Tons to amps

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Re: Tons to amps

Rattus when I first got into this field in the late 60s the heat pump was fairly new and it pumped out 2 watts of heat for every one watt consumed.The 8.5 is equal to around 2.5 watts for every watt used.This is based on a SEER of 12 which I think is currently the highest.

Ronald :)
 
Re: Tons to amps

Originally posted by Ronald:
when I first got into this field in the late 60s the heat pump was fairly new and it pumped out 2 watts of heat for every one watt consumed.
Click to expand...
Ronald I would say you phrased that wrong.

It can not produce more watts then it consumes.

A heat pump does not 'make' heat, it only relocates it. :cool:

So we could say a heat pump moves 2 watts of heat for every watt consumed.

Bob
 
Re: Tons to amps

Bob and Rattus you all are killing me.

I did a job a few years back and when I would shout to my fellow worker, Less go eat Dave my super over the construction job would say are you going to eat Dave?

His wife was a grammar teacher go figure.

Ronald :D
 
Re: Tons to amps

Let's talk "efficacy"!

"Efficieny" cannot be greater than 100%, but "efficacy" can. So the heat pump/AC pumps more heat energy, than it consumes in electrical energy.

These numbers have no units as opposed to the SEER, Seasonal Effective Efficienty Rating, which carries the units of BTU/watthour.
 
Re: Tons to amps

No Ronald, we are not trying to kill you, just build a little character. I had a boss who would tell me that when I was faced with a difficult assignment.

Ronald, go back and check your AC book. See if the example was really comparing the effectivity of a heat pump or AC relative to resistive heating.
 
Re: Tons to amps

Bob thats not completely true about the heat pump.
It does concentrate and relocate the heat from the outside air and move it inside.

But I wonder how much heat is given off by the mechanical friction of the compressor since it is not a hundred percent efficient?This heat would add to the head pressure.

Maybe Rattus and others can figure that one.
Would that be just a few hundred watts or more?

Ronald :)
 
Re: Tons to amps

Rattus that did not come from my book but it was comparing the two.

For a reference to where I got the numbers click here


Ronald :)

[ February 26, 2005, 11:09 AM: Message edited by: ronaldrc ]
 
Re: Tons to amps

As an engineer, I often have to try to estimate the full load amps of an older AC unit armed only with the size of the unit expressed in tons. One ton (refrigeration) is equal to 12,000BTU/hr. One BTU/hr is equal to .239 amps. Therefore, the straight conversion of tons to amps (assuming 100% efficiency of the mechanical components' transfer of electric energy to refrigeration) is found by the following equation;

I = (#tons) x 12,000 BTU/hr x .239

Since there is no such thing as an ideal machine, I usually assume an efficiency of 80% (.8). The best estimate of tons-to-amps is then found by dividing the answer for "I", as calculated above, then dividing it by .8. This may be a little on the conservative side but that is a good place to be when calculating feeder size.
 
Re: Tons to amps

thirdbase, Yer out! Out of the ballpark that is. Your formula yields thousands of Amps and it does not consider the voltage or PF. Of course you have another at bat coming.
 
Re: Tons to amps

ronald,

I think the frictional losses would be relatively small. The iron and copper losses in the motor could be as much as 20% of the real power. This extra heat would boil off the dribble of Freon coming from the suction line in a capillary system, and some would be pumped out to the condenser. I think it would be like the full sun shining on the condenser, something we would rather not have because it hinders the condensation process.

Amy comments?
 
Re: Tons to amps

The significance of the motor heat losses depends on how the compressor is applied. If it is on a freezer, the low pressure vapor is really thin and doesn't cool the motor as well as an AC application on the other extreme. Sometimes an external fan blowing over the compressor is specified for low temp.

I guess one could estimate the amount of motor loss by comparing the performance of a heat pump between heating and cooling at similar differences of inside and outside temperatures.

Jim
 
Re: Tons to amps

Rattus
I didn't even think about the effect it would have on the change over valve it probably would have an effect on about any type expansion or capillary but thats a side effect thats going to be there regardless.

I was talking about the added head pressure giving the heat pump more heat.Probably wouldn't amount too a hill of beans though.

Rattus did you post twice by mistake or did the site do that? I have did that before.

Ronald :)
 
Re: Tons to amps

ronald, the xtra heat would tend to increase the head pressure and vapor temperature. If we have a 75% efficient 4 ton unit, that is about 1 KW wasted, or 3412 BTU/hour out of 48,000 BTU/hour. Doesn't sound like much, could I be wrong?

I don't post twice on purpose but there is a gray, fuzzy thing in front of the screen, so I don't always see what I am doing.
 
Re: Tons to amps

laughabove.gif
Should I ask what the gray fuzzy thing is ?
 
Re: Tons to amps

It is half dark in here, so I can't see for sure, but it makes purring noises when it is happy.
 
Re: Tons to amps

Jim

Just considering a heat pump I think the added heat from the compressor would be a extra cost on the air conditioning cycle and since its going to be there reguardless a plus on the heating cycle? I'm probably wrong.

Ronald :)

[ February 26, 2005, 11:29 PM: Message edited by: ronaldrc ]
 
Re: Tons to amps

Hey Rattus I grew up during the vacuum tube error.

Since the transistor can be of either polarity pnp or npn.

Do they still use the term B+ in solid state circuitry? :)
 
Re: Tons to amps

ronald, for single channel bipolar transistors, we use Vcc (collector). For single channel MOS we use, Vdd (drain) and Vss (source). For CMOS we use Vp (plus) and Vm (minus). There is a bit of variation amongst the various users though.
 
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