Grundfoss 15/50 problems

[me0u70d0]

Hi, I was just wondering if I can pick your collective brains...

I've recently developed a problem with my CH, narrowed down to the pump.

A few months ago I had a problem where the pump wasn't working but when I removed the bleed screw I found the pump to be seized...a quick spin with a screwdriver and it started working fine.

A couple of days ago, again no CH, boiler cutting out sounding very hot. I removed the bleed screw again, released the pump which now spins very easily. The problem is when the boiler fires up and the pump is meant to start pumping, it doesn't (at any speed) until I remove the bleed screw and give it a 'jump start' with a screw driver when it then runs normally. If I lower the speed to 1, it stops again and I have to use the screwdriver to start it up once at speed 3. The system has been bled ok and the FE tank is as it should be. I'm guessing the pump is well over 10yrs perhaps double that...is this terminal and should I just replace the pump?

Cheers in anticipation,

Simon

 

[moggridgeplumbing]

Time for a pump change i'm sorry to say

 

[me0u70d0]

Cheers, as I suspected! Is changing only the pump head a viable option or should I replace the whole unit. I'm a bit wary whether I'll be able to release the valve pump unions easily due to its position in the airing cupboard.

Thanks

 

[rossobonks]

One of the windings on the armature of the pump motor has gone open circuit. New pump head required.

D

 

[matt1e]

One of the windings on the armature of the pump motor has gone open circuit. New pump head required.

D

Or it only requires a new capacitor

 

[boabcelt]

I agree with matt1e, it sounds like the capacitor is away.

 

[me0u70d0]

Thanks for the advice regarding the capacitor... I've had a quick look online for suppliers but nothing obvious. Does it need to be grunfos or would any appropriate capacitor do (am waiting til morning to turn power off and dismantle)

Thanks again everyone

 

[commercialman]

Change the complete pump , only a fool would do otherwise.

 

[twgas]

If it only needed a capacitor, would it stop when the speed was turned down?

 

[rossobonks]

If it only needed a capacitor, would it stop when the speed was turned down?

What I was thinking. I thought caps where only for starting the motor and not running. If one of the windings was o/c there is not enough EMF to pull round at low speed. Any way getting too technical! Change the pump head to be safe.

D

 

[matt1e]

If it only needed a capacitor, would it stop when the speed was turned down?

What I was thinking. I thought caps where only for starting the motor and not running. If one of the windings was o/c there is not enough EMF to pull round at low speed. Any way getting too technical! Change the pump head to be safe.

D

No mate, the capacitor is for starting and running
the motors fitted to these are PSC motors, the cap and start winding stay in circuit all the time.
The cap provides the phase shift in the start winding necessary to self start then they both stay in circuit and the start winding becomes an auxcillary winding
if the cap has lost a lot of capacitance then the motor could stall at a lower speed

Matt

 

[rossobonks]

Great info there Matt thanks alot

D

 

[me0u70d0]

Thanks everyone. I know it might be a short term fix but thought I'd keep it simple to start with so I replaced the capacitor and its now working fine. Cheers for all the advice, will keep it in mind when it does pack in!!

Simon

 

[twgas]

So moving on, how does one determine whether the capacitor or windings are faulty?
I have never changed a cap on a pump, we at BG, as far as I know, have never stocked them.

 

[matt1e]

So moving on, how does one determine whether the capacitor or windings are faulty?
I have never changed a cap on a pump, we at BG, as far as I know, have never stocked them.

You take out the capacitor and test it
If OK then fault is internal to the pump

Matt