Noisy Grundfos Twin Impeller Pump (+ unnecessary activation)

[ledgers]

We just installed a Grundfos STC-1.5 C twin impeller pump to provide the pressure required for high pressure bath taps.

We’re suffering two problems:

1. First the pump is much noisier than I had expected, reading 82 decibels versus a claim of less than 70.

2. Despite taking separate water feeds (Essex flange from HWC) and being completely separate from the hot water elsewhere in the house, the pump is activating when other hot taps are opened and then closed (activates on close).

We have installed the pump according to all recommendations:

* 2m+ head from cold water tank (at level equivalent to base of HWC)
* Essex flange (Techflange) 60mm below seam
* Mounted on concrete footing
* Flexible hoses used, at angles no greater than 45 degrees
* 22mm pipework supply and outlet (with swept bends rather than elbows)
* Filter mesh used in inlet
* Purged by running both hot and cold water for 5 minutes prior to switching on power
* Bled air from the hot supply

Does anyone have any other things we could test to help rectify this?

Thanks

 

[Agile]

Why do you think the noise measurements have been made in a comparable way?

What were your measuring parameters?

Mounting can have a huge effect on noise levels. I use a paving slab on foam rubber!

Tony