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Old 02-05-2007, 11:15 PM   #1
Join Date: Feb 2007
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Fujitsu Heat Pump Concerns


I am a new member with my first post. I am hoping that someone here can help me out.

First a little background. We just completed a 400 ft2 one-story addition to our home in San Diego. I decided to go with a dedicated heat pump for this room because it will have several computer servers in it that need to operate in a relatively cool environment. I wanted to be energy efficient and did not want to have to cool the entire downstairs of my home to keep this one room cool. I worked with an HVAC person who I have used on and off for 15 years (he has installed several traditional air conditioners at previous homes).

We went with the Fujitsu Halcyon ASU24RL. The unit was connected about 10 days ago. After my installer left I tried to use it and the lights on the indoor unit were flashing. I could not get it to work. I called Fujitsu today and they told me I needed to reset the unit by pulling the fuse out of the outdoor unit and waiting 15 minutes. I did this. The unit started blowing air. However, the cooling feature is not working. I have the remote control set to 66 degrees, yet after one hour the room temp only dropped one degree from 76 to 75 degrees. Outside the air temperature is probably in the low 60s.

Is there something wrong with my unit? Or do heat pumps only work when the outside temp is higher than the indoor setting (a very scary thought)?

On a more serious note, the Fujitsu technician said several things on the phone today that have me feeling I bought the wrong unit. Here is what he said.

1. The unit is turned on and off based on a temperature reading on the wall mount unit itself (and not the remote control). The temperature on the remote control can differ from the actual temperature by as much as 8 degrees. This means that I may set the remote to cool the room to 76 degrees, but the unit may not kick on until the room is a balmy 84 degrees (or it could turn on even if the room was already a chilly 68 degrees).

2. The delta between the remote and the register is NOT fixed. So during the morning the remote may be 6 degrees lower than the real room temp, but in the afternoon the difference may be only 2 degrees.

If the above two are true, it means that:

a) Setting the heat pump to maintain a room temperature of between 68 and 74 degrees, for instance, is impossible. The amount of error with the remote control means the actual temperature can fall between 60 degrees (too cold to work) and 82 degrees (too hot for the servers).

b) The timer function that let's you program when the unit turns on or off is also worthless because you have no control over the temperature.

Has anyone else experienced this with their heat pump? Did I make a mistake with the technology choice (should I have went with a window mounted A/C)? Or is there a better brand of heat pump?

I am quite stressed out about this as I spent over $4,000 to have this unit installed and I am going to have a major heat problem in 2 months when the temperatures start to rise. Without any AC, my servers would heat the room to 95 degrees in the summer. I have allergies so opening a window is not an option either.

Any help/guidance would be greatly appreciated!


SanDiegoCool is offline   Reply With Quote
Old 02-13-2008, 06:50 PM   #2
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Just a quick question.. have you got any response to your problem from this site? I am looking at the same brand, for a small new house I am building, but it does not sound good



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Old 02-13-2008, 09:57 PM   #3
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I just installed the same model of 4 units today in 4 retail stores.waiting for the electriacian to wire up so i can fire up. I cant believe that the remote thermostat will not do what it is suppose to do. I read many great things about fujitsu on hvac and have installed a few years ago with out any problems. your installer should be the one troubleshooting the unit since he installed it.
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Old 03-19-2009, 12:27 PM   #4
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Be Cool

First of all– how much of a cooling load do you have? You can get a good idea of what the computers are putting into the room by measuring the amps to your servers and multiplying by the voltage - that will give you the power dissipated in the room – your AC should be a little bigger (~10%) to take care of heat gains through the structure so it can keep up with the load when it gets hot outside.

Assuming your load is smaller than your cooling capacity, the AC is definitely not operating properly and the Fujitsu people should be dealing with it. I suggest you have your installer chase it down with Fujitsu – they don’t want to talk with homeowners for fear you’ll try to fix it yourself.

I think you’ve also misunderstood the tech’s explanation of the temperature control sequence. The 12RL unit has a variable speed compressopr which responds to varying loads by slowing or speeding up the compressor. If the temp in the room is 6 deg(or more) above the set-point, the unit goes to full speed and stays there until there is a 4 deg temp difference between the set point and the room temp at which time it slows down a notch. If the room temperature increases, the compressor speed increases, but if the load is smaller than the ac capacity, it will eventually pull the room temperature 4 deg. Below the set point – at which time the unit will stop.

I strongly suggest you read the technical manual – your installer should be able to get one for you or if you are clever with Google, you can find it online.

Be Cool,
Bill the Cat
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