Anyone converted a single stage gas atmospheric boiler to 2 stage?

delcrossv

Thinking about converting the old W-M JB 5 to 2 stage burning. Anyone done a single to 2 stage atmospheric gas conversion?

Any preference for lo fire start controls? Pressuretrol or aquastat?

Or, is the usual to start Hi fire and then drop to Lo? (seems a lot easier-close on rise vaporstat and done.

Seems there are no changes with combustion air (fixed air shutters) for lo/hi on the atmospheric boilers I've seen, so is turndown determined just on combustion readings? I know with new boilers, they're all in the setup manual, how's that determined with a retrofit?

Any recommended materials to look at for these setups?

jumper

Used to be multiple (two) burners on some copper tube.
Raypaks had variable gas valve somewhat like a stove top.
In theory the former makes more sense.

delcrossv

I was thinking putting a typical 2 stage gas train on the existing burner.

retiredguy

Since I did very little work on residential boilers I can only tell you what I have seen. How well they worked or how efficient they were is questionable. I have seen 2 stage and full modulating gas controls installed on these boilers. I was not impressed with how they worked but they were available for those that thought they needed them.

cross_skier

I am looking into this -- there is some info here:  https://forum.heatinghelp.com/discussion/comment/1265736#Comment_1265736

cross_skier

A "ghetto" solution is to use timer controls where the program predicts when short cycling is a risk and then shuts down the system for 30-60 minutes.  So instead of a high-low solution you would have a high-off system.  This would work as the radiators would be hot during the "off" period.

cross_skier

Located the timer solution.  For me this would delay restart of the boiler for 30 minutes on really cold subzero days where my system begins to cycle on pressure (8  ounce cut-out).

https://forum.heatinghelp.com/discussion/182874/crazy-idea-pressure-triggered-time-delay

My next boiler will be Megasteam with Carlin EZ gas burner conversion and this timer

delcrossv

Mine doesn't cycle on pressure, I'm thinking of adding a pressuretrol to go to lo fire at 4 oz or so.
Thinking of dropping input by no more than 40% so i don't get collapse of the steam at the end of the mains.

ChrisJ

The reason I never considered it is the excess O2 on an atmospheric boiler is already too high by nature.

So lowering the gas pressure, to decrease steam output while increasing excess O2 and decreasing efficiency never made sense to me. You're literally making it run longer and less efficient. I'd rather run the boiler more efficiently and shut it off.

I did "convert" my EG-45 to an EG-40 by swapping the parts necessary to remove one burner tube but that kept it's efficiency where it's expected to be.

I have seen others who say the decrease in combustion efficiency isn't enough to matter and they could very well be correct. But I don't like it.

cross_skier

That makes sense. 

I think there are a lot of folks with converted vapor systems.  They see their vaporstat short cycle on a couple of ounces and they are thinking man, my radiators are hot, there must be something better!

ChrisJ

cross_skier said:

That makes sense. 

I think there are a lot of folks with converted vapor systems.  They see their vaporstat short cycle on a couple of ounces and they are thinking man, my radiators are hot, there must be something better!

There is.
A smaller boiler.

EBEBRATT-Ed

I might consider this with an oversized boiler but @delcrossv if your boiler is not building pressure on a normal call for heat then I would leave it as is.

If you want to try this I would lower the gas pressure and combustion test it. See how low you can go and still have decent readings stack temp, Co2 and Co. You may find for what you gain that it is or is not worth doing.

Better than changing controls and gas valves and finding out your not much better off.

cross_skier

@ChrisJ

In my case (cycling in subzero temperatures after firing for hours, more radiation would be the answer, not a smaller boiler)  Boilers can always be downfired some.

I'm not a big fan of large steam radiators, adding more medium sized radiators is probably better.  

ChrisJ

cross_skier said:

@ChrisJ

In my case (cycling in subzero temperatures after firing for hours, more radiation would be the answer, not a smaller boiler)  Boilers can always be downfired some.

I'm not a big fan of large steam radiators, adding more medium sized radiators is probably better.  

That's true.

delcrossv

@EBEBRATT-Ed Makes sense, part of this exercise is to lengthen the cycle time. I'll crank down the regulator and see what happens with the mixture. I do have a lot of slack with the burner shutters as it is now.

EBEBRATT-Ed said:

I might consider this with an oversized boiler but @delcrossv if your boiler is not building pressure on a normal call for heat then I would leave it as is.

If you want to try this I would lower the gas pressure and combustion test it. See how low you can go and still have decent readings stack temp, Co2 and Co. You may find for what you gain that it is or is not worth doing.

Better than changing controls and gas valves and finding out your not much better off.