Keeping an old Steamer going...

PinkTavo

OK, tried to post this once before. So could be a duplicate. 1981 HB Smith. One-pipe system. Everything working great, but am worried about the MM 67-2; original to this install. When I do my blow-down, I have to whack it with a small ball-pean hammer to get the safety to work....first I get water fill, which is good, but it takes a while to get the burner to shutdown. Do I need to get this replaced for safety....or should I continue my routine? It is some bucks$$ to replace the MM 67-2....so want to save those if possible. Is there a way to clean out the crud in the float chamber? I think that this may be all there is that causes the sticking.

Abracadabra

Yes.. you either:

1. probably need to clean out the float chamber if it's never been done
   
2. clean the piping and tubing attaching the LWCO to the boiler
   
3. or test the operation of the switch
   

Fred

Yes, rust/crud builds up on the side walls of the float chamber and the float actually hangs up on those side walls. It is suppose to be taken apart and cleaned annually. If you goggle McDonnell Miller #67 LWCO parts, you can order new parts. For just an annual cleaning, order a gasket set for both the rear electrical box (which you will need to take apart to pull the float out of that end and also a gasket set for the blow down valve. Removing both of those components will allow you to get inside with a narrow scraper and scrape the entire float chamber. While you have it apart, check the float and make sure it doesn't have any water in it . If it does, that means it is leaking and you need to order a new float. If needed, the switch and blow down valve can be ordered as replacement part as well. Sometimes you can find complete, new ones on ebay for $50.00 to $100.00.

JUGHNE

If you price all the parts that may need to be replaced for something this old you will approach the cost of a new one.

You won't be there with the hammer when you really want that switch to open.

This is probably the only LWCO you have on the boiler?

I believe it does the safety switch before the fill valve...or not?

Fred

JUGHNE said:

If you price all the parts that may need to be replaced for something this old you will approach the cost of a new one.

You won't be there with the hammer when you really want that switch to open.

This is probably the only LWCO you have on the boiler?

I believe it does the safety switch before the fill valve...or not?

You're right about the parts separately costing as much/more than a new complete unit. Fortunately, you typically only ever need the gaskets.
It actually does both the safety switch and the fill valve simultaneously. There is a double set of contacts mounted on the end of the housing (top and bottom). When the float is up (floating on the water), it completes the safety circuit when the water level is low enough that the float drops enough, it breaks the safety circuit (top contact) and a second contact (on the bottom) makes to trip the fill valve.

Steamhead

Actually, it's the other way- the fill valve contact closes first, and if the level keeps dropping, the burner contact opens.

EBEBRATT-Ed

Realize that your talking about a 35 year old safety control. McDonnell Miller recommends replacement every 10 years.

Don't take a chance on the possibility of loosing a boiler and install a new #67. The labor and the cost of the parts are not worth it

Koan

@Fred is right. I think your float is hanging or even resting on build up in the chamber. Our #67 had the old blow down valve which was not working well. The newer replacement part is a full port quarter turn ball. With the old valve, water just would not drain very quickly. Turns out there was so much trapped in the housing that the "old style" valve would not let it all out. I was finally able to get a slug of garbage out after many blow-downs.

Immediately after that, the float sank because it was filled with water and kept cutting out the burner even when the boiler was full. When I went to replace the valve and float, the amount of rust and crap I got out of the housing was amazing. The old style valve can trap a lot of stuff, enough that even a water-logged float will rest on it. Compensating errors. You don't want that.

There is no doubt the full port quarter turn valve in the newer #67 will allow for better blow down. If you have the older style valve I suggest you replace it with a new quarter turn blow-down valve and new gasket. At the same time, replace the float and its gasket. While both the float and valve are out, clean the housing out really well with a screw driver and an internal copper fitting brush. Do this with the float out as you may easily puncture it.

In the process of replacing the float and valve I was able to completely clean the float housing above the valve. I aslo agree with @EBEBRATT-Ed - unless you want to take out the float from the back and the valve from underneath every ten years and clean it, replacing it is not a bad idea. I assume you are comfortable doing this, If not it is really important you get a qualified person here on the forum to do so.
I have attached pics with part numbers to help. You will need numbers 3, 4, 8, and 9 on the picture, Parts numbered 318800, 344200, 310447, and 313200 respectively.

hope that helps.