Motor fluid

[Dave Chamberlain]

I have a Grundfos KP150 sump pump that's no longer working. The impeller is very stiff to turn so I've taken it apart to attempt to fix it. Looking at this video, they show some "motor fluid" under the bearing. What is this stuff?

[dave]

Forgot to link to the video:

My motor didn't have any of this fluid / oil. I assume that means that it's leaking out from round the bearing.

[alan_m]

Maybe this link

[Graham.]

Isn't he just priming the pump with water?

[alan_m]

or

(PDF document)

[quote] "The pump contains approximately 70 ml of nonpoisonous motor liquid that may pollute the pumped liquid if the pump should leak." [/quote]

from other sources The motor is a single- or three-phase synchronous canned motor with liquid-filled rotor chamber and water-lubricated bearings.

Maybe page 32 of

or

(PDF document)

[quote] Motor liquid The motor is factory-filled with Grundfos motor liquid SML-3. Frost-proof down to ?4 ° F (?20 °C). Specification of SML-3

Corrosion protection Grundfos motor liquid protects metals and alloys in the equipment against all forms of corrosion. The combination of low toxicity and FDA-approved ingredients with a high level of corrosion protection makes Grundfos motor liquid unique in the market. The anti-corrosion performance is demonstrated according to ASTM D 1384.

Compatibility and mixability Grundfos motor liquid is compatible with most other heat transfer fluids based on mono-propylene glycol. Grundfos motor liquid should only be mixed with clean water. The product can be delivered as a dilution mixed with the proper amount of purified water.

Toxicity and safety Grundfos motor liquid consists of FDA-approved components for heat transfer fluids with incidental food contact.

Exception: MS6RESDT30 motors are factory-filled with demineralized water. [/quote]

[alan_m]

From another source

SE1/SEV pumps in the motor size from 9 to 30 kW contain motor liquid, type SML-3. This polypropylene glycol (38 %) must be disposed according to local legislation via a public or private waste collection service. The volume of motor liquid varies from 12.8 to 14.1 liters depending on pump size.

Car antifreeze "non-toxic antifreeze"???

[Chris Green]

9 to 30kW is hardly a domestic CH pump! :-)

[Peter Parry]

For other Grundfoss pumps they seem to use de-ionised water.

The KP150 manual at

doesn't mention motor fluid at all.

In the last link above the motor is described in the Technical data and performance curves section as " a single-phase, asynchronous, dry-rotor motor. The axial rotor position is secured by means of a ball bearing. The motor is cooled by the pumped liquid around the motor."

That would seem to say there is no fluid. The usual failure mode of such motors is corrosion of the bearing or shaft as the seal fails allowing water entry to the motor case.

[tabbypurr]

Give it 10 years & it will be. Having lived with huge flow showers long ago, they're a complete waste imho.

NT

[Chris Green]

But the CH pump isn't the one that squirts water out of the shower! :-)

[harry]

Heat from the motor winding is transferred to a cooling fluid. (The motor is sealed inside a can filled with this fluid). The can is cooled by the water being pumped past it when the pump is running. The pump bearing is water lubricated, the motor end bearing is inside the can lubricated by the fluid. The can can lose it's fluid so the pump overheats and the bearing can seize.

[Dave Chamberlain]

Thanks all for your help. I cleaned it up and filled it up with some water from the tumble dryer and it's now working fine. I guess it will lose its water again and I probably need a new bearing, but for now I can empty my pond again.