equalizer sizing

STEAM DOCTOR

How do boiler manufactures determine the size needed for the equalizer? I just went through the I&O manuals for 4 different manufactures and for small residential boilers there are recommended sizes ranging from 1.25" through 2.5".

Rod

Equalizer Sizing

There is a good discussion on Equalizer sizing on page 63-64  in "The Lost Art of Steam Heating".  For residential boilers Dan recommends a minimum of 1 1/2 inches. From what I've observed, the  manufacturer's recommendations tend to be oriented towards the minimum rather than the optimum which maybe because they want to keep competitive in the "lowest bid situation." 

STEAM DOCTOR

sizing

I have read that section(along with rest of the book many times). Personally I don't put in anything smaller then two inch. I just wish there was some type of formula to explain why to use what size equalizer. The size of the equalizer should have to do with amount of water in the header. For example if I were to use either larger or more or higher boiler risers then in theory there would be less water in the header and therefore I should be able to use a smaller equalizer. Don't get me wrong. When it comes to piping boilers I am a big proponent of bigger and more. I would just like to know until what point. Thanks

JStar

Rule of thumb (we love those)

The equalizer should be one pipe size larger than the combined volume of wet returns. One 1-1/4 return requires an 1-1/2 equalizer. Two 1-1/14 returns require a 2 inch equalizer. The idea is that you size the equalizer to accept the amount of return water coming back to the boiler, and to put enough "equalizing pressure" back on the boiler to stop the water from heading out into the larger, or multiple, return lines.

STEAM DOCTOR

Sizing

I'm not sure that I understand the rational. The equalizer is a drain pipe only for the header.It doesn't accept condensate from the wet returns. I would think that the connection from the Hartford loop to the boiler return should be sized based on the size of the wet returns. Any insight would be greatly appreciated.

JStar

...

Sure, you could size the equalizer and the return tapping differently, but then you'd be decreasing and increasing a lot for no reason.

Rod

Equalizer Pipe Sizing

Hi- I think the larger sizing is more so that the condensate and steam (pressure) in the equalizer pipe don't interfere with each other.  If you have water from the header entering the equalizer in "slugs", your boiler water line is going to be really dancing up and down.  I was amazed at just how much volume of water was present in the header when I first saw the attached picture. Blow the picture up a bit and you'll see what I mean. Thoughts?

- Rod

Steamhead

Not sure

but we should never use an equalizer smaller than 1-1/2". I believe Dan covers this in Lost Art.

JStar

I find it helpful...

...when I'm contemplating pipe sizes, to visualize an extremely undersized pipe, then ask myself why it would not work. Sometimes it's hard to conceptualize the difference between very slight changes in pipe size like 1-1/4" to 1-1/2".

STEAM DOCTOR

2":

Personally I never go smaller then 2" on the equalizer. I was just wondering if there was some logic behind the specs given by the manufactures. Its also interesting to note that while most if not all the manufactures give specs for the equalizer almost none of the manufactures give specs for the loop to boiler return connection.

DanHolohan

It does more than that.

It also applies pressure to the outlet side of the boiler to keep the pressure that's inside the boiler from pushing the water out of the boiler. It takes the place of a check valve. This is why it should never be smaller than 1-1/4". A pipe that size doesn't allow for enough surface area within the circle to be effective at keeping the water from backing out. Dead Men stuff. 

STEAM DOCTOR

check valve

I understand that the equalizer functions as a check valve(hence the name equalizer). I just don't understand why the size needed for the "check valve" is determined by the amount of condensate that is returning. Thanks Dan for the response, this wonderful website and for that you have done for the heating industry through your books and lectures.

JStar

I think...

...it has more to do with the tendency of the boiler's water to take the path of least resistance. The more returns, the more likely it will want to back out the returns (larger pipe, less resistance), so a larger equalizer acts to push it back into the boiler.



Think about what would happen if the equalizer were 1/2". You can imagine how the boiler water would easily overcome that 1/2" of surface pressure and go towards the 1-1/4" return.