Downfiring oversized boiler??

Did he say how he would downfire the boiler?

---Reducing the gas pressure to the manifold within limits advised by the manufacturer.
---or
---Reducing the burner orifice sizes again as suggested by boiler manufacturer.

It is a common topic on this site.

The Gorton 2 is good for 20 feet of 2 inch pipe, so during the venting phase as the boiler is just starting to make steam, I would look on your low pressure gauge, and see whether you are letting the air escape at less than 2 ounces, or paying for more fuel to force it out. The Big Mouth vent is a wonderful device, with at least 2 times the Gorton’s capacity, and was invented by one of our genius members on this site.—NBC

There should be some opinions here on that!

> @Nick_37 said:
> HVAC chap said to remove some of the burners.

I’m very looking forward to this discussion. I want to disable one or two of my burners to see what a non-oversized BTU generating system looks like. But only if I can find a tech to do a combustion test on it. Any takers in northern NJ?

Nick_37 said:

HVAC chap said to remove some of the burners.

Realize that if you do it, that baby is totally yours. No warranty, no responsibility for the manufacturer, probably no insurance coverage should something happen and its against code to modify a gas train without the approval of the manufacturer.

If you pull burners you have to block off airflow. Even then you’ll still end up with uneven combustion, and uneven heading of the block which could cause some thermal expansion issues. That being said, Peerless uses only 3 blocks but has I think 6 burner sizes on their 63 series boilers. BUT it was designed specifically for that. I suspect the baffles are carefully configured to make it work.

I’d look at system balance. I suspect you need to triple your venting and then possibly slow down the radiator venting. The goal is to CONSUME all of the steam as it’s made. If you fill radiators unevenly but venting them too fast, you actually consume less steam as the section heat unevenly and don’t get to full temp.

I I have boiler that oversized by 50%, but have plenty of tons main venting and ended up downsizing vents on most of the radiators. Most are ventrites, Hoffman 40’s or smaller Maid O Mist vents. But i have 1 big mount, 1 Groton #2, 2 Groton #1, and 3 varivents, and 2 Groton D’s Scattered along the header. Overall works pretty darn well. Radiators heat up all at the same time and by about the same rate with exception ot deliberat room balancing.

Running pressure is <0.5 oz on a 9oz gauge... ( smallest gauge i could find). It’s possible.

You need to tell your AC guy to stick with the AC. As a matter of fact I’d find a new hvac specialist.......

Nick_37 said:

The truth is that the AC guy actually removed the burners and told my wife while I was at work. They were working on our AC system at the time.

Terrifying.

I have an over-sized boiler as well, 750 EDR on 400 EDR of radiator area. I have the same symptoms with pressure cycling on set-back. I looked in to down-firing the burners, and my research showed that unless the boiler burners are designed for a lower firing rate, changing to down-firing can have unintended and dangerous consequences. In your case , you may want to see if the boiler has an EDR rating and then calculate your radiators aggregate EDR to see how over-sized the boiler is. Using bigger venting on the mains might help, it did for me when I installed a Barnes and Jones Big Mouth 3BM main vent to replace a Gorton no 2. Steam gets through system more quickly now, but a setback of more than 2 deg F still gets me to cycle on pressure.

In the future, I am going to try a TECO controller to limit cycling along with an ASCO solenoid valve on the vent to close once the air is out of the system and the burners shut off.

My system is a 2 pipe Hoffman vapor, YMMV depending on your setup. Others here have had some success with this approach with over-sized boilers. For a warm system, re-firing into a vacuum means the water boils at a lower temp. and the steam goes to fill the void without having to push all the air out again. Also, the process controller limits cycling on pressure using pressure and temperature sensors.

So much angst over boiler size.

The radiation installed with most of our systems was for a continuous coal fire and was well past what was required to heat the house - even on design day. There would be no way to control the continuous fire system if the radiators were ever completely full. So these systems were designed to never have the radiators full. Same with the boiler.The rating on the coal boiler was well past what was ever needed also as it was never intended(read that couldn't be) to be run at "maximum" fire. Both the radiation and the boiler ran somewhere in the middle of their ranges so that even in the bitter cold the system would be controllable. That is why there are so many big replacement boilers out there - they simply matched the rating of the coal one - the max output of which the original designers knew would never be used one time.

So now we have changed to intermittent fire and have a lot of big boilers out there that can ONLY run on maximum fire (hence the mismatch). But there is still no reason to fill the installed (oversize) radiation up with enough steam to build pressure or even close. So I say just don't do it. Limit the single max duration run time so that a pressure stop is literally quite impossible, setback or no. There simply is never a reason to fill up your radiators that much. When you approach the project this way it makes no difference whatsoever how much "too big" the boiler is. You simply match the max run time to whatever boiler you have and space out evenly the firings to the number of cycles per hour that you want.

I think we should stop giving so many people the impression that they own a permanently dysfunctional system simply because they have a lot more boiler than is needed. The expensive controls, at the end of the day, do exactly what I am saying, they limit burn times based on what is needed.

@nick_37,consider shifting your thinking to controlling your run time instead of messing around with the fire and related combustion worries. It is a far less costly and ultimately much more flexible approach to your pressure issues than trying to change anything about the boiler itself. I probably have twice the boiler I really need(because it likely replaced the coal one), but never have more than a fraction of an inch water column pressure. My boiler has been quite happy for 62 years. I'm not changing a thing about it now. I part ways with many here and view it's oversize as an asset, not a liability.