Q: Within the last year, I had Crestron automated lighting installed throughout my house, including into my newly built home theater. My electrician then installed the current 20 kW Generac generator (model 5525: http://www.generac.com/Products/Residential/AirCooled/20KW.aspx).

These two aren’t working with each other.

When the generator is on, any light on the automated circuits flickers up and down constantly (though the non-automated lights work fine and do not flicker at all).

When the generator is off, Crestron and non-Crestron lighting works fine.

Crestron engineers haven’t been able to help. They said crystal generators, very expensive and used professionally but not residentially, would be stable.

Crestron offered to swap all of the variable lighting controls for simple on-off units, but then I don’t have lighting “themes” anymore.

Help! How do I get an air-cooled residential generator to work with my Crestron lighting ... now that I have paid for everything to be installed?

This bridge has to have been crossed before ....

Help! - Greg Searcy in Columbus, Ohio

Just an idea here and cannot say yes or know it will help you, but worth looking into….

Has anyone verified that the generator is indeed providing 60Hz A/C? The Crestron dimmers and other electronic modules may be trying to sync to a slightly different frequency than the local utilty is providing which is usually dead on 60Hz. The regular lighting loads will function fine at basically any frequency, but the dimmers may not. I know other manufacturers look for a zero-cross time which is based on the line frequency and possibly the Crestron modules do as well. The Generac distributor should be able to check this for you.

Another idea…are the Crestron processors on a UPS so that when power is transfered to the generator feed they do not lose power? There is a few milliseconds of time between utily and generator transfer that may be throwing the system off from it’s standard state and causing the issues.

Hope this helps.

KED

Greg-

please contact me at .(JavaScript must be enabled to view this email address) and I can put you in touch with someone to help resolve your issue.

i can almost guarantee you that it is the generator being in 50hz mode. i have seen it several times. contact your generator dealer and let us know!!!!

I am working on resolving an identical issue on a new house for one of my clients. The house is equipped with a QT80 (80 kilowatt) generator. The lights in the house work fine on regular line voltage from the power company. When the generator comes on line initially they remain normal until you introduce a new load (240 volt) onto the generator and then they go up and down for several minutes until they level out. Other lights in the house on non lighting controls remain normal when on generator power. These wireless dimmers can detect the smallest of hertz change even if you hit 60.1 hertz they wig out. I have used other light control systems with this same generator with no issues before. I must find a fix before my clients go crazy.

Lutron’s HomeWorks lighting control system has devices specifically designed to deal with poor power, like that off of a generator.  It would even adapt to the 50Hz you indicate.

Choosing Crestron light controls was not a matter of convenience, as Crestron has a proven track record for producing good products. However, with that said they do need to address what I consider to be a major design issue in their wireless light control products related to the slightest Hertz deviations. The wireless light controls are hyper sensitive to frequency destabalization’s of even .1 Hz. To my knowledge this is strictly related to the wireless products and not the module based light controls.

Dimmers in general are designed to be powered by the utility service which usually does a good job of holding the line frequency stable. Since electronic dimmers use the AC line frequency to set their timing and zero crossing circuits, they expect line frequency to remain stable. Most generator systems which are residential grade will naturally have a dip in line frequency as the demand on the generator increases. I suggest verifying this by using a scope meter to monitor line frequency when running under generator power. This will indicate if the line frequency is varying under load.

What was the resolution of the issue?

No solution so far. 

Spoke with the Crestron electric engineer, who suggested setting all lights to 100% and to “buffer” each panel (software-speak for programming each individual switch to recognize whether the generator is on, and if so then to only provide 100% which avoids the uneven load of a dimmed level).  The lighting was set to 100%, and the fluctuations were no better.  The local A/V project electric engineer said if 100% still fluctuated, then “buffering” each panel would make no difference - only recreate the safe fluctuations.

The electrician verified that the Generac generator is indeed producing a steady 60Hz.

Today we tried another brand of generator.  A Kohler rep came over today for 4 hours (at $400) to show me that their generator doesn’t do any better with my Crestron lighting.  Identical result.  Needless to say they unhooked the Kohler, hooked the Generac back up, and left.

Next week we are going to hook up a Lutron switch (where one of the Crestron switches used to be) to see if that produces a steady level of lighting. 

Frustrating.

-Greg

Typically the issue with generators is that either a) your frequency fluctuates and/or b) the voltage fluctuates.  In either case, if the dimmer isn’t designed to handle it, the result will be flickering lights.

I do know that if you put a Lutron dimming module in its place, it will fix the problem.  Lutron has a patented circuit built into their products that compensates for voltage and/or frequency shift… search the Lutron site for RTISS.

If you put one of their wallbox type dimmers in there that has a microprocessor - i.e Maestro, it may work, but depending on how bad the generator is, it may produce the same results.  The Lutron dimmers are pretty robust, but a wallbox is not conducive to packing in a lot of special circuitry because of the size.

-cd

We have run into this before with Lutron Homeworks lighting systems. Though the new “adaptive” modules are more tolerant to generators, there is a limit. We haven’t done a Crestron system with a generator yet, so I cannot comment on that.

The problem is usually related to frequency or harmonics, and 60Hz is not always 60Hz. Generac seems to be the biggest offenders, and Onan seem to be the best. This is certainly not a recommendation as we have typically been dealing with Generators in the 65-250kw range, which is a whole different world from 20kw.

Regardless of brand, it is important to have headroom. If you are drawing 15-18kw, then a 20kw generator isn’t going to cut it. You should be in the 30-35kw range. We also recommend the permanent magnet option and low-rise option available on some of the better Onan models. They are mainly used for medical or communications applications, and usually aren’t offered under 50 or 60kw.

I’ll post info from one of their spec sheets below since it won’t fit in one message.

This is the info from Onan that I referenced in my previous post:

Separately Excited Permanent Magnet Generator (PMG) System - This option uses an integral PMG to supply power to the voltage regulator. A PMG system generally has better motor starting performance, lower voltage dip upon load application, and better immunity from problems with harmonics in the main alternator output induced by non-linear loads. This option is recommended for use in applications that have large transient loads, sensitive electronic loads (especially UPS applications), harmonic content, or that require sustained shortcircuit current (sustained 3-phase short circuit current at approximately 3 times rated for 10 seconds).

Alternator Sizes - On any given model, various alternators sizes are available to meet individual application needs. Alternators sizes are differentiated by maximum winding temperature rise, at the generator set standby or prime rating, when operated in a 40oC ambient environment. Available temperature rises range from 80oC to 150oC. Not all temperature rise selections are available on all models. Lower temperature rise is accomplished using larger alternators at lower current density. Lower temperature rise alternators have higher motor starting kVA, lower voltage dip upon load application, and they are generally recommended to limit voltage distortion and heating due to harmonics induced by non-linear loads.