I'm going nucking futs here!!!

[Gotta_Try_It_Once!]

Hi all,
I'm a newbie who cannot, no matter how hard I try, figure this one out on my own. I'm hoping by posting here, someone can help me.

I live in a 2-story private house with 3 bedrooms on the second level. The second floor is the equivalent to living in Antartica and I'm NOT a polar bear! The vents for the heat don't work very well up here so my son, daughter, husband and I tried to resort to space heaters. However...we found we can only run ONE of them at any given time. If we try to run 2 of them, the breaker trips. I went so far as to buy all different types of heaters with various BTUs and it has not helped at all. We've also tried running different types at once to the same end result.

However, during the summer, we can all run 3 average-sized window air conditioners full blast at the same time and the breaker doesn't trip. They all get plugged into regular 120-volt outlet, not a 240-volt. We've used the heaters in other homes we lived in and never had this problem.

I'm so tired of being cold! Is there a logical reason for this to be happening and how [if at all] can I fix it?

Many thanks!
Jessica

[LazyPup]

The first step of your problem would be to find out why your heat vents are not supplying a sufficient amount of heat.

First check your air filter. If the filter is dirty it will reduce the airflow and while there may still be a sufficient flow to maintain heat on the ground floor there may not be sufficient air flow to satisfy the further reaches of the duct system.

Check to make sure that the supply registers or return air grilles are not obstructed by furnishings or personal belongings. Return air grilles are especically critical because you cannot push air into a room unless there is provision for an equal volume or air to leave the room.

It is quite possible that your ducts have balancing dampers which are initially adjusted by the installer to insure a balanced air supply throughout the structure. Once balancing dampers are set they should never be moved but in the real world people often mess with them and get the whole system out of balance which then results in an uneven air flow throughout the structure.

Now in order to understand why you can run three AC's but only two heaters we must consider some mathematical constants.

12,000 BTU = 1 ton of Air Conditioning.
1 Ton of Air Conditioning = 1 Horsepower of Mechanical Energy
1 HP of Mechanical Energy = 746 watts of Electrical Energy

Typically a small room AC is rated at 5,000 to 6,000BTU's or .4 to .5 Tons of AC. Understanding that 12,000BTU = 1Hp we can then say that the AC compressor is a .4 to .5hp motor.

Allowing that 746watts of electrical energy = 1Hp we can then say that the compressor draws .4 to .5 x 746watts or 298 to 373watts.
These small room AC's also have a fan motor which is typically rated at about 1/5HP or 746/5 = 149watts. Thus the combined load of the compressor and fan motor would typically be:

298watts + 149 watts = 447watts
to
373watts + 149watts = 522watts.

Using the formula
P= E x I
Where
P= equals power expressed in WATTS
E= Electromotive Force expressed in Volts
I=inductive Force expressed in AMPS

We can then say that if P= E x I then I = P/E

Typically your supplied voltage (E) = 120Volts
The AC draws approximately 522watts(P) so we can then compute the amp (I) draw for you AC as:

I=P / E
I = 522Watts(P) / 120v(E)
I = 4.35amps.(I)

In order to allow a slight safety margin most small window AC's are rated at 5amps on the data plate.

The small electric room heaters are typically rated at 1,500watts.

using the same formula:

I = P / E we find that a 1500watt room heater draws;

I=P / E
I = 1500 / 120
I = 12.5amps.

The electrical outlets in your bedrooms are computed as "General Lighting" circuits and they are typically supplied by a 15amp breaker.

From this you can easily see that the small room AC's draw approximately 5amps each so theoretically a 15amp circuit could supply 3 of them. However we must also consider that there are other loads on these circuits. From the computatons i would suspect you have at least two breakers for the three bedrooms on the 2nd floor therefore you could run the three AC plus the lamps, clocks, TV's or other small electrical devices common to bedrooms. On the other hand each portable heater requires approximately 83% of the energy supplied by the breaker which explains why you cannot run multiple heaters.

[snowman04976]

So if you want to get warm today, find another outlet in the house that is on a different circuit, and run an extension cord that can handle the heater!

[leodlion]

Lazy Pup analysis is right on the dot. You need to make the heater vent work.

As a temporary measure, get some long extension wires and use the outlet from the 1st floor kitchen if you can. Usually, the kitchen outlet breakers are higher than room lightning (e.q. 15 amps versus 30 amps). Remember this is a temp measure because I dont like space heaters at all. They tend to topple and cause fires.

[ElectricGuy]

Extension Cords and Space heaters

IF YOU USE AN EXTENSION CORD FOR A SPACE HEATER MAKE SURE THE CORD and the ends are IN GOOD SHAPE AND THE WIRE USED IN THE CORD IS AT LEAST 14 AWG. NEVER use those cheap ungrounded extension cords, they are NOT safe to use with heaters!!!!!

[HayZee518]

Above all be safe. Even a 14/3 SJO cord [extension cord] will get warm. Spend the extra bucks and get a 12/3 SO, SJ or SJO cord. Another thing to consider is voltage drop - no more than 3% per 100 feet!