Limit on BTUs?


  #1  
Old 09-06-08, 08:12 AM
B
Member
Thread Starter
Join Date: Sep 2008
Location: New York, NY
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Limit on BTUs?

Hello everyone. I live in a very old "pre-war" Manhattan walkup in which the landlord forbids A/Cs above approximately 6000 BTUs because the old electrical system cannot handle them if everyone were to install one (there are 30-40 units in the building). I have heard of prohibiting dishwashers but not limiting the BTUs on A/Cs. He said he just wants to make sure we don't install industrial sized A/Cs meant to cool apartments much larger than what is in that building; he also said we CAN get 2 air-cons below 6000 BTU each but don't run them at the same time.

Of course I didn't realize until after I moved in that a one A/C limit of <6000 BTUs for EACH apartment is really inadequate. Fortunately I have a 1-br, but I can't imagine adequately cooling even a Manhattan-sized 2-3 br with one little 5-6K BTU A/C. My question is, should I be able to run two <6000BTU air conditioners at the same time at a LOW setting?

You probably need more info about the electrical system - I don't know much else other than that the building is obviously old and was built I think in the 1920's - one of the old Manhattan "tenements" with high ceilings. I know that when we do turn on our 5200 BTU A/C, which is usually set on Low Cool with the temperature knob turned mid-high, the lights in the whole apartment "blink" once. Not sure if that's helpful. Thanks in advance!
 
  #2  
Old 09-06-08, 09:23 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Received 39 Upvotes on 31 Posts
My question is, should I be able to run two <6000BTU air conditioners at the same time at a LOW setting?
The selector on room air conditioners ONLY controls the fan speed, it has almost nothing to do with the total amount of electrical power that the unit will "draw" from the building's electrical system.

Now I may have some choice words and a derogatory title for the building owner, but in my opinion limiting the size and number of individual room air conditioners in a building with inadequate and deteriorating wiring makes a great deal of sense.
 
  #3  
Old 09-06-08, 12:32 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,500
Received 68 Upvotes on 62 Posts
Hello boris,

I agree that it seems unreasonable to limit your power consumption but it will assure that the building's main cct breaker or the fuse on the pole does not trip.
Overloading circuits on a large scale could also cause the building wiring to run hot if overloaded.

Running a window a/c on low fan will actually cause it to draw slightly less power as the compressor does not have to work as hard but the difference is only slight.

The only suggestion I can offer is to research the tech of small window unis to see if there are any more efficient models that will cool with less power consumption.
The import models have come a long way.
 
  #4  
Old 09-06-08, 02:40 PM
B
Member
Thread Starter
Join Date: Sep 2008
Location: New York, NY
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
thanks

Thanks for the replies thus far. I really have no idea about how electrical systems work. The owner said he just wanted to prohibit people putting in giant industrial-sized A/Cs, which seemed more than reasonable to me. Of course as I found out the hard way, we are in fact limited to only one of the tiniest A/C sizes available per apartment. That is NOT consistent with "just making sure people don't put in giant industrial A/Cs". So I certainly don't have a problem with ensuring the health of the aging electrical system - I simply thought the statements he made were misleading.

Anyway I'd appreciate it if someone could explain some electrical basics. There are 4 settings on my very simple A/C: lo fan, hi fan, lo cool, and hi cool. There is also a temperature knob - turning it up obviously makes the room cooler. I would think that the temperature knob has no effect on the two fan settings. To adequately cool my bedroom, I usually have the unit on lo cool with the temp knob on mid-high. If the settings have nothing to do with the amount of energy drawn from the building's electrical system, then logically I should see no difference in my electric bill if I run my A/C on hi cool continuously vs. lo cool continuously - right? (I would think that there is little electrical difference between lo FAN and hi FAN). But I think someone was saying that there is little power-drawing difference between lo FAN and lo COOL settings, regardless of how the temp knob is set. That means to me that turning my A/C down to lo fan periodically won't actually reduce my electric bill. I think I am misinterpreting?
 
  #5  
Old 09-06-08, 08:59 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Received 39 Upvotes on 31 Posts
There are several factors that may come into play. The size of the electrical service to the building, the number of apartments, the electrical load for the "common" areas and the electrical feeders and panels to the individual apartments. More likely than not the problem (if indeed there is one) exists on the feeders and panels to the individual apartments. There is nothing the individual tenant may do about this other than: a) request the building owner to upgrade the necessary electrical, or b) move.

Depending on the size and age of the wiring in the individual apartments along with the number of circuits and the "load" on those various circuits the prohibition for A/C units over a 6,000 BTU rating may be wise or it may be unnecessarily conservative. No one on this board can state differently unless they have intimate knowledge of your particular building and apartment.

Now, with the four settings (five if you count OFF) there are two that run only the fan and the other two run both the fan and the cooling machinery. The fan only settings take a minimal amount of power and the cooling settings take a much higher amount of power. The temperature setting only controls the cooling machinery being on or off when the main control is in one or the other cooling positions. The cooling machinery is either running or not depending on the temperature setting, the cooling coil temperature and the room temperature. When the unit is on low cooling the fan moves air past the cooling coil at a lower rate and the thermostat will tend to have the cooling machinery OFF cycle be longer due to less airflow and therefore less heat removed by the cooling coil for any given amount of time. The OFF cycle will be shorter when the control is set to high cool because with the fan blowing a greater volume of air past the cooling coil it will warm the coil at a faster rate.

The bottom line is that while low cooling MAY (but not necessarily) use a lesser amount of total kilowatt hours of electricity the peak load on the electrical system when the cooling machinery is operating is the same as the high cooling setting and it is that peak load that determines the necessary wire size and circuit capacity.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: