Gravity Return vs Pump return

GrockMan

Background:

• I've been talking with many contractors to try to get my steam boiler replaced for my giant 7000 sq.ft. house with 30 rads, and hopefully made it more efficient and less likely to fail in only 20 years.
• My 1998 condensate pump has had an issue of running continuously, thereby flooding the boiler to the top, thereby accelerating rusting and cracking. We opened up the wiring boxes to find that the condensate pump is NOT connected to the boiler's sensors in any way, despite clear correlation with blowing down the boiler on the one sensor's side (first image) remedying the condensate pump.(And according to several contractors so far, the main pipe size is too big compared to the return pipe size to consider hydronic without a massive overhaul.)

Question:

A few contractors I'm talking to are recommending omitting the condensate pump and just using gravity to return the condensate to the boiler. Others suspect that would not be a good idea, thinking the pressure would not be enough or there would be too much condensate buildup in the wet returns that might make them burst or leak perhaps.

Edit: I guess a better question to answer is: "what are the pros and cons of using a pumped resevoir vs a gravity return?"

What do you all think?

(Any other advice for this project would be massively helpful. I am very new to this, but learning fast. I got some of the holy books, have not read them yet.)

Equipment:

• Weil-McLain LGB 5 Low-pressure Steam Boiler: installed 2001

• [DISCONNECTED ] Sterlco - Sterling inc - 1/3 HP Pump??: Installed 2001, same day as boiler. Looks completely defunct and gutless

• Smaller condensate pump: installed 1998 - but still connected (didn't get the make/model)

• Wet return, running below the boiler, feeding into the boiler, running through about half of the basement
• Dry returns running parallel to the main pipe throughout the whole basement, feeding into the wet return

mattmia2

the pumped vs gravity return has to do with the water content of the boiler. If the system has too much of the water from the boiler in the system in the form of steam while the system is running, the water level in the boiler may fall too much. bigger boilers have more water content but modern boilers have less water content than older boilers did. if the boiler doesn't have enough water content, more volume can be added with pieces or large pipe or a passive tank that is set up as a reservoir. Usually there are better options than a pumped return.

the other reason to have a pumped return is if you have emitters below the boiler so that the condensate can't return by gravity.

Where are you located, there may be some pros here that are nearby.

Jamie Hall

Lose the condensate return pump and rely on good old gravity. The only reason why you might not be able to do that is if the piping is such that somewhere a wet return is above the water level in the boiler or if there is a radiator which is below the water level in the boiler.

There is a possible pressure concern as well. If this is a true two pipe system, any dry returns must be high enough above the boiler water level so that they don't flood. I can't tell from the photos whether or not this is the case. This is not usually a problem, but easily checked.

EBEBRATT-Ed

Post your location.

You need someone that knows steam well and there are not many that do. You don't want this to turn into a horror show.

JUGHNE

The reservoir tank mentioned above gives you more water to work with on a large system.

Think of it as a large horizontal tank sitting alongside your boiler……larger boiler but no fire under part of it. You have extra water available for steam production.

The tank will have the same water level as the boiler, and must have steam pressure above that water line and the bottom connected to the returns.

I have a couple of these in use and they work well.

GrockMan

I'm in Pittsburgh, PA.

I have had some local pros look at it, and they have polarized views on needing a pump or not needing one. One local pro was the one who suggested I come here to ask you all.

Are there pics I can share that would help the decision?

GrockMan

I guess a better question to answer is: "what are the pros and cons of using a pumped resevoir vs a gravity return?"

More info:

All rads are above the dry return line, and the wet return is pretty far below the boiler.

Here are the dry and wet returns with relation to the boiler.

Boiler, decomissioned pump, in use pump:

Steam Trap central where everything returns:

View of the return piping up and back down (and disconnected piping):

JUGHNE

This reservoir pipe was added to this boiler which has a lot of 4" steam pipe and

2 1/2" return. Has only 4 remaining CI rads connected.

The center of the reservoir pipe is set on the water line of the boiler.

It has a steam connection, from the header drip, (well above water line), to the top and water line to the lower half, (well below the water line).

The 6" pipe was salvaged from the old header of the removed boiler and had caps welded on the ends with coupling ports welded top and bottom on each end. (ports for clean out flushing if needed. )

Legs are 1" pipe salvaged from old system with couplings welded on bottom for connection……so the whole thing built from scrap parts.

It was just a guess of being necessary, but was the time to do it.

The length was based on what was available of pipe from the old boiler.

Jamie Hall

"All rads are above the dry return line, and the wet return is pretty far below the boiler.:

Given that I have to admit that I really can't see much point to having the pump. Gravity is pretty reliable…

And with that reservoir pipe (II love that! Someone was really thinking!) you shouldn't have to worry about total water volume.

JUGHNE

This was a combined 1 pipe section of 1920 school house and a 2 pipe 1955 building.

One large boiler with zone valves and cond return pump.

This single boiler now does the 3 story building (storage) and 2 others do the remains of the 2 pipe system.

To show how much load, but not piping, was dropped the old 2 1/2" return is now connected to the single boiler with 1" copper (still oversized). The F&T trap was removed and more air vents added.

The 2 pipe system still needed a pump as you see the dry return for that part in the right hand portion of the picture, less than a foot above the floor.

JUGHNE

This feeds the single pipe system. The edges of the other 2 boilers are on the right side of the picture.

You can see the 3" header feeding a 4" riser that is connected to existing 5" steam main. Runs around the building returning with the 2 1/2" reduced to 1" copper.

No traps needed.

PC7060

https://forum.heatinghelp.com/discussion/comment/1906812#Comment_1906812

Spare parts plus access to good welders!

KC_Jones

The fact that the tank is right next to the boiler speaks volumes to me. Gravity is already working at the level of the boiler. Even with the boiler running, the pressures should be extremely low, well under 1 psi if they size the boiler correctly, and 1 psi requires no more than 28" above the boiler water line in a worst case scenario. To my eye you have way more than 28" to work with. Many times the pumps are added by unknowing contractors who think "its big it needs a pump", that's just not how it works.

If, and it's a big if, you need extra water volume the tank that @JUGHNE shows is a much better and simpler way to go. The pumps on these systems just add complexity and in your case, based on what I see in the pictures you have absolutely no need for a pump.

For my bolding above, it seems you have contractors with a varied level of abilities coming into your house. The sizing is critical and you get one chance to get it correct. It's super simple, but gotten very wrong a majority of the time. I'd be sizing things up myself if that was my house. If you want to go down that road we can assist.

GrockMan

https://forum.heatinghelp.com/discussion/comment/1906813#Comment_1906813

Thanks :) Though for clarity, the reservoir pipe posted was JUGHNE's, not mine.

GrockMan

Thanks you all, and after consideration and deliberation with my local guy, we agreed on replacing the disconnected Sterlco reservoir/pump with a new Sterlco reservoir/pump, connecting it and disconnecting the other condensate pump, and feeding fresh water into the Sterlco reservoir pump.

We decided on this for a few reasons:

1. Because freshwater flooding was the cause of the last boiler dying, we wanted to mitigate it happening again, by having the condensate return directly in charge of adding more water if needed.
2. We want the boiler to have control over when it needs to be filled, so that it does not overfilled, get flooded and then have trouble heating water to produce steam.
3. This gives the boiler a reservoir to pull from, it is just not gravity powered.

Thank you all for your comments, if you still do not think this is the correct move, I am still interested to hear why! (There is still time to modify the choice.)

Jamie Hall

Major comment: if you find you have to add more than a gallon or two of water per week, you have a leak — and your new boiler is going to be killed just as fast as the old one.

As to going with a boiler feed pump setup, that's your puppy. You don't need it, and I wouldn't want to have one, but that's your choice. Won't hurt anything if it's wired as boiler feed pump (it's guaranteed trouble if it's wired as a condensate return pump). Cedric — the Weil-McClain — heats 7,000 square feet of building and has never had a feed pump, nor has ever need one — Cedric's predecessor laster 70 years, and Cedric is going on for 20.

109A_5

Is the new boiler sized correctly for the attached EDR ? Is there a good source of combustion air to that room ?

Without doing your due diligence (see below) gravity or gravity with a reservoir or pumped with a reservoir is just a guess. Gravity is the simplest, then gravity with a reservoir. Your existing or a new reservoir could be used to simply add more water to the system. The reservoir (gravity with a reservoir) may need to be raised up to a more practical level to better match the new boiler's water range.

From the old boiler's manual:

From a manual of smaller boiler series.