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Joined on November 14, 2009

Last Post on April 7, 2014

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Time delay relay

@ February 10, 2011 6:49 AM in How low can you go?

Hi Steve,

Like you, I have my system running at very low pressure, 1 to 1.5 ounces, and the pressure doesn't start to increase until near the end of a recovery from setback. I'm also of the opinion that continuing to fire once the pressure gets above a certain point is just wasted fuel. In my case, I have the vaporstat set to cut out at 3.5 ounces and cut-in at a slight negative pressure, around -0.5 oz.

The trouble I ran into was that when the vaporstat trips on pressure, it cuts back in after only 30 seconds or so. So I added a time delay relay that keeps the burner off for 20 minutes after the vaporstat cuts out. This lets the latent heat do its thing. It's been in place since last March and so far there has yet to be a cycle where the flywheel effect failed to "coast" to the thermostat setpoint. The average time for my system to go from "cut-out" to "setpoint reached" averages around 10 minutes.

I posted a couple of wiring diagrams, one for 24V and one for line voltage in this thread:

Both versions are designed to consume no power until the vaporstat cuts out, and the vaporstat is wired to the make-on-cutout side (R-W) of the switch rather than the break-on-cutout (R-B) side. I implemented the 24V version, because I didn't want to mess around with line voltage if I didn't have to, and also because I was able to get the 24V supply voltage from the burner control.

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

@ January 20, 2011 8:14 AM in Advice on vaporstat?


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 (, 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.


The WIKA 0-3 PSI gauge from 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.

Ptrol and Vstat

@ January 20, 2011 6:11 AM in Advice on vaporstat?

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.

Fuel economy

@ December 21, 2010 9:28 PM in Which LWCO? CG400 1060 or 2090

I check my boiler water level and quality regularly, and don't have any problems with foaming, so for me it came down to an issue of fuel (oil) economy. On a 45 minute heat cycle, the LWCO would shut the boiler down twice to do the foam check. Each time it did, the system took three minutes to heat back up to where it was before the shutdown. That's an extra six minutes of fuel burned recovering from the foam test in a single heat cycle. If that happens four times a day during the heavy heating season (say 12 weeks), that's 24 minutes * 12 weeks * 7 days = 2016 mins or 33.6 hours or roughly a week's worth of extra fuel used per season. That's why I opted to swap out the CycleGard for a SafeGard.

So back to your system. Let me say first that I'm not a pro, just a homeowner/enthusiast. From what you've described, my first concern is if your LWCO is working properly. Has the LWCO probe been cleaned/inspected recently, and has the LWCO been tested to ensure that it does in fact cut out on low water?

Is your normal water line at the recommended height when the boiler is not firing? According to the installation manual for your boiler, the water line should be 23-13/16 inches from the bottom of the boiler section leg, where it rests on the boiler room floor or boiler foundation.

Page 16 of the manual talks about installing an optional "reservoir pipe" if the time it takes the condensate to return to the boiler is longer than 10 minutes. This may or may not apply to your situation, but if it does it might explain why your water level drops (although it doesn't explain why the LWCO doesn't cut off).

When the boiler fires up how long does it take for the water to drop out of the sight glass? When it shuts down, how long does it take the water level return to normal?

Please post some pictures of your boiler so we can see what you're dealing with, including the LWCO, the sight glass, the near-boiler piping and the risers to the mains for starters.

Have you checked

@ December 21, 2010 5:46 AM in Programmable thermostat changes

the tstat reading with a datalogger placed in the same location?


@ December 20, 2010 5:53 AM in Which LWCO? CG400 1060 or 2090

[spurious double post deleted]


@ December 20, 2010 5:53 AM in Which LWCO? CG400 1060 or 2090

My boiler had the 2060 model when it was installed in 2009. You're right JP, this is the foam test feature. In the case of the 2060, it shuts the boiler down every 20 minutes for 60 seconds. So just when you've built up a good head of steam, BAM, shutdown, foam test. I ran a test with dataloggers last year and determined that the system takes 3 minutes or so to recover from the shutdown. By "recover", I mean that the temperatures at the measured locations reached their pre-shutdown values.

These units are fine if the HO isn't in the habit of regularly checking the boiler water. I wound up replacing mine with a SafeGard model that doesn't have the foam test feature.

And for the Library...

@ December 12, 2010 9:52 AM in steam heating enthusiasts christmas list.

... any of these books that you don't already have:

By Dan:

- A Pocketful of Steam Problems (With Solutions)
- E.D.R - Ratings for Every Darn Radiator
- Greening Steam
- Lost Art of Steam Heating
- Lost Art of Steam Heating Companion (CD)
- We Got Steam Heat!

Not specific to steam heating, but an entertaining read nonetheless:
- Working - Tales of life, love, mechanical mayhem…and getting even!

Books by others:
- Balancing Steam Systems Using a Vent Capacity Chart
- Lindhardt's Field Guide to Steam Heating


@ December 11, 2010 9:00 PM in Any Non-Professional Wallies Ever Go to Deadman's School?

I went to the one in Baltimore last month, and it was well worth the trip. I'd say go for it!


Just overnight

@ December 3, 2010 6:18 AM in let the data begin...

Just overnight. Still a pretty big difference though. Next time we're away for a couple of day's I'll see what the recovery time is.

With a six hour burn I'd expect you'd be cycling on pressure quite a bit. Any idea what the time span is between initial fire and first pressure cutout in a both setback and maintain situations?

Recovery from setback

@ December 2, 2010 9:42 PM in let the data begin...

That six hour burn time for recovery from a 12 degree setback seems awfully long. By way of comparison, my deepest recovery so far this season has been from 59 to 67 degrees, with an outdoor temp of 30 when the burner fired, and a recovery time of 1:20. I see you've downfired from the stock TR-30 specs (1.1 vs 0.85 gph). What's your steam MBH rating with the new firing rate?


@ November 18, 2010 6:02 AM in let the data begin...

This data is all from the Lascar data loggers, correct? What software are you using for your charting? There's an open-source (read: free) charting package that I'm using on my real-time data acquisition (and eventually control) project - LiveGraph.

One thing learned from all my data collection so far is that the system doesn't start to register pressure until steam is in the main. It takes about 2-1/2 minutes from the time the header is hot (>170 degF) until the main is too, and for that length of time, no pressure. Once in the main, the pressure jumps to 0.6 oz. Seems odd, because steam doesn't know header from main, it just knows Out, and Out hasn't changed.

Incidentally, congrats on achieving 2 oz operating pressure. Last season I ran around the house checking for leaking vents before I was convinced the system was really running that low.


@ November 16, 2010 6:52 AM in vents for 1-pipe TRVs

Hi JP, I've been studying the various outdoor reset control options (Heat-Timer, Tekmar, etc) and I think Mike is spot on when he says that the Heat-Timer model is better suited to commercial buildings. If you're looking for an outdoor reset control the Tekmar 279 may meet your needs. It provides for one or two indoor temperature inputs, and can handle even more using series-parallel wiring of the sensors (thermistors). Check out section F on page 8 in the manual, available at this link.

King valve question

@ November 3, 2010 7:00 AM in so long fitzy ... hello slantie

Nice looking install, JP.

Once you get the skimming and wiring all sorted out, you can always direct your attention to control. My own summer project has been instrumenting my boiler with relatively inexpensive real-time I/O that plugs into the USB port on a PC. Ultimate goal - DIY outdoor reset control. More on that in a later thread.

I have a question regarding your king valve. In pictures of other installs, the king valve is installed either vertically or diagonally. In your case, it looks like there wasn't a lot of choice as to the orientation of the valve due to the piping arrangement, but I was wondering if there were other considerations, and if you have any concerns about water pooling in or near the valve.


Installed a time delay last year

@ October 29, 2010 8:31 PM in Question on boiler pressure

I installed a variable time delay relay on my new steamer late last season to control end-of-cycle short cycling, and I posted a couple of wiring diagrams, one for 24V and one for 120V, in this thread:


@ September 16, 2010 5:54 AM in Aquastat temperature element

Yes it is, thanks Alan. I want to get a real-time temperature measurement from the immersion well, and I didn't know if the a-stat sensor would suit the purpose. Evidently not, so the next step is to see if there's enough room in the well to slip in a thermistor along with the capillary bulb (the thermistor would be connected to a separate measuring device).


Aquastat temperature element

@ September 12, 2010 11:11 AM in Aquastat temperature element

Does anyone know what type of temperature sensing element is used in a Honeywell L4006A immersion well aquastat? Thermocouple, thermistor, RTD, or something else?


Based on the manuals...

@ April 7, 2010 5:02 PM in tekmar 269 question

here's what I think would happen:

If the measured outdoor temperature is higher than the tekmar's "Warm Weather Shutdown" setting, then nothing will happen.

Otherwise, if the room temperature is below the room temperature target, the tekmar will:

1. Fire the boiler until the "steam established" point is reached, as determined by either a condensate return temperature sensor or a minimum "on" time, then
2. Use the outdoor sensor to calculate the "on" portion of the heating cycle and continue to fire the boiler for that amount of time, then shut off.


DHW tankless coil in the off-season

@ March 24, 2010 7:10 AM in DHW tankless coil in the off-season

Now that we're approaching the off-season, I'm considering putting a setback timer on my steamer's DHW tankless coil so it doesn't heat water when there's no one around to use it. I have a couple of questions:

1. Are there any concerns with letting the boiler water temperature swing from 120-140 degrees to room temperature several times a day?

2. I've seen some recommendations about flooding the boiler for the summer. Would this apply to a boiler with a tankless coil?


The ENM meter

@ March 20, 2010 7:29 PM in Temperature-based cut-in for a Vaporstat?

appears to work the same way as Bob's. I had four 2-minute DHW cycles on the boiler today, and the hour meter incremented by 0.1. I can't tell if it totalizes down to the second or not. Mine's also wired in parallel with the burner.


Good question

@ March 20, 2010 8:55 AM in Temperature-based cut-in for a Vaporstat?

That's a good question, Mike. I would expect it to totalize internally any time there's power applied, but I don't know that for a fact.

Weather's warm today, so all the boiler will be doing is running for two minutes every three or four hours to keep the tankless coil hot. I'll check it tonight and let you know.

Try here

@ March 19, 2010 5:52 PM in Temperature-based cut-in for a Vaporstat?

I got mine from
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