Removing a Pressuretrol with a Vaporstat

Steve_211

I have a Honeywell vaporstat, model L408B1131 that I'm looking to exchange with the Honeywell pressuretrol on my boiler. This model has a mercury switch with two terminals. Looking at the vaporstat, when mounted, the switch is in the off position, which tells me that the boiler will not come on when there is a call for heat. How is the vaporstat hooked up in place of the pressuretrol?

Jamie Hall

Just take the same two wires which were attached to the Pressuretrol and hook them up to the vapourstat terminals. Are you sure that it's in the off position when it is mounted? According to my information, that model is a break on pressure rise, so it should show continuity when there is no pressure on it.

If it is a make on rise, you can't use it...

Whatever, the mercury models are very sensitive to being level -- so make sure that it is when you mount it!

Steve_211

After mounting it, I leveled it with a bubble level. The plumb indicator in the vaporstat also indicated it being level. After attaching the two wires, the boiler did not come on when called for heat. The mercury switch is sloped to the right; the contacts of the switch being on the left. It appears to me the switch should slope to the left, and slope to the right when the requisite boiler pressure is reached, thus shutting off the boiler.

Abracadabra

Check for continuity with a DMM. When bulb is tilted left side up and right side down, (mercury on the right side of the bulb) you should have continuity. If not there's a problem with the vaporstat.

Fred

@Steve , that is the wrong Vaporstat. The model L408B1131, makes on pressure and is normally open. You want a normally closed vaporstat.

Steve_211

Thanks for the replies, guys. So, what model Honeywell vaporstat do I need?

Regarding this model vaporstat (making on pressure, being normally open), what type of system would it be used in?

Fred

You want model #L408J1009 (0 to 16 ounce ) or #L408J1017 (0 to 4 PSI). I use the 0-16 ounce Vaporstat but if you know your system runs at slightly over 1 PSI, the 0 to 4 PSI is the one you want.
The one you have is used when there is another device, on a system that needs a minimum pressure before it is engaged.

Steve_211

I went and got the Honeywell L408J1017 (0 to 4 psi) vaporstat. I removed the two wires from the terminals on the pressuretrol.
The two terminals are not marked. The vaporstat has three terminals marked "R", "W", and "B". What terminals do I attach the two wires to? The vaporstat did not have any instructions. I searched the Honeywell website...nothing. I called them, they won't offer any technical support, telling me that I have to contact the contractor that installed it.

Fred

Connect one wire to the top terminal (either one) and the other to the bottom terminal. The center terminal is not connected to anything.

Steve_211

I replaced the 30 psi guage with a 3 psi before exchanging the pressuretrol with the vaporstat. The pressuretrol was set at 1 with a .5 cut in. The rise was greater than 1.5 but less than 2 on the guage before the break. The boiler cut in a little over .5. I hooked the wires to the top and bottom terminals and set the main between .5 and 1 psi and the differential to 4 oz. Turning the boiler on, it would not break. The psi on the guage rose to well over 2 and climbing to 3. Fearing I'd damage the guage, I manually shut the boiler down. What's up with the vaporstat? It should have shut the boiler before 1 psi.

BobC

It sounds like your vaporstat may be defective. I run mine with a 12oz cutout and a 4 oz cut in and it works fine. Mine is a mercury bulb model so you can see the mercury bulb moving as the pressure rises, the microswitch versions don't give any visual indications so it's hard to see whats going on.

Can you inspect the vaporstat to make sure the balance beam between the pressure diaphragm and the microswitch has not become disengaged?

Bob

ratio

Also, they are notorious for being out of calibration. I'd try setting the main down (being careful to not let it drop off the end of the adjustment screw) and see if it will trip.

The scale on these devices is only there as a convenience, they should be set up with calibrated instruments. Don't worry about what the scale shows, the point it actually switches at is what's important!

Fred

Did you make sure the pigtail you mounted it on is not plugged and that the tapping the pigtail is screwed into is also open? A Vaporstat should not be off by anywhere near that much. Make sure the linkages on the springs behind the Main and Differential scales (inside the box) have not become disconnected and that the tiny orifice inside the fitting that mounts onto the pigtail isn't clogged. Did you buy a new or used Vaporstat? If used, it could well be defective.

ratio

Yah, I didn't think of the piggytail. Check/clean it. That would certainly keep the vaporstat from opening.

LionA29

Good ? @Fred, might be used.

Steve_211

The pigtail is clean. I removed it when I installed the L408B1131 vaporstat and the 3 psi guage. The linkages on the L408J1017 vaporstat have not become disconnected, so I assume it is defective. The vendor advertised it as being new. It was in a sealed box, however, for all I know it could have been lying on a shelf a number of years. My last hope is to try the L408A1132 vaporstat; same as the L408J1017, but it has the mercury bulb switch instead of the SPDT snap action switch.

Steve_211

Until I get the L408A1132 vaporstat, I re-installed the pressuretrol and the boiler is working as it did initially before I started down this road.

nicholas bonham-carter

The only common element here is the pigtail, which remains the same. Could it be changing shape with the effect of steam entering the loup? The axis of the pigtail should be at right angles to the axis of the linkage, otherwise it will go out of level as the boiler steams.--NBC

BobC

Have you tried to manually trip the vaporstat by pulling up on the lever between the diaphragm and the microswitch (may have to use a screwdriver)? If that does not actuate the switch there is something wrong with the linkage.

If it does actuate the switch the problem is either a bad diaphragm or the unit is badly out of calibration.

Bob

Steve_211

To segue into the use of a pigtail, to me it resembles a P trap on a sink. When the steam condenses back to water, over time, wouldn't it fill the pigtail enough to block it? And then, wouldn't the pressure of the steam force it up to the guage and/or the pressuretrol or vaporstat?

BobC

The water in the trap will move with pressure but because the top of the outlit is sealed it can't go very far. The water will exert pressure on the air and then on the diaphragm of the pressuretrol or vaporstat.

Fred

Steve said:

The pigtail is clean. I removed it when I installed the L408B1131 vaporstat and the 3 psi guage. The linkages on the L408J1017 vaporstat have not become disconnected, so I assume it is defective. The vendor advertised it as being new. It was in a sealed box, however, for all I know it could have been lying on a shelf a number of years. My last hope is to try the L408A1132 vaporstat; same as the L408J1017, but it has the mercury bulb switch instead of the SPDT snap action switch.

@Steve , You always have the option of getting another 1017 Vaporstat. Because one is bad, doesn't mean they are all bad.

Steve_211

True, but how many before I get a good one? I purchased it online, so the turnaround time is a few weeks. At least with the mercury bulb, I'll be able to see the function of the switch.

Fred

Steve said:

True, but how many before I get a good one? I purchased it online, so the turnaround time is a few weeks. At least with the mercury bulb, I'll be able to see the function of the switch.

It takes the same amount of time to ship/receive either the micro switch or mercury one. Yes you can see the mercury bulb move but the effort to ensure it is level and stays level on the Pigtail has it's drawbacks as well. Not an issue with the micro switch version.