Heating Help

Advice on vaporstat?

Hi,
  This morning my steam boiler was not firing despite a call for heat. The radiators were slightly warm. After some head scratching I tapped on the pressuretrol with my finger and it started right up. The control is very old and is probably the same age as the boiler from 1979. I would like to replace it with a vaporstat and also get a 0-3 PSI gauge.

I've read on the forum to use a 0-16oz vaporstat - is there any downside to a 0-4 lbs control instead? Since I have never run the system at 16oz I do not know if it would be sufficient. I am looking at the Honeywell models L408J1009 & L408J1017. Does anyone have experiences with these to share?

Also I've been searching the Internet for a 0-3 PSI gauge but have not found many options. I did find Low Pressure Gauges made by Wika and alternatively Ashcroft but I am not sure if they are ideal for steam applications. Does anyone know about these or have another favorite that I might be able to find on the Internet?

Thanks!

David Sorkin, North Plainfield NJ

Vaporstat

Hi David:

You might want to search the Steam forum for answers to your questions.  I think I've seen them discussed there before.

Vaporstat?

Thanks Alan - actually I did a lot of reading but haven't found the answers to my specific questions. I did read one additional post though that makes me question using a Honeywell vaporstat at all.

http://www.heatinghelp.com/forum-thread/128249/why-do-Honeywell-vaporstats-suck-so-badly.

What better alternatives are there?

Also - why would a pressure control be used in conjunction with a vaporstat? There's a photo of this setup here:

http://www.heatinghelp.com/forum-thread/129949/Temperature-based-cut-in-for-a-Vaporstat

For the low pressure gauge I found this one http://www.coleparmer.com/catalog/product_view.asp?sku=6893010 but seems a little pricey at $46

Thanks

Ptrol and Vstat

Hi David, that's my setup with the pressuretrol and vaporstat. The pressuretrol is the safety control and is wired into a 120VAC circuit, as orginally equipped by the manufacturer. The vaporstat is an an operating limit switch, wired in the NC position (break on hi pressure) set to cut out at 3.5 oz, and is in a low voltage 24 circuit along with a time delay relay.

My system runs at very low pressure, between 1 and 2 oz, and if it gets to the cut-out point on the vaporstat, I know that the system is completely filled with steam, so rather than short-cycle, the time delay relay kicks in and holds the thermostat circuit open for 20 minutes. The latent heat in the radiators continues to heat the building, and if the thermostat still isn't satisfied after 20 mins, the system will turn on again (though I've yet to have that happen).

I think the point of the "Why Do Honeywell Vaporstats Suck" thread isn't that they don't work, it's that they don't come calibrated out-of-the-box. For pros like Gerry Gill, this has got to be a huge pain to have to take time to set up each vaporstat, but as a homeowner I only had to do itonce, so no big deal. In that thread, Gerry describes a calibration jig he uses, and near the end of the thread is one I cooked up with a low pressure gauge and some 1/4" fittings.

An off-the-deep-end alternative, and other thoughts

Alternatives:

I'm not aware of any other low pressure mechanical controls out there that do what a vaporstat does (not at that price point at least). Depending on how badly you've caught the "steam enthusiast" bug, you could go off the deep end and venture into the electrical control arena.

I've installed a 0-3 PSI, 4-20ma pressure transmitter on a pigtail, wired to (relatively) inexpensive I/O (www.phidgets.com), which in turn is connected to a PC that is running software I wrote to record the pressure, indoor and outdoor temps, far rad temp, tankless coil outlet and tempered temps on a continuous basis. Next season I am looking at writing some more code and adding I/O to use the pressure transmitter as an operating control, replacing the vaporstat and the mechanical relay that's in place now.

Gauge

The WIKA 0-3 PSI gauge from GaugeStore.com is fine for steam, since the gauge is installed on a pigtail that isolates the steam from the gauge.

0-4 lb vs 0-15 oz Vaporstat

The potential downside to a 0-4 lb vaporstat is that, like most controls, they tend to be more accurate in the middle of their range and less so at their low and high extremes. So if you install a 0-4 lb vstat and it turns out that your cutout pressure is, say, 8 oz, you're in the lower 12-1/2% of the operating range. On a 0-16 oz vstat, you're right in the 50% range.

I'd recommend that you first install the 0-3 PSI gauge and get an idea of what your operating pressures are, and use that data to decide which vaporstat to install.

Clean the pig tail

drop it to 0.5 cut in and 1 differential.

Low Pressure Gauge

I finally got all my plumbing parts and installed the 0-3 PSI Wika low pressure gauge the other night.  It took pexsupply a long time to send me all the little brass nipples. The gauge is fantastic and has vindicated the pressure control. I was able to very precisely set the control to cut in at .5 and cut out at 2 lbs. It's strange that the original gauge is 0-30 PSI, it be would like my car having a speedometer that went up to 1,200 miles per hour!

David you need to keep the old gauge

Insurance requires a gauge that is rated twice the relief valve rating of the boiler.