Single Pipe Steam Boiler Undersized?

DetroitSteamer

Just moved into a new (well to us, house was built in 1910) that has single pipe steam. Boiler was replaced 4 years ago by previous owner. The radiators in the house are MASSIVE in size...some of the biggest I've seen, especially for a modest 2,400 sq ft house. Our previous house was a 2-pipe system with radiators that are tiny by comparison, at least visually.

When we first moved in, the upstairs would be sweltering while the downstairs (where the thermostat is) would be cooler, and take longer to warm up. Checked the main vents, and both were ancient, one was clogged almost entirely (the one on the main servicing the first floor, go figure). I replaced the vents with big mouths, now all the radiators start to warm up at the same time...for the most part (upstairs still seems to get hotter faster just slightly). The pressure gauge on the boiler read 0, assuming I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly). Eventually, the thermostat kicks off before the radiators are fully hot.

I know Dan says that heating was sized to be comfortable on the coldest day of the year, and since in Michigan we haven't hit the coldest day of the year yet (but soon), is it possible that the system is behaving as designed considering the size of the radiators? It seems to me the radiators should heat up faster than they are, so I'm wondering if the replacement boiler is potentially undersized? Any way to figure out if it's performing as intended?

ChrisJ

DetroitSteamer said:

Just moved into a new (well to us, house was built in 1910) that has single pipe steam. Boiler was replaced 4 years ago by previous owner. The radiators in the house are MASSIVE in size...some of the biggest I've seen, especially for a modest 2,400 sq ft house. Our previous house was a 2-pipe system with radiators that are tiny by comparison, at least visually.

When we first moved in, the upstairs would be sweltering while the downstairs (where the thermostat is) would be cooler, and take longer to warm up. Checked the main vents, and both were ancient, one was clogged almost entirely (the one on the main servicing the first floor, go figure). I replaced the vents with big mouths, now all the radiators start to warm up at the same time...for the most part (upstairs still seems to get hotter faster just slightly). The pressure gauge on the boiler read 0, assuming I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly). Eventually, the thermostat kicks off before the radiators are fully hot.

I know Dan says that heating was sized to be comfortable on the coldest day of the year, and since in Michigan we haven't hit the coldest day of the year yet (but soon), is it possible that the system is behaving as designed considering the size of the radiators? It seems to me the radiators should heat up faster than they are, so I'm wondering if the replacement boiler is potentially undersized? Any way to figure out if it's performing as intended?

Slower is always better when it comes to changes in room temperature. This is why radiant heat is so nice, it's slow and not noticeable. Vs forced air that's almost instant.

Forget how much of the radiators heat. How is the house? Are the rooms comfortable even when it's extremely cold outside?

If the house is balanced and things work well, that's what I would call a perfectly tuned system. How is the piping around the boiler? Did they do a good job?

DetroitSteamer

ChrisJ said:

DetroitSteamer said:

Just moved into a new (well to us, house was built in 1910) that has single pipe steam. Boiler was replaced 4 years ago by previous owner. The radiators in the house are MASSIVE in size...some of the biggest I've seen, especially for a modest 2,400 sq ft house. Our previous house was a 2-pipe system with radiators that are tiny by comparison, at least visually.

When we first moved in, the upstairs would be sweltering while the downstairs (where the thermostat is) would be cooler, and take longer to warm up. Checked the main vents, and both were ancient, one was clogged almost entirely (the one on the main servicing the first floor, go figure). I replaced the vents with big mouths, now all the radiators start to warm up at the same time...for the most part (upstairs still seems to get hotter faster just slightly). The pressure gauge on the boiler read 0, assuming I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly). Eventually, the thermostat kicks off before the radiators are fully hot.

I know Dan says that heating was sized to be comfortable on the coldest day of the year, and since in Michigan we haven't hit the coldest day of the year yet (but soon), is it possible that the system is behaving as designed considering the size of the radiators? It seems to me the radiators should heat up faster than they are, so I'm wondering if the replacement boiler is potentially undersized? Any way to figure out if it's performing as intended?

Slower is always better when it comes to changes in room temperature. This is why radiant heat is so nice, it's slow and not noticeable. Vs forced air that's almost instant.

Forget how much of the radiators heat. How is the house? Are the rooms comfortable even when it's extremely cold outside?

If the house is balanced and things work well, that's what I would call a perfectly tuned system. How is the piping around the boiler? Did they do a good job?

The house once up to temp is comfortable. With the first and 2nd floor more balanced, it works well. The thing is, it seems to take a long time to increase temp. Need a few month's worth of gas bills to see the efficiency, but I'm worried that the boiler is running too long (burning too much fuel) to get the house warm. Could be just how it is...

Piping around the boiler looks great. Followed the installation manual to a t. Nothing about the piping seems off.

ChrisJ

> @DetroitSteamer said:
> Just moved into a new (well to us, house was built in 1910) that has single pipe steam. Boiler was replaced 4 years ago by previous owner. The radiators in the house are MASSIVE in size...some of the biggest I've seen, especially for a modest 2,400 sq ft house. Our previous house was a 2-pipe system with radiators that are tiny by comparison, at least visually.
>
> When we first moved in, the upstairs would be sweltering while the downstairs (where the thermostat is) would be cooler, and take longer to warm up. Checked the main vents, and both were ancient, one was clogged almost entirely (the one on the main servicing the first floor, go figure). I replaced the vents with big mouths, now all the radiators start to warm up at the same time...for the most part (upstairs still seems to get hotter faster just slightly). The pressure gauge on the boiler read 0, assuming I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.
>
> However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly). Eventually, the thermostat kicks off before the radiators are fully hot.
>
> I know Dan says that heating was sized to be comfortable on the coldest day of the year, and since in Michigan we haven't hit the coldest day of the year yet (but soon), is it possible that the system is behaving as designed considering the size of the radiators? It seems to me the radiators should heat up faster than they are, so I'm wondering if the replacement boiler is potentially undersized? Any way to figure out if it's performing as intended?
>
>
>
> Slower is always better when it comes to changes in room temperature. This is why radiant heat is so nice, it's slow and not noticeable. Vs forced air that's almost instant.
>
> Forget how much of the radiators heat. How is the house? Are the rooms comfortable even when it's extremely cold outside?
>
> If the house is balanced and things work well, that's what I would call a perfectly tuned system. How is the piping around the boiler? Did they do a good job?
>
> The house once up to temp is comfortable. With the first and 2nd floor more balanced, it works well. The thing is, it seems to take a long time to increase temp. Need a few month's worth of gas bills to see the efficiency, but I'm worried that the boiler is running too long (burning too much fuel) to get the house warm. Could be just how it is...
>
> Piping around the boiler looks great. Followed the installation manual to a t. Nothing about the piping seems off.

If the piping is insulated and the house maintaines temperature well a bigger boiler would run less, but use the same amount of fuel because it would burn more when it's on just for less time.

EBEBRATT-Ed

I would have a combustion efficiency test of the boiler done. Also, check the firing rate if oil check the nozzle size and oil pressure. If gas check the gas pressure and orfice size.

shouldn't be running that long during mild weather.

I would check the edr of the installed radiators against the boiler nameplate.

How is the boiler water line? Steady or bouncing?? Boiler may need skimming and boiling out.

Fred

^ What @EBEBRATT-Ed said.

ChrisJ

@Fred and @EBEBRATT-Ed shouldn't be running how long on a mild day? I don't see any mention of typical run times?

Fred

@ChrisJ , OP says:
I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly).

KC_Jones

@DetroitSteamer how much setback are you using?

ChrisJ

> @Fred said:
> @ChrisJ , OP says:
> I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.
>
> However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight.

I may be misinterpreting it, but I assumed this was just an example and not the norm.

Fred

ChrisJ said:

> @Fred said:

> @ChrisJ , OP says:

> I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

>

> However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight.



I may be misinterpreting it, but I assumed this was just an example and not the norm.

The other strange thing he said is he can take a vent completely off of a radiator and there is no change.

DetroitSteamer

KC_Jones said:

@DetroitSteamer how much setback are you using?

5 degrees. From 67 to 62.

So this last night was a great example. This was our first night below freezing in Michigan. I have the thermostat set to drop down to 62 during the night, and then 67 at 6am. I have the day off today, and woke up at 8, and the temp was indicated 65 on the thermostat. 3 degrees in 2 hours. All of the radiators were about half warm. By 9am, the boiler finally kicked off at 67 degrees. So three hours to increase 5 degrees. I checked, boiler still running at 0 pressure, none of the radiators were hot all the way across after 3 hours.

DetroitSteamer

Fred said:

ChrisJ said:

> @Fred said:

> @ChrisJ , OP says:

> I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.

>

> However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight.



I may be misinterpreting it, but I assumed this was just an example and not the norm.

The other strange thing he said is he can take a vent completely off of a radiator and there is no change.

Correct. My first thought was the vents were bad. So to test, I pulled one off one of the radiators during heating. No change in heating at all. I did it on a few, running wide open there's no change. Seems to me that there's something up with the boiler. I have been skimming to get the rust out (not much dirty water comes out by now), and the water level while the boiler is running is "stable" in that it moves up and down cyclically during steam production just like the boiler at my last house did. Nothing erratic.

DetroitSteamer

It's also worth noting that the system is SILENT. No water hammer, banging, or noise from any vents, so there's no indication that there's water in the mains or anything.

Gsmith

it might be time to compare the boiler heat generation capacity (EDR rating) against the combined EDR rating of the installed radiators. Those numbers may help with the diagnosis. Boiler EDR is on the nameplate. Radiator EDR needs you to go around and measure each radiator and use the radiator chart found elsewhere on this site. If I can find it I'll post a link.

DetroitSteamer

> @Gary Smith said:
> it might be time to compare the boiler heat generation capacity (EDR rating) against the combined EDR rating of the installed radiators. Those numbers may help with the diagnosis. Boiler EDR is on the nameplate. Radiator EDR needs you to go around and measure each radiator and use the radiator chart found elsewhere on this site. If I can find it I'll post a link.

Thanks Gary! Very good point.

Gsmith

The book available from the store on this site has ratings for almost all radiators, also the Lost Art of Steam Heating has a lot of ratings if you already have that one.

ChrisJ

So,

You said the system is balanced and has no problem maintaining temperature when it's extremely cold out, correct?

It's also doing a 5 degree recovery and only taking 3 hours.

Most on here will tell you to never ever do a setback with steam because the boiler is oversized and will build pressure because the radiators cannot keep up with the steam supply. Yours isn't. That's a good thing.

If the system can maintain temperature even when it's below design temp for your area, and it can even manage recoveries when it's mild out. I don't see why you need to look at anything. The radiation is most likely way oversized for the space and there's no point in filling it.

When it was cold out, about as cold as it gets in your area, was the boiler running non-stop?

Your system is already doing better than most if it does what I said above.

My own system behaves very much like yours and it wasn't accidental.

KC_Jones

5 degrees is a lot of setback and doing it in 3 hours does not seem unreasonable to me.

I really feel like this standard of fill the radiators all the way isn't valid in your situation. If the system is working, heating the house, able to come back from a 5 degree setback, I honestly see zero issues here.

Do the EDR calcs if you want, but I wouldn't do anything with it, even if the boiler is to be replaced.

DetroitSteamer

Perfect, really appreciate the feedback guys. My biggest question was if it was normal or not because my old 2 pipe system heated the radiators all the way and heated fast. I'm dealing with a bit of a learning curve at the new house.

My last system didn't have a programmable thermostat so I never did a setback. It would make sense to nuke the programming and just keep it at a set temp. I'll give that a try and see how it does.

Fred

As others have said, a 5 degree recovery in 3 hours is pretty good and the real measure is if it maintains the set temp of the thermostat, not if the radiators heat all the way across. I'm still a little puzzled that taking a vent completely off of a radiator doesn't cause that radiator to heat all the way across.

PMJ

The missing data here is performance at more like -20F which the OP doesn't have yet since he just moved in. If the recovery time he quoted had been at those conditions there is clearly no problem at all. The real question is how would that recovery look during twice the demand from outside? Seems iffy to me but then I like extra.

If this is a gas system I would clock the meter while running to make sure you are close to the input on the plate of the boiler. If you are burning at about the rate on the plate then that is all you have and I guess you are just waiting for colder weather to see how she goes. Hopefully there is enough!

ChrisJ

Fred said:

As others have said, a 5 degree recovery in 3 hours is pretty good and the real measure is if it maintains the set temp of the thermostat, not if the radiators heat all the way across. I'm still a little puzzled that taking a vent completely off of a radiator doesn't cause that radiator to heat all the way across.

Since all of the radiators are condensing as much steam as the boiler is creating, taking a vent off will do absolutely nothing. It has nothing extra to give. I can do the same on my system.

PMJ said:

The missing data here is performance at more like -20F which the OP doesn't have yet since he just moved in. If the recovery time he quoted had been at those conditions there is clearly no problem at all. The real question is how would that recovery look during twice the demand from outside? Seems iffy to me but then I like extra.

If this is a gas system I would clock the meter while running to make sure you are close to the input on the plate of the boiler. If you are burning at about the rate on the plate then that is all you have and I guess you are just waiting for colder weather to see how she goes. Hopefully there is enough!

You're not supposed to do setbacks during extreme conditions. Also, is -20F the design temp of their area? I don't know what it is.

PMJ

It's Michigan so design temp is something like that. I'm in Cleveland farther south and have hit that more than once. If it's northern Michigan it is lower than that.

Also @ChrisJ , there are those unwanted setbacks that are known to occur and generally in the worst of conditions. I would want to know that I can actually recover from those.

EBEBRATT-Ed

If it is struggling at 32 degrees it's not going to heat the house at 0. Don't know what your outdoor design temp is but this sounds slow to respond to me.

Again, are you tripping off on low water cutoff or pressure control or is the burner really running non stop. Is the boiler water line steady or bouncing/surging??

First thing I would check if the water line is steady is the stack temp. The heat is going somewhere. Boiler could be underfired. What kind of boiler and burner > Post some pictures

gfrbrookline

I agree with all that have said the setback to way to high but if the radiator's aren't filling, what vents do you have on them?

I am guessing you have a few radiators that are way over vented and are stealing all of the steam. You want to vent all of the radiators slowly but balanced.

Also make sure that you do not have any pipes that are pitched the wrong way so steam is not going into them.

Fred

@ChrisJ , I understand the boiler has "Nothing extra to give" I wasn't suggesting "Extra" but I think we all know that steam will favor a path with lesser resistance and will take away from a smaller vented radiator to give to a larger vented radiator, especially one that has a full 1/8th inch hole in it because the vent was taken off.

gfrbrookline

Do you have any varivents on your system?

ChrisJ

> @Fred said:
> @ChrisJ , I understand the boiler has "Nothing extra to give" I wasn't suggesting "Extra" but I think we all know that steam will favor a path with lesser resistance and will take away from a smaller vented radiator to give to a larger vented radiator, especially one that has a full 1/8th inch hole in it because the vent was taken off.

The path of least resistance is the steam condensing in the radiators under those conditions. There's going to be a slight vacuum in the radiators vs atmosphere so theres nothing to vent out

Fred

Come on @Chris , There is no vacuum in any of the radiators because none of them have heated all the way across, which means none of the vents have even closed. They whole purpose of using different size vents on radiators is to control the speed at which steam enters each of them. The largest vent (in this case the radiator with a 1/8th inch open hole) should fill with steam, possibly robbing others.

ChrisJ

> @Fred said:
> Come on @Chris , There is no vacuum in any of the radiators because none of them have heated all the way across, which means none of the vents have even closed. They whole purpose of using different size vents on radiators is to control the speed at which steam enters each of them. The largest vent (in this case the radiator with a 1/8th inch open hole) should fill with steam, possibly robbing others.

Sigh....

EBEBRATT-Ed

First things first. Does the boiler match the EDR and is the boiler producing its max output and is a pressure control, LWCO thermostat etc interrupting the firing when it shouldn't be.

Hasn't anyone ever seen a thermostat anticipator set wrong and cycling a boiler like crazy burning a ton of fuel with no real output?? Or a boiler that needs skimming bouncing on LWCO. Leaking underground return and water feeder keeping the boiler on etc etcetc

Not enough info to make a judgement

BobC

I agree with @EBEBRATT-Ed above; know what your radiator EDR is and Make sure the boiler is consuming the right amount of gas per it's nameplate.

Can you feel along the mains and see how long it's taking steam to progress down the mains?

Bob

neilc

Are the pipes in the basement insulated?

mikeg2015

For point of reference, my boiler is too big by almost 50% and still takes almost 1 hour from a cold start to heat all the way across. I wouldn’t use that as a measure of performance. It can take 20 minute just to heat the header before laterals even get hot.

My recommendation, increase main venting and reduce the rate of radiator venting. The system was likely a vapor vacuum system originally and radiation was oversized to handle a coal boiler with a 50% swing of firing rate from initial high fire to low fire as temps dropped and it went into vacuum. Vacuum systems are partially self balancing so you oversized radiators a little and colder rooms would get more heat passively, hotter rooms, the radiator capacity was a lot lower. Once under a vacuum, the vents become non functioning and the system operates more like a heat pump and the system simply follows the pressure temperature curve and steam is essentially drawn towards the coolest surfaces.

Its less important that the radiators heat across as it is that the system is balanced. You likely have 2-3x the radiation you actually need at 212F steam temp.

On a couple colder day around a 35F average when the system is running at a constant rate. Read the gas meter. Factor in the 80% boiler effeciency, then double the gas usage. This is the approx. heat loss of your house at a design temp of about 0-10F at a steady state. It’s probably about 1/2 the size of your boiler or less. Probably around 70-90k BTU for a house your size.

Most homes have massively oversized furnaces and boilers. Look at home heated with heat pumps and how little heat strips they actually use vs. the comparatively small output of the heat pump in cold weather. Then look at the furnace size for the same home in the same climate.

IN my house 4 tons of heat pump capacity keeps up down to about 35F. Therefore 96k BTU would keep up at 0F depending on the wind and stack effect. My boiler is 300k BTU output! Radiaton is around 175k BTU.

mikeg2015

I’ll drop down to 200k BUT input when I replace it and add thermostatic vents on several radiators downstairs, especially those in common areas and the kitchen and overall reduce venting rate.

DetroitSteamer

To update, I got rid of any setbacks, and have been running at a steady temp for a week or so now. It's been well below freezing a few times outside, and the house seems to be pretty well balanced throughout the day, though if the boiler runs longer, the upstairs will get hotter than the downstairs a bit. Seems like there might be an opportunity to run smaller vents on the upstairs radiators, and the largest I can find on the downstairs big ones.

BTW, all the mains in the basement are insulated.

gfrbrookline

You need to insulate your mains with 1.5 inch insulation, take care of that before changing the vents.

ChrisJ

> @gfrbrookline said:
> You need to insulate your mains with 1.5 inch insulation, take care of that before changing the vents.

Most of us recommend 1".

gfrbrookline

yes you are correct with 1", my bad.

ImYoungxD

His mains are insulated. He has BM mains installed. It's a matter of switching his rad vents around now to balance the heat.
Fixing the setback is good. Heat rises so 1st floor gets usually cooler than 2nd floor (if your stairway is open). Cold air flows downwards to the 1st floor. I closed off the stairway with curtains so heat on the 1st floor stays.

Here is a venting map with recommendations
http://www.maid-o-mist.com/jacobus.html

Large vents for radiators far away from the boiler
Small vents for radiator close to the boiler.

I used small vents for all my rads and seems to do well since my 2nd floor is always warmer than 1st.

Large vents that are close to the boilers can cause problems. Steam may hit the rad too fast and block the vent before fully heating the rad up. I suggest you play with it and see if it works well.