Joined on November 14, 2009
Last Post on March 8, 2014
@ January 23, 2014 12:38 PM in Thermostats (Honeywell and EcoBee)I had a modulating gas burner installed in the spring that adjusts the firing rate to maintain a pressure setpoint in the boiler, but the time-delay relay is still in place as a backup in case I ever need to run at a fixed firing rate.
When the vaporstat-plus-relay was in more active service, it worked exactly as I'd hoped. When the pressure increased after all the radiators were full of steam, the vaporstat would activate the relay, which interrupted the low-voltage thermostat signal for 20 minutes. This gave the steam in the rads a chance to condense, and more often than not the call for heat would be satisfied by the time the timer expired. If the timer expired and there was still a call for heat, the boiler would re-fire. Tracking pressure shutdowns over the course of two seasons, I figure the control saved 100 gallons of oil or more.
One change I made to the current setup is replacing the vaporstat with a much less expensive pressure switch from Dwyer. With the time-delay relay, I didn't need the cut-in capability of the vaporstat. And it's much easier to accurately adjust the trip point on the Dwyer.
@ January 19, 2014 12:01 PM in Nest ThermostatHBX Controls released a wireless remote temperature sensor late last year.
The resistance curves of the Honeywell remote sensor and the HBX are similar, only 3% different at 70 degrees, so the HBX sensor ought to work with a VisionPro. Downside: it's expensive.
High on my wish list is data logging and reporting. Despite its other flaws, that's one area where the Nest blows everybody else out of the water.
@ January 14, 2014 9:56 PM in ecuacool Name ChangeGuess I'll have to print up a new "logos card" magnet to stick on the front of the Midco cabinet.
@ January 8, 2014 8:56 PM in An Epic Tale: I hear the Trane a comin'!On either side, the union is common to both the gauge and the control (pressuretrol or Dwyer switch). Here's a pic from behind the pressuretrol that might help.
Above the union and before the pressuretrol there's a tee that points towards the back of the pressuretrol. Off that tee there's a close nipple, a 90 degree elbow, then a long nipple and coupling on top of which the 30 PSI gauge is mounted. So disconnecting the union disconnects both the pressuretrol and the gauge. If I need to remove the pressuretrol, all I need to do is to rotate the gauge assembly 90 degrees to get it out of the way.
Regarding the vacuum gauge, it doesn't *have* to be on the same line as the Vaporstat, but if that line is measuring system pressure/vacuum (versus that of a single boiler) I don't know of a reason why it shouldn't be.
@ January 8, 2014 12:30 PM in Steam controllers.....whaaaa?process steam or steam for heating or both?
If it's only process steam then I don't think a Tekmar or Heat-Timer will get you much. If you're heating, those controls earn their keep by adjusting the heat cycle based on the outdoor temperature so you don't overshoot the thermostat setpoint (or, at least, not as much as with the thermostat alone). The Tekmar will also do setback/recovery as NBC noted (not sure about the Heat-Timer), but that's not it's major claim to fame.
Are there any markings or labels in that control box that would give a clue as to the manufacturer?
@ January 6, 2014 6:22 PM in A Steam Enthusiast's Outdoor Reset Controlbut unfortunately list price on it puts it out of reach of much of the target market, and that doesn't even include the pressure transducer/transmitter to tell the control what the boiler pressure is.
@ December 27, 2013 7:10 PM in An Epic Tale: I hear the Trane a comin'!Hi Colleen,
To facilitate maintenance of your pressure controls, one inexpensive and fairly easy thing to do is to install a union between the pigtail and the pressuretrol (or vaporstat). This will let you remove the control and do whatever maintenance you need to, just make sure to leave enough slack in the wiring.
Here's a front-on pic of the pressure instrument stack on my boiler. Pressuretrol (high pressure safety limit) is on the right, low pressure gauge and Dwyer pressure switch (control limit) are on the right. You can see the placement of the unions on each. There's a ball valve on the right side to isolate the low pressure devices when performing a blowdown. Note that there's not a ball valve on the pressuretrol side - having one would effectively disable the safety control and would (I'd hope) be failed by an inspector.
@ December 22, 2013 7:03 AM in My opinion of NEST on steamChris, from what I gather from the Nest website and user comments, it can take a while for it to learn your system and your occupancy pattterns. One person commented that it took more than a week for Nest to learn their radiant system, but after that it performed well, or at least well enough for that user.
As for data display and logging, remember that the Nest guys are orignally from Apple, and Apple is notorious for deciding for you what you need to see and what you get to control. The Nest does do data logging, which is accessible from the iPhone/iPad app, but there again the content and format of the reports is pre-determined for you.
@ December 21, 2013 11:33 PM in Running 2 CPH finally and loving it!The weather here was mild too. Is it possible that the temperature reached setpoint before steam got to the radiators? Are there other heat sources that could have affected the thermostat?
Not sure how changing the CPH ("heat cycle rate" function 0240 in the VP installer setup guide) would affect the algorithm in the thermostat. Might reset it so that it starts re-learning from scratch, or could just confuse it. I'm not sure even Honeywell knows what happens.
The problem with these thermostats is despite all their smarts, they can't tell the difference between heating the mains and heating the radiators.Their heat calculations wrongly assume that steam is ready at the radiators when they signal a call for heat, and most of the time it just ain't so. It's a shame, because all it would take is a $3 snap-disc thermal switch mounted at the end of the main to indicate mains hot or not. It's only one data point, but it tells you a lot about what's going on with the system.
@ December 18, 2013 5:20 PM in Running 2 CPH finally and loving it!You'll get a much better idea of your actual heat loss if you download the free Slant-Fin heat loss calculator software and spend some quality time feeding it the numbers it needs.
@ December 14, 2013 11:26 AM in Running 2 CPH finally and loving it!The other nice thing about mechanical relays is that you don't have to be concerned with the type or amount of the voltage you're switching, as long as it's within the relay's specs. And switch contacts are much better at surviving transient power surges that would fry a transistor output.
@ December 14, 2013 10:09 AM in Running 2 CPH finally and loving it!Yes, the output relays are mechanical. The rest is all solid state, even the digital inputs. Odd thing is though, TECO has a version of the SG2 with transistor outputs making the whole thing solid state.
@ December 14, 2013 9:30 AM in Running 2 CPH finally and loving it!There are a bunch of used 12 volt DC TECO SG2 units available on eBay for $60 apiece. These go for $145 new. Each has 8 digital inputs, 8 digital outputs, and 4 analog inputs. Link: TECO SG2 on eBay
You'll also need to spring for a $33 programming cable from FactoryMation. Link: Programming cable
@ December 12, 2013 6:18 PM in Running 2 CPH finally and loving it!PMJ, if I remember correctly you're using the TECO SG2, yes? I just started working with one to see how much of my heat loss algorithm and burner modulation I can pack into it. I'm doing a fair bit of math so the function block diagram is easier to work with than ladder logic. Nice that it can do either, especially at the sub-$100 price point, though I wish you could mix the two since cycle control logic is better suited to ladders. The current version of the SG2 includes PID algorithm function blocks, and they even have an 0-10 vdc analog output expansion module at a great price (though it's out of stock at the moment). About the only thing missing is historical data collection which you won't find at this level of hardware, and setback scheduling which can be managed by the wall thermostat.
@ December 12, 2013 6:19 AM in Running 2 CPH finally and loving it!MDN, I'm curious what your cut-out and cut-in pressures are, and how long it takes for the pressure to drop to cut-in. Also what your temperature swing is when running in that mode.
@ 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?
@ 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.
@ 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.
@ 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.
@ December 8, 2013 8:29 AM in ultra low pressure ARCO system maintained at higher pressureThe 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".
@ December 7, 2013 9:35 PM in Another Twin System - 6" Drop HeaderHave the modulating control fixed the short cycling you were experiencing on the 2nd boiler?
@ 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!