One or two risers?

ranzerox

I have a new GSA-075, 75K BTU, and it has two openings for risers. In the product manual it displays the product with one riser. The 2nd opening is closed, would it be beneficial to use it for a 2nd riser?

Ironman

Two generously sized risers are always better than one, but not always necessary.

delcrossv

Just make sure your takeoff is after both risers, not between them. 😉

ethicalpaul

My opinion is it's not necessary in your case. Here's my video where I tested exactly what you're asking: https://www.youtube.com/watch?v=4IymyZB4wlI

These tables are very good for seeing the velocities involved:

https://forum.heatinghelp.com/discussion/180180/tools-and-tables-for-easily-determining-the-steam-velocity-in-boiler-risers

cross_skier

I respect @ethicalpaul and his work.  It's a pretty small boiler so one full size riser is ok in this case.

In larger boilers I would use all available supply tappings

ethicalpaul

Thanks! But even a single 2" riser is OK in this case (to clarify, the OP didn't post the table from his instructions, but I'm assuming it's a single 2" specified)

I would always follow the manufacturer's spec unless it's Burnham. They have some crazy velocities

KC_Jones

I agree with Paul, I'd still "overkill" and do a 3" riser and header. You aren't talking a significant cost increase for a few 3" fittings and pipe. Well, not significant to me when considering total cost and how long you will potentially live with it.

AdmiralYoda

@ethicalpaul
What size were the tappings on the boiler sections? Where they 2" or did you need to reduce it to 2"? I'm interested in the Peerless 63-03L as well.

ethicalpaul

I reduced them to 2", they were nice and big--the 03L uses the same castings as the rest of the 63 line so they are large for the greater number of sections of the larger boilers.

EBEBRATT-Ed

@ranzerox

@ 196 EDR that is only 47,000 btus for that little Williamson. I would stick to one riser. If you feel the need install a riser the size of the boiler tapping and put a reducing elbow at the top of the riser. If you enlarge the riser no water will climb up there.

two rises is nothing but money wasted on that boiler.

That boiler has a 3" tapping. I would have a supply house cut or buy a 3 x24" or 30" nipple if you have room and put a big riser on it with a 3x2 elbow at the top.

Water that stays in the boiler does not have to be seperated in the header

That boiler only calls for a 1 2" riser and header

SolarGuy1

I have a similar situation with my Weil McLean SGO-5 except mine has only one two and a half inch tapping and a boss on the last section that is not drilled and tapped. Specs require a 2 and 1/2 in riser and 3-in header but I'm wondering if I would be better off (1) drilling and tapping the last section or (2) using a reducer coupling in reverse to make the riser 3-in with a 4-in drop header since I would be only using one riser instead of two. I'm sure anything at this point would be an improvement over the two and a half inch riser and 2-in header the boiler installers left instead of increasing it. They also left the equalizer pipe at inch and a quarter instead of inch and a half as required, which I will be changing also.

Steamhead

@SolarGuy1 , drilling and tapping that section is more work than it's worth. If you don't tap it perfectly straight, you'll have a heck of a time lining everything up. Follow W-M's specs and you'll be fine.

mattmia2

A bigger riser will give you more benefit than a bigger header. The larger diameter riser will slow the steam down and allow more water droplets to fall out of it. If you want to go bigger than the tapping just use a reducer in a vertical section. Make sure you don't use reducers in horizontal sections in such a way that they trap condensate.

The Steam Whisperer

A single 3 inch riser gives you a velocity of only 9 ft/sec, well below the maximum of 25ft/sec in which water can drop back into the boiler. A single 2 1/2 would even be below the carryover velocity. Anything more than a 3 inch riser is a waste on money. For the extra money buy some main vents and a set of Ventrite adjustable vents for your radiators, or better yet some TRV's.