Mystery part on older 2 pipe steam system

englshjos

Hello,
This is my first post.
Im bidding on replacement of an existing egh-95 steam boiler on a two pipe steam system. each of the radiators has its own steam trap. This part is existing on the condensate main return pipe near the boiler. What is it? and do I need it? or is it an antique leftover from past boilers?

MilanD

Looks like some kind of main air vent. Yes, you do need it ohterwise it would not have been installed there, so do not remove it. It may need an upgrade. I'll leave it to more knowledgeable people to chime in what to replace it with. Definitely not with a plug.

MilanD

See here: BB4V vent. Page 4 & 6.
https://heatinghelp.com/assets/documents/311.pdf

MilanD

4V stands for Vacu-Vapour Vent Valve... Not sure what, if any, is today's modern replacement to this.

See here - page 1194 - lists product, one if which is '4V':

https://books.google.com/books?id=iIJNAAAAYAAJ&lpg=PA1196&dq=bishop babcock air vent&pg=PA1194#v=onepage&q=bishop babcock&f=false

Jamie Hall

Neat! I wonder if it still works... your best bet on an exact replacement would be a Hoffman 76. However, you don't really need the vacuum hold feature, although it might improve overall fuel use very slightly. Therefore you might be better off figuring the volume of your steam mains and basing the vent size on that. Unless the place is absolutely huge, I would imagine that one or at most two Gorton #2 vents would do the trick. You can put them right there, and you shouldn't need any vents anywhere else -- with one caution. Look around the rest of the system. There should be crossover traps at or very near the ends of the steam mains feeding into the dry returns. If there are, and they are working, well and good; leave them be. If they got removed at some point, you have a choice: replace them or add vents at the ends of the steam mains. If they aren't working, repair or replace them.

And one other major caution: that was a vapour system, and designed to work on very low pressures -- like a maximum of 6 to 8 ounces per square inch. You will need a vapourstat to control the maximum pressure, and be careful not to oversize the boiler.

Fred

The EGH 95 is a very large boiler. Make sure you measure the EDR of all the connected radiators and base the replacement boiler on that EDR. Don't just replace it with another 95.

Jamie Hall

Fred said:

The EGH 95 is a very large boiler. Make sure you measure the EDR of all the connected radiators and base the replacement boiler on that EDR. Don't just replace it with another 95.

Indeed. Hence my remark on "do not oversize the boiler". That EGH 95 which you are replacing is not the original boiler, and there is no good reason to suppose that it is the correct size -- or even close to it.

MilanD

> @Jamie Hall said:
> The EGH 95 is a very large boiler. Make sure you measure the EDR of all the connected radiators and base the replacement boiler on that EDR. Don't just replace it with another 95.
>
> Indeed. Hence my remark on "do not oversize the boiler". That EGH 95 which you are replacing is not the original boiler, and there is no good reason to suppose that it is the correct size -- or even close to it.

Modern boilers have less water capacity than the old ones. Is a modern boiler properly sized to edr going to have issue with low water or will it be fine once properly "primed", as in, wet returns filled with water after the innitial fill and few cycles? I tend to think it'll be fine, but again, WM usually suggest a receiver tank when replacing the old boiler. I tend to think this will depend on actual amount of wet return pipes volume. Am I wrong to think that?

Jamie Hall

There's nothing wrong with putting a receiver tank on the wet returns -- it is nothing more, basically, than a wide spot in the pipe, after all -- but I wouldn't think it would be necessary in any reasonably sized system. Cedric is a Weil McClain 580 -- a fairly good sized boiler, currently firing at about 385,000 BTUh gross input (larger than the EGH 95) -- in a fairly large system (7,000 square feet heated floor area), but I've never had any sign that making steam lowers the water excessively. Keep in mind that each gallon of water boiled makes over 100 cubic feet of steam, which will fill a lot of pipe!

The only time it might be a problem, seems to me, is if the wet returns are slow for some reason -- then you might need the tank.

The wet returns will fill automatically as soon as you fill the boiler above the Hartford loop -- they really don't need priming.

Steamhead

The Gorton #2 is a good choice. It's not a vacuum vent, but it will vent air quickly which will allow the system to heat quickly. It will also close against rising water in the pipes, unlike some others. Since that vent is on the return lines, the latter feature is important as there is no leftover steam pressure in those lines because of the traps.

It is possible to do vacuum on a system like this, but the best way is with a small vacuum pump hooked up where the air vent is. @IgorZhadanovsky has been experimenting with this and the results are impressive.

nicholas bonham-carter

Remember the reservoir tank is a bit more than a wide spot in the return. It has to be mounted with its horizontal center at boiler water level height, and connected to the wet returns at its bottom, and to the boiler equalizer at its top.
I really believe that most boilers have an operating water content capacious enough for making enough steam to fill the system.--NBC

DanHolohan

It pays to wander off the Wall.

MilanD

Pure thought process exercise here:

@nicholas bonham-carter could you draw out on a piece of paper what you mean? I think I understand but am wondering if the measurement above water line in the "storage tank" on the wet return has to be equal to the bottom part, or as long as it connects to an equaliser it can be any size, including a larger pipe with a tee on the equaliser? LAOSH has similar concept on p.31 for raising the water line on a return tank with a motor pump.

I am also wonering if just piping a larger pipe into a wet return (everything still below boiler water line) on an eccentric coupling (pipe bulging up from the floor) without equaliser run would also do the trick to increase the water content? I'm thinking yes, all else remaining same, including Dimension A being and remaining adequate.

JUGHNE

Your "fat" pipe on the floor below the water line will always be full of water. There will be more water in the system but not more for the boiler to use. It will just take more water to prime the system.

Your fat pipe needs to be up so it is only 1/2 full of water with equalizer steam pressure above it. As boiler water drops, pipe water drops, but because you have more volume of water the water level will drop less. Think of it as a wider boiler holding more water but the fire is not under all of it.

I have some pictures of one I can find later.

Jamie Hall

Perhaps best to go back to square one, and consider just what it is one is trying to do. The perceived problem -- which may or may not be real -- is that if you boil the water in the boiler and fill the system with steam, there may not be enough water left in the boiler, and potentially the LWCO might shut things off. This you do not want.

However, first, let's be sure that that really is the problem -- and not water getting backed out of the boiler into drips which connect at the top with dry returns at atmospheric pressure. Now a drip -- say 1 1/2 inch -- will only take about a tenth of a gallon per foot of rise, so if we have let's say 6 risers and a foot and a half of rise (half a pound, more or less) we'll lose a gallon that way.

Now the steam. For every gallon of water boiled away, we get about 130 cubic feet of steam (give or take, depending on pressure). That's a pretty fair volume. I have to admit that I've never figured out what the total volume of a typical steam system is -- but I dare say that it's on that order, anyway. That's also about as much steam as a 300,000 BTUh boiler can produce in a minute. So if our wet returns are functioning properly, and the condensate returns in... well, let's say two minutes, for discussion, that's another two gallons or so wandering around out there somewhere.

So we are up to three gallons, total, moved out of the boiler while it is steaming at that rate. Your mileage may vary, of course, as they say -- there are a number of variables, not the least being steaming rate.

Now is that enough to trip the LWCO? Again, that would depend on where the initial water level was, where the trip level is -- and the volume of water in the boiler between those two levels.

Now suppose we do have a problem. There are two things to do. The first, and by far the most important, is to make sure that the wet returns are sufficiently clear as to allow the condensate to come back quickly. Why? Because if they aren't, there is only one place that condensate can go, and that is into the dry returns. This you do not want, for a whole host of reasons.

If we still have a problem, then a source of additional water which will come into the boiler as its level drops due to steaming is required. As I think of the hydraulics of the situation, so long as that additional volume is quickly accessible to the boiler and below its water line, you're fine. Might it need an equalizer connection? Possibly -- but only if the wet returns are slow or the boiler is operating at excessive pressure. Does it need a free surface at the boiler water line? No.

MilanD

@JUGHNE Thanks! There it is! I get it now why equalizer - it's a "false" expansion of boiler volume as it sits at water line. Wet return with proper "A" Dimension will always replentish water that went up the system as steam.

Which brings me to: how does one size the amount of wet return needed? Is this in LAOSH? Haven't gone through all of it yet.

MilanD

@Jamie Hall

I am only wondering if with a smaller replacement boiler there may be issues with appropriate amount and timely condensate return and how to make sure this is addressed should it be needed. So, my question is how does one calculate the appropriate wet return capacity? I see it has to do with btuh ratings and gals needed to replace water that was boiled and converted to steam. How much wet return capacity is enough, given adequate "A" Dimnsion and all else working properly?

At this point, I'm only doing a thought exercise. What can I say, I love thinking about these things...

JUGHNE

This is 525,000 Dunkirk 246B-6 with 1238 EDR connected with 220' of 3" 1 pipe supply and 200' of 2" dry return.
This was installed in early 1980's by NG company. They welded up this tank. It takes 95 gallons of water to fill boiler & tank. They may have overbuilt for the application. The sight glass might drop 1/2-3/4" when fully steaming.

On the far end of the tank the HL goes into the end of the tank just below the water line. Both return taps are used on the boiler from the bottom of the tank. The 2" equalizer connects onto the top of the tank.

I am waiting for the state inspector (twice a year) to consider this a separate vessel that should have a PRV on it.....most don't know what it is for and do not want to comment.

Jamie Hall

MilanD said:

@Jamie Hall



I am only wondering if with a smaller replacement boiler there may be issues with appropriate amount and timely condensate return and how to make sure this is addressed should it be needed. So, my question is how does one calculate the appropriate wet return capacity? I see it has to do with btuh ratings and gals needed to replace water that was boiled and converted to steam. How much wet return capacity is enough, given adequate "A" Dimnsion and all else working properly?



At this point, I'm only doing a thought exercise. What can I say, I love thinking about these things...

Thought exercises are fun! And very useful. And sometimes it is helpful to consider ridiculous extremes. For example, in this situation, suppose we have a flash boiler (they made them for steam cars, back in the day!) which has essentially no water capacity at all -- basically a heat exchanger (back in the day, a coil of copper pipe) with enough area to transmit the heat to the water and boil it. There you need a source of water -- our friendly tank! -- with enough capacity to feed that boiler for as long as it takes the condensate to return. On the other hand, if one has a huge boiler, then it may take forever (or at least a long time) for the water to boil, but the amount boiled off is a tiny fraction of what's in there, so who cares? Most of the time we are in between somewhere...

But it isn't so much the capacity of the wet returns -- if they are any sort of reasonable size at all, the relatively small condensate flow will be able to pass without any significant head loss. What is a factor, though, is how much steaming time is going to elapse before you start to get condensate back in any sort of steady quantity? Hard to say -- too many variables.

And on further thinking about it, what I said above isn't really correct. You really need that wide spot on the pipe to be at the desired water level and equalized.

englshjos

.Thank you all for your input
EDR : 941.73 sq. ft steam. = 226,020 Btu/hr
Weil Mclain sizing instructions ay to choose boiler with a "Net IBR equal or greater than Btu/hr capacity of radiation.
Of course if you look on their web site ratings chart Net IBR is not given for any boiler. What ratings do you guys use?

englshjos

I also did not add for the extensive amount (not exactly sure how many linear feet) of 3" steam mains in the basement. Should I?

Fred

If you look at their rating charts, you will see they list the Net Boiler Sq. Ft of Steam output. Match your EDR (as closely as possible) to that boiler Sq. Ft. of steam. Add nothing for any piping as a 33% Piping and Pick-up is already factored into the boiler's output.

englshjos

I am admittedly not firmiliar with vacuum vapour systems, most of the steam systems I work on are simple single pipe residential systems. This one is also residential, but a very big house. By my figuring going by the WM ratings chart, the egh95 is actally a bit too small.
The existing boiler im replacing has an internal section leak on the outside section, if that gives any clues as to what happened.

Steamhead

If the leak is above the waterline, the section rotted out from too much make-up water. So you have a leak somewhere.

If that were my job, I'd use the W-M 4-80 with a power gas burner. This is a factory configuration, and you have a choice of several burners. With only four sections, assembly is easier, and the header is easy to pipe since only one riser is needed (but it is 4-inch). And if down-firing is needed, you can do a much better job with this setup rather than with the atmospheric burners on the EGH series.

Here's what a smaller gas-fired 80 series would look like. This is a 3-80, but we piped it the same as we would a 4-80:

https://forum.heatinghelp.com/discussion/148298/atmospheric-out-power-burner-in

Fred

I think the EGH-95 is rated at about 866 EDR. That will still leave you a piping and pick-up factor of about 20%. They typically build in a 33% Piping and Pick-Up factor but a 20% Piping and Pick up should work fine. Many on this site believe the 33% is way too much capacity for piping and Pick-up.
How old and what brand is the existing boiler? If it is not very old and otherwise in good shape, you may consider seeing if you can get a new end section. Of course, there is always the risk that if one section goes, others may not be too far behind, especially if the boiler has been neglected or if the water quality is an issue.

Jamie Hall

I'll second -- happily -- @Steamhead 's choice -- the Weil-McClain 4-80. Cedric is a 5-80. Good boilers.