Posts Tagged ‘light bulbs’

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Finding a More Efficient Lamp

Monday, July 13th, 2009

As I was finishing up my previous post about efficiency pitfalls, I realized that I had started an example which could be useful in and of itself. So I’m going to take it a step further.

Situation Summary: I have an existing fixture in my home that I want to make more efficient. It is a surface mount that looks like a glowing bowl stuck on the ceiling. It uses two 75 watt bulbs. The light in the room is more or less acceptable, although it is a little dim and I would like it to be slightly brighter if possible. Looking up the information about the existing bulbs, I see that the total lumen output of both bulbs is 2,340, so I know I want to at least match that and if possible increase it slightly.

I could have just substituted my 75 watt incandescent bulbs for 20 watt self-ballasted CFL bulbs, based on the label on the box that says to replace my 75 watt bulbs with the 20 watt CFLs. The energy savings is good, since now my fixture only uses about 40 watts instead of 150, meaning I’m saving about 73%. However, the mean lumens of those CFLs are only 965, so the new total would only be 1,930. Since I thought the room was already a bit too dark, going from 2,340 lumens to only 1,950 is going to make me unhappy over the long term, and I run the risk of someday switching back to the incandescents. (Note, the initial lumens of this bulb are listed as 1,150, which brings my total up to 2,300 and almost a perfect match to my existing. However, that is initial lumens and won’t last for the lifetime of the bulbs. They will continue to depreciate and my room will get darker and darker, so it is an unfair comparison to use the initial lumens.)

Fearing the decreased light output, I buy two 26 watt self-ballasted CFLs because I see that the mean lumens for those are 1,365, meaning my new arrangement will provide me 2,730 lumens! I’d be saving about 65% energy by using 52 watts, but I discover that the 26 watts lamps are bigger than my existing incandescents and they won’t fit in my fixture. The bowl hits the ends of the lamps preventing me from reattaching it.

Now I recall reading my own post from yesterday. I go to my local electrical supplier and buy a replacement fixture for the existing. Based on my post, I’m now using a long “blob” instead of a bowl on the ceiling. I get 2,772 lumens, so I am very happy with the new lighting level in the room, and I’m only using 32 watts. That’s a savings of about 75%, better than the savings from those CFLs! Granted, I’ve now bought a new fixture as well as lamp, and I had to be very careful about my lamp and ballast choice, but I’m much happier with the final result.

Of course, this just shows that in order to make the best choice you need to have some knowledge, but that’s what this blog is for. Feel free to send me questions or reply to my postings to get more information.

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Posted in Fluorescent (and CFL), General Knowledge, Homeowner Tips, Uncategorized | 4 Comments »

Efficiency Comparison Pitfalls: Systems

Friday, July 10th, 2009

Another pitfall with comparing lamp source efficiency is the entire system’s efficacy.

With incandescent and halogen sources, the wattage on the label is pretty much what you get.

  • Technical info, you don’t have to read or understand this: the “what you see is what you get” assumes that the voltage matches. That is, a normal 100 watt light bulb will consume 100 watts at normal household voltage of around 120V. If the voltage is increased, the wattage increases, and if the voltage is decreased the watts consumed also decreases. Some manufacturers use this effect to create longer life and energy savings bulbs; for example, GE sells a 100 watt 130 volt lamp (3,000 hour life) which is labeled for 120 volt use as using 89 watts (8,300 hour life). Of course, the light output also decreases, and it decreases faster than the energy savings: losing 25% of the light output while only saving 11% of the electricity consumption.

Discharge sources, like fluorescent, require some form of control gear to regulate the electricity being consumed. The wattage label on the bulb is not the wattage which will actually be used in the system because the lamps can’t regulate their energy consumption themselves. They require a ballast to do that for them.

Since the ballast is what actually controls the wattage consumption, you have to calculate the efficiency of the system using both the lamp (for the lumen output) and the ballast. Professionals use the term efficacy instead of efficiency to remind themselves that they are dealing with the multipart system rather than just a lamp. So if you compare the efficiency of an incandescent bulb to a fluorescent replacement, you have to make the comparison against the system’s efficacy, not the lamp efficiency.

For the self-ballasted compact fluorescents you pick up at Wal-Mart the comparison is still fairly easy, since the ballast is included as a part of the lamp and the wattage listed on the box is for the ballast. In that regard, you can compare a regular light bulb off the shelf with the CFL next to it. However, if you live somewhere like California, where they have outlawed the use of medium screw based sockets in new construction (emphasis on new), you can’t use a self-ballasted CFL anymore.

Instead, you have to look at the efficacy of the lamp/ballast combination. Different ballasts will have all kinds of different ratings and properties that make reviewing them mind-numbing for the average person who just wants a light bulb. The take away is that the lamp ballast efficacy will be different than the lamp source efficiency. Usually it is less, although sometimes a system can have better efficacy than its lamp’s efficiency.

  • Technical info, you don’t have to read or understand this: Ballasts affect the lumen output out the lamps they control separate from the age issue I discussed previously. The affect is known as the “ballast factor,” which is the ratio of what the ballast does to the lamp it is powering versus the fictitious “perfect laboratory ballast” which is used to give the lumens shown on the lamp box. The number is a percentage (real output divided by “perfect” output) and written to two decimals (0.77 or 1.53). You will see ballast factors greater than 100%, accompanied by a wattage higher than the wattage listed for the lamp alone. To determine actual lumen output, you have to multiple the listed lumens by the ballast factor. This new lumen value is what you use to determine the efficacy of the system, along with the ballast’s wattage for that lamp. One ballast may have different ballast factors for different lamps, which will be listed. For easy comparison of ballast factors among different ballasts, there is also a “ballast efficacy factor,” which is the ballast factor divided by the input watts. The higher this BEF the more efficient the lamp/ballast combination, so you can compare ballasts for the same lamp that may have different wattage usage.

An example to demonstrate that you have to look at both the lamp and ballast:

I’m using a 4′ long linear T8 lamp, like you see in a 2′x4′ office fixture that is recessed in a grid ceiling made up of 2′x2′ tiles. To be specific, it is a GE F32T8/SPX35/ECO, which provides 2800 (mean) lumens for 32 watts. My first ballast option is going to be a GE “Residential Grade ProLine” ballast (GE232-120-RES). The lumen output for one lamp is 2,772 (mean lamp lumen times the ballast factor). The system wattage is 32, so the efficacy of the system is 86.6 LPW. I then substitute the “Residential Grade” for a regular “ProLine” ballast (GE232-120-N). The lumen output for one lamp is now 2,632. The system wattage is 36, so the efficacy is now 73.1 LPW. I want to try one more ballast and I choose the “UltraMax Instant Start Multi-Voltage High-Efficiency” because the name sounds cool and highly efficient (GE132MAX-L/ULTRA) The lumen output is now 2,156. The system wattage is 25, so the efficacy is 86.2 LPW.

To choose my ballast, and because I don’t care about how much each one costs for this example, I discount the “ProLine” ballast since it gives me similar output to the “Residential Grade” ballast with less efficacy. Now, I have to choose between the “Residential Grade ProLine” and the “UltraMax.” They have similar efficacies, so I have to choose which I want based on the lumen output. What I haven’t told you yet is that I’m replacing a surface mounted fixture in my home that uses two 75 watt bulbs. The lumen output of the existing fixture that I am trying to match is 2,340, which falls between the 2,772 of the “Residential Grade” ballast and the 2,156 of the “UltraMax.” Rather than decide based on the efficacy or the wattage of each individual ballast I have to select the ballast based on the light output. I decide that I always though the room was a little bit too dark anyway and so I choose the “Residential Grade” ballast. Now, I’ve got a touch more light than before while saving about 75% of the energy, dropping from 150 watts down to just 32!

PS: I’ve written this using fluorescent lighting as the examples, but the same is true for all the gas discharge sources, like metal-halide, high-pressure sodium, etc. High-pressure sodium is an especially efficient light source, although it suffers from all those color temperature and color rendition problems discussed in previous posts.

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Posted in Fluorescent (and CFL), General Knowledge, Homeowner Tips, Incandescent | 2 Comments »

Efficiency Comparison Pitfalls: Age

Thursday, July 9th, 2009

Following up on yesterday’s post, efficiency pitfall number one: age.

An incandescent or halogen light bulb is a fairly closed system. It can be stuck in a socket and what you see is what you get. A 100 watt light bulb is going to be pretty consistent over time. There will be some decrease in the light output as the tungsten filament gets burned up and bits of it get stuck to the inside of the glass envelope, darkening the glass. However, for the most part the lamp will burn out and the filament break before the decrease in light output becomes much of a factor. Tungsten-halogen lamps do slightly better, since the halogen gas inside the bulb makes the tungsten that gets burned off reattach to the filament and basically “recycle” itself, but even though the lamp will last longer and suffer from less darkening it will still break before those changes tip the efficiency equation too much.

Unfortunately, the same cannot be said for the various discharge sources like fluorescent, compact fluorescent, or the various HID types. While a filament does exist in these lamps, the real work of making light is done by the gas discharge. (Check some of my previous posts about fluorescent lighting for a summary of how it works.) The light bulb does not just “burn out,” but instead slowly degrades over time putting out less and less light.

This means that the efficiency of a fluorescent or compact fluorescent decreases over time if you are just using the lumens per watt calculation. For example, the day you install a brand new CFL 26 watt twist self-ballasted lamp you’ll probably get about 1,700 lumens. However, since the output of fluorescent lamps decreases over time, manufacturers also publish the “mean lumens,” which is the lumen output at about 40% of the lifespan of the lamp, which in our example case is 1,365 lumens. So the efficiency has dropped from 65 LPW when brand new to 52 LPW. The lumen output will continue to drop until the lamp reaches the end of its life.

Granted, the lower efficiency of 52 LPW is still much better than the 17.5 LPW of the 100W lamp we’ve replaced (see yesterday’s example). However, remember that you also have 20% less light. So after a while, the new CFL lamp isn’t providing the amount of light you used to have with the old incandescent lamp. This is the point when some people give up and go back to the old lamp, or they add a reading lamp using another incandescent lamp.

Professionals try to counterbalance the lumen decrease by working depreciation factors into the system when they are planning out what lamps to use in a project. We will intentionally over-light a space from day one knowing that eventually the lamps will decrease in output to the level we want for the longer term. The first 100 hours of a CFL or fluorescent is when the decrease is the most rapid, which is called “seasoning.”

As another age related problem, fluorescents don’t necessarily “burn-out” like incandescents and simply stop working. Sometimes, often times, they will just continue to get darker and darker and darker and don’t simply stop turning on. This is why professionals recommend having a maintenance schedule for replacing your fluorescent lamps based on time, not waiting for the lamps to stop working. (What? No one told you this? Yes, if you are going to use CFLs you should keep track of how old the lamps are replace them on  a schedule. And yes, it’s much more of a hassle than just waiting for the bulbs to stop working.)

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How Do I Know What’s Efficient?

Wednesday, July 8th, 2009

I have fielded a variety of questions from people trying to figure out what kind of lighting is more or less efficient than others. Many people understand that lower wattage is better, from a consumption view, but they don’t necessarily feel like they are comparing apples to apples when they try to compare incandescent to compact fluorescent or LED.

The way to determine efficiency of any given source is to figure out how much light you get for the amount of power used. Using the lowest wattage source may not be the most efficient approach if it doesn’t give you enough light and you end up adding more. The lighting industry uses a measurement called Lumens per Watt, or LPW. We take the total lumen output of the source divided by the wattage so we can make direct comparisons.

For example: a regular 100 watt light bulb for a table lamp, with clear glass so you can see through it, will provide about 1,750 lumens (it will say this somewhere on the box). Since it uses 100 watts, you divide 1,750 by 100 and figure out its efficiency is 17.5 LPW. Now you can compare that to a compact fluorescent replacement lamp (with a screw in base for your lamp) and find that it provides about 1,700 lumens for only 26 watts. The CFL lamp has an efficiency of a bit over 65 LPW. Therefore, we can say that the CFL lamp is almost 4 times as efficient as the incandescent.

To provide some general guidance I’ll type up a quick list of some sources and their LPW ranges:

  • Standard incandescent bulbs range from around 4 to 20 LPW
  • Tungsten-halogen bulbs range from around 18 to 22 LPW
  • Low wattage compact fluorescents range from around 20 to 60 LPW.
  • High wattage compact fluorescents range from around 50 to 80 LPW.
  • Linear fluorescents range from around 65 to 95 LPW.
  • LEDs range from around 5 to 40 LPW, although there is so much development of LED sources right now this range is likely to change quickly.

As with everything I write about lighting, there are some caveats. I’ll discuss a few of those in upcoming posts.

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Color Temperature Basics: Fluorescents

Thursday, July 2nd, 2009

The real meat of the color temperature discussion is with regards to fluorescent and HID (high intensity discharge) sources. Color temperature is tricky for fluorescents because it is based on heating the black-body object to get a color. However, fluorescent sources do not have an object to heat since there is no (functional) filament. Instead, it is a gas discharge process, so color temperature doesn’t really apply. Instead, we use the CCT, or “correlated color temperature.” This is just an approximation of the color temperature the manufacturer is trying to achieve with their mix of phosphors inside the lamp.

The reason CCT is important is because there are so many different phosphor mixes that can be used. Unlike incandescent lamps, there is a wide range of mixes and each mix, relating to a CCT, establishes what we see as “white.” It is this establishment of “white” that makes any and all of this matter.

By using a different phosphor mix, we make white objects appear either warm or cool, based on the (correlated) color temperature of the light source. All other objects, from artwork to skin color, reflects the same “bias” toward the color we have established as white light. This is why early adoption of fluorescent office lighting was so painful. The phosphor mix and color temperature of the light was shifted so far toward the higher, cool end of the lighting range people didn’t like the way things looked. There were other problems, but the main thing most people took away from the experience was an association of fluorescent lighting being “cold.”

However, we could just as easily make our fluorescent lighting “warm” by using lamps with a CCT with a lower number. For example, you could use lamps with a CCT of 2700 to try to match the incandescent lamps you are used to having in the home. In my experience, most people don’t like a fluorescent lamp with a CCT of 2700K either, since it doesn’t look like a regular incandescent lamp with a color temperature of 2700K. That’s part of the “correlated” aspect, and there is also some color rendering issues which I’ll discuss in following posts.

The trick to good fluorescent and compact fluorescent lighting is finding the CCT you like for any particular use. In more residential settings, a 3000K lamp may be preferred, whereas in an office or kitchen 3500K may be better. You can’t just pick one and use it for everything, although that would be preferable to not picking at all and just installing whatever shows up. Selecting the right color temperature is a part of the lighting design process.

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Color Temperature Basics: What is It?

Wednesday, July 1st, 2009

Color temperature refers to a “black-body radiator.” This is a theoretical object (as in, it doesn’t really exist but we pretend it does because we find that useful) that will absorb all electromagnetic radiation cast upon it; it will reflect or transfer none. Visible light is a small portion of electromagnetic radiation, which you can think of as the stuff coming from the sun that provides light and heat.

When a black body radiator is heated it begins to glow. There’s a cool java applet on the Olympus Microscopy Resource Center website that demonstrates this idea with a picture of a horseshoe. At the lower range it begins by glowing red. Then as it gets hotter it goes through yellow and white phases, eventually shifting into the very bright blue-white range. At any particular color, we refer to the temperature of the blackbody as the “color temperature.” (A note on that java tutorial, the temperature indicated on the scale refers to the tips of the horseshoe. The other colors move down the horseshoe to show that the tips are being heated and the bottom is cooler than the tip. The temperature does not relate to all the colors shown in the image.) The temperature is on the Kelvin scale, which is the same as celsius plus 273. That is, -273˚C is 0 K, 0˚C is 273 K, and 100˚C is 373 K.

For lighting, it is easier to refer to the temperature generating a color than trying to describe the color itself, which changes slowly and is not really part of our language of color. If you are looking at that java applet from Olympus, try to describe the difference between the color of the horseshoe tips at 2700K, 3000K, and 3200K. You’ll quickly realize why referring to a color temperature is easier.

A bit of confusing terminology, however, is that we refer to red the red side as “warm” and the blue side as “cool.” This is based on our traditional color associations of red and blue. It can be confusing because the bluer tint comes as you increase the temperature. Hence, you may hear people refer to “raising” the color temperature to “cool” the light source.

The filament of a regular incandescent lamp is not a true black-body, but it does go through the same color process as it is heated. That’s why when you put a regular lightbulb on a dimmer it shifts toward the red as you dim it down: it’s the horseshoe in reverse. Therefore, if you’re looking at incandescent lightbulbs color temperature isn’t a very useful metric. Regular and halogen lamps at full power usually end up around 2700K to 3050K, and that can be changed by adjusting the voltage. The real purpose of discussing color temperature is for fluorescent lamps, which I’ll get to tomorrow.

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Color Temperature Basics: Why Should You Care?

Tuesday, June 30th, 2009

I mentioned during the introduction to fluorescents that I would have follow-up posts about color temperature and CRI (color rendering index). I’m going to kick this off with color temperature and an explanation of why anyone would care about it.

relative-color-2One of the biggest problems with artificial lighting is that our eye and brain determine a lot of color information by comparison instead of some sort of mental color wheel. I’ve stuck an image file into this post to provide an example. The image to the right is made up of exactly 3 colors, but the purple color appears to be either a lighter or darker purple depending upon whether the adjacent color is the blue or the pinkish color. Also, the purple bar that runs all across the middle seems to change color from one side to the other.

The issue for artificial lighting is that as we look around us, our eye spots the brightest source of light and our brain “sets” that as white light. We are mentally doing the opposite of the what my sample image shows: instead of using relativity of colors to “see” either bright or darker versions of purple when the purple is actually the same, we are using relativity of colors to see different versions of “white” and then perceiving that as always the same “white.”

For the common user, a lightbulb (unless a specialty colored lamp) is going to be perceived as white. For the professional, we know that different sources are giving us different whites and we need a way to document the differences. We do that by specifying the “color temperature” of the source.

For the next post, I’ll explain what color temperature actually is and how we come up with the numbers.

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Last Full-Spectrum Post, I Promise

Monday, June 29th, 2009

I have just a couple more points to make about full-spectrum lamps.

  • They are more expensive. Since “full-spectrum” lighting is a marketing term, you should expect it to be an attempt to get you to pay more for a light bulb. There are reasons to pay more for a light bulb, such as increased efficiency or better color rendition, but paying more for a “full-spectrum” lamp should be approached with caution. You can sometimes get the exact same spectral distribution with greater efficiency from a non-full-spectrum source.
  • They are only worth it if they make you feel better. Some people will just like them. If that is you, and you don’t mind the cost, go ahead and use them. The increased UV isn’t too bad (remember: 8 hours of full-spectrum lighting to equal UVB of 1 minute of sunlight).
  • (A follow-up claim) Full-spectrum can make your whites whiter and paper brighter: This is slightly true, as you can increase the luminance about 1.7 to 2.3% of a piece of white paper or white cloth treated with whitening agents, but at the cost of 30 to 40% less efficacy.
  • Generally speaking, full-spectrum sources are less efficient than the standard version of the same thing. When making a choice, I recommend using the more energy efficient lamp.

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Full-Spectrum Lighting Health Claims

Friday, June 26th, 2009

I realized there are a couple of other things to mention, but so much of what I’ve been hearing relates to the health claims that I want to address that today and let the other things spill over into next week.

When the full-spectrum term was coined in the 1960′s it referred to both visible light and the invisible ultraviolet (UV) light. The health claims of full-spectrum lighting mostly revolve around the UV end of the range. All fluorescent light emits UV radiation, since it is the UV rays created by the mercury vapor striking the phosphor coating which makes a fluorescent light work. Full-spectrum lamps just emit more UV radiation than normal lamps.

The typical recommendation is to avoid as much UV exposure as possible. UV exposure has been linked to sunburn and skin cancers as well as cataracts in the eye. UV exposure also cause the degradation of textiles, paints, and architectural materials. Museums typically require all wavelengths shorter than 400nm to be filtered out of artificial lights.

  • Technical info, you may ignore: Visible light is 760 nm to 380 nm, UVA is light wavelengths between 400 nm and 315 nm, UVB is light wavelengths between 315 nm and 280 nm, UVC is light wavelengths between 280 nm and 100 nm. Visible light is broken down as red from 760 to 610 nm, orange from 610 to 591 nm, yellow from 591 to 570 nm, green from 570 to 500 nm, blue from 500 to 450 nm, and purple from 450 to 360 nm. These are defined by the International Organization for Standardization in ISO 21348:2007.

Full-spectrum lighting to treat SAD (seasonal affective disorder): Using full-spectrum lighting does not fit into the standard treatment of SAD, which involves exposure of the eye to a white light source in a light box. The light box typically generates 10,000 lux and it is used for about 30 minutes. Lower intensities might be used for longer periods. At 10,000 lux, any light source will be effective to treat SAD. Most importantly, these light boxes shield out UV rays, which is the opposite of using full-spectrum lighting. Using full-spectrum lamps in normal overhead lighting will have no effect upon SAD treatment.

Full-spectrum lighting and vitamin D production: Vitamin D is important, but the production is stimulated by the UVB band (315 to 280 nm) of light. Full-spectrum lamps typically use phosphors to generate UVA radiation (400 to 315 nm), and they typically peak around 355 nm. You are better off eating fish and dairy products and–if you’re really worried–taking supplements. Various studies have been done showing exposure to full-spectrum lighting for vitamin D production is impractical. For example, to spike vitamin D production in your body you may need 30 hours continuous exposure to a full-spectrum lamp to get the same affect as 22 minutes of mid-day sunlight. Or, 8 hours of full-spectrum office lighting has about the same UVB exposure as 1 minute of direct sunlight.

Also, the UVB rays that are generated by full-spectrum lamps often don’t bounce off surfaces. That means that if you are hoping to increase your UVB exposure you will only get it when in direct line of sight from the lamp to your skin. Everything else is absorbed by the materials and clothing around you. That also increases the deterioration of those materials.

In summary, there really are no serious health benefits to using full-spectrum lighting.

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Full-Spectrum Lighting

Thursday, June 25th, 2009

I’ve been running into people, Tweets, and marketing articles about full-spectrum lighting recently and I want to set some things straight. Full-spectrum lighting is a marketing term used by people selling you lighting products; it does not have any technical meaning in the lighting industry. Full-spectrum sources often cost much more than a standard product, sometimes more than 10 times the cost, and the overall benefits have not been proven.

Common claims:

  • It is closer to “natural” daylight, which is its own benefit: This claim is more or less meaningless. Daylight changes throughout the day due to atmospheric conditions (is it cloudy or clear) and time of day (mid-day sun or morning sunrise). All artificial lighting sources are static in their output, what you get at 3:00 PM on a cloudy day is that same as 2:00 AM at night. Some LED sources are collections of LEDs that can be programmed to change color, but that has nothing to do with mimicking daylight. Trying to hash out the meaning of this claim gets you mired in spectral distribution curves which is a huge topic, so for now just keep in mind that “full-spectrum” sources are just modifications of existing fluorescents. Except GE Reveal and the like, which are modified incandescents.
  • You get better color from full-spectrum sources: This is sort-of true. Full-spectrum fluorescents use a different phosphor mix that can sometimes have a higher CRI (color rendering index) than a typical fluorescent. The increase in CRI is often accompanied by an decrease in efficiency. You can also get non-full-spectrum fluorescents with higher CRI ratings than standard for slightly more cost than a standard lamp but still less than a full-spectrum lamp. The stand-out exception to this is the incandescent full-spectrum sources, which decrease the CRI of their bulbs.
  • You get increased worker productivity with full-spectrum: There are two parts to this: the first is just based on the ability to see tasks well. In most circumstances productivity for visual tasks is linked to monochromatic tasks, such as reading black ink on white paper. For these tasks it is the amount of light that determines good visibility, not the color or quality of the light. In this regard full-spectrum offers no benefits. There is some research suggesting that since the rods–which are blue-green sensitive–control the size of the pupil, light to the cool, bluish side causes the pupil to constrict and thereby increase acuity and you can get equal acuity with less power by using bluish light. I think it is unreasonable to get into this kind of detail when you just want to buy a lightbulb, so the simple answer is “no.” However, if your work is very color sensitive, such as fine art or clothing production, you want to maximize the CRI of your sources to affect productivity.
  • It has psychological benefits: This is the second part of the “increased productivity” claim. By definition, a psychological benefit is “all in your head,” so in terms of the benefit claim it is true. If you like full-spectrum lighting and don’t mind the disadvantages then you are getting a psychological benefit. Does everyone feel better equally, there’s no way to say, which is why it makes a good marketing claim. I have never found any research that shows a physiological link that leads to a psychological benefit. This is also often linked to the “natural” daylight claim. It is true that most people feel better working and living under daylight than artificial light. However, daylight changes throughout the day and with the weather, and I think the change over time is one of the main reasons people like daylight.

This post is getting longer than I like for a daily reading, so I’ll deal with the health concerns tomorrow. That will give you a chance to rest up and stay with me.

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