Joined on November 14, 2009
Last Post on December 4, 2013
@ April 15, 2013 12:34 PM in CondensateTank...Why?We're converting from oil to gas, so the annual fuel cost savings alone were enough to justify springing for the Midco burner. You'd most likely see a longer payback period if you were replacing a gas burner with the Midco.
If you haven't already done so, suggest you read Dave in QCA's thread on his vapor-vacuum system: http://www.heatinghelp.com/forum-thread/143629/New-Boiler-at-the-Best-Mansion. Fascinating stuff.
The other high turndown burners on the market that I know of use mechanical linkages to control the fuel-to-air ratio, while Midco's LNB is all electronic and, hopefully, more reliable.
@ April 15, 2013 11:04 AM in CondensateTank...Why?Hi Colleen, just wanted to clarify that there's a difference between a two-stage burner and a modulating burner.
A two-stage burner fires at two fixed output rates. They're adjustable insofar as you can set the high and low firing rates when the burner is installed. But once they're set, the controls can't change the output rates other than selecting high or low fire.
A modulating burner, on the other hand, can continuously adjust between the high and low fire rates based on whatever you're using as the modulating control signal - boiler pressure, for instance.
@ 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.
@ April 14, 2013 6:02 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectHere'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?
@ April 14, 2013 5:49 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectThought 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?
@ April 8, 2013 8:48 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion Projectis 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.
@ April 8, 2013 8:39 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectHi 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?
@ April 8, 2013 6:36 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectThe 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 ProjectIt'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.
@ April 7, 2013 8:37 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectHadn'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.
@ April 7, 2013 1:42 PM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectWould 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 Projectresponds 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.
@ April 7, 2013 11:34 AM in A Steam Odyssey: Midco Low-NOx Burner Oil to Gas Conversion ProjectFollowing 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.
@ 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. www.pipersgathering.org
@ 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 MansionThanks, 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.
@ January 30, 2013 8:29 PM in New Boiler at the Best MansionThanks 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.
@ January 30, 2013 8:44 AM in New Boiler at the Best MansionDoes running in either of the override positions have any effect on the adaptive algorithms in the Tekmar control?
@ January 30, 2013 7:07 AM in New Boiler at the Best Mansionof the High / Low / Auto switch?
@ January 28, 2013 2:06 PM in Calculating flue gas condensing temperatureThanks SWEI. I found a dew point chart on EngineeringToolbox.com 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?
@ January 28, 2013 1:03 PM in Calculating flue gas condensing temperatureIn 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.