Could my boiler be oversized?

Jamie Hall

No. The efficiency of a boiler is defined in terms of how many pounds of steam it will produce for a given amount of fuel. It has absolutely nothing to do with the size of the boiler. For example, let us suppose that a boiler is fired with an oil burner operating at 1 gallon per hour. That is the gross input to the boiler, and would be 140,000 BTUh. And let us suppose that it manages to boil 14.7 gallons of water in one hour (which, of course, is replenished by the condensate return). That represents 119,000 BTUh (which is the net output). That equates to an efficiency, for that boiler and burner, of 85%.

The volume of the boiler doesn't enter into it.

The same kind of calculation, but with different numbers, can be done for hot water boilers. Much more water is involved, of course.

Now to your concern, a boiler with 15 gallons of water in it will take half again as much energy to bring that water to boiling. But how much energy is that? Let's go back to our boiler fired with 1 gallon per hour, and let's suppose that the boiler is sitting cold -- which in most cases means around 60 Fahrenheit. Now we do have to be concerned about the amount of water. It will take about 19,000 BTU to bring that boiler to boiling. It will take about 12,500 BTU to bring a boiler with only 10 gallons of water to boiling with the same burner. This is an efficiency loss, but it is related to how the boiler is operated, not to the boiler itself.

I the boiler is operated on short cycles, with time between them to allow the boiler to cool, the overall operating efficiency can be significantly affected -- but this is an operational consideration. If the length of firing is long, relative to the warm up time, and if the time between firings is short enough that the boiler doesn't cool off, the impact is much less. A very short off cycle -- such as might be found in a boiler cycling on pressure -- has almost no impact at all, as the water never drops much below (a degree, perhaps) steaming temperature. This is, however, one of the arguments for choosing a boiler of the correct size for the system.

deyrup

@Jamie Hall One thing I am a little unclear on is how a boiler would ever cycle off pressure. I assume the general is the ideal gas law PV = nRT so as you increase the temperature enough the pressure will increase enough to cause the cutoff. However doesn't the pressure gauge measure the pressure of the whole system and not just the boiler pressure? So that even though pressure increase ~1,600 times for each unit of water going from a liquid to a gas the gas will spread through the pipes and distribute its latent heat and turn back to a liquid and decrease the pressure. So as long as heat exchange is happening fast enough it shouldn't cycle off pressure. Does low heat exchange happen mostly if there is air getting trapped or something else that prevents proper distribution of heat? Is another explanation that you cycle off pressure in the case of a large boiler that creates steam too quickly for the heat to be disbursed. Would increasing the amount of radiation also be a fix for an overly large boiler instead of downsizing?

@betweentheframe This has helpful information in understanding how the energy flows in the system https://energy.mo.gov/sites/energy/files/steam-tables_power-plant-service.pdf It s

ethicalpaul

Many boilers are heavily oversized. They create steam faster than the connected radiators can give up the heat. Pressure builds.

or as you said, if the venting is inadequate then air in the system will prevent steam from getting to the radiators fast enough. Pressure builds.

Yes, if you added radiation it will lessen the oversized condition. Often radiators get removed over the years. And foolish installers order the next size boiler “just to be sure”

And yes, the pressure is pretty consistent across the system, with some pressure drops and variances.

underdog32

KC_Jones said:

I find it hard to believe that's all the radiation you have for a 3600 sq ft house. There are people on here with that much radiation for 1600 sq ft, so something seems amiss here. Could you post pictures of what you are counting as baseboard? I have a feeling it might be something different than baseboard, but the pictures will tell the story.

I also believe that boiler is most likely grossly oversized for the house regardless. Also, it's not properly piped.

Any chance you could elaborate on what you see wrong with the piping?

KC_Jones

The system takeoffs are between the boiler risers, this is known as a colliding header. Peerless has great documents showing why this shouldn’t be done, but basically it will cause wet steam to be thrown up into the system.

ethicalpaul

Here’s the Peerless document: https://www.peerlessboilers.com/wp-content/uploads/2018/01/OnePipeSteam.pdf

underdog32

KC_Jones said:

The system takeoffs are between the boiler risers, this is known as a colliding header. Peerless has great documents showing why this shouldn’t be done, but basically it will cause wet steam to be thrown up into the system.

I googled it and understand, and I was actually suspecting I had some wet steam. So if I were going to take an amateurish guess on how to fix it, I would swap the first pipe out of the boiler with the last supply pipe? So all the boiler pipes would be on the right, forcing steam to mains on the left?

KC_Jones

Like this, the 3 I scratched out need to move to the end and make sure the equalizer is the last thing dropping back down.

bburd

Yes, like that. 

Jamie Hall

@deyrup , Most of your questions on why a boiler would cycle off on pressure have been hit above, but to summarize. First, in general the pressure loss in the steam piping is very small -- an ounce or two -- even in fairly large residential systems (some larger commercial and industrial systems have more loss), so the pressure measured at the boiler is representative of the pressures throughout the system (there are complications here -- but they needed concern).

And you are quite correct in thinking that provided the condensation rate out in the system is equal to the evaporation rate at the boiler, the pressure will never rise. That is the golden objective we all strive for in designing and installing these systems! For various reasons, we don't always manage it.

As you note, trapped air can do it -- which is why one needs to pay attention to venting. If the steam can't get there, it can't condense! By far the most common problem, though, is that the boiler and the radiation are mismatched. This clearly can be solved by adding more radiation (often impractical and seldom needed for the structure) or downfiring the boiler or changing to a smaller one (also not always possible, and changing boilers is much money).

Sort of as an aside -- I'd be rather cautious about applying very basic physics, such as the universal gas law, to steam systems. Saturated steam, which is what we are dealing with, is far from an ideal gas, and doesn't always behave as one expects it to!

PMJ

@deyrup has it right. The water volume in the boiler is a very small factor in this. The average temperature raise to boil required is actually quite small. Do the math. Whatever the high gas bills in this case are about, it isn't raising the water to boil. If one is replacing a boiler for other reasons ok, go smaller. But there is no where near the gas money raising to boil to pay for replacing a perfectly good one. My boiler has 33 gallons in it, way more than this one. Not an efficiency issue. The big steam chest and water capacity do make for dryer steam and non-existent water capacity issues. I'm gladly paying for the minimal extra gas to continue enjoying those things being no brainers.

Boiler efficiency itself is not related to size at all obviously as @Jamie Hall said. They are all the same on the chart...they make steam at 80% or so. So just because I put one on my system bigger than necessary the 80% number doesn't change when it is firing and producing steam. When it is off it is not burning gas at all. No one should conclude they are screwed by default on efficiency because their boiler is bigger than needed.

System efficiency is a different subject. What does affect system efficiency is how I attach the boiler to the system and if I allow it to run at pressure and regularly overshoot the target. The bigger the boiler the more the system is at risk for these things. But as long as I pipe it in so it makes dry steam and I cycle it in such a way that no pressure is produced, excess size can be managed easily with negligible negative impact to efficiency. In fact, in the case of natural vacuum operation excess size is a considerable advantage. Anyone considering ever doing that should pause before going small.

All that said, the numbers I am reading in the case here just don't add up for me. A really big boiler, an EDM way too small for the house, a stated $5/hour cost figure that is twice what I would pay for gas on the stated boiler running at max rate. So I'm not following this one at all.

deyrup

Have we already suggested that more/better ventilation and insulation/sealing leaks are going to be more bang for your buck than downsizing the boiler?

acwagner

@underdog32 I forgot to ask: how are you verifying the operating pressure? Are you using the 30psi gauge that comes with the boiler or do you have a smaller range gauge added, like a 5psi or 3psi?

underdog32

acwagner said:

@underdog32 I forgot to ask: how are you verifying the operating pressure? Are you using the 30psi gauge that comes with the boiler or do you have a smaller range gauge added, like a 5psi or 3psi?

30psi gauge. It never goes over 1.

@betweentheframe My gas is $.95/ccf which includes distribution, and gas cost, so every 103k of btu in is about 1$ for me, and the boiler is 500btu...that's where my #s are coming from. I've verified it by checking boiler run time against movement in the meter, etc.

I appreciate what everyone is saying here about efficiency and all that, but I just can't get past the fact that the boiler has a 520mbth input. Unless you are saying that that amount is variable based on system load then there is no way that this boiler can ever run at less than 520mbth. If I understand it (and I'm not fully convinced I do), then if the boiler is on, it's using 520, period. Sure a 280 that runs twice as long as the 520 will cost more, but if the 280 runs the same then it would have to be 40% less money to run. Does that mean I'm ready to fork out 10 grand to get a new boiler? Maybe...we'll see what happens after I repipe the header.

The thing giving me pause is that I don't really have any of the symptoms of an oversized boiler. Other than a periodically rattling bucket trap (the one I installed), the system is silent. No bangs, knocks, clunks, whooshes, or whirrs. I'm kind of scared to change the boiler piping because I'm convinced that it's keeping the steam velocity low to prevent those symptoms, and if I do, then I'll start get all kinds of knocking and clanging. I have no proof that wet steam reduces pressure, but it would make sense if it did since more of the boiler output is going right to the wet return instead of entering the pipes. I'm speculating of course.

I'm sure I have wet steam. The only reason that I don't have another thread going about it is because I don't want you guys to get sick of me. I'm glad @KC_Jones explained the header piping issue because it makes so much sense.

If i remove a pipe from the supply side of a radiator, I get spits of lots of water coming out. Steam too, but a lot more water than I think there should be on that side of the radiator. Both of those pipes between the risers feed a single loop, and that loop was the loop that was mega waterlogged before I fixed the F&T trap...way more water logged after 1 cycle than it should be. I was draining 2-3 gallons of water a day out of that pipe until I fixed the f&t trap. Those branches are the ones I'm having most trouble with.

deyrup

underdog32 said:

acwagner said:

@underdog32 I forgot to ask: how are you verifying the operating pressure? Are you using the 30psi gauge that comes with the boiler or do you have a smaller range gauge added, like a 5psi or 3psi?

I appreciate what everyone is saying here about efficiency and all that, but I just can't get past the fact that the boiler has a 520mbth input.

Boilers will often have a 30psi gauge installed on the side, but those pressure gauges are often inaccurate; mine reads 10 psi, but my system runs at less than 2psi. If you want to get an accurate read of your system you can install a smaller range gauge on the pig tail that connects to the pressuretrol.

In a closed system the heat in the system = btus added. Your house is not a closed system; it is leaky; heat is lost through conduction, convection, and radiation. delta change in heat = amount of heat you add in - minus heat out. So if you want to maintain a temperature the btus into the system must equal btus out. A larger boiler lets you put in btus faster than a smaller boiler, but if you want to maintain the temperature it will be off more frequently. There are several ways to improve the efficiency of the system.
1. Decrease the amount of heat lost each hour
2. Increase the efficiency at which heat can be added to the system.

Each remedy has a cost and some remedies cost less per btu saved than others; high return remedies are insulation of pipes, insulation of your house, reducing leaks and adding enough venting. Other remedies are expensive, but can increase the efficiency of the system like replacing your boiler. If all you care about is increasing the efficiency of the system and money is no object then feel free to do them all.

Jamie Hall

"If I understand it (and I'm not fully convinced I do), then if the boiler is on, it's using 520, period. Sure a 280 that runs twice as long as the 520 will cost more, but if the 280 runs the same then it would have to be 40% less money to run."

Quite true. So far as it goes. Unhappily, there is a fundamental error in your thinking here. Regardless of boiler size -- assuming that it is at least marginally big enough, of course -- or even if it is a boiler and not a furnace or whatever it may be, your structure takes a certain number of BTU per hour to heat. That is not optional, nor subject to wishful thinking. Physics is that way.

Now clearly if it takes a certain number of BTUh to heat, you are going to have to provide that many BTUh to the heating system. That's also physics. Not optional.

Also to the point, you don't have to put any more than that in. If you have a much too big boiler, it will just run for less time, that's all.

As several here have said, some more clearly than others, it is quite true that a right size boiler will be, overall, more efficient at converting the BTU's you buy into BTU's you use. Further, if you have a more efficient boiler in and of itself the same is true. It's also true that one can improve things somewhat with better control strategies.

How much can one improve? Perhaps 10 percent assuming that you are starting off with a really poorly performing system -- but you aren't.

So now it becomes -- at least for most of us -- a question of economics. Cost of operation, cost of fuel, lost capital opportunity cost -- all that boring stuff.

If you really want the best bang for your buck, though, reduce your heat loss from the house. Draught stopping. Better (or some) storm windows. Insulation, where and if you can.

Zman

The energy wasted bring the boiler up to 212 degrees is simple to calc. The energy required to raise the temp of one pound of water one degree Fahrenheit is one BTU. So 8.34 Btu per gallon per degree. Heating up an extra couple gallons from 70 degrees to 212 will take 2,366 BTU's
I think what is missing in this discussion is how much short cycling effects the net efficiency of the boiler. An oversized boiler that short cycles can cost you 10% or more in efficiency (think city driving....)

Jamie Hall

Quite right, @Zman . I covered just that in another current thread. Can't think which one just now -- I can't keep them straight.

underdog32

betweentheframe said:

If you used 500 therms (you said $500 boll and $1 total cost per therm)@ 100k btu per therm at 30 days and 24hrs in a day that is a heat loss of 70k btuh, assume boiler combustion efficiency at 80, that’s 56,000btuh . And november wasn’t even cold! 

340 sq feet of radiation at 240 btu per sq feet can only output 81,600 in a perfect world. So your radiators would have had to be completely hot and full of steam 16.5 hours a day.

at this point I don’t even care about any numbers other than was your tstat set to 80? Am I missing something here? I was mad when I paid $320 for 160 therms for al1900 sq feet nov 4-dec 9 at $2 a therm! And that gave me a heat loss epr day via same calc of 15,200 and I have an uninsulated walls sill balloon framed wood lath stucco spanish revival from 1929 with coved 25 foot ceiling in living room and heat at 70 degrees. I do have about 6 inches of insulation in the attic. 

This is what I'm trying to get at. I'm using too much gas. Everything everyone is saying is true. It's an old house. It's a big house for sure, but not a mansion. It's R12 at best, but even given all of that, 596 CCF used for the month of november (11/11-12/11) was too much.

Again, there were problems that I fixed over that span, so it's hard to say how much it has affected it, and I won't really know until into february probably, but based on what I'm seeing on the meter, I'm still using 5CCF per heating hour, and heating up to 7 hours a day. Right now, I'm already at about 500CCF used since my last meter read, and there are 10 days to go until my next one. Temperatures are too inconsistent right now. Yesterday I heated for 4.5 hours, today I'm up to 5.5 and I was gone for 3 hours and it went into eco mode and didn't run.

I forget which poster said they had 7k square foot and their bills are around 600. That's the worst I was expecting based on past history. There is no legitimate reason to have a 600 gas bill in november. I wish I could see my thermostat history for november, but it doesn't go back that far so I can't see how much it ran.

Let say I fixed it and got it down to 6 hours a day (i don't think i did. I'm sure it will go back to 8 when it gets really cold). 6 hours * 5ccf/h = 30ccf per day, and 30ccf x 30d is 900, so even the best case is a 1000$ bill at 6 hours a day.

So something is very wrong. I'm hoping at this point that fixing the near boiler piping will fix something. I'll probably take a pick of the side and ask for input on that too. I've very little confidence that anything about it is right currently.

underdog32

If I run this, which is no way scientific because it asks some very limited question, and I answer every question the "worst" that i can, it still comes up with 180k btus, so I really don't think my EDR is off that much. I probably screwed up by measuring in wall convectors as fin/tube baseboard, but again, I doubled the number and went with 200k btus.

https://www.supplyhouse.com/sh/control/BTUCalculator

Jamie Hall

I was the one with the uel cost figure -- which, as you will recall, is the average cost over the year, since we pre-buy. The peak month, without pre-buy, would be around $1500.

Now, having said that, I'll say it again. Your boiler is a factor, yes, in your use of fuel. But -- a relatively minor one. Regardless of your heating system, it is going to take a certain number of BTUs to keep the building at a particular temperature. Period. End of story. If you want to reduce the number of BTUs used, you either have to improve the insulation and tightness, hence less heat loss at a given temperature, or reduce the interior temperature you are trying to maintain.

Don't fight it. Physics is not subject to hope.

acwagner

@underdog32 I think there's room for improving how your system operates for sure. My point way back early in this thread is that there are many members here that have oversized boilers and were able tame them and run them efficiently. But, there will be a limit to how much savings you can get simply because you're unfortunately stuck with an uninsulated home.

So, since you have a separate forced air system, you could run that to heat the home and see what the baseline gas usage is. My guess is the bills will still be high since you mentioned the previous owner used the forced air instead of the boiler, and that same owner was complaining to your neighbor about the high bills.

In any case, with the steam system, I'd recommend getting a 3psi pressure gauge on it and verify that you are in fact running at 0.5-1psi. You may be actually running at a much higher pressure and just getting a false reading on the gauge. The 30psi gauge isn't accurate on the low end.

Also, is your system using lots of water? What's the waterline look like while the boiler is steaming?

On your other posting I saw that your original main vent was a vacuum vent, which means your system was a vacuum setup at some point. Have you considered going back to using a vacuum system? There are potential savings by doing that.

I'm not a two pipe expert, as my house is a single pipe system. There may be other things to check for on a two pipe system.

PMJ

Ok so fuel cost is a bigger part of the issue here than I would have guessed possible. I looked up the HDD for Wilkes-Barre and Cleveland for December and they are identical. I used 37.6 MCF for the month and it cost me $185.

So if I am doing the math right @underdog32 pays double for gas what I do and @betweentheframe 4 times. So the same project is a lot harder out your way and we aren't looking at things through the same lenses.

Be all that as it may I still say any boiler that delivers dry steam controlled in a way that delivers to the radiators with no pressure or even vacuum is not going to be beaten by more than single digit percentage points in efficiency by a smaller one. However, at multiples of fuel prices even single digit improvements eventually become real money, even enough to perhaps justify buying a different boiler.

underdog32

I switched over to my forced air system last night at midnight. Today was 40 degrees, so not real cold, but i have 40 degree days on steam to compare it to.

Asof now, my forced air has run 7 total hours since midnight last night. That's 7 hours across 3 separate 60k btu furnaces, so 7 hours of 60k btu heating.

My gas meter has barely moved. I didn't check it at midnight, but I checked it twice today. Several hours ago it was 488, now it is 491. When the boiler is on, I can physically stand there and watch the small gauge spin an entire circle in a few minutes. When the forced air is running, the little needle's movement is barely perceptible.

Even if it runs for 10ccf every day, it would equate to a $300 gas bill. I don't think it will run for 10ccf every day.

I'm thinking maybe the $200 average bills they mentioned were forced air bills, and the $2000 my neighbor mentioned might have been the steam system.

I simply can't run the steam system as it is now. I love the steam heat, but this boiler just costs too much.

underdog32

betweentheframe said:

And that comes out to a heat loss at .80 efficiency of 21kbtuh, which is almost 1/3 of the 56kbtuh heat loss average for november hahahahaha

Lets assume the furnace is 80 percent efficient, so that oversized steam system is running at 31 percent efficiency hahahahahahahaha

The furnaces are 92% high efficiency models. The boiler is reportedly supposed to be 80%.

I heated the house we were in before this house, which was a 1900sf chalet with cathedral ceilings using a 68k btu pellet stove that used nothing more than convection. The entire season cost $1600 for like 5 tons of pellets delivered.

underdog32

I don't know how I'd get it out of there. Damn thing weighs 1000lbs according to specs.

The prior owner of this house was a commercial contractor. I'm absolutely sure that he got this thing in some sort of deal, like maybe it was mis-ordered and they couldn't return it so he got it cheap, but didn't know much about steam heat so didn't understand how bad it would be to run.

He also had a granite bar in the front porch area, probably cause he had left over granite from a job or something. I put it on facebook and 5 guys showed up and carried it away. That probably weighed more than this boiler.

2 of the doors in the house are commercial doors.

I just feel like half the crap in this house is left over stuff from his job sites. There is some real questionable and shoddy work in this house too. As a DIY homeowner I feel like I put out more quality work than this guy did, but he was maintaining it for his ex-wife, so maybe he just didn't care to do it right. Who knows.

ethicalpaul

I don’t know why someone keeps laughing, but your boiler isn’t 31 percent efficient.

the boiler no doubt uses more fuel per minute than those furnaces, but 80-some percent of it is definitely ending up in your house.

DanHolohan

@deyrup, that’s correct. 

WMno57

This thread makes me think of astronomy.

Black holes can not be seen but we are able to infer their existence by what we do see.

Jamie Hall

There's one question which I don't recall seeing -- I beg pardon it it's been answered already. How much water are you using?

underdog32

Jamie Hall said:

There's one question which I don't recall seeing -- I beg pardon it it's been answered already. How much water are you using?

I was using a lot before I fixed two traps, now I haven't heard the water feeder run at all. If I'm losing water, then it must be very slowly.

From midnight to 9am today, the forced air ran for 7 total hours (3, 3, and 1), and the meter moved from 494-499.

I don't think I have a insulation problem in the house. The house isn't well insulated, but if that were the issue then the forced air would run constantly as well.

The house isn't as warm with the forced air. There are 2 rooms that aren't as well served by forced air as they are by radiators, and that's irritating, but overall comfort is the same in most rooms. My basement isn't as warm as it was because the boiler isn't running.

I just feel like this is the difference between driving a f150 and a focus. They're both going to do the same job if you need to drive across town, but one will be way more expensive to run (and easier to haul drywall in).

I feel like if the forced air can heat this house at 180k btu, then a boiler should be able to do the same. Considering I have the forced air running and it's doing a serviceable job, I'll probably just roll with that until I can do something about the boiler.

Jamie Hall

Gotta admit I'd still be much more interested in figuring out the message -- so where is all that heat going? Is it real? -- than shooting the messenger -- the boiler. But that's me. I don't like band-aids.

At least with your truck analogy, the answer is clear -- the truck is heavier and bulkier, so needs more energy to move (it has nothing at all to do with the efficiency of the engines). With your house, the answer is much less clear -- somehow you seem to be putting a lot more energy into the place with one approach than with another, and blaming it on the boiler isn't the answer.

underdog32

Jamie Hall said:

Gotta admit I'd still be much more interested in figuring out the message -- so where is all that heat going? Is it real? -- than shooting the messenger -- the boiler. But that's me. I don't like band-aids.

If you have any suggestions, I'm all ears.

I've traced all the lines and fixed any leaks I could find.

All of my supply pipes are now insulated, aside from 2 of the risers on the boiler because I ran out of insulation.

I fixed any steam traps that were not working (still waiting for one part)

I'm not fully convinced that my pressure gauge or pressuretrol are working. I pulled them off the other night and the pipes were very gunky. Seems odd for those pipes to be gunky since only steam should enter them right?

I was able to force the system to shut off by adjusting the safety pressuretrol to it's lowest setting, and then tapping it with a screw driver.

If I hold my hand over the main vent and let pressure build up, it seems to come out at a good velocity, so pressure is building, but I don't know how much. I've never observed the pressure gauge changing during operation.

I'll probably still try to fix that header piping, but I don't know if I'll get to that until next weekend.

So my current symptoms:

1) High fuel usage
2) Suspected more water than there should be in main supply
3) No pressure buildup on gauge
4) Radiators don't get fully hot
5) Dry returns VERY hot. I cannot put my hand on one and keep it there.

acwagner

I could be wrong with the insulation value of your wall assembly. It's obviously performing pretty well. You do have a great experiment with two separate heating systems available to directly compare against each other.

I think there are two areas to focus on: getting a realistic pressure reading during operation and focusing on your venting. I suspect the system is operating at much higher pressure than you realize. That's what causes high operating bills.

What's your main venting like now? I think on your previous post you mentioned you have a single big mouth vent. Is that still the case?

underdog32

acwagner said:

I could be wrong with the insulation value of your wall assembly. It's obviously performing pretty well. You do have a great experiment with two separate heating systems available to directly compare against each other.

I think there are two areas to focus on: getting a realistic pressure reading during operation and focusing on your venting. I suspect the system is operating at much higher pressure than you realize. That's what causes high operating bills.

What's your main venting like now? I think on your previous post you mentioned you have a single big mouth vent. Is that still the case?

Yes, one big mouth vent, and one vent on a radiator that will most likely be closed after I fix that trap.

I suppose it's possible that the pressure gauge and pressuretrol both failed at the same time? It seems unlikely. When the plumbing store opens tomorrow I may run over and get a new gauge (or 2).

acwagner

The pigtail might have been clogged, or partially clogged. Debris does get in there from time to time. The 30 psi gauge may never have worked properly or has gotten fouled up.

PC7060

Regarding the lack of insulation, adding even 1” foam to exterior walls will make huge difference. Best solution is a exterior application but if that not feasible, it’s possible to add 1” RMax (R10) to inside of exterior walls, then drywall, reset trim, etc.  Even 1/2” @ R5 will really help.  Would take some time but yield big benefits. 

Ask this old house did something like I’m describing for a basement additions.  They used XPS which is good below grade. I prefer RMax or similar for applications above grade because of the higher R value. 

https://youtu.be/oKQdo88Ne74

Jamie Hall

Entirely agree with @acwagner -- you have all the symptoms of a clogged pigtail, or entry into the boiler from the pigtail. They can and do more or less routinely get gunked up, from water splashing in as the system is steaming -- and, if they are iron, just plain corrosion.

Your item 5 -- and probably related, item 4 -- are a major concern. Hopefully it is related to running at much too high a pressure, but it's something you need to track down and fix. A true dry return on a two pipe system should never, ever be much over 120 -- which you can hold your hand on, at least for a short time. In most systems, at any distance from a radiator outlet, 100 or less is more like it. A very hot dry return is one which has steam getting into it from somewhere. This steam in a dry return will also kill the heat in any radiators attached to it -- which is why it may be related to item 4.

There are two major possibilities. The first, and perhaps more obvious, is traps failed open. If your system has crossover traps, these are often overlooked. Recheck them al (since a crossover takes no condensate, the outlet from it should be no hotter than warm, being heated only by conduction from the inlet)l. The second, and somewhat less obvious, is water seals on drips. These may or may not connect to a wet return, but -- particularly if they don't, but in any case -- excess steam pressure will blow the seal, and steam will quite happily zip around and get into the dry return. Even a floor to ceiling loop seal will be defeated by steam pressure over 3 psi.

If you do find that your system has been running at anything much over 2 psi and you have loop seals, see what it's like when you get it tamed. However, a note: if you should find that it has been running much over 3 to 5 psi, go back and recheck all the traps, every single one of them. They are not meant to function on pressure differences that large, and may have been damaged. Also check the vents -- they aren't meant to run at those pressures either, and also may have been damaged.

underdog32

PC7060 said:

Regarding the lack of insulation, adding even 1” foam to exterior walls will make huge difference. Best solution is a exterior application but if that not feasible, it’s possible to add 1” RMax (R10) to inside of exterior walls, then drywall, reset trim, etc.  Even 1/2” @ R5 will really help.  Would take some time but yield big benefits. 

Ask this old house did something like I’m describing for a basement additions.  They used XPS which is good below grade. I prefer RMax or similar for applications above grade because of the higher R value. 

https://youtu.be/oKQdo88Ne74

If insulating the outside of a house costs less than a new boiler then I'm in! Point me to the guy, he's got a gig!

My understanding though is just re-stuccoing the outside alone would cost as much as a new boiler, if not more. Add in the moisture barrier and god knows how much foam board, and I'm sure it would be double the price.

Inside couldn't be much better. Foam board to cover all the walls, wood to screw into, and new drywall and someone to mud it, not to mention moving all the trim. I can't even screw into my exterior walls without drilling pilot holes into the clay block and using masonry screws to secure whatever.

Insulation would be a giant expensive job.

underdog32

@Jamie Hall What is the best way to check a trap? I put 2 brand new barnes and jones crossover traps in. One of them is one where the pipe gets very hot afterwards. Since it's new, I assume its functioning. I haven't verified the other.

The bucket trap I installed also gets hot on the outlet side and rattles a bit after the system has been running for a while. It does sound to me that it is operating at higher pressure than it should be, but it's just a gut feeling.

My theory is wet steam. If it's wet, maybe it's condensing early and getting into the condensate return at near steam temperatures and heating up the returns.