Lights have started to flicker while heat pump runs

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wahoowad

wahoowad

Minister of Fire
Dec 19, 2005
1,669
Virginia
Yesterday I noticed lights inside my house would flicker while the heat pump was running. By this I mean a quick, almost unnoticable flicker every minute or so and not just when it initially kicks in. It has not been doing this very long as I would have noticed, so probably started recently. At first I thought it was a problem with the power coming down the power lines as it was the kind of quick flicker you might get during a storm (and we were having heavy rain yesterday) but I quickly noticed it stopped whenever the heat pump stopped running. Sometimes my emergency heat kicks in but I watched and this has not been happening as I tried to figure out this flicker. It is just the regular heat pump heating and the fan running.

I have a 3 year old Honeywell digital thermostat that has worked flawlessly so far. I have watched the display to see if perhaps something like the emergency heat was kicking in incorrectly and everything looks OK. I notice nothing on the thermostat display that coincides with the flicker. I stood by both my indoor air handler and my outdoor unit and heard nothing cycling or out of the ordinary.

I hope it doesn't harm my TV or computer or other electronics before I figure this out. The TV doesn't flicker and my computer UPS doesn't give the alarm it sometimes does when the power blips. I don't have anything new plugged in that uses electricity that could be causing a singificant load when coupled with the heat pump running.

Any ideas?
 
I would try a couple of things.

First make sure all the connections are tight in the heat pump, disconnect and breaker panel. It could be a loose connection from vibration etc.

Then i would get a volt/amp meter and measure voltage while the heat pump is running and see if there is any fluctuations, also throw the amp probe on there and see if the current draw changes while the unit is running. With my limited knowledge of heat pumps is this a 2 stage and by that i mean on minimal heating loads the compressor has one speed but for larger heating loads it has a 2nd speed, or electrical resistance that is kicking on? If the compressor is always the same speed and there is odd voltage/current fluctuations this could mean the compressor pump is failing, or something silly like refrigerate level.

Edit also had a similar problem just last week. The light on my desk would get ever so slightly dimmer for a few seconds and then come back up to full brightness. I thought i had a loose connection somewhere. After i tore apart the panel and made sure all the connections were tight it was still happening. I started going through every box on the circuit looking for a loose connection, still nothing! The culprit? My roommate left her iron on and plugged in. As the element was kicking on and off this was causing my light to flicker.
 
Under heavy loads loose connections frequently appear and become odious. With your lights being on another circuit my guess would be it could possibly be one of many things. I have seen inside main breakers start to fail because of moisture getting in through the service entrance cable, loose connections or corrosion at main lugs(above breaker), inside meter socket or at point of attachment where utility power connects to your house. You may want to get a professional down to find the weak link in your service. The utility company probably will come out no charge for there end. Keep us posted.
 
my goofy electrician buddy says a loose connection is most likely the culprit for that one. he says he finds it is the power companys connection at the pole more times than not.
 
One item that is often overlooked is the outside ground wire . Corrosion can form on the ground rod connection. Be careful as a shock hazard exists when disconnecting the ground connection.
 
One real life experience here- about 10 years ago we had an 'open neutral'. Saw a lot of flashing lights, etc. What happens is that the loads can be unbalanced so half of your stuff is getting 160VAC at the same time the other half is getting 80VAC and so forth. So the line voltage measured at any outlet may measure higher or lower than 120VAC nominal, and it wanders all around in voltage as loads switch on and off. BTW 160VAC is *real* hard on your appliances, light bulbs, etc. When I reported this to the local power company, they got out here real quick and fixed it!

If you have an AC voltmeter and know how to use it safely, check the line voltage at a number of outlets. If it differs much from 120-125VAC in either direction, call your power company and get them out there for a look. Especially if it falls outside of, say 115 to 130 VAC. BTW you have to watch it a while, especially when you are seeing flickering. Sometimes it will look fine, then it will wander way out of spec. Your bigger loads like compressors and maybe a well pump could cause this visible light flickering, and often only momentarily as they switch on or off. But then you think the lamp is running normally but the measured voltage turns out to be way out of spec.
 
Here is an example on Cluttermagnet broken neutral issue he had. Each light bulb or appliance acts like a resistor completing the circuit, electricity always is trying to find its way back to ground. Depending on how low or high the resistor is on the circuit will determine the voltage. By the example you can see the voltage can range from 0 to 240 volts on the branch circuits.

Edit: If there is a ground rod in the mix it will only give you so much resistance and be rendered useless. A cold water pipe may will take a lot of current if bonded to a city water system but will eventually burn out because if inadequate wire size to handle all the current.
 

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I see the light flicker often in houses around here with wells whenever the pumps kick on - is this likely a similar issue of a poor connection (ground or neutral)? Would seem to make sense as they often do not have the advantage of a copper water line to ground to, given the nature of well based water supplies.
 
Just this last year I had a bad connection on one of the hot lines coming into my house. It was on the utilities side of the meter and up in the air right near my house. So I was getting that one phase dropping out on occasion, usually when a large draw was applied. Then the one phase would drop out which is bad mojo for the 220 volt appliances in the house that are only getting 110. The worse mojo is the flickering and the low voltage situation caused by the bad connection.

The second time I had the power company out the good man found the problem.

They blamed it on my utilizing much more power than the previous resident so the crappy connection made itself known.
 
Great stuff, guys. Thanks for the advice.

First thing I did was go check my clothes iron because I have seen it do this in the past so seige101 brought back that memory. Unfortunately that was not it. Then I pulled the digital thermostat out of the housing and plugged it back in. Oddly that seems to have resolved the issue! I am a little skepticle that this was the cuplrit but can not deny that the flicker seems to have stopped. I will continue to monitor the situation, but also will check my voltage at the outlets. I understand what you mean about losing a leg of my 220. Usually when that happens the stove will run weak or the dryer won't dry, and both of those are running fine. I'll still check though.
 
Having a problem with your neutral won't give the same symptoms as losing one of the hot legs... As CM said, a bad neutral will give wierd voltages on the 110v appliances. However the 220 stuff will work just fine!

Gooserider
 
oconnor said:
I see the light flicker often in houses around here with wells whenever the pumps kick on - is this likely a similar issue of a poor connection (ground or neutral)? Would seem to make sense as they often do not have the advantage of a copper water line to ground to, given the nature of well based water supplies.
Click to expand...
Probably not abnormal. Certain appliances such as motors (well pump) and especially compressors (refrigerator, air conditioner, heat pump, etc.) can pull a tremendous slug of current right at the instant of turn on. It is of very brief duration, but long enough to briefly dim incandescent lamps. Not all lamp dimming indicates a wiring problem. Especially if it is just a flicker, as opposed to many seconds of obvious dimming. The later could be abnormal.

What I'd be concerned with is if I was seeing for the first time a dimming of lamps- where none had been noticed before. OTOH if it 'always' has dimmed lamps when the well pump kicks in, that can be completely normal. The definitive test is to monitor the line voltage (120V 'phases') for abnormal high or low readings, as discussed above.
 
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