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MarkS

MarkS

Joined on November 14, 2009

Last Post on April 7, 2014

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Steam coming

@ December 11, 2013 10:54 PM in Running 2 CPH finally and loving it!

From those numbers, your preheat time is 3:10. How long is/are your main(s)?

What's "steam coming", when the main at the boiler is hot?

Thermistor or Snap-Disc switch

@ December 11, 2013 10:50 PM in Running 2 CPH finally and loving it!

A thermocouple is a bit overkill for this application. I'm using a (much cheaper) 10K thermistor to detect steam at the end of the mains, but a 160 degF snap-disc temperature switch would do just as well. You don't really need to know the precise temperature at the end of the main, just that it's hot.

Preheat

@ December 11, 2013 10:13 PM in Running 2 CPH finally and loving it!

"Preheat" is the time it takes to heat the mains. In an outdoor reset system, that time doesn't count towards the heating cycle time because you're just heating the mains, not the living space. Shortening the overall time between cycles reduces the preheat time because the boiler and piping are still hot.

Me too!

@ December 11, 2013 9:53 PM in Running 2 CPH finally and loving it!

I've been running > 1 CPH since the weekend before Thanksgiving. It's really reduced the temperature swings versus 1 CPH. Today at a setpoint of 68 degF the temperature range was 67.8 to 68.4.

I currently have the heating cycle set at 20 minutes, which would be 3 CPH except that it doesn't include preheat which today ranged from just under 2 minutes to 5:15. The outdoor reset/heat loss algorithm calculated "heat on" times between 3:16 and 9:50, or 16% to 50% of the cycle time.

I'm going to leave it like this at least for the rest of the month, and then look at the btu per degree data numbers to see if it uses more fuel than 1 CPH. Gut feel right now says no, but even if it's slightly higher the perceived comfort is worth it.

Pressure Control

@ December 8, 2013 8:29 AM in ultra low pressure ARCO system maintained at higher pressure

The transmitter is off the shelf, but the control is not. Won't help this boiler unless the burner modulates.

A few years back I developed a much less complicated control to better manage end-of-cycle short cycling for single-stage on-off burners, using a time-delay relay and a vaporstat. There's a schematic around the middle of this thread in the post titled "Adding a Time Delay to Vaporstat Cut-In".

Controls

@ December 7, 2013 9:35 PM in Another Twin System - 6" Drop Header

Have the modulating control fixed the short cycling you were experiencing on the 2nd boiler?

I think you win the "tallest riser" contest

@ December 4, 2013 8:30 PM in An Epic Tale: I hear the Trane a comin'!

Wet steam has no chance against those risers. Wow!

More! More!

@ December 4, 2013 8:28 PM in An Epic Tale: I hear the Trane a comin'!

There's beauty in the process too, Colleen, so keep those install pics and commentary coming.

And besides, isn't HH everyone's personal blog? :-)

JStar

@ December 4, 2013 5:50 PM in Steam Pro in Philadelphia PA

Call JStar. He'll do right by you and your system.

Steam Arrival (Preheat) Timing

@ December 4, 2013 11:23 AM in Got an estimate

Here are typical times on my one-pipe system from a cold start in mins:secs. The distance from where steam enters the main to the preheat sensor is 38 feet. Other factors to consider are that this system is well-vented and preheat pressure is one ounce per square inch or less.

--> Burner On to Header Hot: 07:00
--> Header Hot to Main Hot: 02:30
--> Main Hot to Preheat Sensor Hot: 02:45
--> Total Preheat Time: 12:15

Trend Charts

@ December 1, 2013 2:45 PM in Midco Low-Nox Burner Performance Report

I don't have a sensor in direct contact with the boiler water, but I do have one in the aquastat thermowell on the tankless coil that's pretty close.

Here are several trend charts showing 1) Long heat cycles from 11/20, 2) Short heat cycles from 11/30, 3) Focus on setback recovery from #2, and 4) Focus on maintaining temperature from #2. In #3, you can see how the heat loss algorithm reduces the on time as the indoor temperature approaches setpoint.

I used a program called DatPlot to produce these charts. It has a lot of nice features, especially for a free package. You can download it at http://www.datplot.com/

Anticipator

@ December 1, 2013 1:03 PM in Midco Low-Nox Burner Performance Report

Maybe I'm mis-using the term. In my system, there's a differential and an anticipator value. The differential is the amount below temperature setpoint that will start a heat cycle. The anticipator is the amount below temperature setpoint that will shut off the burner ("anticipating" that the temperature will coast to or past setpoint). I usually keep them within 0.1 or 0.2 of each other.

Physical improvements

@ December 1, 2013 12:56 PM in Midco Low-Nox Burner Performance Report

Hi Rod - Two things might help: insulating the returns and bringing in outside air for combustion.

I have almost 100 feet of return piping, some of which is behind a false wall, not to mention that much 1-1/4" insulation is around $200. Unless someone has some hard data, I don't see the return on investment.

Outside combustion air is probably the better bet, since it should decrease stack temps and increase efficiency, which in turn might cut preheat times. To do it right I need to break through two 1-foot thick stone walls. I might try rigging something temporary through a window to test it, but that's still almost 25 feet from the burner. Plus I wouldn't be able to tell anything without a combustion analyzer, so I'd need to wait until JStar was in the area again, unless I can locate the one that our combustion controls group at work is rumored to have.

One operational change that is having a big impact on preheat times is an experiment I'm currently running where the heating cycle times are reduced 50-66 percent (roughly 2-3 CPH). A nice side effect of this is that the pipes are still hot when the next cycle starts, so preheat times are down to just a couple of minutes. The sample size is still too small to draw any conclusions about fuel economy, but once I have more data I'll post a report.

Sensors sensors everywhere

@ December 1, 2013 11:59 AM in Midco Low-Nox Burner Performance Report

Sensors everywhere except for snap disc thermal switches on the steam header and the exits from the steam takeoffs at the mains. Temperature sensors are all 10K thermistors. Pressure sensor is a 0-3 psi, 4-20 ma transmitter. Stack temperature is a type K thermocouple.

All sensor data is logged and time stamped at least every five seconds, more often if the data is changing rapidly such as when the burner first fires. Event data such as a cycle change, temperature switch closure, etc . is logged, time stamped, and marked with a unique heat cycle ID.

Performance Summary, Oct-Nov 2013

@ December 1, 2013 11:29 AM in Midco Low-Nox Burner Performance Report

Performance Summary for Oct 1 through Nov 30, 2013:

Number of Heat Cycles: 274
Total Run Time (hrs:mins): 81:08
MBtu Consumed: 15,662 (21% less)
Degree Days: 865
Fuel Cost: $154.22 (70% less)
Btu per Degree Day per Square Foot: 6.02 (32% less)

Equivalent Oil MBtu Consumed: 20,203
Unit Cost of Gas vs Oil per MMBtu: 62% less
Oil Btu/DD/sf from 12/2003 thru 4/2013: 8.80

Averages:

Preheat Cycle Time (min:sec): 05:14
Heating Cycle Time (min:sec): 12:32
Total Cycle Time (min:sec): 17:46

Preheat MBH: 239 (2% less)
Heating Cycle MBH: 187 (24% less)
Total Cycle MBH: 193 (21% less)

Notes:
1. Percentages are gas compared to the single-stage oil-fired burner.
2. Oil MBtu consumed is based on an oil burner firing rate of 245 MBH for the same run time.
3. Unit costs for fuel are based on average as-delivered costs in the Philadelphia area for Oct/Nov 2013

Midco Low-Nox Burner Performance Report

@ December 1, 2013 11:26 AM in Midco Low-Nox Burner Performance Report

First in a series of reports on the performance of the Midco LNB-250 modulating gas burner on a residential one-pipe steam system.

System Info:

Boiler: Utica Starfire III SFE, 152 MBH Net
New Burner: Midco LNB-250 Low NOx modulating gas burner, 75-300 MBH
Old Burner: Beckett 245 MBH single-stage oil burner
Radiator EDR: 607 sq ft
Building Living Space: 3009 sq ft

Click here for more details

System Operating Characteristics:

The overall heat cycle is divided into two sub-cycles: Preheat and Heating. The Heating cycle is further divided into Heat On and Heat Off segments. A new heat cycle begins when indoor temperature is below the comfort setpoint.

Two snap disc temperature switches are used to indicate when steam has reached the drop header and has entered the mains. The switch contacts close at 160 degF and open at 150 degF. An analog temperature sensor is used to indicate when steam has filled the mains and the Preheat cycle ends.

Two PID velocity algorithms modulate the Midco burner under either pressure or stack temperature control.The pressure control setpoint is 0.8 oz/sq in. The stack temperature control setpoint is 670 degF.

At startup, with no pressure in the system, the burner output increases until the stack temperature is reached. The burner output then modulates to maintain the stack temperature until pressure builds. Once pressure reaches setpoint, the burner output modulates to maintain pressure. Depending on the length of the heat cycle, the burner output gradually decreases from 240 MBH to 78 MBH.

Typical Preheat times from a cold start (mins:secs):

--> Burner On to Header Hot: 07:00
--> Header Hot to Main Hot: 02:30
--> Main Hot to Preheat Sensor Hot: 02:45
--> Total Preheat Time: 12:15

The length of the Heating segment is determined by a heat-loss replacement algorithm that calculates the btu input required from the burner to achieve the indoor temperature setpoint. The burner runs for the calculated time or until the indoor temperature setpoint (minus an anticipator value) is reached, at which point the burner is turned off and the system enters the Heat Off segment.

The length of the Heat Off segment is the difference between the Heating segment and the overall Heat Cycle time. After the Heat Off time, the system enters the Idle state and is ready to run another heat cycle.

Valves

@ November 30, 2013 9:19 AM in Hydrolevel VXT alternative install

The way you have it laid out, you won't be able to feed water to the boiler if the VXT needs to be removed for some reason.

Gauges

@ November 28, 2013 9:43 AM in New steam boiler

0-3 psi gauge

If you're running less than 1 psi you can substitute one of these:

0-15 in/H2O (about 9 oz)
0-30 in/H2O (about 1.1 psi)

Utica SF pins

@ November 25, 2013 5:26 PM in Weil-McLain EGH ratings lowered

Hi Rod, just as a point of interest my 2009 Utica SF does have pins all the way up the sections, and they're shown that way in the I&O manual. The T baffles that JStar installed rest on the pins of each section. I think he took a picture, maybe he'll post it.

And if Burnham/Crown wants to donate a free MegaSteam or FSZ block I'd be happy to take it. :)

Height

@ November 24, 2013 2:53 PM in Gorton Water Fountains

Are the vents on an "antler" 6" or more above the main? If not and you have the room I'd do that first.

cfm

@ November 24, 2013 11:13 AM in Two Men and a Burner (A Midco saga)

The LNB-500 burner is rated at 229 cfm. Mine has an orifice plate to bring the max btus down to 300 MBH, so if it's a linear relationship the max cfm is 137. I never run at more than 80% of full speed since my btu input requirements are lower, so again if it's linear that's 110 cfm.

How do you keep critters, leaves, bugs, water, etc. out of the intake pipe?

Outside combustion air

@ November 24, 2013 10:25 AM in Two Men and a Burner (A Midco saga)

I'm sure it would help. It'son the list of things to try, but it involves breaking through two 1-foot thick stone walls to bring in outside air.
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