[jorgy]

I have an eng a mua unit with a fireye control. This unit has been giving me nothing buit problems. When I first started on this unit I found a bad burner ground, cleaned ground to solve that problem. also found burning poorly, cleaned burner, burner very well, good blue flame. Have had fire eye trip out several times with just the alarm light on. Yesterday however it did lock out with the op ctrl and alarm light on. This is telling me line frequency noise alarm, any ideas. Also it has been tripping out for about two months now intermitantly. I have checked static pressure drop across burnes at 5.7 to 6. My low pressure switch is set at .1 and high presssure air flow switch is at 1.5. Checked my gas pressure at it is set properly. My da sensor hooked to my maxitrol amp all seems to be working fine. I also have another unit of the same type with out a vfd in it. I switched the fireyes around thinking it was in that burner control, still the bad one trips out and other one keeps running. Any ideas would be great, I can't even think of any thing else to try. And if any info on line frequency lock out would be great. Thank you for your help

 

[seathop]

HUH !

WOW !!! 5.7"W.C. across the burner seems very high. With the High airflow switch set at 1.5", I would think it would keep the safety ckt. open.
Are you moving too much air?

 

[ascj]

I have an eng a mua unit with a fireye control.

What is an ENG A make up air unit?

 

[Moose]

You said it has a vfd - are the control cables routed near the fireye control cables? You also stated that you switched modules with another operating unit & the bad one still locks out....on the good unit? Maybe you need to replace the intermittent module w/new.

 

[maxpower]

Couple of things to check. Make sure your ignition control/flame sensor has a good ground. Run a new ground from that point to the green ground at the electrical box. Make sure high fire gas pressure isn't more than the rated on the unit tag.

 

[hvac248]

If its a direct fire unit, seek help from the manufacture.
to many things can go wrong. is it 80-20,100%????

 

[gasguy]

What is an ENG A make up air unit?

Engineered Air (brand name)
Make up air unit (MUAU) is meant to supply tempered air to replace air exhausted by other fans. Often seen in/on resturaunt kitchens, garages etc.
Also refered to as DFMUAU for Direct Fired MUA meaning there is no heat exchanger.

Now you know, and knowing is half the battle!

 

[cmajerus]

Had a sterling doing that, turned out there was too much pilot gas, and was lifting the flame off the rod, backed it down and worked with no lockouts. Cost alot of money before finding the simple answer.

 

[jayhawker]

Being in Minnesota, could the intake air filter be frosting up and by the time you get there the frost has gone away. Is the unit located outside,and could the gas pressure regulator at the unit and could it be freezing up? I took one loose off of a unit that was locking out and took it inside and let it warm up, the water poured out .

 

[cmajerus]

another MN thing I have found is the gas train filling with condensation, had a burner manifold full of water, modulating valves could not open against the water and burner would light, and shut down, very erratic operation, broke the union loose and tons of water poured out, most likely would be frozen at this time of yr though, so I doubt that is your issue, mine was still in the fall, but it is another weird one to look at.