water level in wet returns when system operating

thfurnitureguy_4

I think if you take the pressure that your boiler is building at actual operating pressure and multiply by 28" rise per lb of boiler pressure. So if you run at 2psi you will drive water back up the returns or radiators about 56" This is another reason why you want to keep pressure low.

mel rowe

determining water level in wet returns when system operating

I've measured and determined that the approx. cross sectional area under steam in my boiler is 185 sq. in.. When operating, the level in sight gauge drops about 1 1/2 to 2 in. With a 2 in. equalizer and 2 -1 1/4 in. wet returns, how high does the water level rise when steam is up? I'm trying to make sure that my "A" dimension to the lowest horiz. steam pipe is adequate. Thanks.

mel rowe

Can anyone give me a clue as to how to figure this out? Thanks.

john_27

when steam is up, your water line should be dropping, not rising. I measure the a dimension from a cold boiler.
Do you have Dan's book"LostArt"....he has an extensive section
on a and b dimensions.

mel rowe

Yes, the water line drops in the boiler, but I'm trying to determine how far it rises in the wet returns. I have a copy of Dan's excellent reference book, but it only gives calculations to estimate a min. for the "A " dimension in order to prevent water getting into steam lines. I've read and reread the book, but can't find anywhere that it shows how to calculate the actual water level to be expected in the wet returns during boiler operation. I'm suspicious that the water level is rising a lot more than I would have expected. In trying to figure this out, I drained a gal. of water from the boiler and measured the drop. From the drop in water level, I calculated approx. 185 sq. in. of cross sectional area in the boiler. When the system is operating, the water level in the gauge drops about 1 1/2 to 2 inches. To me this means I am moving at least 277 cu. inches of water out of the boiler and into the wet returns. With a combined cross sectional area of 3.54 sq. in. in my 1 1/4 and 1 1/2 inch wet returns, this would calculate to be a rise of 78 inches (277 divided by 3.54), which seems way too high. Sure would appreciate someone telling me where I'm going wrong here.

mel rowe

Sure need some input on this.

Ryan_10

Same level as the boiler water within an inch or two. The "missing" water is steam and return condensate in the pipes.

You're positing that the wet return water level is higher than the level in the boiler. I don't understand why. If anything, it should be a bit lower. Where are you getting all this pressure or vacuum from to drive or draw the water up the pipes?

I hope this makes sense. In an unpressurized system, there should be no difference in water level between any two points when all flowing water has gotten to where gravity is taking it. You're throwing in lots of math and forgetting how fluid operates. The steam leaving the boiler theoretically will pull that colder water in the return slightly lower than the level of the hot water in the boiler.

Bob W._3

When the system is pressurized the water level will be higher than the boiler. The weight of the water and the leftover steam pressure is what allows the condensate to slide back into the boiler while it is steaming. Thats the A dimension.

Ryan_10

Well,

you're assuming a safety margin for a system building unequal pressure in the real world! No fair!

Anyhow, I think the basic reasoning for why he isn't going to get a 6 foot column of water holds. Couldn't you just measure the pressure drop? A 1" water column is .58 ounces of pressure, so by measuring the pressure differential between the boiler and return, you should get a water column raised roughly that amount, if the influences of water weight due to density variations is ignored.

Just a thought. Could be way off too.

mel rowe

Well, all your replies convinced me my calculations had to be wrong, so I decided to remove some pipe and check the water level in one of the wet returns with a makeshift dipstick. I easily confirmed that the water level was only changing by about 16-18 inches. So I realized that the rest of the water drop was accounted for by the volume of steam in the system. Even though it hadn't seemed possible that at a ratio of 1700 to one, there was that much water being utilized to fill up the system with steam,I guess that is the case. Thanks for pushing me in the right direction.

Ryan_10

Sort of...

but not exactly. You'd have something really wrong then, and every steam system around would be flooding out. When you pressurize a single pipe system the whole system should be under *some* pressure. If it isn't, it's broken.

If you have two PSI at the boiler, you'll probably have close to that on the return as well, or will very shortly after some nasty water hammer. The differential or drop is what is driving water up the returns, as well as other harder to calculate factors.

Incidentally, if you just pull the pipe apart to see where the water is, it won't work because you'd be interrupting the opposing forces noted above. You'd have to use a clear tube to mimic actual operating conditions. Some sort of "dipstick" like mel suggested would work too, provided you ddin't open a big hole that let all the pressure out of the pipe above the return water.