Rack inconsistencies

I know it's a fact of life that on tall racks, the top ones are hotter than the bottom ones. I have a tall rack controlled by one thermostat. So far during the cooler months there was not much of a difference top to bottom, only 2 degrees F or so. So I've just been using this arrangement for the past few months.

However, it is getting hot, and using my airconditioner to get the room down to acceptable ambient temperatures, I now notice a 5 degree F difference between top and bottom, with the EXCEPTION that the LOWEST level is as warm as the top one! The bottom level has styrofoam insulation underneath it. It really is strange because the airconditioner makes an air current which I thought would make temps more consistent in the room, and also it is located high up, so I thought it would cool the upper part more than the bottom. (?)

I know the best way is to separate into two thermostats, but the earliest I can get another thermostat is in 3 and a half weeks from now for reasons I will not get into. I wonder if in the mean time I can put styrofoam insulation on the back of the bottom half of the rack's back to even out the temperatures?

Anyone done this?

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Originally Posted by hungba

I know it's a fact of life that on tall racks, the top ones are hotter than the bottom ones. I have a tall rack controlled by one thermostat. So far during the cooler months there was not much of a difference top to bottom, only 2 degrees F or so. So I've just been using this arrangement for the past few months.

However, it is getting hot, and using my airconditioner to get the room down to acceptable ambient temperatures, I now notice a 5 degree F difference between top and bottom, with the EXCEPTION that the LOWEST level is as warm as the top one! The bottom level has styrofoam insulation underneath it. It really is strange because the airconditioner makes an air current which I thought would make temps more consistent in the room, and also it is located high up, so I thought it would cool the upper part more than the bottom. (?)

I know the best way is to separate into two thermostats, but the earliest I can get another thermostat is in 3 and a half weeks from now for reasons I will not get into. I wonder if in the mean time I can put styrofoam insulation on the back of the bottom half of the rack's back to even out the temperatures?

Anyone done this?

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The styrofoam may help, you could also try just taping black trash bags or something similar to just the warm side of the rack. That'll keep some of the warm air in, just enough to heat up those tubs to the same temps as the rest, likely enough.

-Jen

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Originally Posted by LLLReptile

The styrofoam may help, you could also try just taping black trash bags or something similar to just the warm side of the rack. That'll keep some of the warm air in, just enough to heat up those tubs to the same temps as the rest, likely enough.

-Jen

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Well the sides of my rack are closed, it is a melamine rack that is open front and back. Do you mean put black trash bags if the sides are just pillars?

I am also quite confused about temps sometimes. I have thermometer probe placed on the back corner of the tubs. This was put in before I got my temp gun. I find that the temp gun finds a spot in the middle of the hot spot that is let's say, correct at 89 - 90, just that middle spot, if I move the temp gun even an inch it will lower the temp. The rest of the hot spot is like 85 - 86, as shown in the thermometer probe. So what should I go by? That one little spot in the middle?

You want to go by the middle temp.

Quote:

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Originally Posted by hungba

Well the sides of my rack are closed, it is a melamine rack that is open front and back. Do you mean put black trash bags if the sides are just pillars?

I am also quite confused about temps sometimes. I have thermometer probe placed on the back corner of the tubs. This was put in before I got my temp gun. I find that the temp gun finds a spot in the middle of the hot spot that is let's say, correct at 89 - 90, just that middle spot, if I move the temp gun even an inch it will lower the temp. The rest of the hot spot is like 85 - 86, as shown in the thermometer probe. So what should I go by? That one little spot in the middle?

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If the sides were just pillars, the trashbags would help. Maybe try just covering the back exposed areas on the bottom half?

I would take an average the entire hot spot with the temp gun. How do you create the hot spot? With a heat pad, heat cable, heat tape? If it's not a heat pad, some inconsistency in temperature between the spaces of the heat cable or heat tape is not unusual.

-Jen

-Jen

Thanks for the advice people, but apparently one thinks I should take an average when the other says to use the hot spot (I presume by middle temp you don't mean average, but mean the temp in the middle?) so I still don't know! LOL

I don't "create" the hot spot. It is in every tub in the rack. It is heated with heat tape. You know how the heat tape is hotter in the middle? Not lengthwise but along it's width the middle between the two metal parts are hotter than the sides? Well, the rack has the tape running "along" the tubs. It is a one column rack and the heat tape is 11" just enough for my 11" wide tubs. So the middle of the hot end is the middle of the heat tape's width.

The person who said go with the hot spot, that is even so if it's only literally one spot? I search for the spot and if my hand moves a little bit it disappears. So far I HAVE been going with the hottest spot, just second guessing myself sometimes.

I also have struggled with stable and consistent rack temps. I use heat tape a bit so yes I have noticed it is variable start to end but again so is flexwatt. I personally check the hot spots of all the levels and accept from 89-91 range on any level.

My thoughts are two fold, I think the ac is generating variation in the room from when it is running to when it is not. Do you see a large change that way? I would try to direct the air from the AC to the ceiling to help mix the cool ac air and room air. A fan may help too. It is an easy solution. I don't know about adding stuff to the rack it may work but I am guessing the room is varying a lot and the t-stat probe is not reacting to the room changes.

The second thought is that if you use a second string of cable run off the same t-stat (exactly the same strings) and run the second opposite of the first (top to bottom or bottom to top) it is unlikely that the two strings will have cool spots in the same place. this may help as well. Hard to be sure.

My problem is to heat not cool so the solutions I have used are not as likely to do so in your case.

You could put a fan in the room, and just position it so it creates a cuurent.