Blown fuse each time the central pump about to be triggered on ( EKO VIMAR RK-2001E)

I have this old Orlan 40 and lately, when i fire it and wait for my water temps to reach 150 degrees F for the main circulatory pump to be turned on, the power on the control unit shuts off and the fuse gets blown. Up until then the fan is working, but as it reaches 148 degrees it completely shuts off.

I first thought it was their crappy RK-2001E controller, but a company man told me it was most probably the main pump that needs replacing.

When i turn on the unit i get a P4 then a FF code.
Is this really the pump at fault or rather the controller ?

Sodbuster said:

Agree with the company man, something is bound up, and popping the fuse.

Click to expand...

Well, i've manually checked for seized pumps, then plugged them invidually in the mains, and all 3 of them are rotating fine.

But they never get turned on by the controller at any temperature.

Yes, i've unplugged all the pumps from the controller and plugged them in the mains for 30 min, and they all rotate fine.

The company man didn't say anything about the error code.

But you're right, there's a relay between the pumps and the controller; it looks ok, but i'm going to pry it open and check for a short.

maple1 said:

What I meant was, do that, and leave them plugged in. Then start a fire & see if the controller still errors & blows a fuse.

Click to expand...

I see.

What would you deduct if the fuse still gets blown in that situation?
That it's the relay that's defective?

I've left the 2 main circulatory pumps turned on and started the boiler; the water temperature cannot go high enough to reach 150 while they're permanently on, as the cold temperature in the house cools it constantly.

If i don't turn the 2 pumps on, the water temperature rises to 150, and again the fan stops, the green light for the 2 main pumps starts lighting up for 1 sec, then the fuse blows.( the 2 main pumps, as i've said, are plugged separately to another mains).

The relay between the pumps and the controller is a generic modular contactor type iec/en 61095
I have no clue if there's something wrong with it or not; there's nothing wrong with it from the outside.







Should i attempt to open it?