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Old 05-30-2013, 11:19 AM   #1
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Problem controlling temps with Fujitsu split system


I bought a house that has a Fujitsu Hyclacon split system heat pump, Model ASU18RLXS and am installing a UTB-UUB Programmable Wired Thermostat Remote Control.

The indoor unit is located in an upstairs vestibule and I have alway had trouble controlling the adjoining room temps, through the open doors. I attributed this to the temperature sensors being located in the indoor unit itself. I figured the best way around that would be to install a remote thermostat, in an adjoining room.

I bought the UTB-UUB as a brand new unit, off the web. Got it installed and it is now controlling the Fujitsu - kind of. When I plugged the connector in circuit board on the wall unit, I did not disconnect the two internal thermistors. Fujitsu tech support (they really didn't like talking to a non-contractor) said there was no need to unplug them.

Right now, I have the remote controller set to 74F, and it has been set there for the last 12 hours. However, I have a thermometer sitting close to the controller and it reads 79F. Why the big difference? Is there an internal calibration I can perform? How can I be sure the remote is doing the sensing, and not the internal thermistors?

Another screwy thing about this UTB-UUB, is it apparently doesn't display the room temperature. WTF? Is there a setting I don't know about? What kind of goofy engineering logic would have someone design this fairly complex and expensive thermostat and not include a temperature readout?

Does anyone have experience with this setup? I would appreciate your experience.

Thanks!

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Old 06-03-2013, 02:17 PM   #2
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Problem controlling temps with Fujitsu split system


Well, no response, so I guess no one has experience. Turns out my experience is all bad. After going through hell to route the wire from the indoor unit to the wired remote controller (remove drywall, run wire, patch, and re-paint), I was extremely disappointed to discover that I am screwed (by Fujitsu).

Long story short is that remote wired thermostats do not work with my indoor unit. I wish they had told me that when I asked if the remote controller I was using was compatible with my system.

Here is the response Fujitsu tech support:
I understand but that setting does not work on the indoor unit you have. While the remote might show the thermo sensor is on, the indoor unit does not recognize it and will continue to read temperature at the indoor thermmistor located inside the indoor unit. Unfortunately the thermo sensor on the remote does not work with every indoor unit.

The remote will work it just will not read temperature at the remote, it will always sense temperature at the indoor unit. Even if you changed out the remote to the UTY-RNBYU, the remote will work but it won't sense temperature, it will always sense temperature at the indoor unit. The indoor unit you have will always sense temperature at the unit itself. This cannot be changed with any of our remotes unfortunately.


ARRRAUGGH!

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Old 06-03-2013, 11:26 PM   #3
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Problem controlling temps with Fujitsu split system


I am confused how you expect one head to control multiple rooms.....
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Old 06-04-2013, 09:22 AM   #4
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Problem controlling temps with Fujitsu split system


Quote:
Originally Posted by carmon View Post
I am confused how you expect one head to control multiple rooms.....
Good point - explanation warranted.

This system is for a small second floor. I guess they call the house a 1-1/2 story home.

There is a little 3' x 10' vestibule at the top of the stairs and that is where the indoor unit is located. There are two adjoining rooms, both with the doors removed. The stairwell does have a door, shutting it off from the downstairs. I use one room as my office and the other is the wife's little art studio.

You can see from the photo how the indoor unit is tucked into the vestibule, and how it would be lousy at regulating the temperature in my office. That is the crux of the problem. The vestibule heats (or cools) to satisfy the controller, but the office temperature lags way behind. You can see where I located the wireless controller, as well as the old hand held remote, which no longer functions.

After I simmered down after receiving the last correspondence from Fujitsu tech support, I figured how I can DIY this to my satisfaction. The problem is, the room temp sensor is located at the intake of the indoor unit. I could relocate that sensor to the inside of the remote wired controller that I just installed. I could use some 18ga thermocouple wire. Yes, I would have to go into the drywall again, but not such a large section since the holes are already drilled into the studs.

I can do this!
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Old 06-04-2013, 11:32 AM   #5
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Problem controlling temps with Fujitsu split system


I can't imagine what thought process made you decide to install the indoor unit in a vestibule (closet with the door removed), but now it's there and now you're realizing why it maybe wasn't the best location or the correct indoor unit to use.

Try making a temporary section of duct work out of some cardboard or whatever else you have handy to bring the discharge air out past the doorway. Not just a short section..... a continuous section so the air has no choice but to discharge past the doorway frame. Give that a try. By doing this you effectively move the unit out into the room........ kind of. If this shows an improvement in performance then have this duct work permanently constructed out of materials that will look good, last and won't sweat from the cold air going through it.
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Old 06-04-2013, 11:43 AM   #6
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Problem controlling temps with Fujitsu split system


Quote:
Originally Posted by old_squid View Post
I can't imagine what thought process made you decide to install the indoor unit in a vestibule (closet with the door removed), but now it's there and now you're realizing why it maybe wasn't the best location or the correct indoor unit to use.
I didn't. It was here when I bought the house, last year.

It's not a closet. You can't see from the photo, but the stairs come up into the vestibule. The stairs door is just opposite the indoor unit. The wife's art studio is mirror image from my office. I guess their reasoning was to have the one unit feed both rooms without adding ductwork.

Thank you for your suggestion, but I will not be adding any ductwork - the problem isn't that bad. I think the main thing is to get the temperature sensing out of the vestibule.

Last edited by MurphyMan; 06-04-2013 at 11:48 AM.
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Old 06-05-2013, 05:50 AM   #7
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Problem controlling temps with Fujitsu split system


Or just set the remote to 68 or 70 and see if it cools the rooms ok. Set the remote to run the fan continuous while you are in your office, or wife in art studio.
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Old 06-05-2013, 08:38 PM   #8
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Problem controlling temps with Fujitsu split system


I would contact Fuj. and verify that the temp sensor is not actually a coil temperature sensor prior to removing it from the unit.
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Old 06-07-2013, 04:30 PM   #9
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Problem controlling temps with Fujitsu split system


Success!!!

I substituted the Fujitsu thermostat wire with 18ga 5 wire thermostat wire. Three wires were for the original setup, then two additional for the temp sensor. Soldered everything and used heat shrink tubing on the joints.

You can see in the back of the thermostat the sensor that came with the thermostat (on the right), and the one I clipped out of the air handler itself on the left, and mounted into the remote controller. Potted the wires (not the sensors) with a dab of silicone calk and we're good to go.

As soon as I turned it on, I could tell it ran better! The wired controller (they don't really call it a thermostat) has settings for the fan speed, High, Med., Low, & Auto. I had it set to Auto, but it always seemed to run on Low.

Previous to my modification, it would run on high for about 30 seconds, then run at a lower speed. I'm sure the room temp sensor was picking up the air in the vestibule and the unit controller told it to moderate the temperature. Now, with the room temp sensor in the actual room, It stayed on high for a good deal longer, until the room actually stared cooling down a bit.

BTW- while I was searching on the web, I found this account of similar frustration due to the placement of the room air temp sensor. Here is the link to that article: http://www.lemis.com/grog/product-reviews/fujitsu.php My room air sensor was a little different, but same idea.

Chalk one up for the common man!
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Last edited by MurphyMan; 06-08-2013 at 12:07 AM.
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Old 06-24-2013, 06:02 PM   #10
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Problem controlling temps with Fujitsu split system


I have a fujitsu 24cl1 driver and buy a remote uty-rnbyu and followed all the instructions in the manual but can not activate the sensor of the temperature even e followed the tips of the people from fujitsu. When press the temperature boton in the remote control only flashing the key.
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Old 06-24-2013, 06:21 PM   #11
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Problem controlling temps with Fujitsu split system


Quote:
Originally Posted by andres1 View Post
I have a fujitsu 24cl1 driver and buy a remote uty-rnbyu and followed all the instructions in the manual but can not activate the sensor of the temperature even e followed the tips of the people from fujitsu. When press the temperature boton in the remote control only flashing the key.
You can try sending their tech support an e-mail. servicehvac@fujitsugeneral.com

But you need to provide a better explanation of the problem for them.
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Old 06-24-2013, 06:45 PM   #12
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Problem controlling temps with Fujitsu split system


When tray the activate sensor the sensor not activate only appear in the control display flashing key. I am read the manual and only indicate for activate temperature sensor press simultaneus set temperature botton and fan botton for 5 second appear the screen to activate temperature sensor. Press the timer boton to function 42 this function is for activate this sensor when the function 42 appear press set temp boton to 01 and press timer set and the 01 01 should stay but only (--) this symbol appears.
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Old 06-25-2013, 07:53 AM   #13
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Problem controlling temps with Fujitsu split system


Quote:
Originally Posted by andres1 View Post
When tray the activate sensor the sensor not activate only appear in the control display flashing key. I am read the manual and only indicate for activate temperature sensor press simultaneus set temperature botton and fan botton for 5 second appear the screen to activate temperature sensor. Press the timer boton to function 42 this function is for activate this sensor when the function 42 appear press set temp boton to 01 and press timer set and the 01 01 should stay but only (--) this symbol appears.
Send an email to the address I already gave you. Tell them the exact model of the remote controller and your inside unit. It is possible that the two units are not compatible, or do not have all the functions enabled. That was the case with the remote controller I bought. Here is the answer I got from them about my system:
I understand but that setting does not work on the indoor unit you have. While the remote might show the thermo sensor is on, the indoor unit does not reconginze it and will continue to read temperature at the indoor thermostor located inside the indoor unit. Unfortunately the thermo sensor on the remote does not work with ever indoor unit.
You need to see what they say about your system.

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