Can I re-route a wet return into the bottom of my loop seal?

veteransteamhvac

I have a 2 pipe vapor system with a loop seal at the end of my main that connects to the beginning of the dry return. The main is pitched down to the loop seal and the dry return is correctly pitched down to the boiler return line.

In the 1950s an addition was made onto the back of the house and the 2 radiators added there were fed into a 1 inch wet return that runs the perimeter of the basement. However, the 1 inch return is interrupted at one point with a 1/2 inch copper line that runs into the basement slab under a doorway. I'm nearly sure that thing is clogged.

Rather than mess with that I could more easily run the wet return to the base of the loop seal. Are there any concerns about doing this?

Jamie Hall

Um... yeah. If the loop seal is just that, and doesn't have a wet return, where would the water go from your now rerouted condensate wet return?

Are you sure that the main involved doesn't have a drip to a wet return somewhere? Because if it doesn't, that loop seal is going to be full to the level of the dry return on one side -- much higher than the wet return you are thinking of connecting to it.

veteransteamhvac

Jamie Hall said:

Um... yeah. If the loop seal is just that, and doesn't have a wet return, where would the water go from your now rerouted condensate wet return?

Are you sure that the main involved doesn't have a drip to a wet return somewhere? Because if it doesn't, that loop seal is going to be full to the level of the dry return on one side -- much higher than the wet return you are thinking of connecting to it.

No, there is no wet drip from the main. It's a simple out and back vapor system. Up from the boiler, main out pitched down to the loop seal, down about 5 feet towards the floor and then back up to the dry return at a level below the steam main and that is pitched down to the boiler return loop.

Isn't the loop seal generally full to the level of the dry return anyway? The condensate in the loop seal is what arrives there from the pitched main and any steam that happens to condense in the radiator feeds and flows back into the main. Condensate added from the main into the loop seal will dribble into the dry return to flow back to the boiler return loop.

Presuming I'm operating at low enough pressure the system should not blow through the loop seal and get steam into the dry return. The weight of the water in the pipe back up to the dry return should do that. I suppose what I'm asking is adding more pipe filled with return condensate shouldn't affect how the loop seal gets the water in it back to the boiler return loop.

Jamie Hall

Certainly your thinking is correct enough on loop seals -- that is exactly how they do operate. Though I'm minded to ask how air gets out of that main. Is there a crossover trap? If not, what is there?

Which brings up the question of how does air get out of the runout and the two added radiators? I presume there's no dry return out there with them?

But if those radiators are no lower than the rest of them, then so far as condensate is concerned, bringing the pipe back up or just connecting into the bottom of the existing seal should work.

veteransteamhvac

Jamie Hall said:

Certainly your thinking is correct enough on loop seals -- that is exactly how they do operate. Though I'm minded to ask how air gets out of that main. Is there a crossover trap? If not, what is there?

I have a 2 pipe vapor system with vents on the radiators and, of course, one at the end of the dry return near the boiler return loop.

Jamie Hall said:

Which brings up the question of how does air get out of the runout and the two added radiators? I presume there's no dry return out there with them?

They both have vents just like the rest of the house. No traps on the feed or return at the radiators.

Jamie Hall said:

But if those radiators are no lower than the rest of them, then so far as condensate is concerned, bringing the pipe back up or just connecting into the bottom of the existing seal should work.

I'm not wedded to the idea but as I had the loop seal off anyway to clear out the pipe (a maintenance item I'm sure isn't on most lists) I was considering trying it. Should not be difficult to run the 12' or so of wet return to the return riser of the loop seal. If it seems to interfere with the system I will just go back to the longer wet return run and dig up the under slab portion.

EBEBRATT-Ed

@veteransteamhvac

I am assuming that the two radiators in question that the returns are connected above the water line.

Do those rads have traps or some kind of vapor elbow on the outlet?

I would be inclined to bring both rad returns back to the loop seal seperetly and ty them together below the water line, but if it works now and they are connected above the water line you should be fine

veteransteamhvac

EBEBRATT-Ed said:

@veteransteamhvac

I am assuming that the two radiators in question that the returns are connected above the water line.

Thanks for your insight. Yes, the two radiators have returns connected above the water line, then a common wet return (now).

EBEBRATT-Ed said:

Do those rads have traps or some kind of vapor elbow on the outlet?

No traps or vapor elbows of any kind on my radiators anywhere in the system.

EBEBRATT-Ed said:

I would be inclined to bring both rad returns back to the loop seal seperetly and ty them together below the water line, but if it works now and they are connected above the water line you should be fine

As it is now they tie in not far above the water line so it might not be too difficult to separate them.

EBEBRATT-Ed

@veteransteamhvac

I would think there would have to be something to keep the steam out of the returns unless this is a two ppe air vent system. Do you have air vents on the rads and valves on the supply and returns at the radiators?

veteransteamhvac

EBEBRATT-Ed said:

@veteransteamhvac

I would think there would have to be something to keep the steam out of the returns unless this is a two ppe air vent system. Do you have air vents on the rads and valves on the supply and returns at the radiators?

Yes, there are air vents on the radiators, but only valves on the supply side, not the return. Feed is high, return low. The return elbow is exactly that, an elbow in all cases.

As I can best understand my system is a two pipe vapor system with vented radiators but no traps. Dry return (for the most part now) with air relief at the end just prior to the boiler return. I've seen similar to it discussed here but not very often. The original design would have been for a coal fired boiler.

The system works well enough up until the clogged wet return.

dopey27177

Try to clean out the wet return with a wet vac, or use an small air compressor to to blow out the crud.
You would need to disconnect the piping on both sides f the wet return and at that juncture install clenout Ts for future cleaning.

Jake

KC_Jones

veteransteamhvac said:

EBEBRATT-Ed said:

@veteransteamhvac

I would think there would have to be something to keep the steam out of the returns unless this is a two ppe air vent system. Do you have air vents on the rads and valves on the supply and returns at the radiators?

Yes, there are air vents on the radiators, but only valves on the supply side, not the return. Feed is high, return low. The return elbow is exactly that, an elbow in all cases.

As I can best understand my system is a two pipe vapor system with vented radiators but no traps. Dry return (for the most part now) with air relief at the end just prior to the boiler return. I've seen similar to it discussed here but not very often. The original design would have been for a coal fired boiler.

The system works well enough up until the clogged wet return.

I'm not familiar with this. I've seen 2 pipe air vent systems, "true" 2 pipe systems and what you are describing doesn't match either.

2 pipe air vent is basically a 1 pipe system with condensate return. It has both connections low, with valves on both ends, at least every one I've seen posted on this site or listed in Dan's books.

Your description sounds like true 2 pipe that someone added vents to, possibly because something else in the system went wrong and they mistakenly thoughts vents were missing. I've seen this more often than a 2 pipe air vent system on this site.

Not all true 2 pipe systems have traps on the radiators.

DanHolohan

Is the end of the main where that wet return begins higher than the main that has the loop seal? If it's not and you tie into the bottom of the loop seal, the condensate from that wet return will just back up into the main from which it came.

veteransteamhvac

DanHolohan said:

Is the end of the main where that wet return begins higher than the main that has the loop seal? If it's not and you tie into the bottom of the loop seal, the condensate from that wet return will just back up into the main from which it came.

Yes, the end of the main with the wet return is indeed higher than the main leading to the loop seal. If I'm imagining this correctly previously in the wet return the condensate level was usually equal to the water level in the boiler. The condensate level on both sides of the loop seal was and will be equal to the lowest point of entry on the elbow leading to the dry return (the end of the feed main being higher by a few inches). By feeding into the loop seal the condensate level on the wet return will move about 36 inches higher in that pipe, equal to the top of the dry side of the loop seal, but will still be lower than the end of the main feeding it.

veteransteamhvac

KC_Jones said:

I'm not familiar with this. I've seen 2 pipe air vent systems, "true" 2 pipe systems and what you are describing doesn't match either.

2 pipe air vent is basically a 1 pipe system with condensate return. It has both connections low, with valves on both ends, at least every one I've seen posted on this site or listed in Dan's books.

Your description sounds like true 2 pipe that someone added vents to, possibly because something else in the system went wrong and they mistakenly thoughts vents were missing. I've seen this more often than a 2 pipe air vent system on this site.

Not all true 2 pipe systems have traps on the radiators.

I appreciate your point and I was of a similar mind until I read something here regarding radiator valves on two pipe steam systems that have a sort of metering orifice that is used to balance the fill rate of each radiator. Each valve has a circular indicator with pointer that corresponds to 4 holes of varying size on a cylinder inside the valve. The vents on the radiator play their role of air elimination as there are no vents on the main, only one at the end of the dry return. As I also have a loop seal the pressure has to stay low enough to not blow out the water column. Somehow all that is designed to keep steam from getting into the dry return, though I don't exactly know.

I've attached two images of one of my valves deconstructed which shows the orifice cylinder and selector knob.

veteransteamhvac

dopey27177 said:

Try to clean out the wet return with a wet vac, or use an small air compressor to to blow out the crud.
You would need to disconnect the piping on both sides f the wet return and at that juncture install clenout Ts for future cleaning.

Jake

Thanks, that is a part of the plan right now. As I mentioned above the 1 inch iron wet return is downsized to a 1/2 inch copper pipe for the drop under the doorway which is a perfect way to catch gunk. I suspect it's going to take some effort to clean out the years of accumulated slag. I have visions of me breaking up slab at this point to get at that pipe! The pipe then continues all the way around the perimeter of the basement to arrive back at the boiler. Oy!

Why I'm considering the loop seal route is because it's only about 12' to the base of the loop seal with no drops to worry about. I'll make an attempt to clean out the door drop anyway and leave most of the wet return in place just in case this doesn't work.

DanHolohan

@veteransteamhvac, then it should work.

KC_Jones

veteransteamhvac said:

KC_Jones said:

I'm not familiar with this. I've seen 2 pipe air vent systems, "true" 2 pipe systems and what you are describing doesn't match either.

2 pipe air vent is basically a 1 pipe system with condensate return. It has both connections low, with valves on both ends, at least every one I've seen posted on this site or listed in Dan's books.

Your description sounds like true 2 pipe that someone added vents to, possibly because something else in the system went wrong and they mistakenly thoughts vents were missing. I've seen this more often than a 2 pipe air vent system on this site.

Not all true 2 pipe systems have traps on the radiators.

I appreciate your point and I was of a similar mind until I read something here regarding radiator valves on two pipe steam systems that have a sort of metering orifice that is used to balance the fill rate of each radiator. Each valve has a circular indicator with pointer that corresponds to 4 holes of varying size on a cylinder inside the valve. The vents on the radiator play their role of air elimination as there are no vents on the main, only one at the end of the dry return. As I also have a loop seal the pressure has to stay low enough to not blow out the water column. Somehow all that is designed to keep steam from getting into the dry return, though I don't exactly know.

I've attached two images of one of my valves deconstructed which shows the orifice cylinder and selector knob.

You just agreed with me, I'm confused. That is a true 2 pipe non vented inlet valve. You continue to confirm those air vents should not be on the radiators. I only make this point as it could influence the responses you get about your modification. It seems by everything you are posting the system has been bastardized multiple times and it would be a shame to continue with that.

To be clear 2 pipe air vent systems have standard inlet valves, no orifices, no metering device of any kind. This is because the air vent is the metering device. From everything you posted those vents should not be on the radiators.