Boiler blow down?

ansky

How do you blow

down the LWCO in a boiler? Is that even necessary to do?  I'm new to steam, and the only thing I was told to do weekly is open the valve at the bottom of the boiler and let the water drain until it runs clear.  Then I add more water to make it return to

the correct level.  So should I be doing this when the boiler is

firing?  I have always done it when the boiler was off. 





<a href="http://www.heatinghelp.com/forum-reply/1182932/How-do-you-blow-down-LWCO">Reply</a>

Unknown

Boiler Blow Down

You should blow down the LWCO when the boiler is firing. This should be done weekly. While the main idea is to clean out any accumulated dirt/rust etc. which might foul the float inside the cutoff, it also is a check to whether the LWCO is actually working. You should leave the blown down valve open until the water level drops and cuts off the burner.

If you're new to steam heating you want to get a book that is available on this site called "We Got Steam Heat" 

http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

It's written for the homeowner with a steam system. It's easy, humorous reading,crammed full of information and pictures on residential steam heating. In an evening or two of reading, you'll know a lot more about your steam system.  Blowing down the LWCO is discussed around page 130. (I can't tell you exactly as I recently gave away my copy to a neighbor and now need to get another one)

I might mention that is also very important to bring the new water in the boiler to the boil (make steam) as this drives off the excess dissolved oxygen in the water which can be very corrosive to your boiler.  - Rod

FJL

Blowing Down

If the water level drops, will the LWCO begin to refill the boiler to replace the water?  Won't this result in putting new water into the system every week?  I thought the idea was to avoid putting water into the boiler. 



And from where is the dirty water draining?  From the inside of the LWCO or from somewhere else in the boiler?  I've always done this while the boiler is off and has cooled for a while (that is what I was told to do by someone).  Sometimes the LWCO turns on and refills the water causing a lot of sediment to mix around and it gives me very dirty water. 

ansky

Weekly

I drain from the bottom of the boiler weekly, and then add back water to make up for what was drained out.  That's what my home inspector and heating person told me to do.  Obviously if you keep draining water out every week then at some point more water is going to need to be added.

Jamie Hall

LWCO and autofill

Low water cutouts are sometimes, but not always, associated with an autofill valve.  If they are, the theory is that the autofill should come on before the LWCO shuts off the burner, unless the flow is large.



Many LWCOs have a float assembly, which has to drop to activate them.  It is essential to drain any accumulated sediment out of the float chamber so that the float is free to move.   There is a valve for that purpose.  And that is as good a place to "blow down" the boiler as anywhere.



Some boilers -- particularly larger ones -- will have two LWCOs.  Typically one is self-resetting, and usually associated with the autofill.  The other, set at a lower level, must be manually reset.  If you do have two, clean them both out.



Do not confuse this procedure with a boiler "blow down" which is intended to reduce built up dissolved solids in the boiler water, and which is needed from time to time on any boiler which has a consumptive steam use (such as a steam laundry -- or a railway steam locomotive!).  Very different problem.  Very differenct procedure.

ansky

LWCO?

Now I'm confused after reading the post above.  It sounds like we are talking about two different things.



1. LWCO blow down

2. Boiler blow down



I only see one valve near the bottom of my boiler - it looks like the type of valve you would connect a garden hose to.  That's what I open up weekly to drain out the sediment and rust.  I assume this would be "boiler blow down".  So how exactly would I do a LWCO blow down?  I don't see any other valves.

jpf321

have a look at ....

Have a look at this picture .. [url=http://picasaweb.google.com/jpf321/Fitzgibbons400Boiler?authkey=Gv1sRgCNOPnfifvI7MNA#5407071493887838658]http://picasaweb.google.com/jpf321/Fitzgibbons400Boiler?authkey=Gv1sRgCNOPnfifvI7MNA#5407071493887838658



Here you will see a LWCO Blow Down Valve .. this system does NOT have an auto-feed.



In this picture .. you will see the LWCO as well as the MUD LEG drain. http://picasaweb.google.com/jpf321/Fitzgibbons400Boiler?authkey=Gv1sRgCNOPnfifvI7MNA#5407071485907783234



All system pics link available in my signature.

FJL

LWCO

I have two LWCOs on my boiler.  One if a probe device (I believe) and the other is a ball device, and the ball device is the one that I "blow down" once a week.  I've been doing it when the boiler is off, and I do it by pulling up a yellow lever, which happens to be connected to a pipe that travels to a drain in my boiler room.  This LWCO contains an automatic water feed, which I assume, based on the info in this thread, fills the water to prevent the boiler from turning off.  A few times that I've opened the valve to drain water the auto water fill has been activated and it then fills the boiler with water, a process that almost always stirs up sediment and gives me rusty, dirty water. 



So does this type of LWCO device allow me to blow down the LWCO to the point that it turns off the boiler? 



A picture of the device is here:  [url=http://i585.photobucket.com/albums/ss297/EasilyFound/LWCO.jpg]http://i585.photobucket.com/albums/ss297/EasilyFound/LWCO.jpg



I don't seem to have a valve that allows me to drain water from the bottom of the boiler to remove sediment.  From what I recall, there is a tapping, but I don't think it contains a valve.  I'd have to look.

Joe V_2

Blowdowns

If you have a probe type LWCO, you will not have a blowdown valve but you can test its functionality by bottom blowing the boiler while the burner is firing.   If it is working, the burner will extinguish when water level drops below probe.  If it doesn't, you must repair.  I think the typical excercise is to clean and test prior to each heating season.  The birth of the probe type LWCO came from home owners not performing weekly blowdowns.

Personally, I test weekly.  The basement is the only place I have where I can have some "alone time".



The float type has a valve below it and really does need to be blown down weekly at that valve to test and to remove sediment/rust so the float doesnt get stuck in the normal water level position if you have a leak.

In either case, test with the burner firing so you know it is functioning. 



Happy Holidays! 

FJL

But how do you test . . .

if the LWCO has an auto water refill that starts refilling the boiler before the water gets low enough to turn off the boiler.  

jpf321

temporarily...

you should have a valve on the water pipe connected to the auto-feed .. temporarily turn that off so that even if the auto-feed activates, it doesn't get any water .. don't forget to turn the water feed back on after you're done testing if you are used to having it do the work.

nicholas bonham-carter

dity water from autofill

sounds like your wet returns, and boiler need blowing down, if you are fortunate enough to have a blow down valve in the wet return. some wet returns can be valved off from the boiler, and connected to a hose for a power-flush, but that is unusual to see, so you may only be able to drain and refill through the wet return valve. that will get all the old rusty mud out.--nbc

Joe V_2

There has to be....

a way to valve the feed water off.  Look upstream of the water supply for a valve.  If you don't have a valve, put one in.

Jamie Hall

Indeed you can

test the cutoff feature of the one that you blow down -- find the valve that controls the autofill (you have to have one somewhere) and turn it off.  Then blow it down as you have been doing -- the burner should quit.  Don't forget to turn the autofill back on.



And yes, you will stir up sediment and crud.  That's the idea.  It's also why I blow float type LWCOs just long enough to get the water a little clear, then refill (with the autofill, if there is one), then do it again until the water is a little clear, then refill, and repeat until either I'm tired of it or the water is sort of clear when I first open the blowdown.



I am never too concerned about whether the water is really clear.  I figure, particularly on older systems, that if the water is clear enough so I can't walk on it, even if I don't want to drink it, that's enough.  In the building I actually super, I don't think I could get the water to run really clear if I ran it forever!

lutorm

My question too!

I looked through the owner's manual for my burnham and they don't say anything about draining out dirty water, but say a lot about how bad it is to fill water more than once per month. So at what point do you start doing more bad than good by draining out the dirty water?

Jamie Hall

My approach to that question

is a very simple one: I would suggest checking the LWCOs, if they are floats, twice a month (every other week) and draining them, as I suggested in a different post, only enough to get the water vaguely clean.  No more, as I quite agree that at some point one does a lot more harm than good.  As long as the actual boiler water is reasonably clear (look at the water glass!) and it steams quietly, there is no point in worrying about the water quality.  What you are trying to do -- again, in my view -- is to make sure that the floats in the LWCOs are free to move enough to do their job.



Again, as I noted in another post, you are not doing what I would call a true blowdown, the objective of which is to reduce the dissolved solids in the boiler water to the point where it won't foam.  This is a problem in consumptive use, but not in a heating system (unless you have a good size leak somewhere!).

Johnny13

Changed habit

Earlier someone mentioned doing the maintenance when the boiler was cool, and until the water is clear. That was the way I was doing things until a couple weeks back. I read in the We Got Steam Heat book that it should be done while the boiler is running, and only about a quart of liquid needs to be purged. This is still the accepted thinking on the subject I would think, right?

Jamie Hall

Don't know

about the "accepted" part, but basically that's the way I do it...