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Joined on November 14, 2009

Last Post on July 16, 2014

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Isolation valve

@ November 4, 2013 7:28 PM in TwinBoiler Schematic

Under operating conditions you'd leave the isolation valve open, so there shouldn't be any impact to pressure or water lines. You'd only close it when you were blowing down one of the boilers. I've edited your drawing to show the location of the valve in red.

The Midco is running great. Had our first real heating day today, ran seven heat cycles with one or two more to go tonight. I'm collecting lots of data on system performance and will be posting reports periodically throughout the heating season.

When's installation day?

King Valves

@ November 3, 2013 7:27 AM in TwinBoiler Schematic

Hi Colleen,

If space permits, I'd suggest mounting the king valve for the left boiler in the vertical position, like the right one. Depending on the valve's internals, you might get a small amount of water pooling with the valve in the horizontal position.

You're also going to need an isolation valve between the two boilers on the common return line. Otherwise, when you go to blow down the boiler on the right, you'll end up pushing the water to the left boiler. Also note that with the common return, you won't be able to blow down the left boiler while the right boiler is running. It's not a big deal, I just wanted to make sure you're aware of it.


@ October 14, 2013 5:21 AM in Burnham MST.....

Has Burnham said why they're opposed to a gas burner on a MegaSteam?

Wish I had

@ October 3, 2013 9:48 PM in best boiler between two

a MegaSteam.

Glad I have: JStar as the go-to guy to make the most of the equipment I do have.

If you do have a CycleGard

@ October 3, 2013 7:09 PM in New System but short Cycling

Caveat: the opinions that follow are those of an informed homeowner, not a pro. Your mileage may vary.

If your new boiler does, in fact, have a CycleGard LWCO installed, and you are conscientious about checking your water level on a regular basis, then ditch the CycleGard and replace it with a SafeGard, which doesn't shut off the boiler periodically to check water level.

When my boiler was replaced in '09 it came with a CycleGard. I found that each time it shut down the burner to check for foaming, it took three minutes or more to re-establish steam pressure. Shutdowns every 10 minutes over a 40-50 minute heating cycle mean more money up the chimney and not in your radiators. I'm pretty diligent about boiler maintenance, and replaced the CycleGard within a month.

On the other hand, if your expectations of your heating system are in the "set it and forget it" camp (which I doubt given your interest in venting), then leave the CycleGard in place. It will give you peace of mind, but at the expense of higher fuel costs.

Vote for the EcoSteam boiler control project!

@ September 24, 2013 11:52 AM in Vote for the EcoSteam boiler control project!

I've entered my EcoSteam boiler control project into a competition sponsored by Phidgets Inc., who make the sensors I'm using for measurement & control. EcoSteam is an outdoor reset control that calculates boiler run time based on the heat loss of the building, and controls a Midco Low-NOx modulating gas burner to prevent short cycling on pressure.

If you're on Facebook, please consider casting a vote for my project. Click on this link: EcoSteam Project

Then click 'Like'. Thanks!

I Am!

@ September 17, 2013 5:31 PM in It's that time again!

There's still a few more weeks here in PA before it'll be time to run heat. The new burner has had pretty light duty so far, just making DHW. I'm looking forward to colder weather to put the new control system through its paces.

Sticker shock

@ September 17, 2013 5:26 PM in Wireless Temperature Sensor for a Tekmar 279 (?)

It's a bit pricey for what it does, on the other hand it looks like a good fit anywhere you'd need a thermistor-based non-contact temperature sensor. I'm interested in trying one out on my home-grown controls as an indoor temperature sensor I can move around.

I asked HBX how the unit would behave in the case of a bad sensor or dead battery; they told me the base unit would retry for some period of time then default to a constant 0 degF reading.

Math please

@ September 14, 2013 2:26 PM in Steam Formulas

Hi Joe, this is interesting stuff. Can you break down the math you used to get these numbers?

Wireless temperature sensor

@ September 5, 2013 8:50 PM in residential internet control

HBX's new wireless temperature sensor is something I've been looking for to transmit a thermistor's reading from a remote location. Depending on price, might get two, one for outdoor and one for an indoor sensor that can be moved around.


@ September 4, 2013 5:22 PM in A Mid(co) Summer Night's Dream

On this burner the only real adjustment is on the Dungs regulator. I can borrow an analyzer but I'm not comfortable messing with the air/fuel mixture, so it'll have to wait until JStar or the Midco guys are out this way again to try it.

Combustion analyzer results

@ September 3, 2013 5:41 PM in A Mid(co) Summer Night's Dream

See attached pic for combustion results; two from the oil burner, then low/high fire on the gas burner. Efficiency numbers aren't great but the emissions are impressive. (I should add that the stack temps I listed in my first post are from a thermocouple, not an analyzer.)

Low fire temps

@ September 2, 2013 5:39 PM in A Mid(co) Summer Night's Dream

At lowest fire (2 volts) I clocked 75 MBH on the gas meter, with temps 400 degF at the boiler and 195 degF at the chimney.

A Mid(co) Summer Night's Dream

@ September 1, 2013 10:51 PM in A Mid(co) Summer Night's Dream

It's been a few months since we converted to gas and installed the Midco LNB-500 modulating burner, and I wanted to provide an update. When the Steam Odyssey 2 thread ended in April, the system was performing well except for high stack temperatures. Over 40 or so spring heating cycles, the modulating controls did a good job of controlling the burner to maintain a steam pressure setpoint at the boiler, even though the controlling voltage was at the low end of the range (max 2.8 volts on a full scale of 2-10 volts). The burner has seen light duty over the summer producing DHW.

In an attempt to mitigate the stack temperatures, the folks at Midco developed a new LNB-250 burner head that's rated for 50-250 MBH. The development rep and an engineer from Midco came out in mid-August to install and test the new head, which uses the same blower, valve train, and controls as the LNB-500. If nothing else the new head is better matched to the boiler's rating of 245 MBH. The new head is shorter (14" vs 28"), with the burner mesh centered in the firebox and has a smaller orifice plate at the inlet than the LNB-500.

We ran tests with the firebox insulation installed, and another set of tests with it removed. While we unfortunately did not see a large drop in stack temperatures, removing the insulation did yield a 30 to 50 degF reduction in stack temps. At high fire we're seeing 800-850 degF at the boiler and 500-550 degF a foot from the chimney, so I'll be replacing the galvanized vent pipe between the boiler and chimney with something that's rated for 1000 degF continuous before the heating season sets in.

Over the summer I added a few new features to the EcoSteam modulating controls. Each of the DHW, Preheat, and Heat On cycles now has an individual set of configurable parameters that define how the boiler is controlled during that cycle. The parameters include the initial output voltage, control strategy (fixed output voltage, pressure control, stack temp control), a control delay time, and setpoints for the steam pressure and stack temperature controllers. I've also added a "setpoint control" option in the outdoor reset model so I can bypass the math and simply run until the indoor temp hits the setpoint-minus-anticipator target.

The website describing the EcoSteam boiler control project in detail has been updated with the recent changes. Here's the link: EcoSteam project


@ September 1, 2013 10:45 PM in A Mid(co) Summer Night's Dream

Thread reposted in Strictly Steam

Necessary or not

@ August 7, 2013 8:20 PM in Emergency Cutoff switch necessary for gas furnace...

Necessary or not, if it was my house I'd keep the switch in the cellar stairwell. Did just that when we converted in the spring. It was a simple matter to tie in the existing switch and wiring into the new system wiring.

Midco is not far away

@ June 9, 2013 8:47 PM in Steam Assoc Planning Meeting...June 21, Chicago

FYI, the Midco plant is only 22 miles or so from the meeting site.

Gotta love

@ May 12, 2013 2:38 PM in Steam at Work

the dog dozing peacefully through all the racket.


@ May 5, 2013 5:38 PM in More on Power Gas Burner Conversions

Given the level of interest in power gas burners you'd think more boiler manufacturers would have done this by now.

Surge protection & UPS

@ April 26, 2013 5:14 PM in A Steam Odyssey (Part 2): Midco Low-NOx Burner

No surge suppressor yet, but will be adding one soon. No plans at this time for a UPS.

User Interface

@ April 26, 2013 6:10 AM in A Steam Odyssey (Part 2): Midco Low-NOx Burner

I'll close this part of the saga with some pictures of the user interface.

If you're ever in the Philadelphia area and would like to see the system in operation, send me a message through the forums or to mstayton (at), and we'll see if we can set something up.

Instrumentation and Controls

@ April 25, 2013 8:48 PM in A Steam Odyssey (Part 2): Midco Low-NOx Burner

The control system has two outdoor and two indoor temperature sensors. The pairs can be configured to use the first good sensor, a specific sensor, or the highest, lowest, or average of the two values. The system also fetches the wind-chill temperature from a local weather station over the internet; if the wind-chill temp is lower than the outdoor sensor value, the system will use the wind-chill temp in the outdoor reset equations.

On the boiler there are temperature sensors for the tankless coil and the DHW temperature after the mixing valve, a type K thermocouple in the stack, and a 0-3 PSI, 4-20 ma pressure transmitter on the pigtail.

Off-boiler there is a temperature sensor on the riser to the farthest radiator, and temperature switches on the steam header and the (newly divided thanks to JStar) large and small mains. There's also a flow switch in the DHW line that will heat water on demand (with a 3-4 minute heatup delay if the boiler's cold) during scheduled DHW "off" periods.

I had good results with the Phidgets line of sensors on the previous version of this system, and selected their PhidgetSBC2 single-board computer as the platform to host the boiler control software. The SBC2 has an ARM processor and runs Debian Linux as the operating system. The sensors, control outputs, and control software are all on or interfaced directly with the SBC2; the system does not rely on a PC connection as was the case with the previous version. The user interface communicates with the the SBC2 over Ethernet on the home's local area network. While the SBC2 supports wireless, for this application I felt a wired Ethernet connection would be more reliable.

Safety & Backup Controls

The boiler is equipped with the usual safety features. On the 120 VAC side there's the Pressuretrol, LWCO, auto-feeder, and emergency stop switches at the boiler & in the cellar stairwell. During the conversion, JStar installed a flame rollout safety in the 24 VAC circuit to the Fenwal ignition control unit in the Midco cabinet.

Because this is still in the experimental stages, I've included some additional backup features.

There's a "Control Mode" switch on the front panel that selects between the Outdoor Reset/Modulating control, and the wall thermostat. In the "Thermostat" mode, a fixed voltage is supplied to the LNB burner. The control mode can also be selected from the user interface. And in the (hopefully unlikely) event of a computer or program failure, all of the control outputs are automatically set and held at their OFF state; this forces the system into Thermostat mode, and power must be cycled on the control box to return the system to modulating control.

A vaporstat is installed on the pigtail, wired to make on cut-out and break on cut-in. It is set to cut out at about 3 ounces of pressure and to cut in at slight negative pressure. On cut-out, an interval time delay relay is activated that cuts power to the burner for 30 minutes. This was added in the previous version of the control software to eliminate end-of-cycle short cycling on pressure, the idea being that if you're building pressure in the boiler then the radiators are probably full of steam and continuing to run the boiler is just a waste of fuel. Now that the new system is controlling on pressure, in theory the vaporstat should never activate, but I opted to keep it in for when the system is running in the fixed-output "Thermostat" mode. This limit control is always active and operates independently of the boiler control software.

There's also an emergency stop switch at the control box that removes power from the solid state relay that switches 120 VAC to the burner.
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