Couple questions vapor system

Dave0176

Replacing a boiler and trying to rebuild a vapor system that’s been ravaged over the years. One question is the end of the steam mains have F&T traps before the main drips into the wet return, this don’t make sense if it’s going into the wet return? Also none of the vents are right previous contractor put Hoffman 79s on dry returns lol and both mains have the main vent locations plugged. So another question is do I put Vac vents on the mains or B&J big mouths? The radiators are another work in progress. EDR measured at 517 sq ft and the 17 year old rotted Utica is 299,000 btu and 760 sq ft steam output. I’m putting in a Weil-McLain EG55.

mikeg2015

Not sure about the other issues, but you can’t use vacuum vents unless all radiators have them and you can guarantee the whole system is sealed completely... including all radiator valves. Otherwise it will be a nightmare to balance.

Vent radiators slow, mains fast and you should be surprised how it smooths out.

Dave0176

mikeg2015 said:

Not sure about the other issues, but you can’t use vacuum vents unless all radiators have them and you can guarantee the whole system is sealed completely... including all radiator valves. Otherwise it will be a nightmare to balance.

Vent radiators slow, mains fast and you should be surprised how it smooths out.

@mikeg2015 this a two pipe system. The radiators have steam traps on them.

EBEBRATT-Ed

If a gravity return and the mains (individually) drip into a wet returns I see no need for traps. No condensate pump correct?

No alternating receiver or boiler return trap??

Don't think you can get vac vents anymore

Dave0176

EBEBRATT-Ed said:

If a gravity return and the mains (individually) drip into a wet returns I see no need for traps. No condensate pump correct?

No alternating receiver or boiler return trap??

Don't think you can get vac vents anymore

No condensate pump or return trap, return trap was probably ripped out years ago. The vac vents I’m taking about are Hoffman 76 main vents the last vacuum vent made.

And I’m running a vaporstat on this boiler.

Mike_Sheppard

Being a 2 pipe system wouldn’t you want some form of trap on the mains - mechanical or water seal? I guess if it drips to a wet return and you have enough B dimension it wouldn’t matter.

A pumped return or return trap would be a different story though I’d assume.

Edit:
I worked on a couple of Dunham two pipe systems that had no traps on the steam main returns, they dripped into a wet return and went right back to the boiler. The radiator returns on the other hand went to a boiler return trap because there wasn’t enough B dimension to overcome the boiler pressure.

Dave0176

I have about 4' of height "B dimension" from the dry returns drop to the wet return.

Mike_Sheppard

That’s good for about 1.73 psi. I would guess if you can keep the pressure down there then traps wouldn’t be needed on the mains if they drip into wet returns.

Edit: is that measurement from the water line in the wet return to the bottom of the dry return?

Even with the mains trapped you’d still have to have sufficient B dimension. As long as it drips to a wet return where steam can’t go backwards into the dry returns, I agree with @EBEBRATT-Ed, you wouldn’t need the traps.

Dave0176

Mike_Sheppard said:

That’s good for about 1.73 psi. I would guess if you can keep the pressure down there then traps wouldn’t be needed on the mains if they drip into wet returns.



Edit: is that measurement from the water line in the wet return to the bottom of the dry return?

@Mike_Sheppard opps yep to the waterline probably only 36"maybe a touch more, I plan to set the vaporstat cutout to 10 oz.

Mike_Sheppard

Picture attached. From what you’ve described I think this is basically what you are working with.

End of main drip doesn’t need a trap dripping into wet return, and will be an A dimension. But you need the B dimension on the return from the radiators because those are trapped.

Dave0176

Its not a big deal I'll replace those two F&Ts however if their not needed.

JUGHNE

How does the air get out that is vented by the F&T's?
Is that a wet return coming up thru the floor/equipment pad, in your last picture?

Steamhead

From the looks of that piping I'd say the F&Ts were added later. They may or may not be needed.

Questions:

1- Is this gravity or pumped return?

2- Have you found any original radiator valves and/or traps? What brand are they?

Dave0176

Steamhead said:

From the looks of that piping I'd say the F&Ts were added later. They may or may not be needed.

Questions:

1- Is this gravity or pumped return?

2- Have you found any original radiator valves and/or traps? What brand are they?

Its all gravity. Nothing original, like I said its ravaged. The current radiator traps are Hoffman 8C .

Dave0176

JUGHNE said:

How does the air get out that is vented by the F&T's?
Is that a wet return coming up thru the floor/equipment pad, in your last picture?

I had thought the same thing..........

The wet returns are from the steam mains that are coming up through the floor.

JUGHNE

So are the steam mains vented before they drop?

Dave0176

JUGHNE said:

So are the steam mains vented before they drop?

Nope both of the tees are plugged on both mains, where the vents probably once were.

Mike_Sheppard

The mains should be vented at the ends before they drop into the wet returns and there should be vents down there on the returns from the radiators before they drop into the wet return as well.

clammy

Dave I did a trane 2 pipe without traps using convectors . No traps no return traps no nothing , I was replacing the original ideal oil fired and she still held a vacuumed at over 85 years ol$ . I used Hoffmann 78 vacuume vents put them on both end of the mains n end of the dry returns they all dropped into a wet return . When she is satisfied by t stat as she cools the vacuumed forms down to about 12 inch hg . On start up in a vacuumed the distrubition is amazing fast once she is steaming at header the complete main is hot within 2 to 3 minutes very amazing And the Hoffman’s hold that vacuumed each time I’m there and fire her up The is no air vented there’s was very little dirt in the system for that age I used a vapor stat get to bout 10 ounces I would have done a 2 stage valve but $ wasn’t there even though the boiler doesn’t short cycle it would be a benigit on the shoulder months . This is there second season and they are yet to add any water tight system also I installed a total of 8 vapor vacuumed vent 2 on each main and 2 on each dry return I had thought of using a crossover but had seen the total original system untouched and figured I stay the course instead of rocking i5 an$ I’m glad I did the systems balance is something to behold I installed a 64 07 w a false water line at the boilers original water line hope that helps peace an$ good luck clammy

Jamie Hall

@Dave0176 -- couple of quick thoughts and I'll look some more. F&Ts -- don't need them. In fact, don't want them on drips. Get rid of them. Second thought -- is there any evidence of crossover traps having been on the ends of the steam mains going to dry returns? If so, can you restore them? Then you can and should do all your venting at the ends of the dry returns where they drop to the wet return. You'll need good big vents on the dry returns anyway. Are the dry returns hooked together at the boiler before they drop? If so, that's fine -- and that's where the vents go.

Hoffman 76 vents are still available, but they're pricey. Not sure you need the vacuum. I'd go with Gorton #2s...

Got to run. I'll think some more...

PMJ

@Dave0176 , If you are really going 2 pipe natural vacuum you only need one small vac vent or check valve and it can go anywhere on the dry return. I recommend the garage if you have a rad in there. Nothing else required. First time up all the air leaves the mains through the rads and that one small vent no problem. After that there is next to no air to remove ongoing. Simply doesn't get more simple.

Like @clammy said, no air, no dirt(corrosion), no water add, amazing fast/even distribution.