Two Pipe conversion

Tim_14

is a one pipe ( that was my mistake ) system.
The mains are 8in I used Dans book and I see lots of changes that have to be made.
By the way there was another company there when we where tracing things out and guess what they say its the boilers fault I didnt say anything.Some one put a condensate pump in and............ well exsactly like the book I need a carton full of traps, 2 transfer pumps, a boiler feed pump, lots of vents,and a smaller boiler.But should i still use the 1.6 pickup factor for one pipe.
They only need about 2,000 sq ft for the stores being used,
and they have a 5,000 sq ft in there now. what pick up factor sould i use to resize the boiler 1.6?

Tim_14

Two pipe conversion

I have a client who owns a 5 story building with a 2 pipe steam system.
He rents out 3 large units on the first floor.
The rest of the building is vacant and condemmed.

He would like to replace the old boiler that serves the entire building with a smaller one to serve the first floor stores only.

How do i size the new boiler ( by the way Dan reccomends in Lost Art)?

What else do I need to consider with this 2 pipe system.

Thank you for your input
TK

DanHolohan

Size it

based on the radiator that the new boiler will serve, along with a big pickup factor for the large mains that once served the entire building. I'd probably go with 1.6 and then pick the boiler from the Gross column.

Hard to say what else to look for since I'm not there but the book is a good guide.

Boilerpro

Hot water conversion ? NM

DanHolohan

I misunderstood

Sorry, and I'm glad you caught me! Do a heat loss calculation on the space. Figure out the output of the existing radiation in sq. ft. EDR. From there, you can calculate the required design temperature. The flow rate and pressure drop, which shouldn't be much, follow that and the piping will need a close look to see what stays and what goes, and whether it can hold the water pressure.

Boilerpro

Actually, Dan..

Even if it was steam, I still think he could size it to the heat loss, not radiation. All you would need to do is balance the radiation with the supply valves.... assuming they work. I beliee Noel's engineers would agree and so do my Hoffmann reps. I started working on a procedure for sizing steam boilers to heat load (or there about) for one pipe based on the concepts from the master venting technique and using adjustable air vents on the rads based on the heat load of the room and the air volume of the rad, not justthe size of the rad and its air volume. When doing a simple balancing of a system this is what I believe is usally done anyway. Adjust the vent until the room is in balance with the temperature of the rest of the home, even if the rad only heats half way when others are heating completely on that coldest day. Hope to get it to you someday soon, once the fall rush ends.

Boilerpro

DanHolohan

I'm not

following. The boiler's ability to produce steam has to match the system's ability to condense steam, regardless of the building's heat loss. You have to bring the metal from ambient temperature to 215 degrees. That's going to require a certain amount of BTUH.

Boilerpro

But does the boiler have to, or ever,see all the metal?

I'm sure you've seen that in most older systems on the coldest day of the year, the rads only heat part way. The radiation that boiler "sees" is only that which is getting hot, the cold sections just could be yanked and junked.... they are just sitting there taking up space. It's alot like the old vapor systems with orifice valves, the boiler only sees about 80% of the rad because the orifice only allows so much steam into the rad, so you size the boiler for only 80% of the radiation. With a standard two pipe system, you can throttle the steam flow, just like vapor orifice valves, effecively reducing the radiation load. If this throttled radiator output is all that is needed to heat the space on that coldest day, the rest of the radiator is not needed and for practical purposes doesn't exist, other than taking up space. The boiler never sees the additional sections of the radiator. On one pipe steam, the adjustable air vent becomes the throttling device... if air can't get out, steam can't get in. Again like a vapor system, in warm weather and lower pressures, only a certain amount of steam will enter the rad. On the coldest day, if the full output of the rad is not needed, the air vent will limit the amount of air vented and the amount of steam that can enter. If the boiler is sized closer to the heat load, instead of the radiation, it will fill all the rads in proportion to thier venting, which is adjusted to the heat loss of each space a radiator serves. At some point hen the boiler is runing at full output for a long time, the rads will no longer heat any further. the steam will be condensing as fast as it enters. There will be no air vented, since ther is no pressure in the radiator, only the steam lines, again like the orifice vapor systems. Its master venting with a slight variation, Vent the mains quickly and proportinally to thier volume and then vent the rads in proportion to thier rooms heat load, not thier size. Following me?

Boilerpro

DanHolohan

I understand

master venting but what of the oversized mains in this case? And this is two-pipe, yes?

Boilerpro

Mains

That's were the "about" comes in sizing the boiler. I was focusing on the size of the rads and whether you need a boiler to heat all that metal. The big question is what is the heat loss on the mains. If they can be measured, it can be calculated and added to the building heat loss,if they are not heating a space served by rads...similiar to hot water. If the loss of the mains is greater than the space they heat, I'd use the loss of the mains for boiler sizing. The oversized mains present a challenge, I suspect, but also some benefits. If they can be vented in a minute or less and the boiler has the capacity to heat them up that quickly, great. I would measure them and see how much heat it is going to take to get them up to temp. and see how long the boiler needs to fire to do this. What's an acceptable time? When they are already warm from a previous cycle, I expect that a minute or so is fine. For a cold startup out of setback, I'm sure much longer is fine since the system cycle is also proportionally much longer. They will allow very little pressure loss and,I suspect, make the system a vapor system, instead of a steam system. Helping out in favor of good operation, is that if the boiler is sized close to the heating load, it will have a much longer firing cycle (more like a coal fire?) so the main will almost never get very cold before the next steam cycle...less pick up load. A hotter main with good venting should give quicker steam distribution. I've toyed with an idea I saw in one of your books about a setup which only allows air to vent from the mains and once steam gets to the end then the vent for the rads opens. I expect it could be done with standard main vents with a zone valve on the outlet of the rad return vent and an aquastat mounted on the end of the steam main. Zone valve closed on boiler startup (rad return closed), steam main vent open, steam comes to end of main, aquastat senses increase in temp and opens rad return line vent and then rads all begin filling together. I've seen some "undersized" boilers working beautifully, heating evenly and efficienctly for decades in one pipe (with adjustable rad vents). Put in an "undersized" boiler in a Moline system...vapor only and is working very well with the system balanced with the rad valves.. Still haven't done a two pipe, but I expect it will be quite similiar to the Moline system. Working a bit at the edge on this, as you probably suspect, but I always like pushing beyond the norms if it can be backed up with sound logic.

Boilerpro

DanHolohan

It's fun

to think about steam in this way. Thanks. I did a piece on undersized boilers. It's here: http://www.heatinghelp.com/newsletter.cfm?Id=107

Not sure if you've seen it but let me know what you think. I'll be away for a couple of days on a seminar trip. Let's catch up on Thursday. Thanks for the stimulating conversation!

Boilerpro

Check another post too

I am bringing some of these points up in my post "Dan H. "undersizing" steam boilers". Looks like Dan H (the Proprietor of this establishment) hasn't been around yet today.

Boilerpro