L408A Vaporstat

68GMC

I'm hoping someone can help me diagnose a vaporstat. A neighbour of mine rescued this one from the garbage man, and gave it to me to try out. I read the manual, and have tried testing it myself with no luck. I know that if I personally move the mercury over, it will kill the boiler when it is in the middle of a heat call.



<a href="http://www.energytek.com.tw/catalog/Honeywell/L408A,B-L608A.pdf">http://www.energytek.com.tw/catalog/Honeywell/L408A,B-L608A.pdf</a>



If a Controller Seems to Operate Improperly

If the controller is suspected of operating improperly, it may be

checked further as follows (see Fig. 10):

1. Disconnect all power to the controller, loosen the cover

screw and remove the cover.

2. Disconnect the wires from the controller.

3. Connect an ohmmeter between the switch terminals.

4. Lower the setpoint of the controller (simulating a

pressure increase) through a range greater than the

differential. The switch should either make or break,

depending on the model of the controller. (An L408A

should break, an L408B should make, and an L608A

should break R-B and make R-W.) If it makes, the

ohmmeter will read zero; if it breaks, the ohmmeter will

read infinity.

5. Raise the setpoint of the controller (simulating a

pressure decrease) through a range greater than the

differential. The switch should break or make, just the

opposite of the result in step 4.



I have 0.004 ohms resistance on my multimeter touching the two probes together, with the boiler running on a heat call, the two wires read 0.009 ohms. I read 0 volts being present. If I physically move the mercury switch over, the multimeter reads 1 . 000. Which I believe is infinity. If I adjust the main or the differential screw like the manual suggests, with the ohm meter connected, I can see the mercury move over to the left, but not far enough to trip the circuit.



Is that enough information?



Thanks everyone!!!

Steamhead

That control

must be level to operate properly. If it is, and the bulb doesn't move far enough left to trip, the control is bad. 

68GMC

I hope

these pictures are clear enough. I took them yesterday when I was testing everything. Boiler was off. The third picture was as far over as the mercury would tip performing the test. It would never go past that point.



I assume to start saving my pennies for a new one? Should I reinstall the pressuretrol for now, as a safety?



Thanks.

will smith_4

Vaporstat

I'm looking at the pic on the far right, and it seems to me that according to the pressure gauge, the vaporstat should be made. The switch should open on a pressure rise-I can't tell what the cut in/ cut out is on the control, but it does seem like the leveling pointer is off kilter in the pic. Like Steamhead said-if it's dead nut level and won't make or break at pressure, it's a bad switch. And don't use a bad switch as anything other than a paperweight-it's a jumper wire in disguise.

All the best-

Charlie from wmass

do you have a 3 psi gauge?

also that iron pigtail needs retired to assure the vaporstat can be easily leveled. Brass will bend much easier.

68GMC

My 0-3 psi gauge

is on order, I hope it will be here next week. I should look into the brass pigtails as well I guess, I hope my local supply house can get one. I ordered the 0-3 psi one. I had to order the gauge from the USA, my supply house couldn't get a gauge that low.



I realize it's kind of hard to tell if a vaporstat, in ounces, is working on a 0-30 psi gauge.



And I didn't realize the vaporstat had to be dead-nuts level, in the first pic you can see the needle is off the pointed by 1/32", I thought that would be close enough. Should you go just by that, or throw a level on top of it?



Thanks for all your help, I'll throw up new pictures once the new stuffs installed.

68GMC

I'm assuming

my vaporstat is pooched. Heres pics of the new gauge.



Thanks everyone.

Charlie from wmass

Did you check

where that nipple goes into the boiler from that elbow? I have seen them clog many times.

68GMC

I checked

it before I installed the vaporstat last spring. I ordered a brass pigtail earlier this week, I'm hoping it's in this week. Thanks.

Steve_175

Bad Vaporstat

Don't toss the old one in the trash. Most towns will take mercury switches off your hands as part of hazardous waste.

World Plumber

Garbage

If your neighbor rescued it from the garbage there may be a reason it doesn't work!!!



I built a jig that I connect to a hand pump so I can watch what pressure it opens and closes at. If it's not working correctly don't leave it on the boiler!!!