Our company had a service call come in from a customer we had installed a inverter heat pump for. The guy informs me that since we installed this heat pump two of his clocks started running faster. His bedroom clock gained 40 minutes overnight. I sent a service tech out oh, and he found when the heat pump runs in heating mode, the Hertz go up to a hundred and ten. And cooling mode stays right at 59. Tech support is lost lol. I'm just curious as to why this would happen? FYI we are changing out the heat pump, I just like to know why things happen.
Clocks running fast!
- Thread starter Ngreene
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Welcome to the forum.
I would contact the manufacturer, and approach it as a warranty claim.
I would contact the manufacturer, and approach it as a warranty claim.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
It's very likely that the customer's clocks are using the 60 Hz powerline as a timebase, and so they trigger their internal digital counters at the zero crossings of the supply voltage waveform. But the inverter drive of the heat pump is putting noise onto the power line and that causes the clocks to trigger at additional times beyond those at the zero crossings of the 60 Hz waveform (and it's therefore speeding up the clocks). It also sounds like the meter that's being used to measure the frequency is also false triggering on the noise.
Clocks that have a quartz crystal timebase would be much less likely to be effected by such noise on the powerline (such clocks often say "Quartz" in a visible place for marketing reasons). And very old clocks with synchronous motors would be essentially immune to any reasonable level of noise. Putting a filter in line near the heat pump might help.
Are any other electronics like entertainment systems affected? If not it might be cheaper to just replace the clocks with more robust quartz based units.
Clocks that have a quartz crystal timebase would be much less likely to be effected by such noise on the powerline (such clocks often say "Quartz" in a visible place for marketing reasons). And very old clocks with synchronous motors would be essentially immune to any reasonable level of noise. Putting a filter in line near the heat pump might help.
Are any other electronics like entertainment systems affected? If not it might be cheaper to just replace the clocks with more robust quartz based units.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Digital clocks often count the zero-crossings of the powerline for their time reference.
When a lot of noise is introduced onto the line, it can create additional zero-crossings which cheap clocks (and, apparently, your tech's frequency counter) misinterpret.
When a lot of noise is introduced onto the line, it can create additional zero-crossings which cheap clocks (and, apparently, your tech's frequency counter) misinterpret.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
FCC rules require electronic doohickeys not to put out noise that negatively affects other equipment. If the inverter heat pump is negatively impacting these clocks it is not in compliance and as such is a warranty issue. A line filter may we'll be a simple and cheap fix.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Cheap? It is not about cheap. The line frequency is more precise in most cases than any crystal oscillator.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
I assume they are going to supply everything and pay you for the installation?
-Hal
-Hal
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Might be cheaper to buy new clocks…
That is true, but anytime anything electronic goes bad from then on, he would be looking at us to replace it.
Lol I would hope so, but I highly doubt it. They're supposed to call me in 15 minutes
ptonsparky
Tom
- Occupation
- EC - retired
9 minutes and counting...
Lol they called. I have to send a service tech up to install their parts oh, and let them know how it goes. On my dime. If it doesn't work, then they will give me a new unit to put in. On my dime LOL.
Nope, they will supply the ferrite cores and I have to supply the labor SMH we will see, my supply house will make it right with me for sure
We have this occasionally also with a variety of things. Arcing connection on our side being one.
On the customer side I would say it’s a lot of noise and hertz counting as suggested.
kwired
Electron manager
- Location
- NE Nebraska
IOW something they were too cheap to do at the factory.
Ferrite cores on the supply conductors to the effected clocks possibly works also.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Why spend the money to make it part of production when you can just wait for the infrequent complaint then send the parts out to some sucker who will modify the equipment for you for nothing.
-Hal
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Of course. But cheap digital clock designs don't bother to include a low-pass filter, Schmitt trigger or any other sort of noise rejection.
kwired
Electron manager
- Location
- NE Nebraska
Some might do that, many probably sell it as an accessory and you just missed it when selecting your product. I see that sort of thing often with stand alone economy drives like from Automation Direct. But an HVAC unit the mechanical guys don't know this stuff and I have higher expectations they should have this sort of issue already covered in the base product.Why spend the money to make it part of production when you can just wait for the infrequent complaint then send the parts out to some sucker who will modify the equipment for you for nothing.
-Hal
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