Beckett CG4 Natural Gas Lockout with Retrial Only in Morning

KeddyLad

Good morning everyone, I am writing in regards to a peculiar issue I'm encountering with a Beckett CG4 conversion burner that was installed over a month ago in an oil-fired water heater for house heating. The CG4 was a replacement for an old oil-fired Beckett burner, and I have been highly impressed by its performance. The only odd thing is that as the outside temperatures have started to dip further, I will come home to find that the burner is in "soft" lockout (slow flash of red LED), awaiting retrial after a designated period (4 hours). The CG4 uses a Genisys 7590D burner control module, and I confirmed with Beckett technicians that the 7590D has a 4 hour retrial interval.

I have been able to determine that the burner enters lockout at roughly the same time every morning (between 5:30 am and 7:00 am) by waiting for the retrial time to lapse and observing what time the burner retries automatically. If the burner retries at 11:00 am, I know it must have tripped at 7:00 am. If it retries at 10:00 am, I know it tripped at 6:00 am. The burner succeeds in these retrial attempts every time like a champ with no failures. The burner will also fire at all hours of the day at varying intervals without a hitch as well. It seems that only that narrow time period in the morning is problematic. I can also bypass the retrial timer by cycling the main power. After a brief cycling of the power, the burner will fire with no problems.

As per Beckett's literature on the Genisys control module, the control will enter Lockout with Retry when:

1) The control fails to prove flame during the trial for ignition period (or repeatedly loses flame after flame has been proved

2) The air pressure switch is closed (stuck) at the beginning of the ignition sequence

3) The air pressure switch fails to close after the motor/blower starts (or repeatedly opens during the same call for heat)

That is all well and good, but what I'm scratching my head about is why the problem only seems to occur in that brief window in the morning? I know there are a lot of variables at play, so please let me know what additional details I can provide.

Jamie Hall

And what else is happening at that time of day which might affect gas pressure? When I see a time sensitive thing like that, the first thing I look for is... OK. What else is going on?

KeddyLad

Thanks for the reply Jamie.

I have no other appliances that would be calling for gas, so my thoughts were that it was perhaps related to ambient temperature? Are the outside temps coolest at that time and would that affect how the system drafts, and consequentially affect the air switch? The waterheater/burner are located in a basement that experiences a wider temperature range than the living space upstairs, but nothing below 60 degrees.

I also have the aquastat, thermostat, and anticipator dialed in so that the system only cycles 3 times per hour, so I'm fairly confidant the system isn't short-cycling and causing unforeseen problems with the burner control programming.

Big Ed_4

I would check the gas pressures as well as the O2 adjustments

Jamie Hall

Big Ed_4 said:

I would check the gas pressures as well as the O2 adjustments

I didn't say it was your appliances. I meant to imply that the timing is suspiciously like when your street or neighbourhood may all be calling for heat to recover from a setback, and the gas pressure goes low. Not at all uncommon. If the pressure at your boiler is marginal to begin with -- which it might well be -- that's exactly what will happen.

Ironman

Was the burner setup with a digital combustion analyzer and manometer?

KeddyLad

Thanks for the input, I'll do a deeper dive into the pressures and adjustments. I don't have a combustion gas analyzer but can bring someone in to double check.

On the residential side, the gas service to the house is new, and I was part of the design, installation, and testing. The main trunk line is 1.25" with a short 3/4" drop leg to the burner as per the installation specs, so I don't think pressure drop is a problem. On startup, we had 7.5" W.C. on the house side and 3.5" W.C. at the burner gas valve.

KeddyLad

Ironman said:

Was the burner setup with a digital combustion analyzer and manometer?

Manometer yes, but the tech doing the startup used flame color to dial in the air settings. I'm looking at getting them back out here to do test and fine tune and will let you know the results.

Big Ed_4

Sounds right ,but what was the pressure on the inlet side when the burner fires up ?

KeddyLad

Big Ed_4 said:

Sounds right ,but what was the pressure on the inlet side when the burner fires up ?

We'll have to test the inlet side. Since we had 7.5" during the gas service test and 3.5" downstream of the gas valve we didn't check the inlet pressure. Do you think it might be starving for gas on startup? Would that correlate with the temperature at the time of day?

Jamie Hall

Not the temperature. The time of day and usage in the area. It wouldn't be the first area which has marginal mains pressure under high usage -- which you wouldn't see except under those condtions.

Oh -- and you can't judge the burner settings by eye.

EBEBRATT-Ed

You need someone with a combustion analyzer to go through the burner ans set it up properly. Also check gas pressures at gas valve inlet when it fires.

Also be on the lookout for any electrical issues and check the line voltage.

Low line voltage =low voltage to the igniter=maybe no spark and will also cause flame signal issues

Jamie Hall

And at the risk of sounding like a stuck record (what's that, I hear the younger generation say...): you really should do this at the specific time of day that you have noted the problem.

Big Ed_4

Same time of the day ,early in the morning . First thought as Jamie stated ,the neighborhood are all burning gas too at that time. You can guess or know but as mentioned you need to be there .

Static pressure and running pressure . You can have a blockage the size of an pinhole and show 7.5" on static and watch it tank when burner turns on ..

Conversion burners can be tricky , Some jobs they work great and some could be pain in the **** .. Some are ok with chambers and some are not ..

They all have a sweet spot to set the O2 with an eye on the CO ... Another thought , is the burner in a shed or basement ? With temperature O2 will increase as intake air temp falls .

What type boiler is the burner installed in ?

KeddyLad

Thanks everyone for the leads. I'll follow up on those ideas, collect some more data, and get back to you when I have something conclusive. In the meantime, here are a few answers to your questions:

-Line voltage: I am fairly confident the electrical is okay. When the burner arrived from Beckett, I had an issue where I wasn't getting spark. It turned out they had clamped the electrodes too far back so they were grounding out the igniter circuit, but in the process of that troubleshooting I tested all the line and control circuits and everything was in order.

-We'll do a running test of the gas inlet/outlet pressures, but I am inclined to say it isn't an issue with a restriction in the house piping. I was part of the installation and was on hand when the gas utility performed their purge tests on all the appliance drop/service runs, and there was ample pressure coming from the isolation valves. There might be something going on in the 3 feet of flex line that leads to the gas valve, a running test will tell us more. Or else the gas valve wasn't dialed in right coming from the factory.

-The boiler is located in a basement, but temperature swings in the boiler room are not too dramatic. I have some thermometers on order for another project, and will record high/low temps and report that information.

-It is plausible that there is extra demand on the gas utility which might be causing pressure/flow issues in the neighborhood. The gas utility here is reputable and their infrastructure is solid, but we had a week of sudden low temps that caught everyone off guard and every HVAC company in town was running around responding to calls as people fired up their home heating systems. I don't know what adjustments or if the gas utility makes adjustments to the system during the cooler months to account for the increased demand? Perhaps they were caught off guard also?

-I work in a trade where I do 7 days/nights on and off, so while my last set of nights I was unable to be home to witness the conditions that led to the lockout, this week I was home. As of 11/2 the problem has not repeated itself. On 10/31 I made an adjustment to the system by tweaking the heat anticipator from .69 to .641 (gas valve + burner control), but this adjustment was for a different reason and I don't think it should play a factor?

-Once I have gas pressure and combustion analysis I'll let you know more. Thanks again.