House HVAC issue while on generator power.

Dozerboy

Dozerboy

Well-known member
Jun 23, 2009
4,917
496
83
TX of course
I decided to get a portable generator to power some of my house during the next power outage. I got a 11,500/9,200 watt Champion generator. I had it tied into the panel. Everything worked including the AC. But the AC didn't seem to be running right. The air coming out of the vent was 5* warmer then when not on the generator. I'm not sure what to make of that. The generator was running at a little less then 1/2 it's output. I have a 2.5 ton unit. The AC doesn't have a hard or soft start capacitor or anything that I can tell. Could that be the issue? I don't mind the idea of putting a soft start on it. I just don't want to be out $400+ and it still not work right.

Any ideas?
 
M

Mikey52

Active member
Sep 20, 2018
135
32
28
It is getting 220 volts and not just one leg right. And make sure when everything is running that you hz don't drop to much.
 
2004LB7

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,108
2,213
113
Norcal
Check Hz and voltage. You may have 240v to the house but 200v at the generator

It would be a good idea to also measure the current draw on the unit when running on house vs generator
 
Leadfoot

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
904
31
28
48
Western MA
www.matpa.org
2004LB7 said:
Check Hz and voltage. You may have 240v to the house but 200v at the generator

It would be a good idea to also measure the current draw on the unit when running on house vs generator
Click to expand...


Neighbors had a similar issue to this when a tree took out power last week (they said a/c was not as effecient). The HVAC technician did some testing and found low voltage and said it was not good for the compressor. He advised him not to run on the generator until they could remedy it. Not sure if he was blowing smoke (as they have not fixed the issue yet), but just in case you may want to be careful. I think their issue was generator was not sized appropriately to run everything they wanted to AND the A/C. If they resolve the issue, I'll update.
 
THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
44
48
44
ZEPHYRHILLS, FL
On mine running on genny power I noticed the inside fan doesn't run at normal speed, it ran much slower. Most all newer AC units and especially higher SEER units use motors that are called constant torque(my AC friend called them X13's) meaning they vary there RPM's so that they maintain the same airflow even if a filter gets dirty/plugged or your coil gets restricted. The controller in these fan motors do not like dirty power and it causes issues with them. Due to all the electronics in them, you just about need an inverter generator or at least a quality brushless generator to provide them clean enough power to run properly. I know on mine I was maintaining 238 volts at 60-60.5 hertz(virtually identical to my incoming line power) with the AC unit running, but it still wouldn't cool like it does on regular line power. So I have an old style window unit to use during outages so I don't chance burning up my fan motor in my AC. If you have an oscilloscope, hook it up and see the power coming out if your generator, and you will probably not like what you see.
 
2004LB7

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,108
2,213
113
Norcal
THEFERMANATOR said:
On mine running on genny power I noticed the inside fan doesn't run at normal speed, it ran much slower. Most all newer AC units and especially higher SEER units use motors that are called constant torque(my AC friend called them X13's) meaning they vary there RPM's so that they maintain the same airflow even if a filter gets dirty/plugged or your coil gets restricted. The controller in these fan motors do not like dirty power and it causes issues with them. Due to all the electronics in them, you just about need an inverter generator or at least a quality brushless generator to provide them clean enough power to run properly. I know on mine I was maintaining 238 volts at 60-60.5 hertz(virtually identical to my incoming line power) with the AC unit running, but it still wouldn't cool like it does on regular line power. So I have an old style window unit to use during outages so I don't chance burning up my fan motor in my AC. If you have an oscilloscope, hook it up and see the power coming out if your generator, and you will probably not like what you see.
Click to expand...

If it is dirty power causing the electronics to act up then installing a large isolation transformer should help clean it up
 
Dozerboy

Dozerboy

Well-known member
Jun 23, 2009
4,917
496
83
TX of course
Well I finally got back around to this. Looks like I don't have enough power for the in rush. My AC pulls 81A on start up and on the generator it only gets 61A. I watched a video on YouTube about Micro Air soft start dropping in rush from 73A to 31A. They seem pretty popular among RVers. Probably going to look into a whole house surge protector, but I'm not sure how nessary they are.
 
NC-smokinlmm

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,214
364
83
At Da Beach
I use an isoboost on boats to prevent overamperage, it acts as a amperage buffer, I'm sure you could find something that could cushion you on start up.
 
  • Like
Reactions: Dozerboy
You must log in or register to reply here.
Top Bottom