is Hartford loop needed if all returns are above the boiler water line ,

eagle20mark

if all return lines are coming from the ceiling above, is the Hartford loop needed in the system

JUGHNE

To get returned to the boiler won't they have to drop below the water line and actually be a bit of wet return?

eagle20mark

yes , replace,, but this is a good question,
replacing old revised coal boiler , there will be new hoffman F&T installed so the return will be in the new boiler

jumper

eagle20mark said:

if all return lines are coming from the ceiling above, is the Hartford loop needed in the system

Depends?

eagle20mark

so i was going to install it anyway because of the focus of it always being needed to most people

KC_Jones

The dry returns aren't supposed to be tied above the water line. So they drop below the water line to create a seal from one to the other. Now that portion is a wet return and could drain the boiler so the Hartford loop is then required.

jumper

KC_Jones said:

The dry returns aren't supposed to be tied above the water line.

Why?

Fred

jumper said:

KC_Jones said:

The dry returns aren't supposed to be tied above the water line.

Why?

If it's on a one pipe system, the "Dry Return" is typically that part of the main, after the last radiator Run-Out. In that case, it will let steam leave one dry return and enter another, causing hammer.
I'm not sure that's the case with a two pipe system where the dry returns shouldn't have steam in them, unless a trap fails open.

JUGHNE

The dry returns would have different pressures at the boiler and perhaps pressurize the weaker return, or the condensate could cross over.
I had this situation with a tee bullheaded down to the few feet of wet return, but both sides were nearly equal pipe lengths and EDR. I did correct it eventually but not for this reason.

You need to keep their feet under enough water.

mikeg2015

KC_Jones said:

The dry returns aren't supposed to be tied above the water line. So they drop below the water line to create a seal from one to the other. Now that portion is a wet return and could drain the boiler so the Hartford loop is then required.

Yes, but the potential for the same failure is unchanged because even with a Hartford loop, you still have some external piping below the water line. That's unavoidable. If all you have is a vertical drop on a 1 pipe system, or a 2 pipe where returns remain above the boiler until the final drop, I don't see any value. Just drop into a Tee, with 1 end to the return header the other to the equalizer. Why add all the extra piping? Maybe I'm missing something.

mikeg2015

I'm assuming we were talking about a single return header. If multiple returns, then yes, you'd need to connect them below the water line and then, with that many Tee's I'd want a Hartford loop.

Fred

On a one pipe and even on a two pipe, that Hartford loop also creates a water seal that prevents steam from getting into the return pipe. Especially if you pipe it into the equalizer, just a couple inches below the boiler water line. If you pipe it lower, into the equalizer or directly into the boiler, then you run the risk of the water level being way too low, in the event of an external leak. Of course, that also assumes the LWCO fails. IMHO I would want the water seal.

KC_Jones

mikeg2015 said:

KC_Jones said:

The dry returns aren't supposed to be tied above the water line. So they drop below the water line to create a seal from one to the other. Now that portion is a wet return and could drain the boiler so the Hartford loop is then required.

Yes, but the potential for the same failure is unchanged because even with a Hartford loop, you still have some external piping below the water line. That's unavoidable. If all you have is a vertical drop on a 1 pipe system, or a 2 pipe where returns remain above the boiler until the final drop, I don't see any value. Just drop into a Tee, with 1 end to the return header the other to the equalizer. Why add all the extra piping? Maybe I'm missing something.

The Hartford loop makes it impossible for the boiler to be drained from a leak in the wet return piping. I could open the drain valve on mine run the return dry and the boiler will be plenty happy until it steams all the water off. Without the loop it would empty in minutes or even seconds.

Now that being said there are those that say the probe low water cut off is so good now there is nothing to worry about, but I am a belt and suspenders kind of guy.

Jamie Hall

It's not rocket science...

First, the return -- dry or wet, hooked together above or below the water line, whatever -- must be protected from the steam pressure, however low, in the boiler. Otherwise the steam won't flow.

Second, this means that either the return is connected to the boiler below the water line or some way is found to isolate the return from the steam.

If it is connected below the water line, and a leak develops, the boiler will drain rapidly. This can ruin your whole day.

So... you connect it above the water line, but with a water seal to separate the two pressures (return at atmospheric, usually).

But...

That means that you will have a siphon arrangement. You don't want that. So you connect the top of what would be the siphon to the equalizer, which will prevent it from acting as a siphon. And you call it a Hartford loop, after the name of the insurance company (Hartford Steam Boiler) which got tired of replacing dry fired boilers and mandated its use.

jumper

Yes but I asked why you shouldn't hook together dry returns? I was thinking specifically about two pipe. But the question also arises for downfeed systems.

Jamie Hall said:

It's not rocket science...

First, the return -- dry or wet, hooked together above or below the water line, whatever -- must be protected from the steam pressure, however low, in the boiler. Otherwise the steam won't flow.

Second, this means that either the return is connected to the boiler below the water line or some way is found to isolate the return from the steam.

If it is connected below the water line, and a leak develops, the boiler will drain rapidly. This can ruin your whole day.

So... you connect it above the water line, but with a water seal to separate the two pressures (return at atmospheric, usually).

But...

That means that you will have a siphon arrangement. You don't want that. So you connect the top of what would be the siphon to the equalizer, which will prevent it from acting as a siphon. And you call it a Hartford loop, after the name of the insurance company (Hartford Steam Boiler) which got tired of replacing dry fired boilers and mandated its use.

EBEBRATT-Ed

@jumper ,
most dry returns have air vents at there end before they drop below the water line and enter the boiler. If two or more returns are connected above the water line chances are return #1 being shorter than the other will get steam to it's end first and close it's vent. If it is connected to another return #2 above the water line steam from the first return #1 will flow towards the vent in return#2 and close it's vent. You will now have air trapped in return #2, also the steam from return 1 entering return 2 will oppose steam and condensate flow in return 2

Jamie Hall

@jumper -- I didn't mean to imply that dry returns should (or should not) be connected together. It depends very much on the system. In many vapour systems (such as the Hoffman Equipped which I am most familiar with) all the dry returns are -- and should be -- connected together at the boiler, with one, and only one, vent (or vents, if one isn't enough)(or air eliminator or some other contraption) located there. In principle there should never be any real pressure in those lines under normal operation -- and certainly no steam. (the exception, of course, in the Hoffman system is that when the Differential Loop activates, then full boiler pressure is admitted to the returns, quite deliberately -- but that's another story).

I think, however, that I recall this sort of discussion coming up some years ago, and realising at that time that we weren't all quite on the same page in one critical regard: some of us were using the term "dry return" for an extension of the steam main beyond the last takeoff which allowed condensate to drain back to the boiler. In systems which are piped like that -- one could regard them in some ways as being closely related to parallel flow one pipe systems -- then indeed they should not be tied together at the ends above the water line, but must be water sealed from each other -- and must be individually vented somewhere downstream from the last takeoff (doesn't have to be at the end -- just downstream). The same consideration applies to parallel flow one pipe systems (in counterflow systems that usually doesn't come up, as the steam mains usually end somewhere off in a crawl space or other handy location!).