ratio of water volume in wet return to total pipe volume as it effects LWCO

matthew_rogers

while i wait to rebuild my messed up one pipe steam system i had an insight....

1=water is driven up into small copper pipes above the steam header.
2=the water level in the LWCO drops
3=the water fills up a bit and when the steam condenses the burner is over filled and hammers.
classic....

so what if my wet returns were larger....
more water in the system down low so that the water level wont drop as much in the sight glass.

nicholas bonham-carter

How would the extra water in the enlarged wet returns rise up against gravity to occupy space in the LWCO?
Think not of total volume, but only of water level.
If you have a long hose with water in it, the water level at each end will be at the same level above the floor, no matter how long the hose is. If you cut the hose in the middle, and splice in a length of much larger diameter hose, this property will not change, even though the total volume of water in the hose has been increased.
You could install a reservoir tank, whose water level would be at the same distance from the floor as the desired water level in the boiler. As water is driven up into the header, then some water will flow out of the reservoir tank into the boiler to maintain the water level in the boiler. The tank would have to be very long to have enough water at the correct height.
It would be much easier to correct the piping than to install this tank--NBC

Jamie Hall

@nicholas bonham-carter is right -- no surprise there -- but to look at it another way, the only volume which is affecting the water level in the boiler is the volume of the pipes between the static water line and the level to which it rises when the boiler is at maximum pressure. Unless you have a fairly good sized long horizontal pipe in between those two elevations, that's not going to be a whole lot of water. If, however, you do have such a pipe... it shouldn't be there! It should either be always wet -- below the static water line of the boiler -- or always dry -- depending on your pressure, that could be anywhere from 28" on up. If you do find such a pipe, the first thing to do is to move it to where it belongs.

Actually, the very first thing to do is to check your cutout pressure. It should not be above 1.5 psi.

matthew_rogers

Jamie Hall said:

@but to look at it another way, the only volume which is affecting the water level in the boiler is the volume of the pipes between the static water line and the level to which it rises when the boiler is at maximum pressure. Unless you have a fairly good sized long horizontal pipe in between those two elevations, that's not going to be a whole lot of water.

you are describing my question well. i DO have both i large volume of pipes above the waterline and also a few long horozontals.

i have read the info on the "gilford loop" as an upgrade to the hartford to equalize the pressure in the pipes and thus the water level. i have also witnessed the water getting stuck in the long vertical pipes and hammering against the long horozontals.

since these are undersized copper pipes i know i will be replacing with propper specs in the spring. BUT.... why not add some clever upgrades. i dont care about paying more for pipe or valves or extra tanks. i consider it all tuition!

should i try to aim for a wet pipe volume of 3:1 or X:X? how can i research this further?

matthew_rogers

nicholas bonham-carter said:

How would the extra water in the enlarged wet returns rise up against gravity to occupy space in the LWCO?
Think not of total volume, but only of water level.

thanks for your insightful post... but i a trying to focus on the water level.

i think i have too little water in the wet return and so i boils up and out..... the then feeder kicks in.... then the water cools, and hammer-city. ....when it all cools it is over filled.

my question leans on your clever comment on water level of a hose. ... if there was more water below the wetline... then less should be lost up in system as it travels to the second floor.

(hey another important spec here... decades ago, someone split our home into a two family.. thus the steam supplies the second and third floors.... steam has to travel very far to get into position. this may be more significant to describe than i thought prior)

Fred

The whole purpose of a wet return is to get water (condensate) back to the boiler and keep steam out of the return. The longer the return, the more potential you have of those wet returns getting clogged with gunk. You typically don't plan to make the wet returns any longer than they need to be to get water back from the end of the mains to the boiler. Intentionally making them longer is not an upgrade. It's added maintainence to keep them cleaned out. Just be sure when you replace them that they are below the Normal waterline of the boiler, even down to the floor and then back up to the Hartford or gifford loop. Either works well as long as it too is a few inches below the water line.
Water doesn't get stuck in the vertical pipes. If you have hammer, you either have a wet return that is above the water line of the boiler or improper pitch in one or more horizontal pipes (mains or dry returns above the water line, allowing water to pool in those pipes.
If the water in the boiler sight glass has a lot of bounce and/or pushes out of the boiler then returns very quickly after the boiler shuts down, the boiler may just need to be skimmed well.

SWEI

If the system is so out of whack that the condensate is not returning to the boiler in time to prevent the LWCO from tripping or the autofill from kicking in, the best bet is to clean or replace the plugged return that caused the problem. If this proves impractical or impossible, a simple condensate reservoir can be added, which has the effect of increasing the water capacity of the boiler. http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/service-bulletins/SB0606.pdf is worth a read.

matthew_rogers

SWEI said:

a simple condensate reservoir can be added, which has the effect of increasing the water capacity of the boiler

THATS exactly what i was invisioning! i cant patent it so late in the game, but it seemed like a way to handle some of what im observing here in my new home.

!!!thanks for the link. very good to learn as well that the more im reading and thinking the better grasp i'm getting for the function fo the system(s) thanks for your help making sense of this. i will study it well.

Jamie Hall

One point on which I am not exactly clear -- but which is critically important. There should be no -- repeat no -- horizontal pipes which are close enough to the water line of the boiler to fill with water at the cutout pressure, but be dry when the boiler is off. That translates to this: if you are running at a cutout of 1.5 psi -- the maximum you should be -- there should be no horizontal pipes lower than 28 inches above the water line, nor should any horizontal pipes be higher than six inches below the water line.

If there are, you will have exactly this sort of trouble, and attempting to solve it with an additional reservoir just won't work. You may solve the LWCO problem, but you won't solve the other problems -- such as hammer or poor steam distribution -- which come with it.

If there are pipes which should be wet returns, but which are too high -- not uncommon, as people replacing boilers sometimes forget to match the new water line with the old one -- you can solve that with a false water line.

There is, unfortunately, no such simple solution for a pipe which should be a dry return, but is low enough to flood on occasion -- that is, assuming that you are already running the pressure as low as you can otherwise. The only thing you can do with that is raise that pipe to where it belongs.

matthew_rogers

Jamie Hall said:

...If there are pipes which should be wet returns, but which are too high -- not uncommon, as people replacing boilers sometimes forget to match the new water line with the old one -- you can solve that with a false water line.....no such simple solution for a pipe which should be a dry return, but is low enough to flood on occasion...

my pressure is only .5
but your comments are right on target. i have a wet return (or two) that is in the basement cealing. they are just at or below 28". in general pipes are draining into the steam header and into horozontal equalizer pipes. mucked up for now, but we are helping my prepare for springtimes rebuild plans.

i am almost fully convinced that i must drop my returns straight down from the upper floors and cut into the basement cement so i can tie them into the wet return without cutting the rooms off with sloped pipes.

another note. im looking into false water lines to make sure i understand their use and benefits too. thanks for the intel.

Fred

It's time for you to post some pictures of your boiler, the near boiler piping, the mains, and all of the returns so we can see what you actually have there. If there are some returns in the ceiling of the basement, they can't be wet returns. Wet returns don't have to be below the concrete floor, they just need to be below the water line in the boiler. Also, wet returns don't have to be sloped. They are filled ith water and as long as they are below the boiler water line, the water in them will find its own level, equal to the water line in the boiler.

matthew_rogers

Fred said:

If there are some returns in the ceiling of the basement, they can't be wet returns.

hi fred, i do in fact have wet returns in the cealing. crazy as it seems but there is 1" copper pipe that heads 30 feet to the attic radiator expects the water to drip back down it and into a parallel dry return that then drops into the wet return system.

crazy and micky mouse but it is what it is. no wonder thats the trunk that hammers so often.

sorry i dont have photos to show. but this post has confirmed "my inventions" actually already exist! the resevoir tank and the false water line. The dead men already faced these problems and sorted them out. my task now is to understand them so fully that i implement them correctly. Looks like im going to be sawing through more of the basement floor concrete in the spring

oh, and yes, you are right, wet returns dont have to be below the floor.... but in my case i need to clear the floor to keep it usable space. i'm making/pouring/forming beautiful concrete trenches that will keep things from rusting. complete with deep pits for drainage in nessesary. pictures in the future. thanks fred