any electricians out there?

[reefkeeper2]

I recently installed a new Dolphin amp master 3000 pump. I had a few problems with it and the company sent me another one. Good customer service. My problem was that the RPM on the pump seemed to change and I as having trouble adjusting water flow. So,in searching for an answer I had an electrician check the line in case the voltage was changing. It wasn't, but what he told me surprised me. He said the pump was drawing 1.8 amps. Now the max for that pump is 1.3, and the manufacturer said it was impossible for it to draw 1.8 and it would shut down. The electrician measured the amperage at my service box. The pump is the only thing on that line. Can anyone explain what's goin on to me?

[dnjan]

By measuring at the service box, and not at the pump, the electrician measured the total load in the circuit, not just the pump. Even if you have nothing else on the circuit, the wiring itself will have some load. But probably not a half amp! I would guess you have a bad connection someplace in the circuit - bad plug, loose wire under a terminal screw, etc. A loose connection would explain low/changing pump speed as well.

[Norge]

Did they give you any reason why it should be impossible for the pump to draw 1.8A? The amperage would vary with the load you put on the pump.

Just curious,
Thomas

[Titus]

Hello,
I believe the design of the ampmaster has the armature de-coupled from the impellor, thus allowing it not to exceed its designed amperage draw.
As for checking the load, the electrician should have put a clamp on ampmeter around the pump's wire, not the panel.

Titus

[jgadbois]

Unless there is a very large mechanical load or the voltage is very low the rpm of the pump should be constant. A typical AC motor's speed is determined by the frequency of the input voltage (60 hertz for house wiring) and should not change.

[Rick O]

You have a reason to be concerned with this. If you do have a loose connection somewhere you could have an overheating problem that could cause a fire. The most likely place is in the receptacle. Is the outlet sloppy or loose when you plug the pump in? If it is you should replace the receptacle. This is very easy to do and you don't need an electrician to do it. Just be sure to turn off the power to that circuit at the service panel and install the new one exactly the same way as the old one.

Titus, The clamp on ammeter has to go around one wire only. He would have had to split the wires (strip off some insulation) to check the pump only. Checking at the service panel is much easier and will expose problems in the circuit.

Rick

[Titus]

Hello Rick,
Thanks for pointing that you. You are right.
Titus

[reichard]

Without getting too theoretical, 1.8A reading versus 1.3A on an AC power circuit can be misleading.

If there are large motors on the supply at your house, say, freezer, heat pumps, large AC units, the power factor of the supply will change. As AC is alternating current, the voltage peaks at 60Hz just as the current does. On an ideal (purely resistive) load, the current and voltage will peak and fall at the same time. However, components such as inductors (in all motors) and capacitors (in lots of motors) cause inductive (and capacitive) reactance, essentially making the voltage peaks lag or lead the current peaks. So, with AC circuits we really need to talk about impedance. In DC circuits we talk about resistance.

So, in an AC circuit you'll have impedance which is the sum of resistance plus the vector sum of inductive and capacitive reactance. A clamp on ammeter will measure instantaneous current but will not take into consideration the power factor.

You may have a shorted winding in the motor as well, which would cause the current to increase and increase the speed of the motor (depending on the type of motor, squirrel cage, sailent pole, etc...).

[skipm]

One of the previous posters mentioned a possible loose connection, IME the most common place that I found loose connections was at the receptacle. It seems that alot of electricians nowadays are pushing the wires into the back of the receptacles instead of placing them under the screw, even though the manufacturer designed the rec. to be wired this way I have found quite a few problems with bad connections where the wires were pushed into the back. Also note that if your house is wired this way your problem could be at another receptacle that is on the same circuit before the one where your pump is plugged in. Skip

[reefkeeper2]

Thank you all for your replies, and sorry it has taken me so long to get back. I had the electrician who installed the line come back and check all the connections. That was when he told me about the 1.8amp draw. He took apart and checked the receptacle and it is fine. There are no other receptacles or anything else on that line. When I spoke with Dolphin and told them of the electricians comments about the 1.8 amp draw, the guy kinda flipped out and ranted about it being totally impossible and that the pump would burn out. He told me to take some prozac and forget about it. Not a comment I really appreciated. He must think I'm a nut.
When the electrician was here he had me turn on other appliances and measured the current at the receptacle. It didn't change. Of course after he left I had 2 more occurances when the rpms of the motor changed. If I uplugged it, and then plugged it back in the rpms returned to normal immediately. I am begining to think that small particles of detritus might be getting sucked into the motor and that this is what is really causing the problem.I have a lot of tube worms living in the sump and they sometimes unattach and float around. Of course this doesn't explain the 1.8 amp draw of the motor. Anyone have any other suggestions? Also, what can I use to prefilter the intake on a 2+3/8 inch bulkhead that won't restrict the pumps intake?