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Old 12-17-11, 09:19 AM   #1
poleikleng
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Default ASHP question

Recently installed Fujitsu 1.5 ton heat pump, last week the heat pump was set to 76 degrees, the temperature of the air coming from the inside air handler was 96/97 degrees. Outside temperature was 45 degrees. Previous to this when we set the temperature to 76 degrees we would have 130 degrees coming from the inside air handler with similar outside temperature. In the afternoon we shut off the heat pump and turned it back on then the air temperature from the air handler was 127 degees. What would cause the unit only produce 96/97 degrees yet when we turned it off and then on again the unit would produce 127 degrees? Thanks in advance for any feedback.

Location: Massachusetts

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Old 12-17-11, 01:17 PM   #2
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Originally Posted by poleikleng View Post
What would cause the unit only produce 96/97 degrees yet when we turned it off and then on again the unit would produce 127 degrees? Thanks in advance for any feedback.
Lots of things could affect it.
  • You might have a defective unit.
  • You might have some activity in the house, like cooking, etc. (or several guests) that is (are) generating heat that you are unaware of.
  • There is a significant difference in humidity of the air inside or outside the house.

The third option is the most likely. Thermometers just measure the dry bulb temperature of the air, but there is significant heat (and cold) content in the humidity of the air, that thermometers do not measure, that the heat pump still has to work against.

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Old 12-17-11, 02:09 PM   #3
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Originally Posted by AC_Hacker View Post
Lots of things could affect it.
  • You might have a defective unit.
  • You might have some activity in the house, like cooking, etc. (or several guests) that is (are) generating heat that you are unaware of.
  • There is a significant difference in humidity of the air inside or outside the house.

The third option is the most likely. Thermometers just measure the dry bulb temperature of the air, but there is significant heat (and cold) content in the humidity of the air, that thermometers do not measure, that the heat pump still has to work against.

-AC_Hacker
AC_Hacker,

Thanks for the response.

No activity, only one person in the house. We also have a 1-ton Fujitsu heat pump upstairs which was not running. We turned this unit on and it was produced 116 degrees of heat from the air handler. This seemed to confirm that the downstairs, 1.5 ton heat pump, was not running correctly. I did call the company that installed the units and asked them to contact Fujitsu and see if this was a concern but have yet to receive a response. Have you had any other's who may have the same issue that I experienced? Also, today outside tempereaure is 40 degrees, remote set to 70 degrees, temperature from the 1.5 ton air handler is now 97 degrees.

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Old 12-17-11, 05:37 PM   #4
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This seemed to confirm that the downstairs, 1.5 ton heat pump, was not running correctly. I did call the company that installed the units and asked them to contact Fujitsu and see if this was a concern but have yet to receive a response. Have you had any other's who may have the same issue that I experienced? Also, today outside tempereaure is 40 degrees, remote set to 70 degrees, temperature from the 1.5 ton air handler is now 97 degrees.
Well, with the inverter technology, your heat pump is capable of outputting a variety of temperatures and air flow rates, depending on what it's little Japanese brain 'thinks' is appropriate at the time.

If it is putting out 97 degree air, that may mean that it is malfunctioning. It also may mean that hotter air is not required to maintain the current temperature.

So, is your unit keeping the part of the house that you want it to heat, comfortable?

Right now, my 3/4 Ton Sanyo is gently wafting out 87.6F air, and it is 40F outside, and the unit is set to 68F, which is exactly what the temp is inside (68F).

Here's an idealized chart that is supposed to explain how a mini-split operated:


The green line is supposed to show how a single-speed compressor would output temp to the room, with big overshoots and big undershoots.

The blue line is supposed to show how an inverter technology system operates, and indicates that in the beginning warm-up, extra power (higher compressor speeds) will bring the unit up to temp fast. Then when it approaches the set point, less power (lower compressor speed) is gradually selected automatically and the overshoot and undershoot are smaller. In my experience the inverter technology gives much smaller overshoot and undershoot than the chart might suggest.

Still think it is defective?

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Old 12-17-11, 06:01 PM   #5
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My first experience with the heat pump in cold weather and lot's to learn regarding their operation. Thanks for your response.

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Old 12-17-11, 06:11 PM   #6
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Hi Poleikleng,
If your Heat pump is a mini-split with Inverter technology, it will not provide
a consistent source of heat, that's unchanging.

With my Sanyo units, I get a big burst of power use and heat output when they
are first turned on, or when I call for an increase in heat.
Their normal operation mode is very variable.
No steady output is possible, when the indoor fan and outdoor fan & compressor
are continuously changing RPMs, depending on temperature sensor feedback,
from indoors (thermostat) and the temp sensors that measure the outdoor temp and refrigerant temps.

The only time power use on my systems is stable, is when the house is at
the setpoint temperature and the outdoor temp hasn't changed.

But, when one of the temperatures being measured changes up or down,
the Sanyo is going to react (and change it's power use).

Right now, Sanyo#1 is using 930 watts total. About ten minutes ago
(when it was using 460w) I moved the setpoint up to 22C.
During the next hour, it may drop back to using 460w again..

But, maybe not, it's getting colder outside.


With the indoor temperature changing (due to heat loss) and changing
weather outdoors, it would be very difficult to say that one of my
units was working better than the other..

Your best guide in checking performance (if you can't monitor power use)
is the room air temperature. Is it staying at your selected set-point??
If it is, then your system is working pretty well..
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Old 12-18-11, 08:24 AM   #7
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Xringer,

Thanks for the response, I appreciate it. Yes, our mini split has the inverter technology (Fujitus 18RLXS). My biggest challenge is finding the correct temperature settings. Last night (we do not need much heat at night) the setting was 70 degrees on the Fujitsu remote and when we woke this morning the temperature inside the house was 62 degrees (outside temperature 21 degrees 4:19 am (and dropping)). I then turned the Fujitsu remote temperature to 76 degrees to increase the heat in the house. The temperature in the house has increased to 63.1 and will slowly increase throughout the day but will not attain 76 degrees.

The mini split is different than what we experienced with our oil fired hot water system. I'm just now learning how the mini split operates in colder weather. Overall I'm happy with the Fujitsu, we have not used our oil furnace for heating.

Thanks again for your explanation, it’s appreciated. Another day maybe we you could give me some feedback regarding your TED unit?

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Old 12-18-11, 10:15 AM   #8
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Yeah we had a chilly night.. http://ecorenovator.org/forum/billia...html#post18416

I can't understand why your temp would drop to 62, if your remote was set to 70..
If your system (21,600 BTUh heating) is correctly sized for your home, then something is not working right.
(I'm assuming your home has good insulation and not a lot of sq feet to heat).


If the remote control was placed so it could communicate with the IDU,
(line-of-sight), it should have maintained 70 all night long. (At the site of the remote).

Did you press the 'Sleep Button' or 'Minimum Heat' button?
Are your air intake filters clean?
http://s3.pexsupply.com/manuals/1298..._PROD_FILE.pdf



One thing I have learned about using ASHPs, is not to turn the temp down too low at night.
Because it's ductless, (a single-point heat source) tt can take a long time to restore the setpoint we want..

So, using Sleep mode or the timer isn't productive. Since you will use a ton
of kWhs to get back up up to comfortable temps.

Unless you have great solar input early in the AM, which will warm
up the house with hardly any help from the heating system.
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Old 12-18-11, 10:21 AM   #9
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My TED is pretty good, when it's working. It will not take data when,
I have the kitchen CFL lighting turned on, or when the nearby Motorola TV (Fios) cable box is on (or is plugged in).
Otherwise, it's okay. Someday maybe when I have all LED lighting
and cable gets too expensive, I'll really like my TED..
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Old 12-18-11, 11:38 AM   #10
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Xringer,

Our downstairs is 1060 square feet, we had three quotes regarding the heat pump, two of those quotes recommended a 1-ton unit downstairs and the quote that we selected recommended the 1.5 ton unit. House was built in 1979 so the insulation may not be up to today's standards. We did replace all of our windows with windows that had a much better energy efficiency ratings but we have too many windows. We do not have our remote set to line-of-sight and I will move this. We did not press any buttons by error and have the setting on heat and the fan on auto. I just recently cleaned the filter (last week). We do not use the sleep mode and I have too noticed that it takes a long time to build the heat up when we turn the setting down at night.

Thanks again for the response it is really helping me learn about the operation of the heat pump and I appreciate the help.

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