AC/Heat Pump

[stellar1dan]

I was reading the owners manual and it say not to use the air conditioner using 15 amp power. Does the same apply for the heat pump?

[SteveH]

Originally Posted by stellar1dan

I was reading the owners manual and it say not to use the air conditioner using 15 amp power. Does the same apply for the heat pump?

Yes, it's using the same amount of power.

[GeocamperAS]

The cooling and heating mode use all the same running parts.
The fan circulates the air. The compressor pumps the freon.
A home style window A/C has the cooling coils (evaporator) on the room side and the condenser (hot coils) on the outside.
If you were to turn the unit around in the window, you would be heating your room.
A "heat pump" uses a valve to change Freon flow through the coils.
In cooling mode the room side coils act as the cold evaporator.
In heating mode the room side coils act as the hot condenser.

[mjayjensen]

If it runs and does not blow the breaker, why does having it on a 15 amp circut matter?
Jay

[SteveH]

Originally Posted by mjayjensen

If it runs and does not blow the breaker, why does having it on a 15 amp circut matter?
Jay

The A/C unit manufacturer probably does not want the unit run on a power circuit that might go into a low voltage situation when the compressor is starting.

[jcanavera]

Originally Posted by mjayjensen

If it runs and does not blow the breaker, why does having it on a 15 amp circut matter?
Jay

The biggest difference is the gauge of the wire that is usually used with a 30 amp circuit compared to a 15 amp. The length of the wire from your circuit breaker to the outlet affects the voltage that is delivered to the outlet. Typically the wire thickness offsets the amount of voltage that is lost from the breaker to the outlet. Here is a paragraph from a site I found.

The voltage drop of a conducting wire depends on both the electrical resistance of the wire and the amount of current carried. A wire's gauge determines its diameter and cross-sectional area. Wires with larger cross-sections have lower resistance values and therefore smaller voltage drops for the same current flow. The increased resistance arising from increasing a wire's length can be countered by using larger diameters for long wires.


In my case putting a voltage meter on an outlet in my trailer shows what happens when I plug the trailer into a 20 amp garage outlet when I turn on my air conditioner. My meter has a 10% variance factor so there is margin for error. When the trailer is plugged into without the air conditioner being turned on we see a voltage level of around 120-118 volts. When I turn on the air (my 15K unit takes about 18 amps when running the fan on high speed), the voltage out of the same outlet in the trailer can fall as low as 104 volts (depending upon the actual electrical load in the house). Since the meter has a 10% variance, it is entirely possible that my voltage could be down below 100 volts which can stress the fan and compressor in the air conditioner unit. Obviously with that in mind I will not run the air conditioner when the trailer is sitting in the drive.

Jack

[mjayjensen]

Jack,
Thank you for the clear explanation!
Jay

[mjayjensen]

At a recent birthday party my brother, my self, and my bride had a discussion about this. In the interest of clarity, I am copying his e-mail.
Please overlook my brothers outspokeness.

Jay



The last guy said what I said. Measure the voltage and if it's above 107VAC the air conditioner will run fine.

His statement that his multi-meter has a plus or minus 10% error is just stupid. If he is using a meter with such bad accuracy then he should not be giving advise on the issue. Any digital meter costing over $25 will have an error rate of about plus or minus 1%.

The only thing you need to worry about is the voltage while the air conditioner is running. If it's above about 105 you will be fine.

The other thing you can do is use a short (10 Feet) #12 conductor size extension cord and keep the distance from the junction box as short as possible. This will lower the voltage drop from the outlet. Also don't use a cable still on the reel. The cord must be completely unwound.

Keep in mind that a park that has only 20A outlets will no doubt have number 12 or higher cable running to the junction boxes. So their #14 wire will be short.

The last thing to worry about is to make sure you don't have other high current devices on the circuit.

Below is a voltage monitor which may work. If you are in the green regardless of the source of electricity everything is fine.

Amazon.com: GenTran Portable Generator Line Voltage Meter LVM450: Patio, Lawn & Garden


Craig J. Jensen
CEO Retired
Crystal Group Inc
Cell 319-431-4887
craig.jensen@crystalrugged.com
Rugged Military & Industrial Computer Systems | Crystal Group
-----Original Message-----
From: mjpjensen@juno.com [mailto:mjpjensen@juno.com]
Sent: Monday, August 05, 2013 8:17 PM
To: Craig Jensen
Subject: Electrical question?

http://www.airforums.com/forums/f37/...mp-103575.html
Craig,
Would you read this page and get back to me with your comment.
Jay

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[GeocamperAS]

Originally Posted by mjayjensen

At a recent birthday party my brother, my self, and my bride had a discussion about this. In the interest of clarity, I am copying his e-mail.
Please overlook my brothers outspokeness.

Jay

The last guy said what I said. Measure the voltage and if it's above 107VAC the air conditioner will run fine.


The only thing you need to worry about is the voltage while the air conditioner is running. If it's above about 105 you will be fine.
]

One way to damage the compressor is high current draw while running. This happens when the voltage is lower than it should be. This could be caused by low line voltage but is usually causes by improper extension cords.
The easiest way to measure this is with an ammeter. Lower voltage causes the current to increase. The amperage draw should not be more than the rating on the units nameplate.
Another way to measure lower voltage is not while it is running or just the source, but "at the instant of start". This is known as 'minimum operating voltage'. To take this volt reading when the compressor normally starts is almost impossible to do since the starting happens in less than a second. However you can take a reading by causing a locked rotor situation. This is done by letting the unit run for a few minutes to allow the system to build up pressure. Have the volt meter attached to the line voltage, when you turn the unit off, then back on right away, the compressor will not start due to the high back pressure. You only have a couple of seconds to observe your volt meter before the overload trips and stops voltage to the compressor. The lowest voltage reading you observed is the minimum voltage.
Minimum voltage should not be less than 10% of the name plate voltage. If the name plate says 115volts then 115 - 11.5 = 103.5 Or if the name plate says 120volts then 120 - 12 = 108