Am I reading this current (amps) chart correctly? - Page 2

Xringer · 03-02-11, 07:37 AM

Nope, as the temperature falls, the RPMs go up as the power displayed on the watt meters goes up.

I'm sure the plots they publish don't take solar gain into consideration.

The lower pressure when colder.?. That's the way these gases act.
And more RPMs isn't going to change their normal behavior much.

Every tried to shoot a CO2 rifle when it was 12 degrees out doors?
The muzzle velocity drops off to practically nothing.

RobertSmalls · 03-02-11, 04:41 PM

Max RPM goes down as temperature falls.

I guess I'm not going to convince you that you have a thermostat that throttles your heat pump's output to suit your needs. *shrug*

Xringer · 03-02-11, 07:11 PM

It's a portable.

It transmits temperature and mode information using an IR diode (like a TV remote) to the indoor unit every five minutes.

If it's out of line-of-sight with the indoor unit for too long, the system starts using a thermistor that's in the air-intake of the indoor unit.

The Sanyo is a bit undersized for colder than average weather.
So, once I set it for 21c, it stays running full-time if it's under 20F outdoors and there is no solar gain.

From start up, (assuming it was about 20c) the power ramps up to 1.5 to 2.1 kW
over a period of 2-4 minutes. It stays at that level for about 1 minute
and then slowly starts back down towards a (*)fixed point that is controlled
by the outdoor temperature.

It will run continuously at or very near that fixed level for hours,
until the outdoor temperature changes.

It only changes it's power very slightly up and down in very small increments, to maintain it's current BTUh output.

And will adjust itself to the indoor temperature of 21c (0ur setpoint)
every five minutes. If we had the door or window open, and it got cold,
we have to wait for the 5 minute timer to click over, before power would increase.

(*)fixed point note
Right now(night time), it's about 32F outdoors and the power is staying around 580 to 600 watts.
The house is staying at a very stable 21c (69.8f). As the night wears on,
the temperature will drop down to around 10F. At that time, the power level
will steady up at 800 to 900 watts (depending on the dew point etc).

So, sitting here tonight, I can observe the outdoor temperature slowly dropping and the power use slowly increasing..

Edit:
11:50PM it's down to 22F and using 820 watts.

Because of these observations, I can see the cart showing colder= less amps is wrong..

Think of it like this, does it take more or less energy to pull the heat out
of extremely cold air? (As compared to cool air)..

Warmth is escaping from this house..
And, it's not at a fixed rate. The rate of loss will increase tonight.

If it was 69.8f outside, no heat would be escaping.
But, if it was 60f, a few BTUh would be leaking out..
And, if it was 10f outdoors, a lot more would be leaking out..

To maintain our 21c comfort level inside, when it's 10f or 20f outside,
we need more BTUh of heat.. So, the Sanyo is going to be working harder.

mrd · 03-02-11, 09:18 PM

The vast majority of the amps being pulled by the system is to drive the compressor. That's it. It doesn't matter if it's 100F outside, or -20F. If the compressor is running at full speed, it will pull a ton of amps, and if the compressor is just putting along, it will pull few amps.

The electronics, in conjunction with the thermostat, control the speed of the compressor, increasing its rate when the indoor temperature strays from the set temperature.

When it's cold, your house loses heat faster, and so the compressor finds itself running faster to maintain the set temperature. But the speed of the compressor is dependent on the difference between the set temperature and sensed indoor temperature, along with some knowledge of how its been running recently.

So, you observe greater amps at colder temperatures because the electronics are driving the compressor faster. The compressor speed is dependent only on the rate of heat loss at the thermostat. A different house would have a different heat loss at a given outdoor temperature.

The chart in the Sanyo manual must be showing the amps drawn by the compressor when it is running at its maximum speed - and apparently the amps for maximum compressor speed are less at lower temperatures.

My guess is the change in temperature of the refrigerant affects the internal pressure and thus power required to drive the compressor at a given rate. Robert is saying the maximum RPMs are reduced at lower temperatures.

Reduction of max RPMs feels like a more reasonable answer when looking at the drastic difference in amps over the outdoor temperature range. But I don't know why the RPMs would be reduced at colder temperatures.. The capacity is lower, but why slow the compressor? Is there too great a risk of icing the outdoor heat exchanger? I would think, higher RPMs, more heat transfer, regardless of the relative capacity.

Xringer · 03-04-11, 09:10 AM

Yeah, maybe the chart is just a theoretical plot, based on some odd-ball conditions.?.
I only know what I see on the metering.

Since I have no good way to measure the BTU output, the watt meter is all I can use.

Anyways, if less power was needed (to heat your house) when it got really cold,
these things would be the only way to heat!

Why waste money digging up the back yard for a ground loop??

RobertSmalls · 03-04-11, 07:51 PM

Quote:

Originally Posted by Xringer

Yeah, maybe the chart is just a theoretical plot, based on some odd-ball conditions.?.
I only know what I see on the metering.

Such a plot would be based on wide open throttle.

03-02-11, 07:11 PM	#13
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	It's a portable. It transmits temperature and mode information using an IR diode (like a TV remote) to the indoor unit every five minutes. If it's out of line-of-sight with the indoor unit for too long, the system starts using a thermistor that's in the air-intake of the indoor unit. The Sanyo is a bit undersized for colder than average weather. So, once I set it for 21c, it stays running full-time if it's under 20F outdoors and there is no solar gain. From start up, (assuming it was about 20c) the power ramps up to 1.5 to 2.1 kW over a period of 2-4 minutes. It stays at that level for about 1 minute and then slowly starts back down towards a *()fixed point** that is controlled by the outdoor temperature. It will run continuously at or very near that fixed level for hours, until the outdoor temperature changes. It only changes it's power very slightly up and down in very small increments, to maintain it's current BTUh output. And will adjust itself to the indoor temperature of 21c (0ur setpoint) every five minutes. If we had the door or window open, and it got cold, we have to wait for the 5 minute timer to click over, before power would increase. *()fixed point note Right now(night time), it's about 32F outdoors and the power is staying around 580 to 600 watts. The house is staying at a very stable 21c (69.8f). As the night wears on, the temperature will drop down to around 10F. At that time, the power level will steady up at 800 to 900 watts (depending on the dew point etc). So, sitting here tonight, I can observe** the outdoor temperature slowly dropping and the power use slowly increasing.. Edit: 11:50PM it's down to 22F and using 820 watts. Because of these observations, I can see the cart showing colder= less amps is wrong.. Think of it like this, does it take more or less energy to pull the heat out of extremely cold air? (As compared to cool air).. Warmth is escaping from this house.. And, it's not at a fixed rate. The rate of loss will increase tonight. If it was 69.8f outside, no heat would be escaping. But, if it was 60f, a few BTUh would be leaking out.. And, if it was 10f outdoors, a lot more would be leaking out.. To maintain our 21c comfort level inside, when it's 10f or 20f outside, we need more BTUh of heat.. So, the Sanyo is going to be working harder. Last edited by Xringer; 03-02-11 at 10:50 PM..

03-02-11, 07:37 AM	#11
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Nope, as the temperature falls, the RPMs go up as the power displayed on the watt meters goes up. I'm sure the plots they publish don't take solar gain into consideration. The lower pressure when colder.?. That's the way these gases act. And more RPMs isn't going to change their normal behavior much. Every tried to shoot a CO2 rifle when it was 12 degrees out doors? The muzzle velocity drops off to practically nothing.

03-02-11, 04:41 PM	#12
RobertSmalls Journeyman EcoRenovator Join Date: May 2009 Location: Buffalo, NY Posts: 344 Thanks: 3 Thanked 17 Times in 15 Posts	Max RPM goes down as temperature falls. I guess I'm not going to convince you that you have a thermostat that throttles your heat pump's output to suit your needs. shrug

03-02-11, 09:18 PM	#14
mrd Apprentice EcoRenovator Join Date: Feb 2010 Location: Milford, DE Posts: 106 Thanks: 5 Thanked 9 Times in 9 Posts	The vast majority of the amps being pulled by the system is to drive the compressor. That's it. It doesn't matter if it's 100F outside, or -20F. If the compressor is running at full speed, it will pull a ton of amps, and if the compressor is just putting along, it will pull few amps. The electronics, in conjunction with the thermostat, control the speed of the compressor, increasing its rate when the indoor temperature strays from the set temperature. When it's cold, your house loses heat faster, and so the compressor finds itself running faster to maintain the set temperature. But the speed of the compressor is dependent on the difference between the set temperature and sensed indoor temperature, along with some knowledge of how its been running recently. So, you observe greater amps at colder temperatures because the electronics are driving the compressor faster. The compressor speed is dependent only on the rate of heat loss at the thermostat. A different house would have a different heat loss at a given outdoor temperature. The chart in the Sanyo manual must be showing the amps drawn by the compressor when it is running at its maximum speed - and apparently the amps for maximum compressor speed are less at lower temperatures. My guess is the change in temperature of the refrigerant affects the internal pressure and thus power required to drive the compressor at a given rate. Robert is saying the maximum RPMs are reduced at lower temperatures. Reduction of max RPMs feels like a more reasonable answer when looking at the drastic difference in amps over the outdoor temperature range. But I don't know why the RPMs would be reduced at colder temperatures.. The capacity is lower, but why slow the compressor? Is there too great a risk of icing the outdoor heat exchanger? I would think, higher RPMs, more heat transfer, regardless of the relative capacity.

03-04-11, 09:10 AM	#15
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Yeah, maybe the chart is just a theoretical plot, based on some odd-ball conditions.?. I only know what I see on the metering. Since I have no good way to measure the BTU output, the watt meter is all I can use. Anyways, if less power was needed (to heat your house) when it got really cold, these things would be the only way to heat! Why waste money digging up the back yard for a ground loop??