GB-142/24 question/problem?

Ron Schroeder

of the Tank would have been done at the gas company yard as it is not a great idea to purge vapors in a residential atmosphere.

Dave_22

GB-142

I posted on here before about strange problems with my GB-142 and heating domestic water in an ST-150 tank. I decided to look last night and the water coming out of the boiler was about 140 degrees for most of the cycle. It did get up to 180 right before the call ended. I took the cover off and looked at the flame, which looked fair, but i noticed that the "plates" on the heat exchanger seemed to have a lot of little pieces stuck between them? Don't know what it is or where it came from? I can't see them making it through the gas orifice and i don't know if it is impeding heat transfer. The manual says to clean the HX with water- has anyone done this before or saw this type of thing?

singh

dave

sounds like the dhw cycle is doing what its supposed to.
I don't know what pieces could be stuck on the HX , I would not attempt to clean without the installing contractor involved.


A question for Joe @Buderus if you read this:

Each time I install a GB I wonder about the extra O-Rings. I never had anything leak but I still wonder where they belong, they don't seem to fit any where on the manifold? Someone told me once, but I forgot.

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Dave_22

The manual talks about 194 degrees out to the tank. If i'm trying to heat the tank to 120 with 140 degree water- it's going to take awhile. The bigger the delta t, the greater the heat transfer. I am wondering if whatever appears to be on the heat exchanger, is impeding heat transfer.

Joe@buderus_2

GB142

The GB142 will modulate the firing rate based on the delta T. It is suggested to check the circulator size that is being used for the indirect tank to be sure it can deliver the gpm at the total head pressure throught the GB142 and tank. The build up on the heat exchanger can be caused by the fresh air intake, the condensation flowing through the heat exchanger instead of the exhaust drain or the type of gas. Please consult with the contractor regarding cleaning of the boiler. It is not recommended a homeowner attempt this procedure.

The "spare" o-rings that are sent are for the supply/return union connections on the bottom of the pipe manifold. The unions should be taken apart before soldering the system supply and return pipes to the manifold.

Big Ed

Sensor

Buderus controls senses if there is a large draw or just a cool off on the storage tank and would respond it the needs....

Dirty heat xchange ? Yes have it cleaned and adjust burner to specs...

P.S. Yah,some one told me once also? What is the extra O rings for?

Dave_22

Joe- the GB modulates based on Delta T even during a domestic call??

singh

Ahhh!

That explains why they sent four o-rings. In case I burned them up twice ; P

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Joe@buderus_2

Modulates

Yes the GB142 will modulate during a DHW call. This is one smart unit!!

Dave_22

Ut-oh..........

Well, the cover is off and this is what i found. The lower "baffles" i will call them look clean-0 the uppers look like this-what is goin on here?????

Joe@buderus_2

GB142

What is the type of gas being used? Is there a condensate drain on the exhaust pipe?

Dave_22

Thanks for the quick reply. It is LP gas and there is a condensate drain on the exhaust pipe. It is piped in accordance with the manual.

Ted_9

Dave

Could you post some pics of the system? Did a qualified person install this?

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Unknown

Joe I have seen this on

other equipment with LP. The end result was the LP during very cold weather was not vaporizing completly and this grey/white residue was the result. I call it white soot for lack of a better definition. It is causing the flame to be quenched and cooled down. I would say once it is cleaned a combustion test when the weather gets cold would be in order.

On the last job I had with this problem we relocated the LP tank to the sun side of the building.

Even though the boiling point of LP is -44 degrees it can certainly start to have problems when outdoor temp and wind chill get down to 0 to 10 degrees.

Just a thought unless you folks have had problems with the GB142 doing this for other reasons???

Dave_22

Never had a problem before, although this unit is only 9 months old!!!!! It does seem to be something with the gas or flame-the lower half of the heat ex looks fine-just the ones closest to the flame look like this.

Guy_6

BACK

How is the venting on this unit? Does it draw outside air for combustion? If so, I would suspect re-circulation of exhaust gases.

Ron Schroeder

Dave

I have seen the same on many LP fired units, have pulled many tankless HWH apart and soaked them to clen but I have fin tube biolers that I have to clean in place a big pain in the but, I don't usually see them this bad for many tears of use though. I would go with Tims sujestion.

singh

yuck

I may have to agree with Guy.
How is the intake piped? In, perhaps from construction. Out, too close to exhaust.
Did you install the unit yourself?
Either way follow Burderus' instructions for cleaning after finding cause.

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Dave_22

Direct vent outside- intake 2.5 feet above grade pointing down, exhaust 3 feet higher than intake, pointing out. No other vent sources anywhere near by.

Joe@buderus_2

Biuld up

I would like to show the picture to our engineering department on Monday. I will post their input. It might be gas related. Was the gas/air mixture ratio checked?

[Deleted User]

Are these vent terminations on the leeward side of the home,

or the windward side of the home.

I've sat and watched vent terminations that were installed according to the manufacturer recycle their flue gasses.

Funny what a low velocity constant breeze will do to the theoretical "It should do that" situations...

ME

Unknown

Dave, once that unit is

cleaned by a professional you need to have a combustion test run to determine if proper burning is taking place. If combustion is good then I would look at possible issues with vaporization of fuel in extreme cold weather.

By the way what is your location?

Dave_22

I will have to try to find out- i would have thought so.

Joe@buderus_2

GB142 \"build up\"

The build up shown in the picture is normal, but a little more than expected for the time installed. This build up is a result of by products of combustion and can be affected by the gas, intake air, amount of condensation and what temperature the system is running at. We feel the unusual amount of by products in this unit may be caused by the methane gas used in the new LP tank, but not purged completely. The build up on the upper part of the exchanger suggest lower operation temperature. This build up should not affect the heat transfer to the point that is being mentioned. Suggest the dhw circulator/pipe size be looked at. I believe the original poster has clean the unit. Prehaps they will provide some feed back.

Joe@buderus_2

Thanks fo rthe input

Hello Tim, Many thanks for the input. I forwarded your information to the engineering department for their input. It would be intersting to know what the gas/air mixture ratio was during start up. We think the methane gas/additive put into new LP tanks is not being purge completely and causing some issues.

Mark Hunt

What about


a combustion test.

Was one performed? I never saw it mentioned.

Surely a digital analyser would have caught this.

Mark H

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singh

silly question

has unit been converted to LP ?

I think original poster is the homeowner and is cleaning unit , I guess does not have digital analyzer, Mark.

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Unknown

Joe, I am going to look

in my LP books to see if I can find anything about procedure. If I remember tanks have to be purged five times before being filled. I will get back to you.

Ron Schroeder

Tim you are correct

new tanks need to be purged five times with vapor only to 15 psi and released to zero each time.Giving you 96.87 percent gas in the initial fill.

Dave_22

I know when the LP tank was installed it was piped, pressure tested and filled- I do not remember any purge process. The unit is cleaned and running again- I cannot get ahold of the individual who checked the burner setup- the next step will be to verify the air/gas mix.

singh

dave

I think the purge process happens off site.
Please have your guy check every thing again with test equipment,
don't forget to check gas pressure with a manometer.
keep us informed, I'm curious, and fond of the GB142, so would like to know.

edit: oops, bruce beat me to it.

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Unknown

Dave as Bruce said

purging would have been done prior to delivery. Purging is required because air and moisture inside a container can create conditions that generate corrosion. It also prevents possible moisture accumulation in the regulator which will cause freezing. Purging along with methanol being injected into the containers will prevent moisture and other problems.

Unknown

Singh, I would think if

it was set for natural gas it would have carboned up with black soot instead of this white stuff. This is typical with some units on LP.