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Joined on November 14, 2009

Last Post on August 29, 2014

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Riser tappings

@ April 15, 2013 6:28 AM in Drop Header:Which way to Go?

Interesting that the front and back riser tappings are different sizes. Aren't they typically the same size? I wonder what the design intention is on those.

How not to pipe a Hartford Loop

@ April 14, 2013 6:02 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Here's a pic of the Hartford loop. It may have the world's longest close nipple. And it's below both the LWCO probe and the boiler's minimum water level.

The wet return in the pic is about 14" off the floor. The wet return at the other end of the house is at floor level, and there's a vertical pipe joining the two just past the takeoff for the Hartford loop. It's odd, but haven't had any problems with it. Maybe it helps keep sediment out of the Hartford?

How not to pipe a steam header

@ April 14, 2013 5:49 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Thought I'd post a series of photos of the piping issues JStar will be fixing this week in addition to the Midco burner install.

When the boiler was replaced in 2009, the oil company installers wanted to do the classic no-no of piping the main takeoff between the risers. I talked them out of that but they still insisted on piping the main run and equalizer in opposite directions. Why? "Because we've always done it that way and we've never had a problem". Mm-hmm. Because you never got called back, maybe?

My boiler

@ April 8, 2013 8:48 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

is rated at 285 MBH input, so I'll be limiting the control voltage to run around that number. Won't know how much turndown we'll be able to achieve until we get the burner in and run combustion tests. The limiting factor will probably be stack temperature (got to keep it high enough to prevent condensation), which is why I've built in a low temperature override to the pressure control, but there's simply no data on this yet. If the stack temps are high enough at low fire, then I'll have full span of control between 100 and 285 MBH.

Don't see why not

@ April 8, 2013 8:39 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Hi Rod, that would be easy enough to do, it's a SMOP (Simple Matter Of Programming). If you wanted to get fancy and you knew the performance characteristics of the system, like how the pressure changes as the TRV's shut off, you could possibly calculate when, say 75% of the TRVs were shut and take that as your "breather" down time. Now, if all of the TRVs are shut you should shutdown the burner anyway since you can't put any more steam into a closed system, so continuing to run is just a waste of fuel.

At what pressure does your friend's system run, and does it have a pressuretrol or a vaporstat? Does it short-cycle near the end of a heating cycle?

Midco specs

@ April 8, 2013 6:36 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

The LNB-500 is rated 100 to 500 MBH. The LNB-1000 is 150 to 1000 MBH. In both cases, the burner is modulated with a 2 to 10 volt dc signal.


@ April 8, 2013 5:56 AM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

It's the 120 vac unit. The probe has never been used; the CycleGard & Safgard use the same probe so I left the CycleGard probe in the boiler when I put the Safgard in.

I'm really excited about this project (and I think JStar is too!). Looking forward to seeing how the Midco performs.

Pressure reset control

@ April 7, 2013 8:37 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Hadn't considered a pressure reset control scheme, Dave, but I would be very interested in learning more about it. I have a variety of sensors on and off the boiler, and built a lot of flexibility into the controls in order to be able to try out new ideas like this. Not quite "plug-and-play", but if a control strategy uses the sensors I've got, it's a fairly simple matter to add it to the system. PM me if you'd like to discuss further.

Interesting idea

@ April 7, 2013 1:42 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Would you place such a sensor in the water/air space in the boiler or on the casting? If the boiler was firing and there was a low water condition but there was still water in the boiler, I wonder what the air temperature would be. I'd think you'd see a measurable change in the casting temp if it was dry firing. Either case, I'm not real keen on dry firing the boiler to test it out :-)

My boiler has a Hydrolevel Safegard-450 LWCO. It came with a CycleGard but I hated the intermittent level test "feature" so I replaced it (anybody want a gently used CycleGard?). Both of those use a conductivity probe, I believe. At any rate, it works well.

It's probably worth noting that nothing I've done will replace or impede the safety limit controls already on the boiler - the pressuretrol and LWCO.


@ April 7, 2013 12:57 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

responds much more rapidly to changes in input than temperature, I've found. Also, the fact that the water in the boiler is boiling doesn't tell you what's happening out in the rest of the system. Could be pre-heating the mains, could be halfway through a heat cycle. On this system the boiling point versus pressure is negligible as I'm running at less than 2 ounces of pressure. Might be different if you were running at 1 PSI, there you're looking at a 3 degree difference, but I still think it would be hard to control to that.

For ideal pressure control you'd probably want a pressure transmitter at the end of the mains, but I have four of those and even cheap pressure transmitters aren't cheap. The single one on the boiler seems to work OK; I can look at a pressure trend from my system and tell you within +/- one minute of when steam gets to the farthest radiator.

Safety: I'm working on a series of posts describing the control system in detail, but for now I'll say that the system is set up to fail over to wall thermostat control in the event of a power failure, program crash, or computer failure.

A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

@ April 7, 2013 11:34 AM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Project

Following a series of technical email exchanges with Charlie Aiello at Midco International, I took the plunge and ordered their LNB-500 low-NOx modulating gas burner to replace the oil burner on my Utica Starfire steamer.

Joe Starosielec (JStar) from ecuacool was out to the house in March to scope out the job. In addition to the conversion, Joe will also be de-knuckleheading the near-boiler piping that the oil company installers put in when the boiler was replaced back in 2009, putting in a nice new 3" drop header, and fixing a few other off-boiler piping issues.

The burner will modulate based on steam pressure in the boiler, with an override control on low stack temperature. I've spent the last several months re-writing the boiler control software that I described here back in November to run in firmware on a single-board computer, and to add new modulating control algorithms for the steam pressure and stack temperature. In March I finished the wiring and continuity checks for the new controls box, and the unit is now in bench testing with simulated sensors.

The burner is scheduled to arrive on Monday; the conversion will be done over two days on April 17th & 18th. I'll post pictures and updates as the project progresses.

Want 1

@ April 4, 2013 9:38 PM in 4" Drop Headers make us giggle

I can haz drop header plz?

Musical Instrument Acquisition Disorder

@ March 19, 2013 11:31 AM in I've always found better musicians here!

If there's a name for what I've got, that's it. Been playing a variety of somewhat obscure instruments for 25 years or so (though none to anything even approaching a professional level), including hammered and mountain dulcimers, anglo concertina, mandolin, pennywhistle, Swedish nyckelharpa and sackpipa, and a variety of bellows-blown bagpipes - Northumbrian, Scottish, Border, Irish Uilleann. I help run The Pipers' Gathering which is the largest annual convention in North America for bellows-pipes enthusiasts.

Just sent you...

@ March 5, 2013 9:00 PM in Midco lonox burner availability

... an email through the forum.



@ February 1, 2013 7:41 PM in New Boiler at the Best Mansion

Thanks, Dave. I appreciate your taking the time to do this. I'm always interested in getting empirical data from other systems to supplement what I'm learning from my own. This will no doubt keep me busy for a while; I'm not up on vapor vacuum systems so it's time to crack open the Lost Art book again.

I had a look at your website for the mansion. What a great building and history! Fantastic that the 1928 conversion was done with such care, and how well it's been maintained over the years.

Cycle times

@ January 30, 2013 8:29 PM in New Boiler at the Best Mansion

Thanks Dave, that's the information I was interested in. I take it you're not running the setback/recovery program on the Tekmar, those would be affected too. Sounds like you've got it dialed in just about perfect. I'm curious what sort of cycle times you're running for preheat, heat on, heat off.

Overrides & Tekmar

@ January 30, 2013 8:44 AM in New Boiler at the Best Mansion

Does running in either of the override positions have any effect on the adaptive algorithms in the Tekmar control?

What's the purpose

@ January 30, 2013 7:07 AM in New Boiler at the Best Mansion

of the High / Low / Auto switch?

Dew Point

@ January 28, 2013 2:06 PM in Calculating flue gas condensing temperature

Thanks SWEI. I found a dew point chart on that indicates dew points for natural gas between 140 and 128 degF for excess air between 0% and 50%.

Are these absolute temperatures, or are they relative to the ambient temperature?

Calculating flue gas condensing temperature

@ January 28, 2013 1:03 PM in Calculating flue gas condensing temperature

In the spring I'm having JStar replace the oil burner on my steamer with a Midco Low-NOX modulating gas burner. Charlie from Midco informs me that they haven't yet determined the actual low fire DC signal required to avoid condensing in the flue.

My boiler control measures stack temperature via a thermocouple in the flue about 3 feet from the boiler. Current operating temperature is about 470 degF.

Is there a way to calculate the condensing temperature? If so, I can design the modulating control with a low limit during turndowns based on the stack temperature.

I wrote to Nest

@ January 15, 2013 1:37 PM in You Can't Set Cycles per Hour on a Nest Thermostat

a while back asking them to compare and contrast their True Radiant controls with an outdoor reset control. The Nest Support person who replied basically said they didn't know anything about outdoor reset systems and then launched into a marketing blurb about how awesome True Radiant is. Really? They couldn't go ask someone in engineering or product development? As much as I like Apple products (the prez of Nest used to work for Apple) the thing that bugs me most is the "you don't need to know what's under the hood" attitude.

This sounds similar

@ December 31, 2012 3:21 PM in New steam control principle

to what I've been working on with my own control. I fetch the wind chill temperature over the internet from a local WeatherBug station, and if it's lower than either of the two outdoor temperature sensors, I use the WeatherBug temperature in the outdoor reset calculations. I've been running a heat loss replacement model for a while now, and find it more accurate than the time-proportional model in calculating the run time. I've recently implemented an anticipator, and while it's not yet smart enough to react to outdoor temperature in the way Dave describes, it's helped keep the indoor temperature swings to 1 degF or less.
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