DH installed them this weekend and they all hum! Any idea why? I can post a diagram of how he set it up if that helps diagnose the problem.
Are you using a dimmer with them? What is the make and model of the dimmer?
Yes, the Lutron Skylark Model #CTCL-153PDH-LA. This is the same dimmer we are using for our recessed LED lighting and have no hum there.
Here is a link that might be useful: Lutron dimmer
The humming is almost certainly caused by the dimmer; you could try changing it out for a regular switch to confirm it.
It's a bit hard to tell, but Lutron's support materials and a review on the Home Depot site appear to suggest that this dimmer is not compatible with ELV transformer loads. The eW Profile strips require a reverse-phase ELV dimmer; Philips does not list suggested dimmers.
The Home Depot review suggests calling Lutron Technical Support at 800-523-9466. I don't have a dimmer on mine, but other members may be able to list dimmers that have worked for them.
See page 100 of the Lutron spec guide PDF linked below; you'll see that while the Skylark dimmer is listed as working with ELV loads, the Skylark Contour is not.
I also found a compatibility chart from Lutron for the eW Profile Powercore strips at http://www.lutron.com/en-US/ResourceLibrary/LEDReportCard/LED_120V%20eW%20Profile-41%20Report%20Card.pdf
This also lists the Skylark SELV-300P dimmer, but not the Skylark Contour dimmer.
Here is a link that might be useful: Lutron dimmer spec guide
Wow- that is very helpful. Thanks! I guess that was a detail we neglected to research. We will try changing out the switch and then decide whether to get the Skylark or forget about dimming. I will call Lutron to confirm that it will work.
The dimmer has to be an ELV dimmer.
There are numerouse ways to dessign the AC to DC power suplies for low voltage devices.
Some of the designs are easily adapted to 'standard' (TRIAC) dimmers, others require some of the other dimmer types available.
You have to ask each manufacturer what dimmer type they recommend, since they often have different power supply designs.
Even power supply size (watts) can affect the type of dimmer it was designed to operate with.