Hitachi Ducted RAS-4HG7E

[aristg]

Hello people,

I am looking for the same answer to the question that has been asked in the following thread in the past, about the outdoor unit Hitachi RAS-4HG7E :

http://www.refrigeration-engineer.com/forums/showthread.php?29402-Hitachi-Ducted-RAS-4HG7E

In short for some reason the lower fan rotates in a much different speed compared to the upper.

So if there is someone that can tell me why or/and i could have a service manual i would really appreciate it.

Thanks

[frank]

Here you go. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.hitachiaircon.su/system/docs/service-manual_ivx_standart.pdf&ved=2ahUKEwjxj7SOpcDxAhWjnVwKHWJ4BuAQFjAIegQIFhAC&usg=AOvVaw1VgCsLncJre1QK9VuTAE4A

The fans are inverter controlled hence the different speeds to control head pressure

[aristg]

Thank you frank!

I was wondering though, is there a way to force it to high speed though to verify nothing is wrong? I am no expert but these days we are having 43*C ambient temps and looks weird not to work at full speed, or at least change speed.

Also the manual link refers to H(V)N(P/C)(E) utopia models, is it the same as the one i am looking for?

[frank]

Is a low fan speed your only concern or do you have any operational difficulties?

Carry out a Test run (see section 7.5) and then fill out the Test report in section 7.6 - this should give you an indication how the unit is performing.

[aristg]

My only concern is the fan speed. In my eyes, given that ambient temp is 43*C and i am asking for 19*C while the top fan blows super hot air, the lower fan should help the system at some point. It always turns at a very slow speed no matter what or when i set the system on any temperature.

I will carry out the test run and let you know though.

[aristg]

I did turn on the test run mode. What i found is werid though.

1) During test run no difference in fan speeds compared to the normal cooling mode.
2) The two fans are turning in the same direction and have the same blade shape

Taking the above observations into account i noticed the following abnormal thing:

I had the test run page printed and while i was holding it in front of the fans to check their rotation direction, i noticed that the lower fan was actually sucking the A4 page on the fan grille and held it there! Double checked its rotation and blade arrangement, same as above. The upper fan is blowing the paper away fast.

I can not explain that, but it definitely looks abnormal. The only thing i can think of is that the lower fan motor has not enough power (maybe some capacitor burnt ?) and given the difference in rotation speed the upper fan is sucking air through the lower fan hole.

Note: because i didn't believe what i was seeing, i inerted a soft cable through the grilles to check the rotation direction of the fans. Both bent the cable in the same direction ..

[B G Scott]

It looks like the lower fan is just free wheeling, ie. the upper fan is drawing air through the lower fan case spinning the blade.

[frank]

Did the Test run finish OK or did you get Error codes?

[redroge]

Block off the back of the coil to get the pressure up and see if the fan kicks in.

[aristg]

I didn't get any error codes during test run, however i will run it once again to make sure, today that temperature is higher.

I don't think that the fan is free wheeling for 2 reasons (thought of it as well so i kind of tested it).
a) They start spinning at the exact same time
b) i touched the center of the fan with a cable and it does not seem to loose speed at all no matter how hard i press it.

Ah, thats a good idea, i will cut a piece of cardboard to block the lower part of the coil and see what happens.

Will report back soon.

[aristg]

So completed the test second time, no error codes. Nothing changed as well.

Now to block the lower coil at some point.

Btw, could this be a faulty motor OR coolant gas missing ?

[redroge]

Do the fans both run in heating mode
Is the room temp ok

[aristg]

I am not sure if the machine will turn on in heating mode since outside temps are close to 40*C. I think there are safety measures to prevent that.

The ducts are at 6-7 meters high, however it seems that it spits enough cold air. It could do better maybe though.

[aristg]

So, i removed the cover to see the inner circuitry. I measured the voltages across the fans plugs, top fan 220V, while the lower 165V while on. I disconnected both fans from the pcb and turned them around (position 1 -> fan 2 and position 2 -> fan 1) and the upper fan dropped its speed to the same as the lower which we are investigating, while the lower worked in full speed. So it is not a fan / capacitor problem.

Disconnected both fans, measured voltages on pcb outputs -> both 220V. When a fan is connected to the lower fan's pcb output, then voltage drops to 165V and hence corresponding fan works at lower speed.

I am starting to believe this is a pcb problem.

A simple solution is to use a relay to connect the output of the pcb (so it won't draw any current from the pcb) and pull a 220 phase directly to the fan through the second set of relay's connectors.

Any other ideas ?

[frank]

There may not be any issue at all and you are trying to find one?

If the room temp is OK, why do you consider there to be a problem - just because you 'think' that both fans should run flat out?

How are you going to monitor head pressure and changes in performance while you mess with the lower fan?

The fan speeds are determined by the electronics based on various sensor inputs. Without knowing what the control strategy is you are guessing what should or should not be happening.

If it was me, I would be leaving it alone and enjoying the cool room, or inviting a local refrigeration guy to come and confirm your suspicions.

[aristg]

I hope it works like that normally. However it is weird that voltage changes when the fan is connected. It should feed 165V from the start not 220 and then when the fan is connected to drop at 165. This does not make sense, since the fan has no speed control on it.

As a matter of fact i asked a local technician who also told me that with 40+*C ambient temps it is not normal for a machine of this size to work @ reduced speeds.

Well, for now i won't do anything. I would like to see how it works during winter as well, in heating mode.

[AlixNevis]

I had this one, it's really good one!