ashful think about this i will take quite a bit longer to go from 180 or 190 to 230 so your are probably burning to much fuel. also i'm not sure of your money situation but 2 small boilers will cost less in fuel than a large one over the season. i installed a computer to run two large budarus boilers because the 9 section boiler that was there cracked from to much heat to quick. she went from a 325 gallon oil tank once a week to the same once every three weeks
Pyrolysis... and setting your house aflame
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So, a few things are likely happening here. I may have misspoke when I said 230, I think it might actually be running up to just 215, or thereabouts. But that's still well above the set points on the , if I'm reading them correctly:
So, it should be holding 150F to 190F, but it is clearly not:
Ignore the pressure readings, as trouble with my autofill valve is what has had me looking at this in the first place, and I'm dealing with that separately. But what is relevant here is that I've already proven with a newer and better gauge attached to one of the boiler drains, that this gauge is reading wrong (sticking) on pressure. I suppose it's possible that it's also reading wrong on temperature, but normally gauges error by sticking within their range, not overshooting it.
I think my next move is to replace this gauge, and if that proves the aquastat is malfunctioning, then to replace that.
A second boiler is not up for discussion. I can afford it, but don't want to deal with it. I'm happy to run this one less efficiently, particularly as I'm pulling most of the load with two stoves fired on oak and hickory. The boiler is being operated at less than one half, honestly probably less than one quarter, of the installer's intended load.
I'm not following. Wouldn't a greater spread between min and max (i.e. higher max temp) cause a longer firing under heat demand, and a greater DIFF cause longer firing in summer mode?
You don't need an open flame to ignite wood. Enough heat will do it and with pyrolization the ammount of heat needed gets less and lessI believe I've seen somewhere mentioned in this forume that pyrolysis might start happening happening @175F, but nowhere in scientific documents, so take that "fact" with a handful of salt.
But you are making an excellent point regarding +100C/212F temp water pipes.
I think there is a slight difference in the environment itself.
While the joists are going to get extra crispy dry, it doesn't matter too much from igniting point of view, cause there is no open flame around?
When we talk about a piece of wood being close to open fire, in theory, the hotter that wood is, the easier it gets on fire? Considering ambers flying around, etc, maybe thus is concern? As well, the pyrolysis decreases the ignition point of wood.
So, while we won't see charring at +100C/200F, it makes sense to keep things around the fireplace as cool as possible, I guess.
Different point from pyrolysis, though.
Here is a picture from wikipedia, that is quite helpful to see what happens when:
View attachment 322519
Pyrolysis - Wikipedia
en.wikipedia.org
As for +60C I mentioned in the other thread, I'm just trying to be super overly safe, and the number might be higher (I'm no expert). But +60 is very hot to the touch anyway. Quick google search tells me that scalding happens in į seconds @ +60C, so even that seems a very high threshold to me.
P.S. thanks for starting a new thread
Pyrolysis is an actual change in the properties of the wood not just moisture content
Your house needs xxx btu to keep at a set temperature. Hotter pipes will emit that heat faster than cooler pipes. If your boiler is short cycling, you can lower the water temp and the boiler will run longer at a lower burn to supply those btus. I'm not sure what summer mode is.
Got it. I don't think this is possible, at least here, and it's something I think I'd have noticed now. The hysteresis programmed into my thermostats is great enough, and the room size / load to available radiator is large enough, that I don't believe we're ever satisfying the thermostat before the aquastat. I suppose I could hang an Emporia Vue sensor on each zone valve and the burner, to confirm that, but I don't believe it's happening. All boiler firings I've ever sat and observed are running thru the full range (LO to HI setting... plus), and so lowering high would only shorten each firing, in this scenario.
Moreover, my thermostats all go down twice a day (midday and overnight), then warm back up morning and evening, and each of these cycles takes multiple firings of the boiler. Lowering HI temp would actually require more consecutive firings, just to get the room back up from wherever it has settled to the desired temperature.
Every boiler setup is different, lol. I've only had 2. The first was so oversized that it broke parts every year, even after I increased the size of the house by 50%. My replacement boiler was still bigger than I wanted and I geeked out tuning it, lol.
Yeah, my prior house was like that. Oil-fired hot air furnace, not a boiler, but similarly over-sized. I can only assume the installer had intended it to be eventually ducted to the entire 2500 sq.ft. house, and sized it accordingly. But then the prior owner did the 2nd and 3rd floors in resistive baseboard instead, so it was only ever ducted to the ~1000 sq.ft. of first floor. Atop that, the duct sizes were small, and some zones done in flexible duct with too many bends and pinch points. I ended up making a lot of changes to that setup, to get it working right.
This house, opposite scenario. The boiler was sized for and installed when they were heating only 2800 sq.ft. Now it's heating 6400 sq.ft. Same boiler, prior owners just kept adding zones, as they finished and heated the basement, then attic, and then added 1800 sq.ft. of new construction. It's actually surprising the little thing carries the load just fine, as every non-boiler tech who ever sees the thing seems to say, "you're heating all this house with that little boiler?"
back in the day they used to over size everything heat and Ac. not an efficient practice. That practice has been largely stopped now days . Still there are some that believe bigger is better.
TomasB
New Member
ashful if you find that the gauges are good then i would still turn it down. that is call a aquastat some aquastats to get to the top temperature you add the hi temp with the differential turn the high temp down 10 degrees you'll probably find the the timing of the heat is the same but you will save on fuel. you should have seen my boiler when it was first installed. i only have a regular aquastat and not a triple aquastat like yours but it was set to shutdown at 180 but the differential was 5 degrees. dumb dumb and dumb. i call the company 2 years ago for support and got the guy who designed my boiler. it's all aluminum. he said "how old is your boiler" i told him over 20. "he said wow we haven't got that boiler to last past 15 years in the lab" it's no wonder.
Yep... aquastat. Familiar with them, but I thought DIFF only applied to LO, not HI?
My recollection of their operation is that without any call for heat, boiler will fire when it crosses LO temp, and continue firing until it reaches LO + DIFF. This is for making hot water only, i.e. "summer mode".
When there is a call for heat, boiler will fire until it reaches HI, then shut off until boiler water drops below HI minus 10F. Differential on HI knob is not adjustable, it's just fixed at 10F below HI.
By that logic, my boiler should never be exceeding 190F, but I routinely see it exceeding 210F.
Actually, just called my boiler tech. I'm having him stop out tomorrow to replace my leaky autofill valve, that gauge, and the aquastat. If it were one of the three, I'd just do it myself, but by the time I get elbows deep in replacing all three components, it's easier to just pay for one service call and have everything new. The gauge is too cheap to even second-guess, but can't be swapped without removing the aquastat, which is blocking it's port. Swapping the aquastat now is cheaper than paying for a second service call, or removing it, reinstalling it, and then removing it again to swap. I'm just too busy right now to waste a whole afternoon on doing it myself, by the time I swap out the autofill valve and then purge and burp all six zones, so I'm calling this justified. 
My oil co told me the ones they use are about $350. Some new whiz-bang digital thing, no more dials. The nice thing is that the new one has a display of measured temperature, so they were able to confirm the new gauge and new controller are reading the same.
I got talking with the tech about set points, and he was telling me the set points become much more critical when you're using the boiler for direct hot water. They usually want to bring them much closer together for that scenario, to get better consistency in DHW temperature. In my case, with an indirect water heater as a separate zone off the boiler, set points are less critical... but do of course impact efficiency and potential for short-cycling.
In the past, I tracked oil usage and HDD's pretty carefully, to gauge impact of heating with wood. I found it's tough making very accurate correlation between oil usage and HDD's in our house, because the amount of wood I burn per HDD or per day is not consistent, and because my kids' hot water usage probably isn't all that consistent either. If I want to mess around with finding ideal set points, I'd probably hang an energy monitor on the boiler to watch burn times (maybe even per zone), and try to make some correlation between that and oil usage. Not sure if all that work would really pay off, though.
Boiler is being used for heat and hot water, although thanks to wood stoves and other heat sources, we've got our oil usage down to about 1000 gallons per year. Subtract 350 gallons from that to account for what's going toward DHW, and our oil usage for heating is down around 650 gallons.
Of course, we're burning completely obscene amounts of wood to get down to that number, plus running two heat pump systems + propane + a small amount of electric resistive.
If I nudge the boiler efficiency 2% by messing with set points, which is probably a stretch, then I'd save 20 gallons of oil per year. Not huge. If that efficiency is only realized when the boiler heads toward the HI limit, for heating, then the savings drops to perhaps 14 gallons per year.
350 gals for dhw? Wow. When I had a setup like yours I installed a mixing valve for the dhw as long as your mixing valve output is below your low setpoint you have no fluctuations
One word: teenagers. Actually two words: wife + teenagers. Somehow, I can manage to get fully showered in under five minutes, including warm-up time. They think I'm treating them with unusual cruelty when I try to cut them off at 20 minutes.
But the ~1 gallon per day is from memory, and it's possible my memory is off. When I bring my laptop back from the lab, I'll pull up that file and double check, I could be remembering wrong.
Not sure what you mean. I have mine set up as a Boilermate indirect water heater, with a separate circulator pump teed into the main heating manifold of the boiler. According to the guys I had check out the setup ten years ago, they claimed it was about the best setup you could have, one even saying he'd have the same rig in his own house if he could afford it.
But I've never really dug into it myself, as it was configured ca.1995 by a prior owner of this house. He owned one of the regional heating oil companies in this area, so I'd suspect it was a "no expenses spared" thing done by his own employees, but don't know their end goal was efficiency, comfort, or reliability.
every boiler and tank is different. mine is a dunkirk 90. as it is 90% efficient, and a 45 gallon superstore. it's a all aluminum block and a cold start my sweet spot is 140 as set on my tank. it does go to 180 but goes down to 150 before turning back on to go to 180 degrees but the difference is i went from 130 to 140 with out burning more fuel. just as it's about to turn on again to hit 180 it shuts down cause the tank came up to temp. as long as people don't take different times for a shower it's the same usage
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