Clocks running fast!

Status
Not open for further replies.

Ngreene

Member
Location
Ohio
Occupation
Electrician/ hvac technician
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.
 

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.
 

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.
 

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.
 

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
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.
Cheap? It is not about cheap. The line frequency is more precise in most cases than any crystal oscillator.
 

Ngreene

Member
Location
Ohio
Occupation
Electrician/ hvac technician
Thank you. The manufacturer wants me to install 3 ferrite cores on the control board and a voltage filter on the line voltage wiring.
 

Ngreene

Member
Location
Ohio
Occupation
Electrician/ hvac technician
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.
 

Ngreene

Member
Location
Ohio
Occupation
Electrician/ hvac technician
I assume they are going to supply everything and pay you for the installation?

-Hal
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
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
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.
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
Thank you. The manufacturer wants me to install 3 ferrite cores on the control board and a voltage filter on the line voltage wiring.
IOW something they were too cheap to do at the factory.

Ferrite cores on the supply conductors to the effected clocks possibly works also.
 

kwired

Electron manager
Location
NE Nebraska
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. :poop:

-Hal
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.
 
Status
Not open for further replies.
Top