Flushing furnace boiler? ? ?

We have a rather old McDonnell & Miller oil-burning boiler which serves a six-unit apartment building.
At some point in the distant past I was told that the boiler needed to be flushed for two minutes once a week. I was told that the system should NOT be running when I started this operation. To flush while the burner was on might crack the boiler, I was told. Knowing nothing abut the system, I accepted this without question.
Recently a plumber told me it was the other way around: The burner should be ON when I do the flushing. I should start the flushing slowly until the water became warm, then open it fully for 30 seconds or so. Then I should repeat twice.
Which of this advice should I follow? I can't find any help in the manual.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You must have a steam boiler and what they are describing is called blowing it down. The burner does not need to be on for this. You are flushing debris from the system and making sure your makeup water valve and floats are working properly. Please have someone come out and check your system and make sure it is in good shape and show you all the things you are to check.
TAB Dude
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Tab,
FOOTNOTE: In blowing down the float assembly the burner should really be ON thus verifing the burner circuit will open in a low water condition. P.S. FOOTNOTE As soon as the feed water makes and the burner circuit breaks= blowdown valve goes to closed. * * If the feedwater does not break and burner contacts make in a timely fashion and closely tracking with the water gauge glass, this indicates the lower equilizer line has a blockage and needs to be investigated ASAP.
You probably know this, however I thought I'd throw it out here for others reading, too.
-zero
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
What you say is true but I do not say so to homeowners. If the burner does not shut down many will not have the knowledge to know that there is a problem and protect the boiler. If the home owner at least does the routine basic maintenance they will have done more for their boiler than 90% the people out there.
TAB Dude
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Second guy was closer to right. You need some pressure in the boiler when doing it so as to flush the minerals and solids. You don't want to blow it down so far as to greatly reduce the water level. Best way is to slowly open the valve, close it, then repeat it twice more. This stirs up the sediment so it can be flushed. Never take the water level down more than 1/2" at a time
It can be done with the boiler firing if you don't take it down too far. This is done on every commercial/industrial high pressure boiler on every shift.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks -- will proceed accordingly.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.