Grundfos Niagara 2.0 twin problem

[iceno9]

Hi all,

I seem to have a problem with this pump. I installed the pump and whole bathroom about a month ago and everything has been fine till tonight.....the bath was running (also powered by the pump) and then suddenly it stopped.
THe pump is located next to my CH cylinder, fed from a warix flange for the hot and has a dedicated cold water feed from the tank in the attic. The output of the pump goes back up via the attic and then down a wall cavity to a thermostatic valve that feeds either the shower or the bath.

Basically, the bath was running fine and then the pump stopped. WHen i went in the airing cupboard, you could smell the resin from the windings - like you get with a new pump. I assumed that it has overheated and stopped itself.....dont know why as it was only running for a few minutes. However, when i waited 1/2 hour and then tried it again....it does not start!

I checked the fuses - fine.
Any ideas?
Matt

 

[iceno9]

Update....
Pump now working again so it must have thermally shut off. However when you set the bathroom thermostatic valve to fully hot it seems fine.....set it to cold and the pump seems to struggle and makes a noise??

Does this suggest the filter might be blocked? hence it trys harder to pull water and more load?
Funny thing is - when you turn the power to the pump off and repeat the same test for both hot and cold water but only gravity fed - it looks ok....im still confused?!?!?!

HELP!

 

[iceno9]

Update from this morning.....
I have checked the inlet filters to the pump and they are ok....very litte dirt there and certainly not enough to restrict flow.

Besides the water seems to run ok when just flowing under gravity.

WHen the pump runs, it does make a funny noise now and then and you can smell the 'resin' smell quite quickly. So to me, the motor is on its way out.....but its only a few weeks old?!?!?!

Still wanting some help here.....

 

[simond]

If you turn off the cold outlet completely you are driving a twin impeller pump into a static head. Not really surprising it struggles.

 

[iceno9]

Hi,

Well as its a thermostatic mixer valve - im not sure how much the cold is off in comparison to the hot. I understand what your saying - but at the same time - these things are designed to work together arnt they so the pump should be capable of that scenario?!?

Personally - i think there is some hot and some cold flowing but obviously not in the same proportions.....i think it would be rare that a twin impellor does pump equal pressure on hot and cold....

Cheers
Matt