Water feeder overfilling/flooding system

a2shutt

Hi, I'm having a problem with my McDonnell Miller Uni-match water feeder on my steam boiler.  It's a one pipe system in a 7 unit apartment building.

 





It used to work great, only activating when about an inch of water showed in the sight glass.  A few weeks ago, it started activating when the water level was almost at the top of the sight glass.  Several days ago, it engaged and did not shut off until the whole system was flooded and water was coming out of the first floor radiator air vents.





I unhooked  one of two wires that attach to the solenoid to prevent it from activating.  However, the green activation light comes on and off randomly, and when I put my hand on the water supply line near the feeder I can feel a slight vibration, like from a solenoid or something.  As well, it seems like (going to verify this tomorrow) the water level increases overnight even WITHOUT the water feeder activating.





No idea where to start troubleshooting this.  My wet return doesnt seem to be plugged, and both LWCOs work fine (one float and one probe).   I have noticed, however, that the float lwco is suddenly taking longer to cut out the burner when I open the valve-it used to cut out immediately (within 2 seconds) and it is now taking up to 10 seconds to shut off the burner.  Everything else seems fine.





thanks for your help!!

MTC

do you blow down the M&M LWCO

at least once a week? It sounds like its full of mud. This stops the float from going down properly to shut off on low water condition, and can cause the float to suction down into the mud, not coming back up properly when the water level rises, and therefore keeping the water feeder running.



You probably need to get a gasket for the LWCO, take it apart, and clean it all out. You may need a new float as well, but hard to say w/o tearing it apart.

MTC

do you blow down the M&M LWCO

at least once a week? It sounds like its full of mud. This stops the float from going down properly to shut off on low water condition, and can cause the float to suction down into the mud, not coming back up properly when the water level rises, and therefore keeping the water feeder running.



You probably need to get a gasket for the LWCO, take it apart, and clean it all out. You may need a new float as well, but hard to say w/o tearing it apart.

a2shutt

Yes

I do (at least) once per week run water through it until it runs clear.











That does make sense.  Do you have any sort of procedure for cleaning it out?  I pulled the four bolts off the bottom and removed the lower section (with the valve) yesterday, but I could only see so much with hot water dripping all over me.  Is it relatively straightforward to determine how well the float is working with it apart?





thanks!

nicholas bonham-carter

Misbehaving auto/over fill

These auto fills are the work of the devil!! They should be valved off most of the time!

1st, determine if the valve is leaking by filling the boiler to the 1/2 mark, and use a clothespin to mark the level precisely. Switch off the power to the boiler, and wait a couple of hours to see if the level has risen.

If it has risen, then do you have a hot water coil?

Valve off the water going into the auto fill, and while off check for any deviation of marked level.

If none, then turn on the boiler, with the auto fill still valved off, and watch for any deviation in the level. It will help to set up the thermostat to make it fire. This presumes the LWCO works, and will shut off the boiler on low water.

If you have wet steam, and high pressure, the water will be blown out of the boiler, and the auto fill will feed. After a while, all the water comes back, and you have too much, untill the next firing where the situation repeats, adding more water each firing.

Keep the pressure down.--NBC

a2shutt

thanks!

for the fill testing procedure.  I'll do that today.





I'd gladly shut it off, but it's in an apartment building.  I can't go there on a daily basis to check it, so I'm stuck with some automation.





By a hot water coil, do you mean a hot water loop or zone?  If so, then yes.





I'll try that out.  The system has been running pretty nicely since I actually started maintaining it (with tons of help from this site) unlike the previous owner.

MTC

dang it,

I always forget the hot water coil in a flooding situation. Thanks NBC for catching that possibility.



What he's talking about is an indirect loop to heat domestic hot water, not a hot water zone (at least not as much). What can happen is the indirect loop springs a leak, which now lets the potable water loop leak into the boiler. Since the cold water refilling the hot water system is pressurized from the street, this leak can flood the boiler.



A hot water zone coil leaking could cause some water level issues, but unless that's one massive zone, or one up high with gravity helping to empty it down into the steam system, it couldn't cause the kind of flooding you're talking about... there's just not enough water in there. Once again, an autofeeder on the hot water zone would change this, and create the same problem as the domestic water loop, since you'd now have probably 12-18PSI of pressurized cold water refilling that loop as it leaks into boiler.



If previous guy didn't maintain system, you should probably clean out that M&M. I maintain a number of steam buildings that were previously maintained fairly well, though probably not quite enough blowdowns at times. When I've pulled these things apart, there's be quite a lot of mud in them. They have a way of blowing down clear anyway, not really sure how.



For the $5 a gasket will cost you, and the hour it takes, it's well worth it. Look up the specific model number online, there will be instructions for how to repair it. But it really is just a matter of removing a few bolts, pulling it apart, cleaning it out, and putting it back together with a new gasket. Unless something goes wrong, which Murphy usually ensures :-P

a2shutt

there is

no loop for heating potable water.  There is a small hot water heat zone on the main level, so it doesn't seem like that is the problem.

 





The system was totally neglected before, but I did have a guy come in last feb.  Here in Michigan I'm supposed to have a CSD-1 inspection done on it every year as part of the boiler licensing process.  He did disassemble the lwco and clean it, but maybe its just time again (even with me flushing it weekly).





Is there an advantage to cleaning the electronic probe lwco while I've got the boiler basically drained?

Rod

LWCO Data

Hi - Attached is some M&M data sheets which maybe of help to you. The 67 LWCO should be disassembled and inspected annually and replaced every 10 years. With rentals you have to be careful to "cover yourself" so I would keep a formal logbook with the date, name, and what service was performed. While you can do a lot of the service yourself, it isn't a bad idea to have an outside pro make a regular yearly inspection.

- Rod

Hap_Hazzard

Series 67 float removal

To remove the float, first remove the switch, which is held in place by two screws at 3 and 9 o'clock. Then you should see the four screws that hold the float assembly. Remove these and the float should slide right out. Make sure there's no water inside the float. If there is, replace it. Clean out the float chamber and replace the float and switch, then test.

a2shutt

thanks!

I'll look through those.

a2shutt

ok

I checked the water level today with the feeder off and it had dropped noticeably.  I do have a steam leak that needs to be fixed so I'm assuming that's why.  Either way, it seems like the water feeder valve is not letting water in.











Tonight I checked the float lwco, and it would not work at all.  When I attempted to blow it down, the burner kept right on going.  Scary.  I filled the boiler up to the top of the sight glass and am hoping that the probe lwco will work if there is a problem!  (how can I test it?)





Tomorrow I've got to tear the float one apart.  I can't get the gasket locally-can I use a thin bead of RTV or something like that?

Rod

M&M 67 LWCO Parts

1. Hi - It sounds as though your water feeder is okay. The LWCO controls the activation of  the water feeder so if the LWCO isn't working, neither does the waterfeeder.  Try to preserve the gasket when taking the LWCO apart. Quite often you can use it again. If you can't get parts locally, try Pex Supply  www.pexsupply.com/   on the internet. They have Mcdonnell Miller 67 replacement parts. You need to get that steam leak fixed as the constant addition of fresh water to the boiler really shortens its life span    - Rod
   
   

a2shutt

yesterday

I pulled the probe lwco and cleaned the end of it.  It had a thin film, but not bad.











I also dissembled the float lwco and thoroughly cleaned it.  There was very little mud.  I fired up the boiler and the blow down cut the burner out, so it is working fine now.  Something must have needed the cleaning.  The only problem is that now the valve body drips (?).





Do the switches on the float lwco ever go bad?





The auto feeder also seems to be operating again as it should, so maybe that was it.  We'll see if it lasts.

MTC

mercury switches

should never go bad, unless you break them. They may need adjustment, but wont' go bad. The newer electronic switches can go bad.