underfiring GAS boiler

Leon in NJ

If you find your oil fired boiler is to big and putting out more steam than the system needs, you have wiggle room and can play with the nozzle size to bring down
the steam Sq. Ft.- BTU/Hr. rating closer to the connected radiator load and piping. But what can you for an oversized GAS fired boiler. I've heard you can take out section tubes but have no idea if this advice is "healthy". Any ideas on how to bring down a GAS boiler into the connected load range is GOLD.(That would be natural gas from the devils at PSE&G)

nj

Turning down gas boiler

I had the same problem in my gas boiler in nyc brownstone. actually the fire was edging over the cabinet. the heating guy just turned down the pilot valve--apparently it regulates the gas volume in. that cut the flame to about 75% of its former self, but playing with it, it can be adjusted all the way to 10%. You might want to adjust it down and then adjust it up if it gets super cold.

gary_6

turning down gas valve

wouldn't just turning down the gas valve produce a poor flame and in turn produce carbon monixide? If the manufacturer designed that system to run at a set BTU output if you as a homeowner or tech tamper with it and something should happen aren't you liable?

MIKE6

down fire

I would take one burner out and plug the manifold.This way the boiler or other burners will fire properly.The gas adjustment on the gas valve should be set once and leave it.

Mike

GW

be careful

If you don't know what the CO is, you can have some real problems, mechanically and health/life and death. Playing with the gas pressure without the proper tools is pure folly.

Gary

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cstehling

plug manifold

I plugged two ports on a manifold to reduce the output of the boiler. This was at my brothers house and it has performed fine for 4 years now. We made the first floor hot water with a dedicated boiler with an outdoor reset.

The steam boiler was now oversized for the 2nd. floor.
Plugging the ports was a simple solution. The other burners work fine and the boiler produces enough steam.

kevin coppinger_4

Most boiler...

manufacturers wouldn't touch this...I have asked W-Mc...no help and said it would void ANY warranty. bummer. kpc

GW

plugging a burner outlet

Safety aside, you'll want to be watching for sooting beacuse you may have a metal surface that's not heating up and crossing the dew point as fast as it should. And build up of soot will come back to bite you.

Gary

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GW

plugging a burner outlet

Safety aside, you'll want to be watching for sooting because you may have a metal surface that's not heating up and crossing the dew point as fast as it should. And build up of soot will come back to bite you.

Gary

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GW

pics

I think I blew a gasket on the server here, let me try this again

Steve Ebels

How did you

How did you check for proper combustion after you did this? What were the CO, CO2 and O2 running at? Did you check with the manufacturer to see if the warranty is still valid after this was done?

cstehling

works fine

The boiler that I plugged was a weil-mclain e series with square cast iron burners.

The boiler is about 30 years old so it's out of warranty.

There's no sooting, I did not check any gas level's after I did this. I did observe the flame on the exsisting burners and they appear to operated as they did prior to plugging the two ports on the manifold.

There is no rollout in front or spillage at the hood.

This was the first and only time I did this and I'm not recommending anyone try this. It did work fine in my case and with no complications.

Unknown

It really gets scary here on the Wall

Let me first say that just srewing down or up on regulators on gas controls is not a good idea. Even so called "pros" who have not had advanced combustion training need to be careful. Atending an NCI course or my course will help you to understand exactly what you are doing. It is also important that when working on design equipment that manufacturers procedures be followed. Having said that there are times when adjustments for fine tuning may require you to adjust pressure, if you are trained - a big IF then proceed with caution. It should be done in conjunction with a combustion test and please check for CO (allowable 400 PPM is really high) I shoot for under 100 and leave most jobs around 50 most of the time (takes a lot of work on some old systems).

For those of you who practice derating equipment by plugging the manifold and removing one or more burners it really does not work real well. You should never derate even if you are going to do it more than 20% of rated input. Keep in mind that boilers and furnaces are designed to burn a certain amount of BTU in order to me heat transfer standards. Notice I did not say combustion efficiency, hey I can put a candle in a boiler and get a good combustion analysis with very little CO, it will just not heat the building. The American Gas Association and Gas Research Intitute conducted many tests doing derating in the past and the findings support my previous statement.
In fact in some cases with degree day analysis and cubic foot usage accurately measured overall efficiency decreased and bills were higher.

Another falacy is what I hear a lot of techs saying "the flame looked good it was blue" you can definitely be tricked by just using observation as a factor in determining flame safety. BLUE FLAMES can still have CO being produced. In fact when you get CO2 up above 9 and 9.5% you could be making CO and it would not be visibly indicating so - YOU MUST TEST. It is still important not to have yellow flames but do not get tricked by a blue flame.

Last of all for all of the PRO's who have attended NCI classes or my classes on combustion. Please do the following:

Whatever changes you make to the equipment please tag it and state what you did and leave name and phone number, if you are not willing to leave your signature on your work then why are you doing what you are doing. Think about it this way the next guy on the job does not know what you did and is going to reset everything to match the rating plate.

Something else no one talks about when screwing down on gas regulators. When that regulator is set to its high end of performance let us say 5" W.C. instead of 3.5" W.C. the performance curve on that regulator changes drastically. Maxitrol has some interesting information on this.

Hope this helps.

GW

yes

I agree Tim

Here's a brain teaser. I had an oil boiler running like doo doo with factory settings. I cranked the pressure to lower CO, and I moved the drawer in to lower it even more.

Now, if I didn't have a analyzer or any type of training, I'm be just scratching my head like the rest of the crowd.

One manual I was looking at recently stated that the setting had to be "ajdusted in the field" for optimum performance, or something along those line.

I think people are afraid to get trained because they don't have the time or money, both of which are issues that fall under a completely different topic!

Gary

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gary_6

McElwain's the man

That is why more techs should go to your school. Keep up the good work Tim. I took your courses and think they are great.

gary_6

McElwain's the man

That is why more techs should go to your school. Keep up the good work Tim. I took your courses and think they are great.