Bringing a 2-pipe pumped-return steam heating system back in service

mattmia2

Can you work a piece of wire through the cock for the gauge glass and clear it out that way? Maybe remove the packing nut and unscrew the stem and clean it out that way.

Jamie Hall

The steam header has a condensate drain back to the condensate receiver? Ah... no. That cannot be. If it is set up that way, the condensate receiver can't be vented to the atmosphere and will be under steam pressure. Please clarify...

JUGHNE

Jamie, it looks like the drop header is almost at the water line and the traditional equalizer would have connected quite low allowing the water and steam to meet there. The pump would have maybe thrown water up into the header.

So the steam pressure equalizer was taken off the top of the header and piped down to the return above the HL/pump connection.

Then in order to drip the header there is a F&T trap going to the cond pump.
This would have kept the steam out of the pump....if working.

Is there any advantage to dropping the header that low other than possibly easier connections to the steam mains?

PEvans, there looks to be 6 drops coming into the condensate manifold, where do they all come from?
Again back up for pictures to show all the boiler piping, minus cobwebs.

Can you follow the steam mains around the basement? And show us what the ends of them look like.

Are the steam mains at the boiler the highest point of the main or the lowest point...or does it change somewhere in the basement. That is running up hill and than change to go downhill.

If the lower sight glass connection is plugged than also the 47-2 LWCO connection is plugged.....not good.

IIWM, I would remove the 47-2 at the union nuts that are in the way, then the sight glass fittings. Insure that the tapping (both parts of the wye) going into the boiler is brushed open all the way into the boiler.

Consider on opening up the 47-2 for cleaning or replacing.

For the sight glass connections, you can get brass nipples, tees and plugs.
Remount the sight glass off to the side to the right. Use the branch of the tee for the sight glass and you will have a clean out plug to brush straight into the boiler.

Also is a good time to replace all the valves for the water feed. Those may not shut off completely allowing the boiler to overfill. This may be why the water line was disconnected previously.

PEvans

mattmia2 said:

Can you work a piece of wire through the cock for the gauge glass and clear it out that way? Maybe remove the packing nut and unscrew the stem and clean it out that way.

I tried to work a wire and a pipe cleaner through, no luck. I also tried to remove the water cock valve stem and the handle started to fall apart. I ordered new gauge glass parts.

PEvans

Jamie Hall said:

The steam header has a condensate drain back to the condensate receiver? Ah... no. That cannot be. If it is set up that way, the condensate receiver can't be vented to the atmosphere and will be under steam pressure. Please clarify...

My 5th picture shows the whole steam header condensate drain running to the condensate receiver. Point taken, that is why I'm posting here!

... and I greatly appreciate the guidance you all are providing.

PEvans

JUGHNE said:

PEvans, there looks to be 6 drops coming into the condensate manifold, where do they all come from?
Again back up for pictures to show all the boiler piping, minus cobwebs.

Can you follow the steam mains around the basement? And show us what the ends of them look like.

The condensate manifold has all of the returns coming in plus the drip lines for the two mains and the drain from the steam header. I can follow the mains around. The ends look like they run radially in to the last radiator and then the condensate return comes back. I will map everything and get you better pix.

JUGHNE said:

Are the steam mains at the boiler the highest point of the main or the lowest point...or does it change somewhere in the basement. That is running up hill and than change to go downhill.

The steam mains seem pretty level, but I can check. They do drop down in diameter. The condensate returns have a definite slope.

JUGHNE said:

If the lower sight glass connection is plugged than also the 47-2 LWCO connection is plugged.....not good.

IIWM, I would remove the 47-2 at the union nuts that are in the way, then the sight glass fittings. Insure that the tapping (both parts of the wye) going into the boiler is brushed open all the way into the boiler.

Consider on opening up the 47-2 for cleaning or replacing.

For the sight glass connections, you can get brass nipples, tees and plugs.
Remount the sight glass off to the side to the right. Use the branch of the tee for the sight glass and you will have a clean out plug to brush straight into the boiler.

Also is a good time to replace all the valves for the water feed. Those may not shut off completely allowing the boiler to overfill. This may be why the water line was disconnected previously.

Right now I am trying to get a working gauge glass (so I don't flood the system again). I ordered parts and I will try your suggestions for plumbing.

The 47-2 says it has 10 year life, and this one has been sitting for longer than that. So I'm not relying on it.

In fact my present hypothesis is that the boiler port for the water cock clogged, confusing the gauge glass and the 47-2, and causing the fill mechanism to malfunction, maybe flooding the radiators just as I did (and with the same results). A tech thought it was a problem with the condensate receiver and replaced that but it did not solve the problem so the occupants shut the system down.

I do plan to clean or replace the 47-2 and re-plumb the feedwater piping, and rig the whole thing for easy blowdown. I don't love the idea of the sight glass and the feedwater valve sharing the same boiler ports but it doesn't look like there is a choice.

PEvans

JUGHNE said:

Jamie, it looks like the drop header is almost at the water line and the traditional equalizer would have connected quite low allowing the water and steam to meet there. The pump would have maybe thrown water up into the header.

So the steam pressure equalizer was taken off the top of the header and piped down to the return above the HL/pump connection.

Then in order to drip the header there is a F&T trap going to the cond pump.
This would have kept the steam out of the pump....if working.

Is there any advantage to dropping the header that low other than possibly easier connections to the steam mains?

So I guess here is where we (really you guys who know something about this stuff) have to figure out what the Dead Men were thinking.

It also sounds like I had better make sure that at least that F&T trap is working.

Jamie Hall

So long as the risers from the boiler have enough height -- perhaps two feet -- it makes very little difference how low the drop header is, provided only that it is above the boiler (Cedric's is only 6 inches above the water line). The condensate drain -- which is also the equalizer -- connects back to the boiler, usually at the T for the Hartford Loop. If it is arranged that way, water simply can't get pushed from the boiler into the header, nor steam get through the equalizer to the Hartford loop. Can't happen.

Going up and over as you describe will equalize the pressures, it's true, but as you note at the cost of having to provide a separate drip -- with a trap on it.

If there are wet returns connected to the bottom of the Hartford loop, they will also be at boiler pressure at that point, and discounting friction losses any drips to them from the steam mains will also stand at the boiler water line (actually slightly above, because of the friction losses in the steam mains). Any drips from dry returns will stand at the boiler water level plus 28 inches for every psi of boiler pressure.

Now in your situation the returns go into the condensate receiver, not the Hartford loop, and therefore the water in them and all the drips will stand at the level in the condensate receiver, which is much lower, nor will they vary with boiler pressure.

It is possible that this may cause a problem out in the weeds somewhere if there is a drip from a steam line which doesn't have a trap on it, or on which the trap is not working.

The F&T on the line from the header to the condensate receiver will indeed keep steam out of the condensate receiver -- if it is working. However, it may also back water up into the header, unless there is a foot or two of head over the trap. I cannot see any valid purpose either for that line and therefore for the trap, except that someone piped an "equalizer" so that it couldn't handle condensate. It should go back as an equalizer to the top of the Hartford loop. I might also point out that there is usually -- even with adequate risers -- a surprising amount of water in the header. An F&T may have trouble passing that much continuous flow, leading to wet steam carried into the steam mains and defeating the whole purpose of the drop header -- while placing a lot of dependence on the ability of the boiler feed pump to supply the lost water.

The boiler feed pump should feed into a wet return -- not the vertical lower leg of the Hartford loop. An acceptable alternative would be almost any opening below the water line of the boiler on the boiler -- and in your situation I'd probably prefer that.

JUGHNE

IMO, it is to your advantage for the 47-2 and the sight glass to share boiler ports.
As you may find out the lower may be plugged and also your LWCO feeder may give you problems.

When the 47 is blown down you should see the same water drop in the sight glass and know that the ports are clear.

PEvans

The manual for the 47-2 clearly anticipates that it would be installed using the same ports as the gauge glass, with two Y-shaped connections like the ones I have. I think the key is the 47-2 and the gauge glass have to be blown down regularly to confirm that they are seeing the boiler water level correctly.

JUGHNE

Yes, they are married together.
FWIW, If you get a new 47-2 you might consider reusing your existing wye fittings, some have said that they are pretty brittle brass and could snap off in the CI boiler.

I see a door next to the sight glass, if you use the tees I mentioned you do not want to block the panel door.

IIWM, I would add brass nipples straight out to give clearance from the wye fittings.
Then reroute the water feed line, replacing all the valves with good ball valves. IIRC it takes 3 valves to install the 47 correctly. And to have unions at the 47 itself, this is for the "broken union test".

You have a condensate return pump....it just turns on when it fills with return water,
whether the boiler needs it or not.
Between that type of pump and your 47-2 water filler you could overfill the boiler at the end of a heating cycle if your return water is slow to come back.

You do not have a boiler feed pump that the boiler tells it to turn on and provide water. This is the preferred method today for small volume boilers. This pump has a larger reservoir of water as it waits for your condensate water to return.

Your boiler probably holds quite a bit of water and has to boil away a fair amount before needing feed water.

If you read the steam books this is discussed in more detail.

IMO, because of the larger water content of your boiler, I would stay with the set up you have.......do you know for sure if the cond pump works??

Do you know if the oil burner works?
How about the tank...is it full of old oil?
I am not an oil burner person, others here can advise you much better concerning the oil part of things.

PEvans

Thank you for clarifying about the panel door. I think when the new gauge glass arrives I will try to install it under the feedwater piping. Later when I replumb the feedwater I can add those set-off nipples.

Yes, the feedback between the boiler feedwater control and the condensate return is indirect. The water volume of this boiler seems pretty huge so maybe it is forgiving.

Can someone suggest a procedure for testing the condensate receiver pump? There is probably water in the tank now. Should I just turn it on?

I feel like I need to make sure the manual and motor-operated zone valves for the two steam mains are open before applying any energy to the boiler. I'm not sure how to do that; I'm open to guidance.

I don't know if the burner works and don't really know how to test it or turn it on. I'm open to guidance there as well.

There is a little bit of old fuel oil. I can possibly contact a supplier and find out what to do with the old stuff and get new.

More pictures coming shortly.

PEvans

I don't know how other posters get such beautiful pictures. It must take many lights. Here are some more:
Again, note that the jacketed wet loop is not used; unfortunately it is in front of everything.


Steam risers, steam header, steam mains, steam main #2 drain to condensate:


Steam header (a repeat):


steam main #1 drain to condensate (on the other side of the boiler):


Another view, showing the steam header drain to condensate and the crossover(?) vent returning back to to the base of the boiler:


Back of boiler (with help from my plumber's work light):


Condensate receiver and condensate manifold:

PEvans

Here are views of typical end-of-mains:



In both cases the supply runs to the radiator and the return comes from the radiator. There is no vent on the main that I can see. The first example has an air vent on the radiator itself, but that is the only one in the entire house.

PEvans

You can seen from the pictures above that the steam header drain has a large drop to its steam trap and the condensate manifold. Regarding the steam header vent, in spite of what I said earlier, it effectively vents the entire steam header; it is ahead of the steam main valve. The return from the condensate receiver is the only other line coming in to that vertical (other than the return from the jacketed wet loop), and it is just under the boiler waterline (assuming the midpoint of the gauge glass).

I still owe you a map of the steam distribution. FWIW the only distribution line (main?) that has a wet return also has a drip and F&T trap on the steam side that joins the wet return (that is, it does not return to the boiler on its own). I tried to get a picture.

PEvans

Here is a map of the steam distribution beginning with the mains #1 and #2 coming off the steam header. The EDR values are very tentative.


Edit: I just realized looking at this diagram that there is one leg missing. I'll update it.

PEvans

Today I installed the replacement gauge glass.

As expected, the water cock valve and boiler tap were completely clogged.



I broke it free with a long screwdriver and cleaned it out with a wire pipe brush. I filled the boiler enough to rinse out the debris.

I decided not to take out the 47-2 at this time; I have been thinking of maybe replacing it with Hydrolevel components rather than spending a lot of money on rebuild parts. With the gauge glass out and better access, I did undo the coupling nuts (I had to go get a 24" pipe wrench to get the lower one loose) and put on new pipe thread tape so it will be easier to disassemble later.

Once the new gauge glass was installed I filled the boiler hoping to see the water come up in the glass. Instead it came out the condensate receiver vent. I had been planning as a next step to see what electrical equipment works, so while scratching my head I tried turning the master power on. The condensate receiver pump came on (!) which makes sense since the tank is overflowing. I remembered that the pump outlet valve is still closed, so I opened it. The condensate receiver pump ran for a while and shut off, suggesting the level switch still works.

I resumed filling the boiler, and this time the level came up in the glass.


So water in the condensate vent must have been due to trapped air. Once the water level got to a reasonable level the 47-2 tripped and the burner came on (!!). This suggests the 47-2 or parts of it might still work.

I shut everything down since I have not serviced the burner yet.

So I don't know yet if the system will work, but more of the components seem to be working.

PEvans

Jughne was right. The feedwater valves leak. After I replaced the gauge glass the next day I found the boiler flooded and leaking water out of the condensate receiver vent again. At least now the water can't get any higher than just under the basement ceiling.

So I drained the boiler down again. Along the way I checked to see if the 47-2 float would actuate the bellows and it does! So for the 47-2 the only question that remains is whether the bellows actually actuates the fill valve.

With the water level visible in the gauge glass I shut off the isolation valve for this part of the cold water system. Now several days later the water level in the glass has not moved. I can live with this for now; I am eventually going to redo all of that piping.

With a clogged gauge glass and leaking bypass fill valves, no wonder this system had a bad rap.

JUGHNE

I have been thinking about how your overfilled boiler could put excess water into the cond pump.
Usually the only connection between the boiler and cond pump is the 3/4" fill line from the pump and it should have a check valve to keep the boiler water from returning to the pump.

But, now I can imagine overfilling the boiler would let water thru the F&T trap on the header "drip" line...usually not needed...but you have one.
The F&T would pass the water to the cond pump as the leaking bypass valve overfilled the boiler, as it should.

It looks like you have a F&T on the outlet of each motorized valve, this is to let any condensate drain from the steam main when the valve shuts, this would be to avoid water hammer the next time the valve opens.

So that accounts for 3 F&T traps, where are the other ones?
And what does the wet return connect to?

You have looked at the install instructions for the 47-2, it shows 3 valves, yes?
And unions at the 47-2 in order to test the water valves.
Perhaps study that diagram and replacing some valves might let you test the water fill portion of the 47-2.

You could install "Sharkbite" (heaven forbid) fittings temporally to test things.

PEvans

JUGHNE said:

I have been thinking about how your overfilled boiler could put excess water into the cond pump.
Usually the only connection between the boiler and cond pump is the 3/4" fill line from the pump and it should have a check valve to keep the boiler water from returning to the pump.

But, now I can imagine overfilling the boiler would let water thru the F&T trap on the header "drip" line...usually not needed...but you have one.
The F&T would pass the water to the cond pump as the leaking bypass valve overfilled the boiler, as it should.

That makes sense. Do you also think it is likely that when I flooded the whole distribution system it was actually from the steam header to the condensate manifold and then through the returns to each radiator? I can't tell for sure, but I think the steam header is actually isolated from the steam mains by the manual and motorized zone valves, which appear closed and I'm going to have to get open at some point soon.

JUGHNE said:

It looks like you have a F&T on the outlet of each motorized valve, this is to let any condensate drain from the steam main when the valve shuts, this would be to avoid water hammer the next time the valve opens.

So that accounts for 3 F&T traps, where are the other ones?
And what does the wet return connect to?

Each dry return has an F&T trap. The wet return connects to the condensate manifold. That part of the distribution system also has an F&T trap on the steam line that ties in to the wet return away from the boiler.

PEvans

So far the burner looks pretty good. I already knew that the motor and fuel unit are not seized. I have not yet pressure or vacuum tested the fuel unit, and I should replace the strainer. I also need to add a fuel line between the fuel unit and the burner nozzle.

I confirmed that the oil burner primary control sends AC voltage switched depending on the T-T connection (open or closed). With the CAD cell disconnected the ignition transformer arcs over about 1/8 inch after about a two-second delay. The CAD cell goes from OL when it is dark to about 70 Ohms when I shine a flashlight on the eye. So it does vary with the light level, though that seems like a big range.

Presently the burner is not connected to fuel and I don't have any fuel in the tanks.

I also tested the condensate receiver pump again -- with the burner cut out I turned on the main power. The condensate receiver pump came on and I could see the water level come up on the gauge glass. The pump turned off after about a minute.

PEvans

I also confirmed that the controls work and motor operated valves work. There are two thermostats, one for each zone. When either calls for heat its motor-operated zone valve actually does open and the T-T connection on the primary control closes.

I still can't operate the manual steam main isolation valves and I can't tell if they are open or closed.

Down the road there is a question of whether I should use individual temperature control valves on the radiators instead of the zone valves.

mattmia2

With some fairly large wrenches you should be able to take those king valves apart and clean them up and repack them and get them working(is it still a king valve if there are 2 zones and one for each zone?)

PEvans

The manual steam main valves are operable and open.

PEvans

I had the valves around the 47-2 replaced. Maybe not the best investment, but it allows me to keep the water main in service (it serves other things it turns out) without unintentionally filling the boiler, and I might be able to test the function of the 47-2.

JUGHNE

Back to the 47-2 install instructions it shows a broken union test.
I see you have unions on the 47, follow that test procedure to see if the 47 will pass water when it should not.

Also now you never did confirm if the steam supplies above the boiler slope down away from the boiler.....think of these as a drain pipe will the water flow away from the boiler or back into it?

You mentioned level...but steam pipes are never level...always some slope one the way or the other.

Get a level (at least a 2' level) on the pipes above the boiler and then follow them around the basement, all the way to the return pipes, with the level to determine if you have parallel flow or counter flow steam piping system.
The slope may change from counterflow to parallel flow at some point in the piping.

This is a basic point to be established, important for decisions concerning your system.
The difference is explained in Dan's books....which one's have you read?

ethicalpaul

I wonder how close to correct size this thing is...

PEvans

Jughne, you were right about the slope of the mains.

Most of the mains are counter-flow; that is, they increase in elevation running in the steam flow direction and any condensate would run back to the steam main drain or the steam header drain.

The main with the wet return is parallel flow (main elevation is decreasing in the direction of the steam flow), but has a drip with F&T trap at the end, before the risers. This drip joins the main's wet return.

I have attached a revised steam distribution diagram.

I used the 47-2 to fill the boiler. At low water level the fill valve opens, and once the level gets above the fill line the valve closes. It actually reaches about an inch above the line on the valve casting. The fill valve itself leaks water everywhere both when it is open and when it is closed, so I have to open it up and replace the o-rings and any gaskets (at more than $120 for the kit). That valve has not operated in years.

I had already determined that the LWCO works. When they replaced the valves around the 47-2 they did not put in unions, so I can't perform the broken union test just yet. I don't plan to allow the 47-2 to manage feedwater supply wholly on its own for now.

JUGHNE

Do you have "The Lost Art of Steam Heating" by Dan Holohan?

PEvans

Yes, sorry. I have The Lost Art revisited, Greening Steam, and EDR. I have read Greening Steam thoroughly, cover to cover and taking notes. I have read parts of The Lost Art. I had interpreted the discussion on p. 138 to 140 of TLAOSH Revised as applying to a one-pipe system until you clarified your question. It makes sense, though, that even in a two-pipe system there will be condensate in the steam supply lines that you have to get back to the boiler or the condensate receiver.

JUGHNE

It is possible that you have (mostly) a 2 pipe counterflow steam system.

I have not seen this design in any book, only came across one in use.
After studying it, it was pretty obvious how it worked and why it would have been installed as such, it has some advantages.

Low point of piping is at the boiler for the steam supply piping and also the condensate dry returns.

High point of piping is at the end of the piping, this helps for head clearance in the basement.
The farther you get from the boiler, the more head room you have.
Both supply and return would have same slope.

The steam supply pipe would get counter flow condensate water only from the steam condensing on it's way to the rads.

The main bulk of the condensate water (which would be from the rads) would return thru the smaller dry return.

All the air from all piping would have to return thru dry returns via the cond pump vent.

You say you have part of the supply that uses a wet return, how does the air get out of that piping before it goes down to the wet return?
A F&T at that drop point will not vent the air thru the wet return.

You have drips to F&T's at each steam motorized valves? If so then that steam main condensate water will not go back into the header or directly into the boiler...which you don't want.
That water would go to the cond pump.


Does this seem to make sense for you?

PEvans

I was just reading Chs 9, 10, and 11 of TLOASH Revisited (I feel like a college student), and your questions make more sense now.

I do note that Dan pretty much assumes parallel flow steam mains with end-of-main F&T traps in two pipe systems, and that is for the most part not what I have. I don't see, though, why the control valve traps (if you want to call them that) should not also drip the counter-flow mains while the mains are operating with steam. (It is a little unclear in my diagram, but the drip for the #1 main is downstream of the two valves.)

I'll get to your other questions individually in a bit. (And thank you again for staying with this thread!)

PEvans

JUGHNE said:

It is possible that you have (mostly) a 2 pipe counterflow steam system.

I have not seen this design in any book, only came across one in use.
After studying it, it was pretty obvious how it worked and why it would have been installed as such, it has some advantages.

Low point of piping is at the boiler for the steam supply piping and also the condensate dry returns.

High point of piping is at the end of the piping, this helps for head clearance in the basement.
The farther you get from the boiler, the more head room you have.
Both supply and return would have same slope.

The steam supply pipe would get counter flow condensate water only from the steam condensing on it's way to the rads.

The main bulk of the condensate water (which would be from the rads) would return thru the smaller dry return.

All the air from all piping would have to return thru dry returns via the cond pump vent.

That all makes sense. For what it is worth the returns have far more pitch than the supply.

JUGHNE said:

You say you have part of the supply that uses a wet return, how does the air get out of that piping before it goes down to the wet return?
A F&T at that drop point will not vent the air thru the wet return.

This is a head scratch. I don't know. They had something in mind when they built this. The return was originally buried in the floor, but has been replaced to run on the floor. It seems like they could have run a dry return but they didn't.

The condensate manifold is presumably emptied when the condensate tank is emptied, so any air can reach the condensate receiver, but I think the bottom of the wet return would remain full.

JUGHNE said:

You have drips to F&T's at each steam motorized valves? If so then that steam main condensate water will not go back into the header or directly into the boiler...which you don't want.
That water would go to the cond pump.

Yes, that is the way it is done. To me it looks like those F&Ts are also draining the condensate from the counterflow mains back to the condensate receiver when the valves are open.

PEvans

There was some back and forth a couple of weeks ago about the layout of my system. Did you all finally conclude that the drop header would work? Presumably it has in the past...

In terms of venting, if I read LAOSH Revisited right a vent to atmosphere on the condensate receiver can vent the entire system if the traps are working and no air is blocked, and the condensate pump will overcome lack of height to get condensate back to the boiler. Do you all agree?

There was also a concern about the condensate pump flooding the boiler. This is less likely with an old boiler with a big water volume, right? And if I end up replacing the 47-2 I could get a programmable feedwater system where I could set a delay.

Several expressed concerns about the condition of the traps. Should I rebuild them proactively or wait to see how they do?

I am stumped by the question of how the wet return gets vented.

JUGHNE

Show us a picture of the F&T on the wet return...include the steam main at the ceiling and the wet return on the floor....all in one picture...back up to include it all if possible.

PEvans

I think I can get better pictures at night, with less backlight from the basement windows, so I'll try.

It occurred to me that all of the radiators on the main branch in question are cast iron baseboard. Perhaps there is a different approach for air venting here since there is basically no elevation difference inside the radiator for the steam to force air out through the trap.

TLAOSH Revisited at pp. 164-166 talks about baseboards a little bit, but seems to dance back and forth between one-pipe and two-pipe applications and gravity-drained vs. pumped condensate. Anyway, evidently air is supposed to be vented from the baseboard and condensate returns via a wet loop.

Online documentation by the manufacturer for BASE-RAY radiators (which is what I have) recommends these only for two pipe systems but anticipates having the radiator vented anyway (by that I assume not relying on the condensate return for venting).

This seems like it might be the beginning of an explanation, anyway.

mattmia2

I think the "wet loop" is making a small 2 pipe section in a 1 pipe system to use CI baseboard which doesn't deal so well with steam and condensate heading in and out on the same end.

JUGHNE

Have you ever found the BTUH input rating of the boiler itself?

The oil burner would have a maximum and minimum oil nozzle size (in GPH) listed on a nameplate, usually. Maybe with an oil pressure rating in PSI.

These will be 2 separate numbers.

You should come up with the BTUH input rating and compare it to your connected EDR of all the radiation....see if you are grossly oversized.

Also it looks like you have a pretty high water line above the floor, you should note the height. Also measure down from the ceiling joists. (ceiling may be more level than the floor)
Then go to that drop pipe to the dry return with those measurements and try to show where the water line is on that pipe. Mark with white tape or such that it will show up in the pictures.

Jamie Hall

Cast iron baseboards -- such as what you are playing with -- are actually better on two pipe systems with a trap. But... two things are necessary. First, there must be at least some pitch towards the trap, so that condensate will naturally go that way. Doesn't have to be a whole lot -- but it has to be there.

Second, and perhaps a little less obvious, is that that trap has to have somewhere for the air to go. In a true two pipe system, this would be the dry return -- a true dry return. The condensate and air would bot go into that, and the main vents on the dry return would handle the air.

Now... you mention a wet loop. Problem. If you don't have a dry return -- a true dry return -- that won't work. The condensate can, in principle, be handled by a water seal (I suspect what you are referring to as a wet loop?) going back up to... somewhere? but, of course, that won't allow air to pass. So... If you don't have a true dry return on this system, then you do need a vent on the outlet. You notice the "somewhere" up there. That somewhere has to be either a wet return (in which case there's no need for it to come back up...) or some other pipe. Unless the steam main -- if that's what it is connected to -- is well below the trap, however, it just won't work. By well below at least that 28 inches per pound boiler pressure...

PEvans

I think I misused the term "wet loop". I meant "wet return."

Here is a link to the BASE-RAY installation manual
https://file.ac/sjX8zTp2UtE/Baseray%20Radiator%20I%26O%20Manual.pdf
The two-pipe steam system diagram on p. 5 is similar to this one main branch. Clearly the return is wet return. In later diagrams they show the air venting, even on a two-pipe system.

To clarify, all of the baseboard radiators appear to have steam traps at one end (17Cs). From LAOSH this would be appropriate where there is a condensate pump (I guess because the condensate receiver is at atmospheric pressure, not boiler pressure). I have not been able to actually see air vents (too much stuff in the way). I can't tell if the radiators are pitched to drain to one end.

The diagram I provided earlier has all the height measurements taken from the basement ceiling.

I have never found a nameplate for the boiler itself. The burner is rated for 1.25-5.5 gph. Sizing might be a soft concept. Main #2 may not have been in original design, and I know over the years a sunroom was added (in 1905 it is said), a wet loop was added to heat a greenhouse in 1956 (and many radiators replaced or resized), and this branch with the baseboards that we are looking at was added in the 1950s. Also, the insulation was taken off. Somewhere in there or after this particular boiler was installed.

Here are some pictures of the steam main branch with the wet return. You can see pretty clearly in the first picture that the return really drops all the way to the floor. Before it gets to the condensate manifold it rises up just above the condensate tank level. The F&T trap is just on the steam main drip. The condensate returns from the baseboards join the return after the outlet of the F&T trap.

On p. 163 and 164 of LAOSH Revisited Dan talks about using a loop seal in the condensate return for a baseboard radiator. I don't know if this applies to my situation (the return does connect indirectly to the steam main drain via the condensate manifold). It certainly looks like they were trying to maximize the height difference between the steam main and the wet return.


Image #1


Image #2


Image #3


Image #4