anyone w/similar problems on MUA?

[Trublshter]

I'm curious about the fact there is a vfd involved if this is a direct fired make up air unit. I've serviced and started up many Greenheck, Reznor and Cambridge Air units and never had a vfd involved. On my understanding of their desired design and application I would think a vfd would affect the operation. I'm not saying I'm right, just never seen it since burner velocity and exchange of air are critical on those. I would like to hear from others who have.

[ascj]

I'm curious about the fact there is a vfd involved if this is a direct fired make up air unit. I've serviced and started up many Greenheck, Reznor and Cambridge Air units and never had a vfd involved. On my understanding of their desired design and application I would think a vfd would affect the operation. I'm not saying I'm right, just never seen it since burner velocity and exchange of air are critical on those. I would like to hear from others who have.

Mostly they are installed, where you have a variable exhaust load in the building. But the OP said it was just used as a soft start, which I have seen also.(But what a waste in money)

[Trublshter]

Ah Ok . Thanks ascj. for that. Maybe I'll get to see one set up like that since people do see a lot of weird stuff in this trade.

[relay320]

I am able to see the flame fairly good when lit, or burning. Flame looks fine. There is no actual separate pilot for ignition. It lights on low,or min. flame. Once burner lights, and flame is proven amplifire and modulating valve takes over. I did adjust min. fire rate so had suggested reading (1-2 uf) on flame sensor. Do not know if ignitor has been replaced or not, but did clean and set gap to specs. I did try swaping out w/dif ignitor and still had same issue.

[emcontrols]

I wouldn't worry about it at this point. A couple questions;

Are you able to see the pilot being lit?
What is you pilot regulator pressure?
Is this a interrupted or intermittent pilot?
Do you know what manufacture of burner is it? I thought those ran Maxon burners.
If it is a Maxon burner......was the ignitor ever replaced?
If it was.....make sure the right ignitor is in there. They come in a couple of different lengths, depending on the end plate.

There is no pilot on a direct fired burner. Just the burner unless were not talking about a direct fired burner!!!!!!!!!!!

[emcontrols]

My gut feel is your on the right track with adjusting up low fire gas pressure, it should in turn increase your flame sensor signal strength, but the big question " is it constantly maintaining the proper gas pressure" or sporadically dropping when the building is under a high gas demand condition. I suspect with a known building gas pressure issue that I would strongly urge that be resolved first. ( It is possible that the unit gas pressure regulator may be under sized or sticking. If its outdoors Ive even had them freeze up. All they are is a diaphram with spring) Then see if your still having flame failure problems. I know it sounds strange but trust me on this one.

[relay320]

just dawn on me! there is a co-ray-vac system in building also that runs very occasionly. Will check that out mon. morning with it under full load. THANKS!
(only took mentioning full load twice)

[supertek65]

I have dozens of greenheck model KSU MUA units.
The ones I have are from 1992.
Do you still adjust the burner profile?
Dose yours have the outide air dampers with a mod motor that closes when unit is off?

I have had many issues with the KSU models but have worked them all out over the years!

The old ones I have have rm7800 burner contrilers!
The new ones have fireye!

Tell us more
I am sure I have already been there!

Frank

[relay320]

believe from '05
not to fireye control yet on this one, but have seen around on other units.
has fenwal ignition control and maxitrol amplifier.

[supertek65]

is this the unit you have??
http://old.greenheck.com/pdf/makeup/...vember2007.pdf



-----------------------------------

I guess I have not seen a FENWALL burner controller???

I am used to the rm7800 like shown in this pdf??

[relay320]

that would be the bad boy. should be the 20 series for unit with. I should say its fenwal flame safe guard/flame generater, and maxitrol series 44 amplifier.

[supertek65]

funny!!!!!!!!!!!!!

I used to have hundreds of Cambridge units with Fenwall controllers!

Never had good luck with them!!!!!!!!!!!!!

I remember having to order parts from Johnstone supply!!!!!!!!!!!!!!

good luck bro'!

that would be the bad boy. should be the 20 series for unit with. I should say its fenwal flame safe guard/flame generater, and maxitrol series 44 amplifier.

[ascj]

There is no pilot on a direct fired burner. Just the burner unless were not talking about a direct fired burner!!!!!!!!!!!

I would disagree most of the direct fire burners have a pilot. It's not a separate burner, but a orifice on the end plate. Some don't like the Cambridge units.

[emcontrols]

I would disagree most of the direct fire burners have a pilot. It's not a separate burner, but a orifice on the end plate. Some don't like the Cambridge units.

Im not being argumentative, the only ones I have seen have the ignition source located at one end of burner assembly (Ignites the burner instead of a pilot) and the flame sensing probe on the other end (sensing the burner instead of a pilot flame). The burner is the shape of a V and it has no heat exchanger. There is no CBM or IDM just a supply fan that pulls the gas from the burner orphices which is where the negative gas pressure derives from at the manifold. (Can only be measured with a magnehelic or digital manometer that reads negative pressure.) The outside air delutes the carbon monixide to less than 20 ppm therfore not needing to vent the products of combustion. This applies to heat recovery units as well as MAU or OAU

[ascj]

Im not being argumentative, the only ones I have seen have the ignition source located at one end of burner assembly (Ignites the burner instead of a pilot) and the flame sensing probe on the other end (sensing the burner instead of a pilot flame). The burner is the shape of a V and it has no heat exchanger. There is no CBM or IDM just a supply fan that pulls the gas from the burner orphices which is where the negative gas pressure derives from at the manifold. (Can only be measured with a magnehelic or digital manometer that reads negative pressure.) The outside air delutes the carbon monixide to less than 20 ppm therfore not needing to vent the products of combustion. This applies to heat recovery units as well as MAU or OAU

Again...you sure those burners didn't have a pilot tube going to the end plate? If you are......then I would be real curious what burner manufacturer that is. And what kind of burner primary? If it's a Honeywell RM7800 series or R7700 series...I would guarantee a pilot is being used.

Cambridge is the only one I have ever seen lite off the burner directly, with hsi. All the others use a ignitor to lite of a pilot, that is tucked in the corner of the burner and then lite of the burner. Older ones use intermittent pilots(horrible and unsafe) and newer ones use interrupted pilots.

[supertek65]

EMC,
there is so much different stuff out there and at so many different levels!
I have leaned on this site to NEVER say NEVER cus I have always been proven wrong! All the Greenheck units I have worked on are positive gas pressure and all have either 7800 or fireye controllers, they all have pilots, some are intermittent and some are interrupted but always have a pilot.
If you said on this site, "every compressor has electricity!" you would be shot down in 30 minutes!!!!
LOL!!!!!!!!!!!

anyhow, have a good day!

Frank

There is no pilot on a direct fired burner. Just the burner unless were not talking about a direct fired burner!!!!!!!!!!!

[Gunn427]

I've never worked on a MUA without a pilot, Most of my equipment is larger and require flame proof for the SSOV. Post some pics, could be something that hasn't received approval up here in the Great White North.

[relay320]

I'll take a pic and try to show what I've got as I get a chance.

[Control Man]

Does this units act up at any specific time of day or just whenever. Any chance of monitoring the supply voltage to the unit.

Had 1 site with 2 End Air MUA units that acted like yours but always at night Monday to Friday but never on the weekend.

Found that there was a DRASTIC voltage drop as a result of the plant next door when they took ( 2) 1500 HP diesels generators off line for service and switched over to the GRID.

[hvac ddc]

I've had MUA burners that had the burner orfices rust over. I would have to take a drill bit and run them into the burner to clean them out again. If they did light up, I would notice that all of the burner wasn't lit. Sometimes the gas would be enough to come across the ignitor and light and other times it fail.