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MarkS

MarkS

Joined on November 14, 2009

Last Post on April 7, 2014

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If I had to do it all over again...

@ November 24, 2013 1:14 AM in Two Men and a Burner (A Midco saga)

... I would ditch the Utica boiler, buy the Midco and put it on a MegaSteam (or the Crown FSZ equivalent). Because I firmly believe that most of the issues we've been working through have more to do with the boiler than the burner. On the Utica, it's a straight shot from the burner 26" up through the sections to the stack. I think the out-of-the-box stack temps and efficiency would be much better and require much less, if any, tweaking with a Midco on a 3-pass boiler like the MegaSteam.

This all started in 2010 as trying to solve the problem of end-of-cycle short cycling on pressure. I do industrial process control software by day, and knew that the "right" solution was to adjust the burner to maintain an even pressure. Problem was, there weren't burners that could do that in my btu range, until the Midco came along. And so far as I know, there still isn't a commercially available pressure control that's plug-and-play for this. Ah, the joys of adapting 21st century automation to 19th century technology.

Let me add that I'm neither discouraged nor disappointed by the experiences thus far. No one knew exactly how the burner would perform on this particular boiler. At some point you need to get these units out of the lab and onto real-world systems. Early adopters of any new technology need to expect a few bumps along the way, to smooth the road for those that follow.

The performance data is telling me it's all worth it.

Two Men and a Burner (A Midco saga)

@ November 23, 2013 9:46 PM in Two Men and a Burner (A Midco saga)

Last month JStar came out to help diagnose a hard light-off issue I'd been occasionally experiencing with the Midco burner. Long story short, we ended up rotating the burner head so that the spark rod assembly was on top of the burner, rather than below as supplied from the factory. Once we could watch the spark thru the firebox viewport (couldn't see it when it was underneath the burner), we observed that the spark would jump between the ground rod and the burner mesh. After repositioning and re-gapping the spark rod, we saw good ignition every time. I sent a detailed report to Midco describing our observations and changes, and they agreed with what we'd done. In over 200 firings since, there have been no hard light-offs.

In August, when Midco replaced the 500 MBH burner head with a 300 MBH version they made up custom for this boiler, stack temps were still running high at 780 degrees at high fire (260 MBH), efficiency was around 72% (78% at low fire 75 MBH), and excess air was 42%. It was pretty clear that a lot of heat was being lost up the stack, but there wasn't much else that could be done to the burner to fix it.

Today, JStar brought some ideas to try to bring down the stack temperature and increase the efficiency. First he installed some angle iron T baffles between the boiler sections. On the very next firing we saw the stack temperature drop by 100 degrees and the high fire efficiency increase to 78%, with excess air at 34%.

The Midco has a variable speed blower so there's no other adjustment for combustion air. Joe brought in a HUGE PVC ball valve and attached it to the blower inlet. We tried several valve positions to restrict the combustion air to the blower and took analyzer readings for each. With the valve 5/8ths closed, Joe got excess air down to 11.5% with 81.1% efficiency at low fire, but CO went through the roof. The "sweet spot" seems to be with the valve half closed, with the following readings at low and high fire: stack temp = 575 / 685, excess air = 19 / 26.5, efficiency = 80.6 / 78, CO = 25 / 8. If you're interested, here's a link to all of the combustion results: Combustion Results

In addition to the combustion analyzer readings, I was also watching the stack temp and steam pressure readings on my control system. With 1 ounce of pressure at the boiler and a constant firing rate, we saw steam pressure increase almost 2/10ths of an ounce when we introduced the 50% combustion air restriction, and half an ounce when 5/8 restricted. At first I thought it was a fluke but the results were repeatable, a clear demonstration of the actual impact changes like this make to system performance. Pretty neat.

Next Sunday I'll be posting a summary report of the Midco's performance data for October and November.

And finally, a picture of the reconfigured Midco burner with the combustion air restrictor valve in place. Kids, don't try this at home.

Actual pressure

@ November 22, 2013 10:18 PM in Homemade Controller

I think you're right about not scaling pressure. 2 ounces is 2 ounces regardless of whether it's a 1/4" tube or a 3" pipe. I think you'd need to scale the boiler water content and btu input to match the EDR of your test system.

I applaud your scientific spirit and look forward to hearing about your results. For what it's worth, I ran a lot of simulation testing in the six weeks between completing my control software and when the new burner was installed, and it paid off. I'll admit to a few white knuckle, is-this-really-gonna-work moments before it came time to throw the switch, but in the end all I really had to do was adjust the tuning parameters on the pressure control to suit the real-world response.

As somebody once alliterated, prior planning prevents poor performance.

About the same construction

@ November 21, 2013 8:02 PM in Homemade Controller

Those numbers seem pretty good, especially running that big garage rad and a boiler that old. The construction here is similar - 1890-ish four course brick with a 2" air gap between brick and interior wall on 1st & 2nd floors, 3rd floor & attic are insulated, low-e glass in windows. How closely matched is your boiler to your EDR? Mine's about 4% oversized so not a bad match.

No internet

@ November 21, 2013 4:26 PM in Homemade Controller

If there's no internet connection the software will just use the wired outdoor temperature sensor values. The control platform itself is autonomous, it will run regardless of whether an Ethernet link is available or if the client user interface is running.

I've read here that the best method of comparing two different buildings is btus per degree day per square foot of floor space. If I remember correctly, under 5 is awesome, 5-10 is good, 10-15 is OK, above 15 is not so great. Substituting EDR for building square footage ought to work too.

Edited to add: If you change gas cfm to btus in your calculation, you'll normalize that variable so you can compare to systems burning different fuels. I just ran a btu/edr/deg day calc with my current Oct/Nov data and get 29.1. My btu/dd/sq ft is 5.88.

Mad science

@ November 21, 2013 3:28 PM in Homemade Controller

Well, my system certainly falls in the "mad scientist" category, but that's intentional - it's built for flexibility, experimentation and data acquisition. Once I get a handle on the best combination of fuel economy and comfort I'll probably dial it back to a subset of the overall functionality. I'd have to eventually anyway, it's hard to sell a house with Franken-controls in the basement!

That little PLC of yours looks pretty good with a great price point. Might have to get one to play with. I see they have an analog output extender board which I'd need to modulate my burner. It looks like it has function block programmability in addition to traditional ladder logic, is that right?

Regarding heat loss, I compensate somewhat for wind by fetching current wind-chill temperature from a local weather station over the Internet. It will nudge the run times up if there's enough difference between outdoor sensor and wind-chill temps. There are still some variables I don't fully understand, so sometimes it'll miss the target (over or under) by a degree or so, but for the most part the math has been pretty good at getting within -0.2 to +0.7 degree of target temperature. Even so, it's really just a guess. Your "adaptive pulsed modulation" method could replace that.

Curious if you have an atmospheric or a power burner, and if you were able to check combustion efficiencies while you were manually modulating your gas valve.

Details

@ November 21, 2013 1:28 PM in Homemade Controller

This is a very interesting control strategy PMJ, I'd like to learn more details about it. You've got me curious how well your strategy might work on my system, one-pipe running 1 oz or less pressure (someone once called it "near-vapor") with a modulating burner. Right now, once the mains are hot the burner turns down to maintain a low pressure setpoint, and my average firing rate is currently 16% less than a fixed output burner. That's on top of the general cost savings of gas vs oil. I use a "heat loss replacement" model (think outdoor reset on steroids) to calculate run times. It works pretty well, but it would be nice to reduce the cycle-to-cycle heat variance in the rooms if I can maintain (or reduce) fuel usage at the same time. More cycles should mean less preheat time which is also less time at high fire.

Stay tuned

@ November 21, 2013 6:09 AM in Homemade Controller

Thanks. It's been a fun project. I've learned a lot about my own system and steam systems in general, and I'm saving fuel and $$$.

One recommendation I have for you is to make sure your system is tuned up - proper main venting, pipes insulated, etc. Controls can't fix a system that isn't already in good working order.

Stay tuned. Around Dec 1 or so I'll be posting a performance report for October & November. It's something the folks at Midco asked me to do, and I figured I share it here as well.

Phidgets submarine project

@ November 20, 2013 6:07 AM in Homemade Controller

Check out this Phidgets project created by high school students from Phoenix AZ in a program that provides the students with hands-on experience in science, technology, engineering and mathematics (STEM).

Falcon Autonomous Underwater Vehicle

Arduino / Phidgets

@ November 19, 2013 9:55 PM in Homemade Controller

I've been working on such a "homemade controller" for several years. I developed a heat loss model for calculating boiler run time, and more recently added PID pressure control when we swapped out the oil burner for a Midco LNB modulating gas burner back in April.

I chose Phidgets (www.phidgets.com) as the hardware/sensor/control platform primarily because you don't have to mess with low-level circuitry like you do with Arduino and can just get on with the job of programming it to do what you want.

Earlier versions of the control did have a "pressure lockout" function similar to what you describe, but these days it's more or less out of service since the new burner's firing rate is controlled by steam pressure. When it was in service, the "pressure lockout" worked quite well and saved more than a few gallons of oil over the course of a heating season.

The three links in the last line of my signature will take you to a couple of threads on the Wall, and an external web site where my project is described in detail.

Just the one

@ November 11, 2013 7:24 AM in Pipes leaking at shutoff connectors (All of them)

My old instrumentation is mostly pre-1950.

Incidentally, a modern Honeywell vaporstat can be set to cut-in on slight vacuum. I had mine set to cut out at 4 ounces pressure and cut in at about 1/2 to 1 ounces vacuum. You just set the differential to a higher value than the cut-in. I didn't test it below 1 oz vacuum though, so I don't know how accurate it would at higher vacuum.

Your old vaporstat

@ November 10, 2013 8:41 PM in Pipes leaking at shutoff connectors (All of them)

Colleen, does your current vacuum/pressure vaporstat resemble the attached pic by any chance?

Midco

@ November 5, 2013 8:16 PM in TwinBoiler Schematic

Lots of pics of the Midco in April here: Midco

Incidentally, I've recently decommissioned the Vaporstat I had on my system as a control (not safety) limit. It's a 0-16 oz model with a SPDT switch that I calibrated to be more accurate at the low end of the scale (0-4 oz). It's a little over 3 years old, and hasn't been tripped very often since I put in the pressure transmitter a couple of years ago. If you're interested drop me an email through the Wall.

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.

Reason?

@ 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?
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