1 or 2 raisers?

patrykrebisz · 6:46AM

I'm slowly replacing my steam Burnham boiler (capable of producing 515 sq ft of steam) with slightly smaller Williamson GSA-150 Series 2 (390 sq ft). The boiler comes with 2 top opening (1 is sealed at the factory).

My original set-up (Burnham) had two 2in raisers coming together in a header and sending the steam via 2in pipe further into the system. It worked very well.

I'm trying to keep as much of original piping as possible. The new boiler (Williamson) has two 3in openings (despite manual claiming 2.5in). I'm thinking of having one 3in raiser reduced to 2in header to send steam to the system via original 2in pipe. Am i OK in my thinking?

KC_Jones · 11:34AM

The manual for that boiler states 2 1/2” riser and header which is the answer to your question about a 2” header.

ethicalpaul · 11:52AM

the manual should be followed, however it might be quite conservative in its sizes, meaning smaller pipes would work fine.

We’ve all seen big boilers with 2” pipes work fine.

You only have a single 2” main?

Well if that worked with a 515 sq ft boiler, it will work with a 390 sq ft boiler.

The idea that too small pipes will cause water to get “sucked out” or carried over is pure fiction based on what I have seen (and I do mean seen). If anyone has ever seen it happen I’d love to hear about it.

What is the total EDR of your radiators?

Do you plan to skim your new boiler? You must. Water quality is a far greater determinant of success than pipe size

EBEBRATT-Ed · 1:11PM

I would follow the boiler manufacturers minimum requirements.

STEAM DOCTOR · 1:18PM

The fact that the system worked with old piping, doesn't mean that it worked optimally. If you were discussing an existing boiler and system, and it was working relatively well, then certainly would not be a justifiable expense to start repiping. But you are putting in a new boiler. Now is the time to optimize the boiler piping. And of course, optimize the water quality as well.

mattmia2 · 4:53PM

You don't want to do it the find out you have to re-do it.

The larger piping will be more tolerant of the oil that accumulates in the system between skimmings as you get the oil from the new piping out. If it were my system I would keep it the size of the tappings in the boiler or the minimum from the manual, whichever is larger for both the risers from the boiler and the header.

If the water quality is perfect the header doesn't need to separate anything but the bigger piping will let you spend less time skimming.

patrykrebisz · 5:18PM

The manual calls for 2.5in raiser and 2.5in header.
The manual doesn't says whether i should use 1 or 2 raisers.

EBEBRATT-Ed · 5:37PM

look in the manual it wiil show a drawing of the piping for your boiler

109A_5 · 6:17PM

"The new boiler (Williamson) has two 3in openings (despite manual claiming 2.5in). "

Well the way I see it the end castings of that series boiler are probably all the same. The boiler simply gets wider as the capacity increasing and they may also change burners to change capacity with the same size block. So since the chart shows the maximum riser to be 3 inches I would expect that is the tapping size for that whole series to be 3 inches. If you stick with the recommended minimums it will probably work fine.

If you go above and beyond the minimums and have a 3 inch drop header with two 3 inch risers it will work fine too. Maybe it will work better, maybe no real measurable difference with that size boiler. Is the one time cost of the larger pipe and the aggravation of getting the 3 inch pipe plug out worth it to you ? Probably only you can answer that question.

STEAM DOCTOR · 6:36PM

The manual does not say that the boiler has a 2 1/2 in tapping for the supply. The manual just suggests using a pipe size of two and a half inch. The boiler does have two, three inch Supply tappings. But the manual does not recognize the one on the right side. But you are certainly welcome to use it.

EBEBRATT-Ed · 7:08PM

since the tappings are 3” and the riser needs to be 2 1/2” don’t put a bushing in the boiler. Buy a 3” nipple that will get the header 24” minimum above the water line. Come out of the boiler 3” and put a 3x2 1/2”90 on top of the riser. The 3” riser will hep keep water in the boiler and bushings leak

109A_5 · 7:12PM

https://forum.heatinghelp.com/discussion/comment/1901526#Comment_1901526

This seems like an easy and reasonable solution. Unless you really want two risers.

patrykrebisz · 7:20PM

Practical needs aside.

If my old (larger) boiler had two 2in raisers going into 2in header into 2in main… Would the fact that there were TWO 2in raisers rather then ONE 2.5in raiser like i plan to do, REALLY keep the steam that much drier?

EBEBRATT-Ed · 10:13PM

@patrykrebisz

I understand you trying to save work. Don't do it. Steam does not always follow things that make sense.

The inside of the new boiler does not match the inside of the old boiler. It is not the right choice to do a cut and slide.

Might it work…yes

Might it not work…yes

Do you want to pull it all apart and do it over if it doesn't work?

If it doesn't work and you call the mfg they will tell you to do it right. No one can predict what will happen. If you want to try it go ahead.

ethicalpaul · 10:40PM

https://forum.heatinghelp.com/discussion/comment/1901529#Comment_1901529

No. It’s 4.9 sq in for the single 2.5 vs 6.3 sq in for the dual 2”.

However, my observation is that it doesn’t matter. Other people will disagree but I don’t think they can prove it. I’d be welcome to see any contrary evidence though!

ChrisJ · 10:57PM

For those who don't know the easy way to find the surface area of a circle is radius x radius x pie.

For a 2" riser you've got 1 x 1 x 3.14 = 3.14. So 6.28 for two

A single 2.5" would be 1.25 x 1.25 x 3.14 = 4.9

A single 3 gives 7.

1 or 2 raisers?

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