Easiest Way to Convert to Gravity Return?

zackwatt

I've just about had it with the disruption my condensate pump adds to my system...

Even when set at is lowest level, and still starves the boiler requiring more water then necessary. Then once everything is shut down the boiler is practically flooded, adding to the the amount of water that gets sucked into the header and mains when everything comes back on. It also collapses the steam every time it kicks on.

I really would like to be rid of it, but hopefully with as few changes as possible. Since it's the air vent for the two F&T traps at the end of the steam main, and the air vent for the main condensate return line I can't just delete it and reconnect the pipes...

Any thoughts? I'm ready to get my wrench out.

HVACNUT

I dont see one, is there a PRV in the make up water piping? Should have one. Could be the whole trouble right there.

Steamhead

The trouble is, that condensate pump is completely unnecessary.

Each steam main will need an air vent. I think there is one on the main to the right, perched on top of the elbow pointing down. There also needs to be a vent on the dry return. Take some pics of these areas and post them. Also, measure the length and diameter of both steam mains and post the info here, so we'll know what vents you need.

With these three vents, you can drop the return connections from all three lines below the boiler's waterline and tie them together. Then run the line into the Hartford Loop. Note that if the tee at the Hartford Loop has only a 3/4" connection for the return, you'll have to replace it with something bigger.

Jamie Hall

I've never been a fan of condensate return pumps, and I don't propose to change. Though there are situations where a boiler feed pump is required. There is a critical difference: a boiler feed pump is activated by a low water level in the boiler, preferably a second level above where the boiler shuts down on low water (float type LWCOs almost always have the necessary contacts). What happens is that the boiler calls for more water, the boiler feed pump -- set to a low flow rate -- feeds until the water level comes up again (the low flow rate is to avoid killing the steam) and shuts off. If and when the condensate tank gets low, a simple float valve refills it from the water supply (should never happen with a big enough tank). Any overflow goes to the basement floor drain.

So -- first step is to see if you can convert your setup to a boiler feed pump. If you have an LWCO with a higher set of auxiliary contacts, that's going to be pretty simple. You will need a low water feed valve on the condensate tank, that's simple too.

Now if that's not attractive, you can get around the venting problem by adding main vents before the two F&Ts (some have tappings ready made) and on the condensate return line. That may not solve all the problems and allow direct connection, though, as the condensate return will be at atmospheric pressure, and the lines draining the F&Ts may be at atmospheric -- or even lower -- pressure. You would need to make sure you had enough height to ensure that you didn't back water out of the boiler up to them if you connected directly. Could I ask why you have F&Ts anyway, and not a straight drip to a wet return? With either main vents or crossover traps to a handy dry return?

zackwatt

Steamhead said:

Take some pics of these areas and post them. Also, measure the length and diameter of both steam mains and post the info here, so we'll know what vents you need.

The mains are pretty long as they run the full perimeter of the house. Rough stepped off measurements for the left vent is 60-65ft at 2in diameter then a step down to 1.25in diameter for the last 20-25ft. before ending at the left vent and F&T trap. The right main seems close at 60-65ft to the last radiator, then I'm assuming (it's in a crawlspace) a step down to 1.25in diameter for 80ft back to the right vent and F&T trap.

ratio

A simple change you can make would be to throttle the feed pump, enough that it doesn't kill the steam production when the pump runs. This wouldn't solve the level issues, however.

Steamhead

How about the end of the dry (overhead) return line from the radiators?

zackwatt

Steamhead said:

How about the end of the dry (overhead) return line from the radiators?

Here's the condensate return from the radiators. No vent or anything...

Jamie Hall

I think I'm missing something basic here, and feeling dumb. Perhaps @Steamhead can educate me... since there are vents at the ends of the mains, and since it looks to me as though the outlet from the F&Ts goes down to something -- wet return? -- what, exactly, does the F&T trap add to the system? In other words, why is it there at all?

zackwatt

My guess is the F&Ts are directly related to the condensate pump design. The returns are not wet, but dry. Also the condensate pump reservoir is vented open to the atmosphere.

Steamhead

Let's back up a minute. Since there is a return line from just the radiators, this is a two-pipe system, correct?

jumper

Haven't we discussed pressurized receivers in the past? Condensate pump pumps into a non-vented elevated tank which feeds the boiler on demand.

That tank (don't want to mix it up with condensate pump's receiver but technically it is a receiver) should have some sort of pressure release safety.

Holohan has more than once described problem with condensate pump starving/flooding boiler.

Jamie Hall

For what little it's worth... I've never had a problem with a boiler feed pump. There are a number of possible situations where they are required, and a number where they make things a little simpler.

They are designed and controlled to maintain the water level in the boiler within an optimum range for steaming.

However.

A condensate pump isn't either designed or controlled that way. It is controlled only by the level of condensate in the receiver -- which may or may not have any good correlation with the amount of water the boiler needs.

If, for some reason, you need to have a vented tank to receive condensate or, if for some reason, you need to pump water into the boiler rather than letting gravity do its thing, control the pump which makes the transfer from the tank to the boiler by the level in the boiler.

Please...

zackwatt

Steamhead said:

Let's back up a minute. Since there is a return line from just the radiators, this is a two-pipe system, correct?

That is correct!

Steamhead

Put a big vent on that return and the air will vent from the rads when you remove the pump.

AMservices

If your planning on taking the wrenches out, one big improvement I see would be adding a second riser from the boiler block to the supply header.
Adding a second full size riser will cut the steam velocity in half in you will siphon a lot less water into the system.

Try to keep the steam dry by keeping the water in the boiler.

If water is being thrown out of the boiler traveling around the system with steam, not only is it Robbing you of all the good dry steam in the pipe, Your boiler is going off on low water, Then your automatic feeder kicks in topping off the boiler, By the time the automatic feeder shuts off the condensate tank is filling up and the float kicks on the pump to now flood your boiler.

What is your pressure control set to?

I know you said you have 2 pipe steam system, But do you have steam traps on your radiators or are there air vents on all your radiators?

If I was going to convert this to a gravity return What I would do is 1st Remove the F&T's. You don't need them there if the condensate is draining directly into a wet return. Also does a small hole in that the condensate drains through in the F&T. One small enough that could easily get clogged, Restricting the flow of condensate.
The Y strainers can go to. Just bring the drip leg all the way down With a drain at the bottom for servicing.

2nd, If there are steam traps at the radiators, replace the one set have failed. Someone properly installed the F&T traps When they experienced water hammer in the condensate receiver. If the steam traps are working, you won't have steam in the dry returns.

3rd, Make sure you have adequate venting at the ends of all the dry returns Because if air can't get out, steam can't get in.

4th, I would connect all the drops from the dry returns together below the condensate receiver into one of its inlet's. Come out of the other Inlet and into the Hartford loop (make sure you stay below the boilers water line with the piping between tank and boiler, come straight up and st 90° into a full size "T" on boilers equalizer.

Most guys stick with the classic Hartford loop ( Hartford loop connects 2" below boilers low water line).
Not to be different, but because I feel it does a better job controlling the boilers water line, I install what is called a Gifford loop (Gifford loop connects 2" above the boilers low water line).
See attachment below.

The receivers air vent can remain as is. The pump can be left in place and wiring disconnected. Cap off discharge line and you're in business.

PMJ

I have both a boiler feed pump and a condensate return pump on a process steam system. The boiler is in the building basement and steams at 15lbs. The condensate return tank is next to the boiler and a pump required there to overcome the pressure to get water back into the boiler. A Jamie says it is controlled by the water level in the boiler.

The condensate return pump is required on the floor above next to the plating process because the condensate must go an additional 15 feet up and over a piping bridge before it can go back down to the basement. Condensate fills it by gravity and it cycles based on the level inside it.

I can say with confidence that whenever gravity will do the job fussing with pumps at all is never worth it. I can't imagine screwing around with a pump at home on my gravity return two pipe - especially if the GPM of the pump is any percentage at all of the boiler capacity. Sounds like a real pain. Follow the expert instructions here and get the wrenches and remove that thing.

zackwatt

Thanks for all the replies everyone!

What's the best way to vent the air from dry condensate return since there's no steam? Just a tee piped in and left open?

Steamhead

zackwatt said:

Thanks for all the replies everyone!

What's the best way to vent the air from dry condensate return since there's no steam? Just a tee piped in and left open?

There might be steam in that return if a trap fails- obviously this is not usual but you don't want steam to leave the system regardless. Use a Gorton #2, which also has a float to close the vent if water backs up into the return.

jumper

PMJ said:

I can say with confidence that whenever gravity will do the job fussing with pumps at all is never worth it..

Pumps are a shortcut that owner will pay for many times over the years. I've seen industrial users abandon condensate return because they find it easier to treat water than maintain pumps.

zackwatt

Well I finally found a local boiler expert to help with the work I needed. Here are the results:











Now, I'm waiting for most all the oils accumulate in the boiler so I can do a nice long skim. I still need to add some drain valves for the wet return section.

JUGHNE

Great improvement, will give you a quieter basement.

I am curious about the oversized wet return manifold, is it to act as an addition water accumulator or just sludge trapping?

KC_Jones

I'm curious about the wide open pipe on that return?!

zackwatt

JUGHNE said:

I am curious about the oversized wet return manifold, is it to act as an addition water accumulator or just sludge trapping?

It was suggested by the installer for "having some extra water" than a smaller one. I wasn't sure about that, but I liked the idea of the added sludge trapping it would give. So, there it is. Ha.

zackwatt

KC_Jones said:

I'm curious about the wide open pipe on that return?!

Yeah, that was my doing and I know it's probably frowned upon.
My system is two-pipe, and has an entirely independent condensate dry return section that is separate from the two steam mains. Only condensate and air move through that line. Since that same line was vented open to the atmosphere through the old condensate pump (as you can see in my first post) without any vent or float, I figured I'd try it. I was also thinking it would give the maximum venting capacity since all 15 radiators ultimately vent their air to that point.

JUGHNE

So your end of mains are connected to the wet return?

zackwatt

JUGHNE said:

So your end of mains are connected to the wet return?

Yes. Two steam mains and one condensate return.

AMservices

> @Steamhead said:
> Thanks for all the replies everyone!
>
> What's the best way to vent the air from dry condensate return since there's no steam? Just a tee piped in and left open?
>
> There might be steam in that return if a trap fails- obviously this is not usual but you don't want steam to leave the system regardless. Use a Gorton #2, which also has a float to close the vent if water backs up into the return.

You should put vents on that condensate return line.
Maybe not today and maybe not tomorrow, but someday... a steam trap on that line could fail.

You found a good boiler man. Very nice work.

JUGHNE

Would not the same consequences of failed trap show up with the previous cond pump, steam thru the vent?

I redid a 2 pipe system with no traps, only inlet orifices.
We had the same EOM drops and 2 dry return drops.
I was tempted to do the open pipe as the return lines were cool.
But considering the distance to the job and the possibility of over pressuring the system pushing steam thru, I put a G2 on each. After 3 years I do not believe they ever closed.

I believe this is Zackwatt's home and he is aware of the possibilities.

PMJ

I get why contractors feel the need to put a vent on for safety reasons. But as a homeowner just skip it for sure.

@zackwatt , during operation stand there and feel the air coming out on each firing. Then feel/hear the air rushing in when the burner cycles off. Ask yourself what purpose is served by letting all that air back in knowing you just have to push it back out again on each and every firing.

Step 2 - skip all other vents( if you presently have any) and make this the only opening to the atmosphere. Put a really simple check valve on that and don't let the air back in when the burner cycles off. Try it - you'll never go back.