First time sizing boiler options and EDR

ChrisJ

EBEBRATT-Ed said:

If you can heat the domestic with 8878 btu/hr and come out of night setback at the same time then go for it.

This is a family that likes playing with the thermostat. If you leave the thermostat alone you most likely could get away with 0% pick-up with no DHW load. I usually would ignore the DHW load (as long as it is a "normal" load) if the PU factor was in there.

IMHO coming out of set back with a dhw load ---some allowance needs to be made. Guy gets up, turns up the stat and jumps in the shower

Good point,
I forgot about the DHW!

Honestly, if it was me I'd just buy a tanked 240V electric heater. I hated running an oil burner all summer and it kept my basement hot.

I suppose it depends on what electric costs in your area but in NJ I couldn't justify it.

Fred

I guess I'll get on my soap box again We have this discussion so often. We know a boiler whose net Sq. Ft. of steam closely matches the total EDR in the structure and that has a standard 33% pick-up factor works well. I hate to see us try to help a Poster "right size" his boiler to that principal and then confuse them with a concept to significantly reduce or eliminate the Pick-up factor. This poster is considering over-sizing his potential new boiler out of concern the right sie won't be enough and these discussions can cause some posters to do things that very well may undersize their new install.
I'm going to repost my comments from another thread we had going a couple weeks ago. If there is a flaw in my logic, lets discuss it but let's try to ensure this poster is comfortable that he is getting the info necessary to make an informed (and good) decision for his situation. If he chooses to go into a replacement with a mindset to experiment, all well and good. If he wants a boiler that is sized to give him 15 to 20+ years of comfort, let's use real world facts and let him adjust those facts as he sees fit.

Fred said: (From a previous Post)
This topic probably will never be resolved to everyone's satisfaction and I think that is because every steam system has its own eccentricities. Is a 30% pick-up factor right for every house, maybe, maybe not.
In my case, I have about 100 ft of 2.5" and 3" Mains, about 200 ft. of radiator run-outs and 700 sq. ft. of EDR.
Here in Ohio, we probably have 2 months (January and February) where the outside temps are such that the boiler runs every hour and long enough to get my 15 radiators hot. The other months, October, November, a good portion of December, virtually all of March and April almost have to be treated like sholder months where the boiler runs but not regularly enough to keep the piping and those radiators hot enough (even though the Mains are insulated) to not require some pick-up factor.
I get it that the capacity of the boiler can be spent heating the Mains and run-outs first but we need to keep in mind that that infrastructure also has to maintain that heat throughout the heating cycle as well. you can't simply say "OK the piping is hot, I don't need to factor anything in for those components once they are hot." They still require energy to maintain temp. They have an equalivant EDR value.
If one were to calculate the EDR value of the Mains, piping and cycle heating requirements to heat/ or incrementally reheat everything for each house, just like we do for the Radiator EDR, on a case by case basis, some probably can get by with less pick-up.
I think the industry locked in on 30% because it was a reasonable average factor and the small deviations probably don't justify the additional time spent to do that survey on a case by case basis.
To answer the OP's original quetion, No you don't want to build in a Pick-up factor that increases pressure. That is called an over-sized boiler. The lower the pressure, the faster steam moves. Any boiler Steam rating over and above that which matches the EDR of the radiators and whatever it takes to support the infrastructure is overkill. Calculate the EDR rating of your pipes and see how far off the 30% is for your particular house/system.

ChrisJ

@Fred
That's fine, however, I disagree that a 33% pickup "works fine".

Honestly, by modern standards where many want to do nighttime setbacks I think it works like garbage. Building pressure to 1.5 - 2 PSI in the morning during a recovery CAN be avoided and SHOULD be avoided.

Being able to raise your temperature 5, even 10 degrees and never see 1 PSI is a great thing. Your vents stay silent and last much longer.

Honestly, I feel that is like saying we used to use a large pickup on hot water systems, so we still should. Hot water changed, now it's steams time.

The OP will make up his own mind, but I feel he should have all the facts before doing so and fact is, saying you need 33% extra to "heat piping" is wrong.


Steam CAN do setbacks and recoveries and it can do them efficiently. The only systems that can't are in my opinion, broken.

Now, hopefully, you won't take me off your Christmas list after this post.

nicholas bonham-carter

Let's not forget the placement of the thermostat in this discussion. If the thermostat (or its sensor), is placed in the room which gets steam first, due to unbalance, or lack of main venting, elsewhere; then the house will seem cold.
If the control is in the slowest radiator room, then the rest of the house will feel hot. The best location would be in the room which cools first, and with a lower setting. This may be the upper north bedroom, which has been the subject of complaints.--NBC

Fred

@Chrisj I didn't say 33% pick-up was (or is) right. I said that if a HO wanted to best determine the amount of Pick-up they need, calculate the steam required to support the infrastructure for their specific home/building by surveying the equalivant EDR of the Header, Mains, and Run-outs that do continue to require energy to maintain that path to the radiators throughout the entire heating cycle. In my opinion, there is some play in that pick-up factor for many structures and for some there is probably very little. Let's figure that out using something more scientific than to assume no one needs a pick up factor.

I also don't believe the vents are hurt in any way by an occassional pressure swing of of 1.5 or even 2PSI. It keeps the spiders out of the port holes My boiler has the pick-up factor and is over-sized and I keep the max pressure at no more than 12 ounces on those rare occassions it short cycles. Typically it runs at 1 to 2 ounces. A vapor stat is cheap compared to a poorly sized boiler.
As to setbacks, if you take the boiler capacity down enough that it takes as long to get the house back up to temp as it took for it to drop, I'm not sure what you have accomplished. The goal is to be comfortable. Do a setback if you want to do a set-back but don't try to design the boiler for a 10 degree setback to accommodate the few hours you are bundled up in blankets (and maybe under an electric blanket) and compromise the other 16 hours in the day.
Now, I'm Good, You're still on my Christmas Card list. As far as a present, Not so Much

Jamie Hall

ChrisJ said:

@Fred
That's fine, however, I disagree that a 33% pickup "works fine".

Honestly, by modern standards where many want to do nighttime setbacks I think it works like garbage. Building pressure to 1.5 - 2 PSI in the morning during a recovery CAN be avoided and SHOULD be avoided.

Being able to raise your temperature 5, even 10 degrees and never see 1 PSI is a great thing. Your vents stay silent and last much longer.

Honestly, I feel that is like saying we used to use a large pickup on hot water systems, so we still should. Hot water changed, now it's steams time.

The OP will make up his own mind, but I feel he should have all the facts before doing so and fact is, saying you need 33% extra to "heat piping" is wrong.


Steam CAN do setbacks and recoveries and it can do them efficiently. The only systems that can't are in my opinion, broken.

Now, hopefully, you won't take me off your Christmas list after this post.

No,I won't take you off my Christmas list. I will, however, reiterate what I said in another post -- "your mileage may vary". In some situations a boiler sized so that it's actual net heat output, allowing for the efficiency of the boiler, exactly matches the radiation installed may work, and work well. In others which are apparently very similar, it may not.

And you are quite right that steam can do setbacks and do them well; the system I care for uses a 66 day/63 night setback. It does the recovery without reaching the cutout pressure, which is 8 ounces -- in normal weather. In extreme conditions (by which I mean for here an indoor/outdoor delta T of 80 degrees F and a 20 mile per hour wind, which we have had several times this winter) it can still recover, but it will cycle a few times right at the end of the run (of about an hour).

Now I will admit that Charles Garrity and I have spent some time and thought on getting the nozzle size and pressures exactly right, and the combustion numbers spot on. Which makes a big difference.

But the real problem lies in treating an EDR some as some kind of magic exact value. It's not. There are too many variables involved -- condition of the surface of the radiation, space temperature which the radiation "sees", reflectivity/emissivity of nearby surfaces such as walls, etc. etc. In my perhaps not so humble opinion, I would regard any EDR value as being plus or minus at least 10 percent -- perhaps as much as 20 percent. Thus Fred's comment that the industry more or less standard idea of adding the 30% pickup factor is quite reasonable. In other fields of engineering it's called a safety factor! With a specific system in a specific application and a specific burner tuning, you may well be able to get away with an apparent nominal boiler output which exactly matches the apparent nominal radiation load. Honestly, I wouldn't care to design something that way, although bringing the tuning closer to that desired goal once it's up and running is certainly an interesting project.

ChrisJ

Jamie Hall said:

No,I won't take you off my Christmas list. I will, however, reiterate what I said in another post -- "your mileage may vary". In some situations a boiler sized so that it's actual net heat output, allowing for the efficiency of the boiler, exactly matches the radiation installed may work, and work well. In others which are apparently very similar, it may not.

And you are quite right that steam can do setbacks and do them well; the system I care for uses a 66 day/63 night setback. It does the recovery without reaching the cutout pressure, which is 8 ounces -- in normal weather. In extreme conditions (by which I mean for here an indoor/outdoor delta T of 80 degrees F and a 20 mile per hour wind, which we have had several times this winter) it can still recover, but it will cycle a few times right at the end of the run (of about an hour).

Now I will admit that Charles Garrity and I have spent some time and thought on getting the nozzle size and pressures exactly right, and the combustion numbers spot on. Which makes a big difference.

But the real problem lies in treating an EDR some as some kind of magic exact value. It's not. There are too many variables involved -- condition of the surface of the radiation, space temperature which the radiation "sees", reflectivity/emissivity of nearby surfaces such as walls, etc. etc. In my perhaps not so humble opinion, I would regard any EDR value as being plus or minus at least 10 percent -- perhaps as much as 20 percent. Thus Fred's comment that the industry more or less standard idea of adding the 30% pickup factor is quite reasonable. In other fields of engineering it's called a safety factor! With a specific system in a specific application and a specific burner tuning, you may well be able to get away with an apparent nominal boiler output which exactly matches the apparent nominal radiation load. Honestly, I wouldn't care to design something that way, although bringing the tuning closer to that desired goal once it's up and running is certainly an interesting project.

What "safety factor" is being used on modern hot water systems?
As far as I know 15% has been used for a long time, but many guys are doing 0%?

Since, for home heating systems it seems to be you can match your heatloss and ignore the radiation, at least according to Dave Brunnell who has far more experience at this than I do, I'd say you're dealing with the same thing as hot water when it comes to that "safety factor".

Many radiant systems cannot maintain temperature some days because they are sized for design day. What makes steam any different when venting is done correctly?


I will always push for slow, silent steam systems. I've seen a few that had oversized boilers and that was awful. Slow and steady wins the race when it comes to comfort and energy savings.

nicholas bonham-carter

This is why we need a modulating burner for the boiler, (or two assymetricly sized boilers), so that the pickup factor could be automatically dialed in!--NBC

ChrisJ

nicholas bonham-carter said:

This is why we need a modulating burner for the boiler, (or two assymetricly sized boilers), so that the pickup factor could be automatically dialed in!--NBC

I'd vote for that and a 3 pass boiler like the Megasteam.

I'd more than happily pay the extra cost.

vaporvac

That is truly the solution or at least a multi-staged burner. Since the power burners can be adjusted, I say go for the edr and down-fire if needed.

Fred

ChrisJ said:

nicholas bonham-carter said:

This is why we need a modulating burner for the boiler, (or two assymetricly sized boilers), so that the pickup factor could be automatically dialed in!--NBC

I'd vote for that and a 3 pass boiler like the Megasteam.

I'd more than happily pay the extra cost.

Why don't I just drive up to Jersey and take a sledge hammer to your boiler so you can justify a custom engineered system to your liking to the wife? And while we're at it with changable custom components that vary input and output as you deem appropriate, using telepathy. How bout that?

Jamie Hall

Best approach, in general, at least to my way of thinking: measure EDR (n my case, 1468). Pick boiler with slightly greater capacity (in my case, Weil-McClain 580, rated at 1608 sq.ft. at a nominal 4.5 gallons per hour fuel burn). Instal. Adjust nozzle flow rate and pressure to obtain good match of actual performance (better than advertised -- 85% vs. 80% efficiency) and system demand (which eventually turned out to be a 2.75 gph nozzle, but you'd have to ask Charles what pressure it's set at and the actual flow rate).

End result: virtually no cycling, silent very low pressure (less than 6 ounces) operation. What's not to like?

Don't over think it -- and leave yourself a margin if things don't turn out to be quite as optimum as you initially planned on...

Jack M

I think this point of discussion from Burnham is worth discussing. I found it digging around the forum. It's really throwing me for a loop:

"The MST288 and MST396 are for the most part the same boiler. The burner of the MST288 is down-fired using a 0.60 gph nozzle versus the 0.80 gph nozzle in the MST396. In order to do that a Low-Fire baffle is installed in the oil burner housing to choke down and redirect the air through the burner housing. The boiler can't be down-fired any more than it already is for risk of excessively low stack temperatures. You may have noticed that the MST288 operates without the flue baffles installed while the other sizes can use them. This is already as low as it can go. Hope this helps and thank you for your interest in the MegaSteam boiler.
...........
The MST-288 using a 0.60 gph nozzle with 150 psi pump pressure gives you the 0.75 firing rate but with a low fire baffle installed. The MST-396 uses a 0.85 gph nozzle at 150 psi to achieve a 1.05 gph firing rate.
Glenn Stanton
Manager of Technical Development
Burnham Hydronics
U.S. Boiler Co., Inc."

Really? these two are the same boilers? After all the effort to decide which is the best, it just comes down to a nozzle? I'm steaming. I though smaller of the two had one riser and the larger had 2.

Fred

Jack M said:

I think this point of discussion from Burnham is worth discussing. I found it digging around the forum. It's really throwing me for a loop:

"The MST288 and MST396 are for the most part the same boiler. The burner of the MST288 is down-fired using a 0.60 gph nozzle versus the 0.80 gph nozzle in the MST396. In order to do that a Low-Fire baffle is installed in the oil burner housing to choke down and redirect the air through the burner housing. The boiler can't be down-fired any more than it already is for risk of excessively low stack temperatures. You may have noticed that the MST288 operates without the flue baffles installed while the other sizes can use them. This is already as low as it can go. Hope this helps and thank you for your interest in the MegaSteam boiler.
Glenn Stanton
Manager of Technical Development
Burnham Hydronics
U.S. Boiler Co., Inc."

Really? these two are the same boilers? After all the effort to decide which is the best, it just comes down to a nozzle?

@Steamhead has a lot of experience with the Megasteam boilers. Let's see if we can get his take on this and his opinion/input.

EDIT: Nozzle and baffles.

Jack M

The two Megasteam boilers also share the same "near boiler" installation kit. This sounds like installing an oversize boiler and simply underfiring.

ChrisJ

All steam boilers share that piping.

However, I highly recommend you do a 3" or even 4" header. A 2" header is lame.

The larger the header, the drier the steam.

If you look at Gerry Gill's minitube system that he installed in his own home, you'll see he did a 4" header on the smallest Burnham IN series.

https://youtu.be/U_wLnyul-S0

I would've done a 4" but at the time I couldn't afford it. I was barely able to afford 3".

Also, do a 2" or larger equalizer as 1.5" barely cuts it. Don't do a 2" copper equalizer like I did because it costs way too much for no reason. I had bought the fittings and spent a lot of them, not realizing how much a length of 2" type L copper would cost. I'll never make that mistake again.

Jack M

I still can't find any significant difference between the
MST288 and MST396; other than baffles (not sure what those are) and a burner nozzle.
I've never priced out 4". Is it really more more expensive than 3"? I know we don't talk price here. Is there a place online to check the prices out?
On Gerry Gill's system, do the 3/8" mini tubes act as the condensate returns for the radiators as well as the steam feed?
If not how are the returns plumbed?
Burnham baffles:

ChrisJ

Jack M said:

I still can't find any significant difference between the
MST288 and MST396; other than baffles (not sure what those are) and a burner nozzle.
I've never priced out 4". Is it really more more expensive than 3"? I know we don't talk price here. Is there a place online to check the prices out?
On Gerry Gill's system, do the 3/8" mini tubes act as the condensate returns for the radiators as well as the steam feed?
If not how are the returns plumbed?

No, a minitube system is a two pipe system.

4" fittings are significantly more than 3" yes and 3" is a scary a lot more than 2". I think a lot has to do with how popular they are.

If I was you I'd forget about the MST396. Even if they are the same you simply don't need it. I think even with the disagreements here everyone agrees the MST288 is plenty for your application.

Jack M

ChrisJ said:

Jack M said:

I
If I was you I'd forget about the MST396. Even if they are the same you simply don't need it. I think even with the disagreements here everyone agrees the MST288 is plenty for your application.

No question, I agree (don't need a MST396). But the point goes to the issue of oversizing/undersizing. If the MST396 is the same boiler as the MST288 than an MST396 with a downrated nozzle is not oversized. It's as much right sized as the MST288. There no difference in the physical boiler's dimensions or the capacity to produce a volume of steam.

ChrisJ

We aren't allowed to discuss pricing, however I believe we are allowed to post links to stuff sold online.

2" Ward cast iron tee.
http://www.supplyhouse.com/Ward-FCITE2-2-Black-Cast-Iron-Steam-Tee-475000-p

3" Ward cast iron tee.
http://www.supplyhouse.com/Ward-FCITE3-3-Black-Cast-Iron-Steam-Tee-477000-p

4" Ward cast iron tee.
http://www.supplyhouse.com/Ward-FCITE4-4-Black-Cast-Iron-Steam-Tee-478000-p

Mark N

I really wonder if a larger header would make much of a difference on a MST288. If you use 2-2" risers the steam velocity is like 11 ft/sec, well below 15 ft/sec. At that velocity you aren't pulling any water out of the boiler with the steam. As long as the boiler has been skimmed and the water quality is good. The velocity will again increase in the header, but there is no water entrained with the steam. With the larger boilers and the correspondingly higher velocities of the steam, you would want to upsize the header.

ChrisJ

Mark N said:

I really wonder if a larger header would make much of a difference on a MST288. If you use 2-2" risers the steam velocity is like 11 ft/sec, well below 15 ft/sec. At that velocity you aren't pulling any water out of the boiler with the steam. As long as the boiler has been skimmed and the water quality is good. The velocity will again increase in the header, but there is no water entrained with the steam. With the larger boilers and the correspondingly higher velocities of the steam, you would want to upsize the header.

I don't know.
I'm assuming Gerry Gill and the other professionals have seen issues with a 2" on such boilers. Gerry used a 4" on his tiny boiler.

I haven't personally compared a 2" to a 3" or 4" on my own boiler. I would assume even if it does work fine during perfect conditions that it can help with less than perfect water quality as you said.

For now, I'm sticking with 3" with a 2" equalizer as a minimum.

Mark N

Burnham claims 99% dry steam with the Megasteam in their literature. Not much room for improvement there.

RJMCTAFO

On a 288 I use the 2 inch kit with no changes unless the HO wants to upgrade to 3 inch. Everything gets a drop header. Anything else gets 3 inch header. Only installed 1 513. All the houses around here typically fall into the 288 or Inbetween sizes. I try to match by changing the firing rate. Have installed multiple units of both size. They are the same boiler with different firing rates. It is a very common practice across the trade in all boilers including water boilers.

A 288 with a 3" drop header and proper venting on a system is a beautiful thing. Silent efficient steam heat.

Mark N

Gerry did his oversized header on an Independence, a completely different design than a Megasteam

Jamie Hall

I assure you that the initial oversize was quite deliberate, and based on two things: first, we knew we could down fire the Weil-Mclain without any problems at all, and with a slight gain in efficiency. Second, as I said in the earlier post, I do not regard EDR numbers to be completely reliable, and there was simply no way I could have lived with a boiler which was even marginally too small -- and you can't safely up fire a boiler beyond it's rated load.

ChrisJ

Jamie Hall said:

I assure you that the initial oversize was quite deliberate, and based on two things: first, we knew we could down fire the Weil-Mclain without any problems at all, and with a slight gain in efficiency. Second, as I said in the earlier post, I do not regard EDR numbers to be completely reliable, and there was simply no way I could have lived with a boiler which was even marginally too small -- and you can't safely up fire a boiler beyond it's rated load.

I feel the EDR numbers are close enough. Keep in mind though, the colder the room, the higher the BTU/H those radiators will eat. But that doesn't matter because when a system is balanced, it stays balanced.

My favorite part of all this is first we tell people to oversize by 33% for a "pickup factor" and then we tell people not to do a "pickup' with steam because most systems build pressure that eats any fuel savings we had to begin with.

Fred

My favorite part of all this is first we tell people to oversize by 33% for a "pickup factor" and then we tell people not to do a "pickup' with steam because most systems build pressure that eats any fuel savings we had to begin with.
Not too many of us are saying "don't do a pick-up factor" I think most are saying 33% might be too much for some installations but some pick-up is needed, unless the boiler Sq.Ft of steam rating is a few Sq. ft. more than the Radiator EDR. That surplus also becomes added Pick-up.
Having said that, for this HO, it sounds like, while we believe and know the MST288 is plenty, he can buy the MST396 and not use the baffles and use a smaller nozzle and have a MST288 with the comfort of knowing he has everything he needs to upgrade if necessary (which isn't going to be required but, if the costs are relatively close, peace of mind is worth something)
On the other hand, he could also buy an MST288, knowing he can order the baffles and a larger nozzzle if, by chance the 288 doesn't do the job.
I don't see where he can go wrong either way. Now if Burnham ever certifies the Megasteam for gas and the user wants to convert, he will have to make a decision on which size he wants but by then, he'll have experience with his new boiler performance.

Jack M

RJMCTAFO said:

Have installed multiple units of both size. They are the same boiler with different firing rates. It is a very common practice across the trade in all boilers including water boilers.



A 288 with a 3" drop header and proper venting on a system is a beautiful thing. Silent efficient steam heat.

Ok, now I get it. Thanks for setting me straight. I did not know this was an industry practice. So does this mean without the baffles the 288 is not a triple pass? The MST288 is really double pass (not that I know 100% how the combustion gases are channeled in the boiler)? If that is the case (not triple pass), it was not apparent to me when reading the marketing literature.

ChrisJ

Fred said:

My favorite part of all this is first we tell people to oversize by 33% for a "pickup factor" and then we tell people not to do a "pickup' with steam because most systems build pressure that eats any fuel savings we had to begin with.
Not too many of us are saying "don't do a pick-up factor" I think most are saying 33% might be too much for some installations but some pick-up is needed, unless the boiler Sq.Ft of steam rating is a few Sq. ft. more than the Radiator EDR. That surplus also becomes added Pick-up.
Having said that, for this HO, it sounds like, while we believe and know the MST288 is plenty, he can buy the MST396 and not use the baffles and use a smaller nozzle and have a MST288 with the comfort of knowing he has everything he needs to upgrade if necessary (which isn't going to be required but, if the costs are relatively close, peace of mind is worth something)
On the other hand, he could also buy an MST288, knowing he can order the baffles and a larger nozzzle if, by chance the 288 doesn't do the job.
I don't see where he can go wrong either way. Now if Burnham ever certifies the Megasteam for gas and the user wants to convert, he will have to make a decision on which size he wants but by then, he'll have experience with his new boiler performance.

You missed the point.
Most tell people not to do a "pickup" meaning, don't do setbacks and recoveries. That's the entire reason for the so called "pickup factor".

Large buildings like schools benefit from it.

Jack M

"Large buildings like schools benefit from it."
I had a church where we did this. Turned everything down low just low enough to keep the basement bathrooms from freezing, then fire the steam boiler up for service on Sunday. Didn't aways work as planned. We would sometimes get complaints.

Fred

You missed the point.
Most tell people not to do a "pickup" meaning, don't do setbacks and recoveries. That's the entire reason for the so called "pickup factor".

Large buildings like schools benefit from it.
Maybe I am missing the point??? Most tell people not to do a Pick-up factor because the manufacturer has already built one into the boiler, that being 33% and it's not for set-backs and recoveries, it's for maintaining the temps of the Header, Mains and run-outs to the radiators which are not included when one calculates his/her radiator EDR.

ChrisJ

Fred said:

You missed the point.
Most tell people not to do a "pickup" meaning, don't do setbacks and recoveries. That's the entire reason for the so called "pickup factor".

Large buildings like schools benefit from it.
Maybe I am missing the point??? Most tell people not to do a Pick-up factor because the manufacturer has already built one into the boiler, that being 33% and it's not for set-backs and recoveries, it's for maintaining the temps of the Header, Mains and run-outs to the radiators which are not included when one calculates his/her radiator EDR.

@Fred
This is incorrect.
The complete title is "Piping and Pickup factor". The first part is for piping losses, the second is for pickup aka a recovery.

This is the article Gerry Gill posted for me a while back that got me started on the whole subject.

https://www.ideals.illinois.edu/bitstream/handle/2142/4349/engineeringexperv00000i00455.pdf

I bet this will get me back on the presents list!

Fred

Not quite yet. From what I read, any pick up factor of less than 10% was not sufficient to support the system as tested and a 30% pick-up was sufficient to not only handle the piping but to also get heat in the test building in a reasonable time as well as handle a night time set back of 6 degrees.
I'm OK with that, understanding that those conclusions are for a specific house, where three different burner rates were used to get three different pick-up factors, in the same house.
That house is not representative of the world, in terms of the amount and size of piping, the amount of radiation in the house, etc.
I don't know what that study proves other than you can change the affects of the heating system in a home by altering the burner rates. Something we already knew.

ChrisJ

Fred said:

Not quite yet. From what I read, any pick up factor of less than 10% was not sufficient to support the system as tested and a 30% pick-up was sufficient to not only handle the piping but to also get heat in the test building in a reasonable time as well as handle a night time set back of 6 degrees.
I'm OK with that, understanding that those conclusions are for a specific house, where three different burner rates were used to get three different pick-up factors, in the same house.
That house is not representative of the world, in terms of the amount and size of piping, the amount of radiation in the house, etc.
I don't know what that study proves other than you can change the affects of the heating system in a home by altering the burner rates. Something we already knew.

So after reading that study, realizing the piping factor is separate from the pickup factor, and reading Dave Brunnell's report saying we should go by heatloss not radiation, you still aren't going to change eh?

I give up.

I can only hope the stuff I have posted helps the OP in making his decision.

Fred

Stubborn is as Stubborn does, LOL

EDIT: My other concern about Brunnell's use of Heatloss rather than radiation, Somewhere, the boiler still has to be sized up to but not over the max capacity of the radiation. I'll agree it can be sized less than max capacity of radiation if someone comes up with a much easier way to control where the steam goes and still can get and maintain an even distribution. Something that is hard to do with just vents.

ChrisJ

Fred said:

Stubborn is as Stubborn does, LOL

EDIT: My other concern about Brunnell's use of Heatloss rather than radiation, Somewhere, the boiler still has to be sized up to but not over the max capacity of the radiation. I'll agree it can be sized less than max capacity of radiation if someone comes up with a much easier way to control where the steam goes and still can get and maintain an even distribution. Something that is hard to do with just vents.

Your loss,
In my house we give away G2's as presents.

Fred

Your loss,
In my house we give away G2's as presents.
LOL

Jack M

After learning here that the MST396 and the MST288 are the same exact boiler with a different nozzle (and pile of optional drop in sheet metal baffles), and use the same above boiler piping, I have far less anxiety about this. The boiler manufactures have insulated me from making a bad decision. If I install the MST288 (right EDR) and find that it is undersized, I just increase the nozzle gph. It I install the MST396 (obviously too large) and regret the decision, I just downfire it to .75 gph (an pull out the optional baffles). You can't loose either way. Or at least I won't be ripping out a boiler (or trying to remove a section). Just fine tuning things. I thought each boiler model produced a different output because of larger heat exchangers. I've learned that is not the case.

Jamie Hall

Chris, while I admire your persistence, one must admit that it borders on stubbornness and an unwillingness to see that things in other places, under other circumstances, might possibly be different.

To be blunt, it's also poor engineering. When one is dealing with systems with relatively poorly defined parameters -- and a heating system in a previously uninstrumented building surely has poorly defined parameters if anything does -- it is only prudent, if one is the engineer or the contractor, to work in a safety factor. If one doesn't care to call it a pickup factor -- which, I will admit, is a rather poor term but one we have to live with -- that's OK. But a safety factor? Yes. Are the parameters well enough defined in a specific situation to get away with 10%? Then do that. 30%? Then do that. 0%? Not on my license. If I come out of the job with 99% of the capacity I need for the system, I wind up picking up the tab to redo it to 100%, and I don't have that kind of money. If I wind up at 110%... everyone's happy -- particularly if I was smart enough to pick a boiler which could be dialed back a bit.

Your mileage may differ.