Wolf in sheep's clothing?

handson

I had Gerry Gill over for an inspection of the current steam system. He pointed out that the unit I though was a Vaporstat is actually a Pressuretrol with a Vaporstat front cover.

Gerry is a very knowledgeable steam guy!

Thanks to this site I finally found someone who knows what he's doing!

Binnacle

says Vaporstat on the side

And it looks much like the old-style L608A I just acquired and installed on my system.  I'd say you have a L408A.  (L608As are make/break where L408As are break-only, L408Bs make-only--L408A is fine, L408B is not).



The Honeywell doc states in table 3 that all L408A/B and L608A Vaporstats come in 0-4psi scale as well as the more useful (for steam) 0-16oz scale.



So while it is a Vaporstat it's not the version that gives you fine control over low-pressure steam.  Is better than a Pressuretrol for the more refined workings and greater accuracy and calibration.  Should give you decent control at the low-end of the range where a Pressuretrol really won't do that.



Probably Gerry was not feeling like going into the nuances and simplified.



The picture shows that it is set fairly low, but you might be able to experiment with setting it lower still while waiting for a Vaporstat with the 16oz scale if you care to acquire one.



I attempted posting the PDF of the manual but the HH forum software is refusing to allow it--sorry.

Binnacle

pressuretrol picture

Here's my old Pressuretrol before I swapped it out.

Binnacle

Vaporstat manual

Tried again and it worked.

Binnacle

Pressuretrol manual

Posted this for contrast.



The manual is for a slightly different generation than mine and I Googled for Pressuretrol images. Seems there is also a Pressuretrol (model L404A) that looks a lot like a Vaporstat and *nothing* like my PA404A.



The L404As do have the word "Pressuretrol" in red letters on the side *but* have a pressure scale of 0-150 psi rather than 0-4psi. So the L404A would seem to be for high-pressure steam systems.



I'm going to go out on a limb here and suggest that Gerry might have been unaware of the 0-4psi Vaporstat option and/or confused the high-pressure Pressuretrol with the higher-pressure Vaporstat. An honest mistake for sure as the variations are many, especially when one factors in the three-to-five generations each Honeywell control has gone through over the years.



https://www.google.com/images?q=pressuretrol+l404a&btnG=Search&gbv=1&hl=en&tbm=isch

Binnacle

semantics

So there are Pressuretrols that share the Vaporstat design (I did not know this) and the difference is merely that below about 5psi it's called a Vaporstat and above 5psi it's called a Pressuretrol.  I subsequently noticed that some L404As have a range of 0-15psi.



This is the sort of thing marketing people conjure with the intent to confuse everyone and anyone.



Only thing that matters is the scale of pressure the unit addresses and that the 0-9psi Pressuretrols have simplified low-cost design not suited to very-low-pressure operation.

handson

Thanks

for all your research and the manuals.



After all your research I can see why it is difficult to know exactly what you have given all the iterations of this model.

Hap_Hazzard

How to tell them apart.

The limit pictured appears to be a ~10 year old L408A VaporStat® Controller. It has a bigger diaphragm than the Pressuretrol® controller, and the scaleplates are different.



The differential scaleplate on the VaporStat is graduated from 2 to 16 psi by twos, or 1 to 4 psi by ones, while that of the Pressuretrol is graduated from 2 to 12 psi by twos. (See pictures.) The main scaleplate on the VaporStat is graduated from 0 to 16 oz/in² by twos, while that of the Pressuretrol is graduated from 0 to 50 psi by tens.



An L408A and an L404A of the same vintage are pictured for comparison. Both models used mercury switches in this timeframe.

ChrisJ

Vaporstat

That actually looks like the type of Vaporstat I was considering buying.  Having one that only goes to 16oz seemed like it was cutting it close to me.



Here is what my current Pressuretrol looks like.  Sure, its the same style but I believe yours has a larger diaphragm and mine goes to 15 PSI not 4 PSI.  This is currently set to trip at 1.5 PSI and close at 0.5 PSI. 

handson

Only a novice

when it comes to controls and steam heat in general., but I see the difference in the scales.

I have no idea how to set this thing and I don't get a reading on the low pressure gauge even after cleaning out the tube and replacing the gauge piping.

I've included a closeup of the vaporstat to show the pendulum at the back. I thought it was an interesting feature.

After talking with Jerry I plan to replace the old boiler in the spring. Jerry will also be reworking the near boiler piping and reworking the return condensate lines to eliminate the T&P traps. So I'm not going to do much more than keep it running for now.

I will be more interested in the control system on the new boiler.

Binnacle

new gauge

Perhaps replace the low-pressure gauge, especially if the high-pressure gauge is showing pressure while the low pressure gauge is not.  Here is one source:



http://www.valworx.com/category/low-pressure-gauges-25-lower-mount



I recently purchased a 20oz Wika gauge that I very much like.  Many prefer the 3psi gauge, but I half wish that I went for the 15oz gauge.  Running at 8oz now only because the risers are not yet insulated and I expect to go lower once that is complete.  Just purchased a cut-off for the low-pressure gauge so it can be protected if any higher-pressure runs are performed to test for leaks.



http://www.mcmaster.com/#4082t42/=qa95oo



Vaprostat adjustment is simpler than the pipe cleaning you already performed.  Use the screws on top of the case directly above each slide scale.  I find it useful to count half turns when experimenting as the scale on my Vaporstat is approximate at best.  The 20oz gauge is much more accurate.



The pendulum helps one level the control.  It must be level for proper operation.  This is in the PDF document posted earlier.

Pipedope_2

Settings

Binnacle, how low a pressure are you able to achieve in your system with this control? I ask because I am thinking of installing that model on one of my customers single pipe system.

Binnacle

low pressure

I expect it will be possible to take it to 3oz cut-in 6oz cut-out, or perhaps 2oz cut-in and 5oz cut-out.  Without a doubt, the lower the pressure the more agreeable is the behavior of the system.



For now the minimum pressure, per the gauge, that takes steam to the furthest away radiator is 3oz, but this is probably because the risers are not insulated and the main is poorly insulated with pipe-wrap.  Am planning to correct that sometime in the next year.



The other issue is efficiency.  If set too low, this system cycles more frequently and burns a bit more fuel.  So I'm trading probably 1.5 degrees of extra room-temperature overshoot for better economy.  Cycle is something like 2.5 hours with higher pressure and more overshoot and 1.5 hours with a lower pressure maximum, though with lower pressure the house is significantly more comfortable.  Hopefully with good pipe insulation the radiators will heat more quickly and shorter system cycles will become more economical since the burn-time will be reduced.



Each system is different, so this is where a Vaporstat and low-pressure gauge shine.  Lets one fine-tune for the situation.  Some people on HH can run at 2oz and the Vaporstat never turns off the burners.  Here the boiler is a bit large for the current radiators as some are shut off (due to uninsulated risers throwing off heat), so a pressure cut-off is necessary.



The Vaporstat allowed me to find the pressure compromise that works with poor pipe insulation.  The furthest radiator has water-hammer above the 8oz pressure (again due to lack of pipe insulation), so I was able to eliminate the water hammer while keeping the pressure high enough to obtain longer system cycles.



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One thing to be aware of is that some people have found the newer no-mercury L408J Vaporstats to arrive from the factory with poor calibration.  One can adjust the calibration by sliding the scale plates up and down, but for a professional this can be time consuming and of course that's not good.  As an amateur I can fiddle endlessly with my Vaporstat and it's no big deal.   Because of the experience of Gerry Gill who wrote about the calibration problem on HH I purchased a used L608A mercury-bulb Vaporstat on eBay.  But again, I'm an amateur and am not bound by regulations and time constraints.  I suspect that professionals should not install mercury switches.



And that used Vaporstat I purchased has not-great calibration--I can't slide the scale plate far enough to correct it so it's off by about 1oz.  The lowest pressure differential I can achieve is 3oz, though this may be because some of the old L608A models have 3.5oz as the design minimum.



Gerry Gill and his partner Steve Pajek have invented and sell a super-accurate water-column pressure control.  I gather it's a bit expensive, but it might be that the extra cost for this control will be more than offset by less time spent fiddling with a Vaporstat.  On the other hand if the customer is inclined to take on some of the responsibility for tweaking the pressure control, a Vaporstat might work very well.



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But don't get me wrong.  Any of the diaphragm & balance controls is vastly superior to the PA404A Pressuretrols.  If one needs more the 16oz of pressure, perhaps for a very large building, then the 0-4psi Vaporstat or the 0-15psi Pressuretrol would work fine.