Furnace with digital controller keeps shutting off due to power fluctuations?

[Strouty]

After there where some issues with my oil fired furnace, I replaced the coil, replaced the cad sensor and things seemed to be working for a while, had another issue and I decided to bring in someone that knows more than me. They replaced the controller with a digital unit and it works well, I could be using improper terms, it is on the furnace and it is not the thermostat, that is a nest. Then it doesn’t work well, now two more calls to the furnace repair man and we have been told that it is our electrical, apparently it gets voltage either above or below voltage levels it like and shuts down for a few hours. If we reset it, everything works fine again, sometimes for days, or weeks, then it throws a fit again. I don’t see any wiring that concerns me, nothing was loose, we have had no other issues with anything else in the house. Is there a way to add a component that keeps the power stable? Seems like the controller is too sensitive or there is an intermittent issue. The circuit is not on a GFCI outlet or breaker. Any ideas on how to chase this? I am tired of paying $100 for someone to tell me there is nothing wrong.

 

[wyliesdiesels]

Can you measure the voltage of your service?

Phase a to phase b
Phase a to neutral
Phase b to neutral

Post up the results

Also provide the make and model of the controller so we can look up the specs

 

[Strouty]

I can’t get any measurements right now, will have to do it later this week. It just seems odd that this one thing would have a problem when nothing else has issues.

 

[brewchief]

Do you happen to have another thermostat that you can temporarily replace the nest with? We see all sorts of odd issues with the nest stats.

Sent from my SM-G965U using Tapatalk

 

[Strouty]

I have one at the shop, might be worth a try.

 

[ard]

we have been told that it is our electrical, apparently it gets voltage either above or below voltage levels it like and shuts down for a few hours. .

They have any proof that this 'diagnosis' is actually true? or they just making stuff up?

 

[Terry D]

There should be a LED light on the controller. It will flash a code when in fault. The label will tell you what the flashes mean. There probably isn't a code for intermitted voltage fluctuations. If its not showing a code, and its not a thermostat problem. Also check your connections inside the furnace, like the 24 volt. The controller itself could be faulty. Worst case would to check voltages at your panel and your meter socket. See if anything is loose. I would think if you had fluctuations in you voltages, you would see it in your lights in the house. Unless your getting a big voltage drop when a large load is coming on. It also could be a problem with your utility company. You might have to install a monitor on your panel to record voltages, but that would be worst case.

 

[Mattlt]

Could you rig up a UPS temporarily to see if that smooths out the alleged power fluctuations?

 

[Caddybill]

The beckett genisys cad cell relay is susceptible to low voltage and frequency variations.

 

[SGKent]

call you power company and tell them what the furnace people told you. Maybe they have some faulty wiring coming into the home or area. I've seen that 100 times before.

 

[wyliesdiesels]

Could you rig up a UPS temporarily to see if that smooths out the alleged power fluctuations?

Make sure to get a UPS that regulates the voltage. Its called AVR.

The only problem with that is the tolerances of the AVR may be wider than the controller.

 

[TurnipTruck]

I would not use a Nest if it doesn’t have a Common (C) wire. Try a different thermostat.

 

[Strouty]

I won’t be able to get anymore info until this weekend.

Nest has been installed for five years with no issues, all issues arrived sometime after the upgraded controller was installed. The controller has a digital screen and said something like voltage out of range. It happened a dozen times in two weeks.

 

[volleyball]

I had a friend who lived in a development of matching townhomes. A brownout came through and several homes lost their gas furnace. Including my friend.
Repair people "fixed" some of the neighbors but after 3 tech, my friend was still out in the cold.
So I bought a semi universal logic board and while installing it it complained about the Voltage off of the AC transformer. So I swapped the leads and all was fine. 10 years later and most of the other neighbors had failures but not my friend.
Now I know you are all thinking how does the leads on an AC transformer matter, but they did.
Maybe something similar or maybe just a bad ground.

 

[platypus20]

I do industrial boiler for a living, all of the newer digital/solid state controls have voltage sensing circuits, guarding against low or high voltages, usually 125 vac -10/+15%. They are extremely quick, go above or below the limits for mil-second, they trip.

I have about 7-8 jobs, where we had to install a small buck/boost transformer, the variable 125 vac input and get a solid 125 vac output, to the control. After the installation, the issue went away.

 

[theoldwizard1]

I do industrial boiler for a living, all of the newer digital/solid state controls have voltage sensing circuits, guarding against low or high voltages, usually 125 vac -10/+15%. They are extremely quick, go above or below the limits for mil-second, they trip.

The same is true for residential, gas fired, forced air furnaces. That "125 vac -10/+15%" should be within the capability of your POCO ! Usually with a "digital controller" when there is an issue, there is an LED on the control board that will blink out an error code.

I would request that the POCO temporarily a recording device to log what your voltage actually is. Without that data, it is just two companies pointing fingers.

Related : Sometimes people try to use a portable generator to run a gas fired, forced air furnace during a winter blackout be wiring a plug to the furnace. Frequently the furnace will not start. This is because the portable generator is not "bonded" (ie. no connection from neutral to ground). Make your own "bonding plug" for a couple of bucks and plug it into a spare outlet on the generator.

 

[wyliesdiesels]

I had a friend who lived in a development of matching townhomes. A brownout came through and several homes lost their gas furnace. Including my friend.
Repair people "fixed" some of the neighbors but after 3 tech, my friend was still out in the cold.
So I bought a semi universal logic board and while installing it it complained about the Voltage off of the AC transformer. So I swapped the leads and all was fine. 10 years later and most of the other neighbors had failures but not my friend.
Now I know you are all thinking how does the leads on an AC transformer matter, but they did.
Maybe something similar or maybe just a bad ground.

No way it could.

The 2 leads on the transformer are literally the 2 ends of the same coil inside the transformer...

 

[Want2race]

call you power company and tell them what the furnace people told you. Maybe they have some faulty wiring coming into the home or area. I've seen that 100 times before.

Bingo! Power company will install equipment to resolve the problem. Mine added a capacitor on the pole 45 feet away and clean ever since. Didn’t cost me a cent