Could my boiler be oversized?

underdog32

I have a 3600 square foot 1930s four square with steam heat in Northeast PA. My november heat bill was around $500, and it wasn't even that cold. That led me to finding and fixing several problems that i hope will make a difference, but more importantly reading a lot, here, and elsewhere. I'm now concerned that my boiler might be grossly oversized.

It's a peerless 62-14, which if I'm reading the specs right is a commercial boiler that produces somewhere around 400k btus.

http://orders.mitcomfg.com/IMAGES/catalog/20047-114.pdf

It does only seem to run at .5-1psi on the gauge, and for about 20 minutes at a time, so I'm hoping it's sized properly, and the real issue is all the water the system was leaking from the bad steam trap.

I'm more concerned because my wife was talking to the neighbor the other day and the neighbor mentioned that the previous owner complained about heating bills in the 2k range. They told me the average monthly bills were 200 when I was buying the house so 2k would a shock to my budget. But they also have retrofitted 3 forced air furnaces/ac units, so they may have been running those to heat the house. i wouldn't be surprised based on the condition of the steam system so far that they neglected it for years.

danitheplumber

Most likely is... real question is what's the edr of all the radiators? That will tell you what size boiler you need. Also do you have auto feeder that keeps feeding water? maybe check that you don't have white clouds/smoke coming out your chimney otherwise that's money going out the chimney...  

underdog32

danitheplumber said:

Most likely is... real question is what's the edr of all the radiators? That will tell you what size boiler you need. Also do you have auto feeder that keeps feeding water? maybe check that you don't have white clouds/smoke coming out your chimney otherwise that's money going out the chimney...  

My water feeder feeds a crap ton of water, but I believe that's because of a steam trap that's leaking probably at least a 1/2 gallon of water per cycle, maybe more. It has no structural integrity, despite the layers of poly pro that the prior owner tried to put on it. The new one will be here tomorrow, so that problem will be fixed.

I have not seen any white clouds from the chimney. There are white wisps, but it's no different than what i see from my neighbor's chimney, and doesn't look out of sorts.

danitheplumber

Needs to be white like when they call for the new pope...

dabrakeman

The boiler does sound big but total up the EDR of your radiators to determine for sure. A few different guide sheets attached.

underdog32

dabrakeman said:

The boiler does sound big but total up the EDR of your radiators to determine for sure. A few different guide sheets attached.

Thanks for that. I was wondering about how to measure the convectors and baseboards, but the 3rd attachment looks like it covers that. It'll take some time, but I'll try to figure it out.

underdog32

dabrakeman said:

The boiler does sound big but total up the EDR of your radiators to determine for sure. A few different guide sheets attached.

I had to make some assumptions because some are inside enclosures in walls and inaccessable, but I chose high, and I don't think any of the inaccuracies would add up to hundreds of thousands of btus. I calculated about 100k. Even if I doubled that the boiler is still a 400k boiler.



This is the boiler in question:



It's probably worth getting a pro out here and looking at this thing right? This isn't a job I can tackle.

KC_Jones

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.

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.

This is all in the same room which is a closed in front porch area:

Baseboard:


Inaccessable x2 (assuming fin based on others in the house):


I'm totally not a pro, and I could have screwed up the measurements, but even if I doubled it (don't think I screwed up that bad) the boiler is still double that.

KC_Jones

I don't disagree it seems like you are oversized, but if you are going through the exercise let's try and get it right so you know what's going on with any future decisions and to make sure if a replacement is ever done the new one is actually sized correctly. That may be one of the most grossly oversized boilers I've seen on here.

So the top picture is indeed cast iron baseboard, the bottom is a convector and they will usually have a higher EDR rating than baseboard. I am not well versed on those, so I'm hoping someone who is will chime in and help you out with ratings. You may need to pull the cover off and take a picture of what's inside for anyone that's going to help. It either lifts off, or that knob at the top might unscrew, again I'm not a convector expert.

underdog32

My biggest issue right now is cost. From what I can tell, the boiler uses 520mbh of input to heat, so if I'm heating 8 hours a day, then I calculate that to be 5.2 ccf/h * 8 = ~42ccf/d * 30 = 1260ccf/m * $.95/ccf leaves me with "holy effin crap, honey buy more ramen!" as a gas bill.

I'd much rather pay 1 holy effin crap bill to size the boiler properly and hopefully cut my monthly winter bills to "i hate winter" levels.

KC_Jones

underdog32 said:

I'm totally not a pro, and I could have screwed up the measurements, but even if I doubled it (don't think I screwed up that bad) the boiler is still double that.

A lot of us on here are just homeowner like yourself who decided to get educated, this site is amazing, but be careful the steam can become addicting to some.

KC_Jones

underdog32 said:

My biggest issue right now is cost. From what I can tell, the boiler uses 520mbh of input to heat, so if I'm heating 8 hours a day, then I calculate that to be 5.2 ccf/h * 8 = ~42ccf/d * 30 = 1260ccf/m * $.95/ccf leaves me with "holy effin crap, honey buy more ramen!" as a gas bill.

I'd much rather pay 1 holy effin crap bill to size the boiler properly and hopefully cut my monthly winter bills to "i hate winter" levels.

I too am from PA, I'm curious, did the seller disclose the monthly heating cost on the official (PA required) disclosure documents? If so and they did say $200.00 and it's really closer to $2000.00, I believe they actually have some liability here.

Another route to find out for sure what's going on (usage wise) is to contact the gas company, they have usage history for the address and I think they will give you that information, then you know what the truth is. I would also try and get the electrical usage in case they were using the forced hot error (not a typo).

underdog32

KC_Jones said:

underdog32 said:

My biggest issue right now is cost. From what I can tell, the boiler uses 520mbh of input to heat, so if I'm heating 8 hours a day, then I calculate that to be 5.2 ccf/h * 8 = ~42ccf/d * 30 = 1260ccf/m * $.95/ccf leaves me with "holy effin crap, honey buy more ramen!" as a gas bill.

I'd much rather pay 1 holy effin crap bill to size the boiler properly and hopefully cut my monthly winter bills to "i hate winter" levels.

I too am from PA, I'm curious, did the seller disclose the monthly heating cost on the official (PA required) disclosure documents? If so and they did say $200.00 and it's really closer to $2000.00, I believe they actually have some liability here.

Another route to find out for sure what's going on (usage wise) is to contact the gas company, they have usage history for the address and I think they will give you that information, then you know what the truth is. I would also try and get the electrical usage in case they were using the forced hot error (not a typo).

I went through the disclosure and I don't see the 200 number written down. The way I remember it was a conversation with my realtor that went something like this:

"Still waiting on the average monthly bills"

time passes....

"Got the average monthly bills. It's about 200"

I think the seller just tossed out a number. I wish I could find some liability on their end for it.

My gas/electric is the same company and it's all on the same bill, but itemized.

KC_Jones

Long shot no matter what, just wanted to throw it out.

underdog32

KC_Jones said:

I don't disagree it seems like you are oversized, but if you are going through the exercise let's try and get it right so you know what's going on with any future decisions and to make sure if a replacement is ever done the new one is actually sized correctly. That may be one of the most grossly oversized boilers I've seen on here.

So the top picture is indeed cast iron baseboard, the bottom is a convector and they will usually have a higher EDR rating than baseboard. I am not well versed on those, so I'm hoping someone who is will chime in and help you out with ratings. You may need to pull the cover off and take a picture of what's inside for anyone that's going to help. It either lifts off, or that knob at the top might unscrew, again I'm not a convector expert.

So that cast iron baseboard is actually listed as 26' PBB on the standing radiation side because there is a definition for it on one of the documents.

Everything on the "baseboard radiation" side is a fin/tube convector unit by length. I couldn't find any other definition of how to measure those.

acwagner

Getting the EDR is a useful exercise, and I don't want to detract from that. But....

Your house looses a certain BTU/HR based on the outside weather conditions, desired inside conditions, and the building's ability to resist heat transfer between the two. That is independent of the heating system.

The heating system can deliver the heat needed in 5 minutes or 50 minutes, but the same amount of BTU is needed.

What I'm getting at is there are probably other larger contributing factors to why your gas usage is so high beyond the boiler size. There are a number of members on this forum that have grossly oversized boilers without crazy heating bills.

What is your venting like? I'd expect your system to short cycle on pressure all the time if your boiler is that oversized especially with low mass convectors, but you didn't mention that to be the case.

What's the insulation like for the home? Are the recessed convectors on exterior walls with no insulation?

I bring all this up because it sounds like you want to make informed decisions on the next steps. The oversized boiler may be a red herring.

KC_Jones

This might help, but still need to see inside to determine which type you have.

https://www.scribd.com/document/27425454/Burnham-Heating-Helper-Table-of-Contents

Go to page 44

underdog32

acwagner said:

Getting the EDR is a useful exercise, and I don't to detract from that. But....

Your house looses a certain BTU/HR based on the outside weather conditions, desired inside conditions, and the building's ability to resist heat transfer between the two. That is independent of the heating system.

The heating system can deliver the heat needed in 5 minutes or 50 minutes, but the same amount of BTU is needed.

What I'm getting at is there are probably other larger contributing factors to why your gas usage is so high beyond the boiler size. There are a number of members on this forum that have grossly oversized boilers without crazy heating bills.

What is your venting like? I'd expect your system to short cycle on pressure all the time if your boiler is that oversized especially with low mass convectors, but you didn't mention that to be the case.

What's the insulation like for the home? Are the recessed convectors on exterior walls with no insulation?

I bring all this up because it sounds like you want to make informed decisions on the next steps. The oversized boiler may be a red herring.

I have one main vent. Here's the thread where I'm trying to figure that out too:

https://forum.heatinghelp.com/discussion/182384/more-venting-needed-where#latest

The boiler never cycles on pressure, ever. It's usage is almost exactly 20 minutes every hour:



So, to me, 6-8 hours of heating on-time a day seems reasonable, but if that heating on-time is using 520mbh of input then I don't know what I could possibly do to make it more efficient. It's just math at that point. If it runs x hours it will cost y much. the 520 is a constant that won't change no matter what changes I make outside of the boiler. Changing (x) or (520) are the only things that can affect the price. I'd love to reduce x, but is it reasonable to expect to run the heat for 3 hours a day in the middle of January? Probably not.

But yes, the house was built in the 30s, has structural block walls with stucco on the outside and plaster on the inside for an R value of "definitely not enough". All new windows throughout except some vintage decorative stuff that I'll probably try to make inserts for. It is not cold or drafty in here, and it seems very comfortable.

acwagner

Concrete block provides effectively nil insulation value, so your boiler is running that much because that much energy is being lost to the outside through the walls. You live in a pavilion, in terms of thermodynamics.

An oversized boiler increases gas consumption because it produces steam faster than the radiators can distribute it, therefore builds up more pressure than necessary to distribute the steam. If you're operating at 0.5 psi to 1.0 psi, there's room for improvement for sure. Most single family home systems only need a few ounces/in of pressure to operate. Bringing the pressure down will reduce your bills. Probably not as much as you're looking for though.

But, a smaller boiler will still need to distribute the same amount of heat to match the loss to the environment. If your house is loosing 150K BTU/HR to the environment, then the heating system needs to produce that amount or more to maintain temperature. It just means the smaller boiler will run, say, 50 minutes an hour vs 20 minutes compared to your current one. Same amount of BTU/HR consumed to replace the amount lost through the walls.

So, two sides to the equation to reduce your gas bill. You can address the oversized boiler by looking at @PMJ postings on his system. He has a two pipe system with an oversized boiler. He converted it to a vacuum system (to address your venting posting) and also modulates the burner on his boiler so it operates like a smaller boiler (addressing the oversized boiler).

The other side is doing what you can to better insulate the house, but it sounds like you're limited without doing a whole house remodel. Is the attic insulated?

deyrup

Can you pull how much gas you are using per day off of the meter? You can go low tech and just write it down for a couple of days or pull it off electronically. You are going to know ASAP (before your bill) if you are using like 60 therms a day.

nicholas bonham-carter

Several years ago, I was able to get 2 years of monthly gas readings from my gas company, with degree days information for each month. Maybe your gas company can provide the same readout.
Make sure the actual readings are used for your calculations.—NBC

underdog32

acwagner said:

Concrete block provides effectively nil insulation value, so your boiler is running that much because that much energy is being lost to the outside through the walls. You live in a pavilion, in terms of thermodynamics.

An oversized boiler increases gas consumption because it produces steam faster than the radiators can distribute it, therefore builds up more pressure than necessary to distribute the steam. If you're operating at 0.5 psi to 1.0 psi, there's room for improvement for sure. Most single family home systems only need a few ounces/in of pressure to operate. Bringing the pressure down will reduce your bills. Probably not as much as you're looking for though.

But, a smaller boiler will still need to distribute the same amount of heat to match the loss to the environment. If your house is loosing 150K BTU/HR to the environment, then the heating system needs to produce that amount or more to maintain temperature. It just means the smaller boiler will run, say, 50 minutes an hour vs 20 minutes compared to your current one. Same amount of BTU/HR consumed to replace the amount lost through the walls.

So, two sides to the equation to reduce your gas bill. You can address the oversized boiler by looking at @PMJ postings on his system. He has a two pipe system with an oversized boiler. He converted it to a vacuum system (to address your venting posting) and also modulates the burner on his boiler so it operates like a smaller boiler (addressing the oversized boiler).

The other side is doing what you can to better insulate the house, but it sounds like you're limited without doing a whole house remodel. Is the attic insulated?

Just being pedantic, but it's clay tile block/terracotta, not concrete. Probably not much different in R value though.

I have been looking into EIFS systems to add insulation to the outside. That's a pretty high cost project, but may be in the future.

So here's what I'm wondering:


I'm using 520 to produce 1300ft of steam for a system that takes 700 if i double my calculations.

Wouldn't I be worlds better off with something like this:



With that, I'd be using 280mbh to produce 700ft of steam that seems like it would fill all the radiators well. Maybe you're right and I'd just end up with 40 minutes per hour at 280 instead of 20 at 520.

My attic is insulated.

I'm just being hypothetical about it trying to understand the math. At some point I'll probably get someone out here to look at it.

There is a very good chance that the guy who put it in had no idea what he was doing and just happened to get the boiler for cheap because he was a contractor or something. Considering all the problems that I did find and fix, it's highly possible that the system was not heating effectively with an older boiler so he went as big as possible when he purchased one rather than sizing it correctly.

underdog32

deyrup said:

Can you pull how much gas you are using per day off of the meter? You can go low tech and just write it down for a couple of days or pull it off electronically. You are going to know ASAP (before your bill) if you are using like 60 therms a day.

I'll start tracking it there too. I did do some math and it seemed to support my #s. For example, my last reading was 12/13, and since then I've used 500ccf based on the meter reading, which averages out to like 30ccf a day with 14 days to go before the next meter reading. According to my nest, I have used 100 hours of heating since 12/13, which is pretty spot on with the 5.2/h figure that I calculated.

I have absolutely fixed things in the last week though, so it's possible that half of this month was running up the meter due to the problems that have since been corrected.

For example, my auto water feeder is hooked up to my HOT water line, so when it feeds water it feeds it from the hot water heater. Before I found and fixed the leaky bucket trap it was probably dumping gallons of water a day that had to be fed back into the system and then reheated in the water heater.

acwagner

Yes, having a right sized boiler for the radiator load is the best, and the boiler should have been sized properly when it was installed. I'm not trying to say otherwise.

But, most people that have grossly oversized boilers complain of cycling on pressure, noisy vents, big temperature swings, hot/cold areas of the house, hammer, wet steam, etc.

You don't seem to be having any of those problems. So paying big bucks to replace the boiler right now might not be worth it. Others may disagree, but I don't see your gas usage dropping dramatically by changing out the boiler based on what you've said thus far. Obviously knowing the right size boiler for when the time comes that you need to replace the boiler will be a good thing for planning purposes.

I'd definitely wait and see how the other changes you've done thus far have impacted the gas usage.

ethicalpaul

I would agree with @acwagner. If you can get your system to work with not too much cycling on pressure or the other issues he listed, it's not going to make fiscal sense to replace the boiler.

The BTUs of fuel you are burning are getting injected into your house via the radiators. There won't be huge differences in that with a correctly-sized boiler.

The thing you don't want, that would cost real money would be if your massive boiler were running at high pressure with your radiators maxed out. And even that can be solved without replacing the boiler, for example with some timing mechanism that gets talked about often enough around here.

underdog32

Thanks guys. No matter what I'm going to wait this season out and feed my kids ramen if I have to. Hopefully something will get better. I'd be interested in others that have old 3k+sf houses and if they suffer the same high heat bills, and what boilers they are running.

I had a 2000sf house a while back with a 1 pipe system on a weil mclein (don't remember the model) and my bills never went over 400. 400 was the middle of January/February when it was the coldest. It was also an old house with no insulation. I know 3600 is greater than 2000, but I definitely don't think I should be paying $1000 bills all winter, so hopefully something changes.

underdog32

I just looked at my furnaces to get a comparison. They put in 3 high efficiency forced air furnaces for 3 zones. Each is rated at 60mbh in, and 56mbh out.

So, if I chose to run the forced air, which I don't want to do, I would be using a total of 180mbh max, or 1.8ccf/h, for a total output of around 170,000btu.

So, when sizing the forced air, they sized it at 170kbtu.

Jamie Hall

@underdog32 , you asked about others with bigger houses and their heating bills. Cedric's home is 7,000 square feet gross floor area (footprint is just over 3,000 feet). It is older -- circa 1810 to 1893. It is not insulated except part of the roof. The heating system is steam, installed in 1930, and powered by a Weil-McClain 580, oil fueled, installed in 2010.

The heating bill, averaged over the year (we pre-buy oil for the following year in the spring, and spread the payments out over the year), is $600 per month. If we bought oil on the spot market -- which is a mug's game -- the highest month last year would have been around $1,500. I don't regard the monthly cost as high, but we'd be idiots to buy oil on the spot market.

That also includes the hot water (also oil fired hot water heater), but that is minor.

I might also point out, by the way, that we are hardly wealthy: I am a religious, with no income at all, and my daughter and son-in-law are farmers and also care for other people's properties -- not much money in that.

The Steam Whisperer

I have worked with many building with structural clay tile exterior walls and they all have much lower heating costs than typical brick buildings. They seem to perform much better than even the R-values published in my engineering texts.
Another potential source for high heating costs are the forced air systems. The DOE has done studies that have shown that just the presence of ductwork in a typical modern home increases air leakage about 10% ( when the fan is running air leakage increases about 80%) I would look very closely at where that ductwork in run. It is especially problematic when they run it through unheated spaces ( attics most commonly) or areas outside the comfort envelope. They installers somehow think that R-3 insulation on the ductwork will stop all the air leakage from the joints and insulate as well as the recommended R-38 for ceilings.

I also agree, your radiation number looks way short for 3600 sq ft of above grade living space. The room count doesn't look right either...I would expect a living room ( 2 rads quite often) dining room, Kitchen, Foyer, 1st floor bath, maybe a study. On the second floor 3 to 5 bedrooms up, another bath or 2, and then the rads in the attic. Maybe a couple in the basement sometimes.

underdog32

The Steam Whisperer said:

I have worked with many building with structural clay tile exterior walls and they all have much lower heating costs than typical brick buildings. They seem to perform much better than even the R-values published in my engineering texts.
Another potential source for high heating costs are the forced air systems. The DOE has done studies that have shown that just the presence of ductwork in a typical modern home increases air leakage about 10% ( when the fan is running air leakage increases about 80%) I would look very closely at where that ductwork in run. It is especially problematic when they run it through unheated spaces ( attics most commonly) or areas outside the comfort envelope. They installers somehow think that R-3 insulation on the ductwork will stop all the air leakage from the joints and insulate as well as the recommended R-38 for ceilings.

I also agree, your radiation number looks way short for 3600 sq ft of above grade living space. The room count doesn't look right either...I would expect a living room ( 2 rads quite often) dining room, Kitchen, Foyer, 1st floor bath, maybe a study. On the second floor 3 to 5 bedrooms up, another bath or 2, and then the rads in the attic. Maybe a couple in the basement sometimes.

It works out like this:

First floor
Closed in front porch:
23ft of baseboard
2 in wall, convectors

Family Room - 1 Cast iron convector (not fin/tube)
Living Room - 2 fin/tube convectors
Dining room - 1 fin/tube convector
Kitchen - nada, they removed it when they redid the kitchen

Second Floor
Office - 2 radiators
MBR - 1 radiator under a window seat
BR2 - same as MBR
BR3 - 1 radiator (the slow heating one)
BR4 - 1 Fin/Tube convector
2 bathrooms with fin/tube, 1 that is like 55", and one that is 16"

Attic/Third floor:
3 radiators

1 additional radiator on a stairway landing that i missed during my measurements
1 additional tiny radiator in a water closet that I also missed

The two that i missed wouldn't add up to much.

It's a lot of heating units for sure. Maybe I didn't measure the fin/tube stuff right, but on the right side of that sheet is all the fin/tube measurements. Any radiator was measured accurately since they were all accessible. Convectors just had their length measured. The cast iron convector was a estimate, but I chose a high # for it.

2 forced air units are in the basement and run to the floors of the first floor. It's unheated, but the boiler keeps it toasty.

1 forced air unit is in the attic. They basically dropped the ceiling from 9' to 8' in the hallway and ran the vents there (poorly). They really just built a box and insulated it, no actual duct work at all.

I'm going to run the forced air for 2 days and compare how the gas meter moves. I took two readings today at 2:00 and 7:00. The movement on the meter matched my calculations, ie, the boiler ran for 1 total hour in that time, and the meter moved up by 5, so my 5ccf/boiler hour seems correct, leaving me with estimated 1060ccf used for this month.

I'm really just irritated by it all. My wife and I both like the steam/radiator heat, but I'm not willing to resign myself to paying that much yet. If the forced air turns out the same then I'll admit that it just costs this much.

bburd

Those cabinet convectors have much higher ratings than the equivalent length of baseboard. You need to get the covers off and take a look at the charts in the Burnham literature that was sent to you above.

Typically it’s not a good idea to mix cast-iron and fin tube radiation in the same heating zone. What usually happens is the rooms with cast-iron radiators will overheat, and the rooms with fin tube convectors or baseboards will underheat.

it sounds like your system was seriously knuckleheaded over the years. 

JPL941

underdog32

I'm close to wilkes-barre/scranton area.

I may have made this a ton better yesterday. I found a setting on the nest thermostat that was called "true radiant". Apparently what this does is start heating early because it knows that radiators take a long time to heat up, then it shuts off early knowing that they radiate and over heat. It is enabled by default when you pick radiators as your heating type.

I researched it a bit, and it sounds good in theory, but what it was doing is basically running my boiler for 20 minutes every hour because it thought it needed to be 68 in x minutes or whatever, then it didn't let the system heat fully. I turned it off to see what would happen.

So that graph I posted above was solid 20 minutes all day long. Today, it's 24 minutes every 2 hours throughout the night. Asof 8 this morning I used 1hr 55min of heat, compared to nearly 4 hours yesterday. I'm expecting the day to be much less than the night. I may get out of the day using 4-5 hours of heat vs the 7-8 I was using. At 5$ per hour of heat, that's a big savings. We'll see. I'm currently hopeful, and happy that all my fixes weren't for naught.

So I still believe my boiler is oversized, but the whole problem may be the "smart" thermostat on the wall. If i can get down to consistent 5-6 hundred dollar bills then I'll be happy.

Jamie Hall

"So I still believe my boiler is oversized, but the whole problem may be the "smart" thermostat on the wall. If i can get down to consistent 5-6 hundred dollar bills then I'll be happy."

Good call.

EBEBRATT-Ed

Make sure you get the trap fixed and fix any leaks. Cold make up water will kill that boiler not to mention the xtra BTUs needed to heat cold water versus hot condensate. Too much make up will rot the boiler and the piping

kenlmad

The original sum of the standing radiation is 443.1, not 348.6 as initially tabulated. There's a math error somewhere. Then the messages indicated 2 more radiators (water closet and stairway) were missed. Your EDR is off by at least 100.

underdog32

kenlmad said:

The original sum of the standing radiation is 443.1, not 348.6 as initially tabulated. There's a math error somewhere. Then the messages indicated 2 more radiators (water closet and stairway) were missed. Your EDR is off by at least 100.

Agree, it's not perfect. I doubled it and used 7-800 for my hypothetical boiler sizing. Using 800, my boiler is still 500 oversized.

deyrup

betweentheframe said:

it is wasting massive amounts of gas, as 2x btus are needed to heat twice as much water to boil, and you aint getting heat til its boiling

Maybe someone can correct me if I am wrong, but I thought most of the energy usage in steam heating came from converting boiling to steam and not converting water to boiling.

It takes 4.18 degree/joule x 77 degree change = 320 j to raise 1g of water from 23 to 100 C, compared to 2260 j to vaporize 1 g at 100 c; so the amount of water that needs to be heated shouldn't make that much of a difference.

Jamie Hall

Got it, @deyrup

underdog32

deyrup said:

betweentheframe said:

it is wasting massive amounts of gas, as 2x btus are needed to heat twice as much water to boil, and you aint getting heat til its boiling

Maybe someone can correct me if I am wrong, but I thought most of the energy usage in steam heating came from converting boiling to steam and not converting water to boiling.

It takes 4.18 degree/joule x 77 degree change = 320 j to raise 1g of water from 23 to 100 C, compared to 2260 j to vaporize 1 g at 100 c; so the amount of water that needs to be heated shouldn't make that much of a difference.

So, at 15 gallons of capacity to 10, the larger boiler is 50% less efficient because it has to heat 50% more fluid to boiling, and then to steam?