Vaporstat problems

DW_

I have a Honeywell vaporstat L408a1132 on my boiler and it no longer works so I need to replace it. I've looked and it appears that model is no longer in production. Can anyone tell me which model replaced it, and if it's possible for a person with no HVAC knowledge, but very mechanically inclined, to replace one? It looks as if it just threads onto the pipe and has a couple electrical connections, seems easy enough.



Is there any way to fix my defective unit? I have to tap on it to get the mercury switch to kick on, it builds steam and when the pressure reaches the limit the switch kicks off then when it reaches the lower limit it doesn't kick back on unless I tap on it again.



Any help at all would be greatly appreciated, it's cold out!

Jamie Hall

Several things to try before you give up

There isn't much that can go wrong with those things.



First thing: is it still level?  Check very carefully.  If it has gotten off level -- tilted to the left -- even a relatively small amount, that will do it.



Second, are the settings still correct?  The differential must be less than the cutout.  I can't see how it would have slipped, but odd things do happen.



Third, is the pigtail clear?  A blockage might be holding pressure, although I wouldn't think it would hold for too long.  To check the pigtail, you will have to take the vapourstat off and unscrew the pigtail... and to do that:



First, turn the boiler off with the emergency switch.

Second, open the vapourstat and disconnect the wires.

Third, unthread the vapourstat.

Fourth, unthread the pigtail and blow through it.  It should blow freely in both directions.

Reverse the above to put it back together (be sure and use pipe dope or tape, but not too much!).  Make sure that there is some water in the pigtail loop, though before you put the vapourstat back on.

Flip the boiler back on and see if it works right...



If you still think there might be a problem with the vapourstat, the replacement is Honeywell L408J1009.  You need to be a little careful with the wiring; that model can either open or close on rise, and you want open on rise.

MTC

For level...

one more thing... the pigtail loop should not be visible when looking at the front of the gauge, if that makes sense. You don't want the loop itself off to the left or right when looking at the front of a gauge, but towards the back or front. The curve expands and contracts a bit with heat, and can tilt the gauge forward and back a bit (if configured this way), If its to the side, it can actually tilt the gauge out of level when hot, then back to level when it cools, or something similar.



I don't know specifically if there's anything on that model that could "stick," but maybe there's a pivot point that just needs a drop of oil? If tapping it makes it go back, maybe the mercury switch is sticking a bit on the cut in side and tapping it knocks it free... haven't run into that specifically, but just a thought.

DW_

It's level

I'll check orientation of the pigtail, and all settings are correct. There is a lot of corrosion inside the vaporstat, as if the diaphragm was leaking, letting steam out. I spray a little bit of WD40 in it and work the mechanism back and forth a few times and it works for a little while but it eventually won't kick back on.



Would I have any problems replacing this myself? I don't want to pay someone $800 to replace a $175 part if I can safely do it myself.

BobC

Check the base

I've seen a little bit of crud at the base of the vaporstat (inside the brass fitting that screws onto the pigtail) that gets pushed into the small hole at the base of that fitting and that can cause the symptom your seeing.



With the power shut off at the circuit breaker unwire the vaporstat (make a note of the wiring) and thread the vaporstat off the pigtail. Turn the vaporstat upside down and make sure the base of the brass fitting is clean and that the 1/16" hole is clear - you can use a toothpick to make sure it's clear.



Then take off the pigtail and make sure that is clear and check the port into the boiler to make sure there isn't anything lurking in there.  If you find any signs of a blockage or sludge clean it out and reassemble.



Bob

DW_

Thanks

Thanks for all the suggestions, it's working for the moment so I'll wait until tomorrow to check everything out.

BobC

It's not hard

Removing and inspecting or replacing the vaporstat is not hard, just make sure record the way things are so you can put them back the way they were. Just make sure the power is off and the boiler is cold or just warm.



If you have to buy a new one they can be ordered from Pexsupply



http://www.pexsupply.com/pex/control/search/~SEARCH_STRING=vaporstat





Bob

Jamie Hall

Corrosion?

There really shouldn't be corrosion in there.  If there is, one needs to find out why.  Why?  Because if there is some way steam or water is getting in there to cause corrosion, it's not going to stop because you put on a new vapourstat -- and the new ones aren't as bulletproof as the old ones were.



Steam, of course, should never reach the vapourstat anyway.  That's what the pigtail is for.



Was it overpressured at some time?  That could have damaged the diaphragm -- but if the diaphragm were leaking, I wouldn't expect the vapourstat to ever trip.



Needs a little more investigation on the scene.

MTC

Could corrosion be caused

by an empty pigtail? I guess this condition would correct itself with condensate after some time, but that may have been long enough for the damage to be done. Though I guess it still shouldn't have gotten through to do significant damage...