cyberkul
13-08-2010, 11:53 PM
Hi! I recently got an about 15+ years old Porkka 3000 walk in freezer. I had the refrigeration unit serviced by a supposedly qualified tech, and installed it later in the walk in cabinet. The problem was that due to a defective temp sensor the evap. fan would not start. The sensor was no longer available, and the tech just short circuited it. I`m not sure what the sensor function was, but I can enclose a circuit diagram here later if anyone would look at it.
The freezer then seemed to work fine, temp reached -20C, and after a while the defrost cycle started, and I could feel that the evap. bottom tray heater got warm. Then the next day I noticed that the freezer was stopped, and the fuse for that circuit was blown. I reset the fuse, and the freezer stated normally again. When the defrost cycle started I noticed that the bottom tray heater no longer got warm.
I inspected the mechanic timer, and noticed that it lagged a lot, and that the defrosting time was probably 2-3 hours. I also had a look at the electrical contacts of the timer, and they looked bad.
I then replaced the mechanical timer with a Dixell electronic controller (from eBay), but still no heat. From studying the circuit diagram it seems that there is a overheat sensor in series with the heater element.
So if this is open circuit the heaters will not work.
If I remove the evap. fan cover I see a large bulb with a cappilary tube (is this the right term?), sitting just inside the fan cover, not in contact with the evaporator. Is it likely that this is the overheat sensor? It is very difficult to see what else is inside the evap. area, and I don`t know how much I can move the evaporator without damaging anything?
Cappillary tubes from the room sensor and the one that I think might be the over temp sensor leaves the cabinet through a hole in the wall (see picture, covers removed), and goes to a box (controller?) outside near the compressor. It is not easy to get to this box without removing the refrigeration unit, but it might be possible.
With the Dixell controller I got a room sensor and a evap. sensor, so I should be able to get rid of the original sensor(s).
Hopefully someone here has worked on a freezer like this, and can provide some advice...
Gunnar
The freezer then seemed to work fine, temp reached -20C, and after a while the defrost cycle started, and I could feel that the evap. bottom tray heater got warm. Then the next day I noticed that the freezer was stopped, and the fuse for that circuit was blown. I reset the fuse, and the freezer stated normally again. When the defrost cycle started I noticed that the bottom tray heater no longer got warm.
I inspected the mechanic timer, and noticed that it lagged a lot, and that the defrosting time was probably 2-3 hours. I also had a look at the electrical contacts of the timer, and they looked bad.
I then replaced the mechanical timer with a Dixell electronic controller (from eBay), but still no heat. From studying the circuit diagram it seems that there is a overheat sensor in series with the heater element.
So if this is open circuit the heaters will not work.
If I remove the evap. fan cover I see a large bulb with a cappilary tube (is this the right term?), sitting just inside the fan cover, not in contact with the evaporator. Is it likely that this is the overheat sensor? It is very difficult to see what else is inside the evap. area, and I don`t know how much I can move the evaporator without damaging anything?
Cappillary tubes from the room sensor and the one that I think might be the over temp sensor leaves the cabinet through a hole in the wall (see picture, covers removed), and goes to a box (controller?) outside near the compressor. It is not easy to get to this box without removing the refrigeration unit, but it might be possible.
With the Dixell controller I got a room sensor and a evap. sensor, so I should be able to get rid of the original sensor(s).
Hopefully someone here has worked on a freezer like this, and can provide some advice...
Gunnar