hand of God Himself, etc....

The truth of the matter is, i've read some pundit EE's who can parse out photometrics/color renditions/ angsrtomanalytics.. and such words over the usual 2 sylable hand downs sales reps offer

Despite my 3 toed sloth like understanding , i'm aware it's apples /oranges

That said, residing in the bluest green state to ever exist in the lower 48 allows me little wiggle room to do much but high 5 it all

~S~

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