Electrical interference

[50 year Sparky]

Currently troubleshooting a house that when the air conditioning outside unit runs some lights in the house flicker and the dishwasher will beep and the controls will light up. Only does it when the compressor runs. During the winter this does not happen if the auxiliary heat which is propane is used instead of the heat pump. Dishwasher was changed out and Bosch heat pump was replaced.

 

[don_resqcapt19]

Assuming this just happens when the compressor starts, a hard start or soft start kit for the compressor will likely solve the problem.

 

[50 year Sparky]

It’s happens whenever the compressor runs not necessarily on start up. The dishwasher beeps and the control of the dishwasher lights up after a minute it resets itself then as long as the thermostat is calling for heat or cooling and the compressor runs the dishwasher beeps and the controller lights up. This is continuous as long as the compressor is on.

 

[LarryFine]

Currently troubleshooting a house that when the air conditioning outside unit runs some lights in the house flicker and the dishwasher will beep and the controls will light up. Only does it when the compressor runs. During the winter this does not happen if the auxiliary heat which is propane is used instead of the heat pump. Dishwasher was changed out and Bosch heat pump was replaced.

Welcome to the forum.

I suggest reading each L-N voltage and the L-L voltage during the start-up.

Replacing parts is a terrible and expensive troubleshooting method.

 

[50 year Sparky]

Welcome to the forum.

I suggest reading each L-N voltage and the L-L voltage during the start-up.

Replacing parts is a terrible and expensive troubleshooting method.

We have had meters on numerous times, sometimes 3 and 4 meters on the circuit at multiple locations and do not see any fluctuations. The power company has installed their meters also and can’t find an issue with the power. The HVAC contractor changed the heat pump out a year ago and the appliance store replaced the dishwasher at their expense. We only see this problem when the heat pump is on whether it is on cooling or heating.

 

[hbiss]

Apparently, the A/C/ heat pump has a VFD. The dishwasher electronics is sensitive to the "noise" that the VFD puts on the powerline. Not something that you will see with a meter and not fluctuations. The dishwasher needs a noise filter on its' power input, something like ferrite cores or a premade commercial unit. Should have been made that way by the manufacturer.

-Hal

 

[mtnelect]

The problem has already been identified in the attached article. The NFPA has chosen to wait until September 1, 2026, and let all the Electrical Contractors to be stuck with it.

 

[mtnelect]

I believe the NFPA 70 Standards Council made a major blunder in denying TIA 1748. I hope that Mike Holt reads this post and realizes the wide implications of this has on consumers and contractors that are saddled with dysfunctional GFCI's until September 1, 2026.

 

[ramsy]

I believe the NFPA 70 Standards Council made a major blunder in denying TIA 1748. I hope that Mike Holt reads this post and realizes the wide implications of this has on consumers and contractors that are saddled with dysfunctional GFCI's until September 1, 2026.

2023 210.8(F) Exception #2 at NFPA.org show the 2-Pole GFCI exception for HVAC condensers expires 9/1/2026.

What AHJ is going to notice a denied TIA, when the published code Exception #2 will not require condenser GFCI?

 

[mtnelect]

One standard for HVAC Contractors and another standard for Electrical Contractors. Can someone explain the difference between the two ?

 

[Dennis Alwon]

The problem has already been identified in the attached article. The NFPA has chosen to wait until September 1, 2026, and let all the Electrical Contractors to be stuck with it.

Please explain how this solved the problem the op posted?

 

[mtnelect]

Please explain how this solved the problem the op posted?

The problem has not been resolved only identified. The NFPA 70 Standards Council has chosen to give manufacturers until September 1, 2026, to come up with a 2nd Generation GFCI that will work with this new technology.

"There is a technological incompatibility between common loads in the home and GFCIs. The incompatibility is often realized in the form of “nuisance tripping”, where a GFCI trips and no electrical hazard is present. This incompatibility is especially pertinent in the context of home appliances, which are subject to continuously updated, mandatory, Department of Energy efficiency requirements. In order for appliances to meet efficiency standards, home appliance manufacturers incorporate components that operate at frequencies higher than the mains frequency of 60-Hertz. These technologies include switch-mode power supplies, variable-speed drives, and LED drivers".

 

[Dennis Alwon]

The problem has not been resolved only identified. The NFPA 70 Standards Council has chosen to give manufacturers until September 1, 2026, to come up with a 2nd Generation GFCI that will work with this new technology.

"There is a technological incompatibility between common loads in the home and GFCIs. The incompatibility is often realized in the form of “nuisance tripping”, where a GFCI trips and no electrical hazard is present. This incompatibility is especially pertinent in the context of home appliances, which are subject to continuously updated, mandatory, Department of Energy efficiency requirements. In order for appliances to meet efficiency standards, home appliance manufacturers incorporate components that operate at frequencies higher than the mains frequency of 60-Hertz. These technologies include switch-mode power supplies, variable-speed drives, and LED drivers".

Yes I know that but that has nothing to do with what the op is asking.

 

[Hv&Lv]

May be a dumb question, but how old is the house?
Could it be the dishwasher and ac are on the same feeder?

 

[mtnelect]

Yes I know that but that has nothing to do with what the op is asking.

The Original Post stated that the Heat Pump was changed ... so it is a High Efficiency unit and is causing the interference we have been talking about.

 

[winnie]

The discussion about GFCIs is tangentially related and may provide relevant info, but is not a solution to the OP's problem.

The GFCI issue involves VFD compressors causing high frequency leakage currents which cause nuisance tripping on the GFCIs. This is a known issue.

It is plausible that the same sort of high frequency electrical noise is messing with the dishwasher and lamps.

First: it has not been determined that the heat pump has a VFD compressor, but that is a good guess. The OP will need to say.

But presuming this is a VFD issue, then noise filters (suggested post #6) are a likely solution.

 

[50 year Sparky]

The house is about 3 1/2 years old. Since you are talking about gfci tripping, the owner did the state that the gfci on the back porch randomly is tripped with nothing on it. This is the 3rd house I have been called by the GC to troubleshoot problems. One house had lights flickering numerous times a day. After 3 days we found the utility purchased power from a larger utility and they metered every 15 minutes with a system to make sure they were getting what they paid for. When they shut down the system the flickering disappeared. When they turned it back on it started again. Eventually the house was powered by the larger utility company.

 

[ramsy]

This is the 3rd house I have been called by the GC to troubleshoot problems

Is it also the 3rd time you worked for free?

 

[ramsy]

One standard for HVAC Contractors and another standard for Electrical Contractors. Can someone explain the difference between the two ?

Maybe HVAC contractors should not install feeders and disconnects, if their code book requires GFCI.

 

[mtnelect]

Maybe HVAC contractors should not install feeders and disconnects, if their code book requires GFCI.

Agreed, only Electrical Contractors should do the feeders and disconnects.