Run Off / Blow Down Concern...

marcusjh

I've been reading on a few boards that when blowing down the glass, you should do it while the furnace is running (y/n?).... and in connection, check to see if the low water cut off works correctly once in awhile....

-But somewhere, I thought I saw that doing that can crack the boiler, or cause it to explode (?) ....... I've always run the water off while the furnace is shut down (this is what my Dad always taught me), so I need a little reassurance. The lwco hasn't been replaced in many years (it's a Watts 89A model M, max 25psi).

If I drain the water down past the lwco mark (I'm assuming it's the arrow that's on the float chamber), hit the power, and it comes on -obviously I need to replace the float (I know that much). My concern is if the power comes on, whether the boiler will crack (or go boom )

marcusjh

-and yes, I know the plumbing needs to be addressed... i've never done plumbing, so that requires some $ to be saved up to hire someone to do that

Jamie Hall

You should indeed blow down the LWCO -- it has a float in it which can get gummed up. Ideally, shut off the water supply to the automatic feeder, if you have one. Then blow down the LWCO. The boiler should stop. If it doesn't, the LWCO isn't working and that's dangerous. Turn off the power to the boiler until you can get it fixed.

Assuming all is well and it does, you can open the water supply and add water back up to where it belongs. If doing this manually, you can do it slowly and there shouldn't be a problem. Even the automatic feeder is unlikely to feed fast enough to cause a problem.

You can crack a boiler by adding water to a hot boiler. But -- you have to add a fair amount to do it. You can also potentially blow up a boiler that way -- but the boiler has to be red hot and dry fired. All of which is why the LWCO is important.

marcusjh

Thanks -I have been blowing it down faithfully over the last 10 years, but I've never known about the float / or to do it when the boiler is running.

It's not an automatic water feeder, it's manual, and my Dad always said to add the water reeeeeallly reeeeally slowly. Which I do.

So, just to confirm, #1, that arrow on the lwco I'm assuming is the indicator for the switch -correct? Water level any lower than point that should trip it and shut it down?

#2 - no fear of cracking the boiler if I drain the lwco past that point while running... -OR, should I blow it down first, and then hit the power to see if it goes to fire?

Fred

The boiler should shut down within a few (maybe 5) seconds after you start to blow it down. The boiler water level will remain above that arrow. What you are doing is lowering the water level in the LWCO so as to cause the internal float to drop down below that arrow.
Also, when you do test the LWCO, with the boiler running, open the valve slowly initially. If, for some reason, the pressure is higher than it should be, boiling water could splash up and burn you.