Does the Hartford Loop actually do anything today?

DanHolohan

I’m enjoying this conversation, Chris. It’s a good one to have. I often turn questions around to see things from another perspective. It’s a habit I developed during my troubleshooting days. Thanks.

The Wire Nut

Humble home owner here, but as to the question of how often does a return leak, here are some photos of less than 10 year old black pipe returns that I installed when I bought my 1841 stone house 15 years ago, found Heating Help and learned that my steam boiler was installed as if were a hot water system! No header or equalizer, and half buried return with no Hartford loop.

(Original install)




When I re-piped the system I installed the wet return close to my concrete floor, little realizing that it was subject to enough moisture and a small flood or two to end up being chewed through.



(10 years later)





With Dan and John Cataneo's advice and encouragement, I replaced it with a copper return, elevated, but still below the water line.




I don't know how many "humble home owners" might notice the same thing until their basement was full of steam and condensate or their boiler exited the roof. So, give me belts and suspenders.

And, as the "WireNut", I love the idea of using a PLC to monitor and control a heating system. Unfortunately, we don't have many folks outside of the commercial control industry that know how to spec and program them.

jumper

PMJ said:

A little more control is long overdue here. More safety is easy on a PLC platform. Good control really needs some feedback from the field about when and where steam is happening anyway (think preheat sensor). With a PLC a time limit is easily put on the combination of an open gas valve and no steam. That is what I do and I sleep better. Some of this really should have happened on a commercial level by now. Disappointing to say the least. Way behind the curve.

would high water/steam temperature safeties work?

kevink1955

Anyone know where the name "Hartford loop" came from, I am guessing it was an insurance company that required it as a condition of insurance

PMJ

> @jumper said:
> (Quote)
> would high water/steam temperature safeties work?

Sure.

My point was that better control needs a PLC platform anyway(like Ecosteam). I use the same PLC it does. You then find that through many of the regular control sensors you can also automatically know bad things are happening. Like put an absolute limit on a straight run of the boiler with no steam at a certain sensor. Control possibilities are limitless and so are the safety checks.

Many of these things have worked their way into the forced air world. They should have in steam too.

BobC

@kevink1955 That loop was required by the Harford Boiler Inspection and Insurance Company to help stem the number of boiler launchings in the late 19th and early 20th century

https://inspectapedia.com/heat/Hartford_Loop.php

Bob

mikeg2015

I have a 1 pipe with a dry return, but still used a Hartford loop. My rationale:

1) Acts like a great mud leg from crud returning form the radiators. In 1 pipe, since it’s an “open” system you get a lot more crud. The boiler i ripped out was 2/3rd full on the return pipe. I extended my dry return over 1’ below the boiler return so sediment suspended in the condensate has to go “uphill” to reach the boiler.
2) Less pipe strain connecting the equalizer seperate of the return header
3) Adds just a little more water volume to the low volume modern boilers and a little more mass on the water side smooth out shutdown as hte system goes into vacuum... a softer landing so to speak. My vents can whistle when 90’ of 3” header along with all the radiators, collapse into a vacuum.

ChrisJ

mikeg2015 said:

I have a 1 pipe with a dry return, but still used a Hartford loop. My rationale:

1) Acts like a great mud leg from crud returning form the radiators. In 1 pipe, since it’s an “open” system you get a lot more crud. The boiler i ripped out was 2/3rd full on the return pipe. I extended my dry return over 1’ below the boiler return so sediment suspended in the condensate has to go “uphill” to reach the boiler.
2) Less pipe strain connecting the equalizer seperate of the return header
3) Adds just a little more water volume to the low volume modern boilers and a little more mass on the water side smooth out shutdown as hte system goes into vacuum... a softer landing so to speak. My vents can whistle when 90’ of 3” header along with all the radiators, collapse into a vacuum.

Hi Mike,


I wash my boiler out every fall and there's always plenty of "rust" sediment on the return side of it regardless of the Hartford loop.

#2 and #3 I completely don't understand?

Lard

Returns certainly do fail catastrophically, as seen in the attached picture. Had this been a true return (instead of feeding to a trap/feed tank) and not protected by a Hartford loop, the boiler would have drained completely in a few minutes. The hole was about 1 square inch of area.

Electronics fail, floats stick, but passive safety prevails.

ethicalpaul

Lard said:

Returns certainly do fail catastrophically, as seen in the attached picture. Had this been a true return (instead of feeding to a trap/feed tank) and not protected by a Hartford loop, the boiler would have drained completely in a few minutes. The hole was about 1 square inch of area.



Electronics fail, floats stick, but passive safety prevails.

And just so I understand the benefit, how much time would the loop buy you in that case?

Fred

ethicalpaul said:

Lard said:

Returns certainly do fail catastrophically, as seen in the attached picture. Had this been a true return (instead of feeding to a trap/feed tank) and not protected by a Hartford loop, the boiler would have drained completely in a few minutes. The hole was about 1 square inch of area.



Electronics fail, floats stick, but passive safety prevails.

And just so I understand the benefit, how much time would the loop buy you in that case?

Maybe an hour or two. Remember the loop is just a couple inches below the normal water line.

ChrisJ

Lard said:

Returns certainly do fail catastrophically, as seen in the attached picture. Had this been a true return (instead of feeding to a trap/feed tank) and not protected by a Hartford loop, the boiler would have drained completely in a few minutes. The hole was about 1 square inch of area.



Electronics fail, floats stick, but passive safety prevails.

Yes,

Assuming someone just happens to check the boiler in the incredibly short time they have.

jumper

Redundant low water safeties? Why not?

I've seen two pumps on HHW. But nobody replaces dead one. Of course second one fails when nobody is around to notice heat is off. I've even seen motorists continue to drive with a failed brake circuit. The thrill of living dangerously?

ChrisJ

jumper said:

Redundant low water safeties? Why not?

I've seen two pumps on HHW. But nobody replaces dead one. Of course second one fails when nobody is around to notice heat is off. I've even seen motorists continue to drive with a failed brake circuit. The thrill of living dangerously?

Curious if a simple, cheap, reliable bimetal switch bolted directly to the block in a good location would serve the purpose? If it gets above a certain temperature it cuts power to the burner.

No probe or probe circuit to fail and no float to stick.

Fred

ChrisJ said:

jumper said:

Redundant low water safeties? Why not?

I've seen two pumps on HHW. But nobody replaces dead one. Of course second one fails when nobody is around to notice heat is off. I've even seen motorists continue to drive with a failed brake circuit. The thrill of living dangerously?

Curious if a simple, cheap, reliable bimetal switch bolted directly to the block in a good location would serve the purpose? If it gets below a certain temperature it cuts power to the burner.

No probe or probe circuit to fail and no float to stick.

@ChrisJ , don't you mean "If the gets Above a certain temperature, it cuts power to the burner? The part of the block above the water level would be hotter than below the water level. If it were "below" a certain temp, the burner would likely not fire after any period where there was no call for heat.

ChrisJ

Fred said:

ChrisJ said:

jumper said:

Redundant low water safeties? Why not?

I've seen two pumps on HHW. But nobody replaces dead one. Of course second one fails when nobody is around to notice heat is off. I've even seen motorists continue to drive with a failed brake circuit. The thrill of living dangerously?

Curious if a simple, cheap, reliable bimetal switch bolted directly to the block in a good location would serve the purpose? If it gets below a certain temperature it cuts power to the burner.

No probe or probe circuit to fail and no float to stick.

@ChrisJ , don't you mean "If the gets Above a certain temperature, it cuts power to the burner? The part of the block above the water level would be hotter than below the water level. If it were "below" a certain temp, the burner would likely not fire after any period where there was no call for heat.

Yeah........
I fixed it.

JUGHNE

How about this, almost fail safe:
Commercial range hoods have spring loaded melt-able fuse links, which in addition to activating the fire extinguishers, will release the normally closed gas line fire valve......no power needed.....all simple mechanical devices.

This would also cover the stuck open gas valve that causes runaway overheating.

ethicalpaul

Fred said:

Maybe an hour or two. Remember the loop is just a couple inches below the normal water line.

Oh I remember

I don't think I'd get an hour, maybe 10-20 minutes. My boiler has 5 gallons in it.

Fred

ethicalpaul said:

Fred said:

Maybe an hour or two. Remember the loop is just a couple inches below the normal water line.

Oh I remember

I don't think I'd get an hour, maybe 10-20 minutes. My boiler has 5 gallons in it.

According to Peerless, the 63-03L steam boiler has holds 9.3 gallons. You'll get an hour or two, maybe even more if you consider the boiler will only run, maybe 30 minutes per hour, if that much.

ChrisJ

So here's the next question.

Will a steam boiler explode under most conditions from dry firing?

Or, is the bad moment when someone tries to add water to it when the block is cherry red? Does someone have to actually try and add water, or is it known to somehow, some way just make it's way back via piping.

I.E. Will a steamer explode just because it loses all of it's water all on it's own? Does water tend to some how make it's way back to a dry firing boiler under typical conditions?

There's a video online of a commercial steamer exploding, I think they said a failed, or bypassed LWCO. What caused the actual explosion? Did a feed pump turn on for some reason?

To me, this is actually a very important question.

I know this is a separate subject from the Hartford loop. But, I believe it's important and could save a life.

DanHolohan

https://heatinghelp.com/heating-museum/category/boiler-explosions

Lard

> @ethicalpaul said:
> (Quote)
> And just so I understand the benefit, how much time would the loop buy you in that case?

The boiler in this case steams around 2-2.5 gallons per minute, water capacity is ~80 gallons, so roughly 20-30 minutes of steaming before things start getting scarier. The big benefit if all other safeties fail in my opinion is less thermal shock/things going pear-shaped slower and less violently. The boiler may be junk, but the structure/lives are intact.

The BLEVE failure mode I visualize is a sudden dump of *nearly* all of the water in the block. The residual water is still there on all of that hot iron (and in various crevices and possibly entrained in scale) with no other heatsink anymore. This residual water gets very big, very fast—-BLEVE happens.

ethicalpaul

> @Fred said:
> (Quote)
> According to Peerless, the 63-03L steam boiler has holds 9.3 gallons. You'll get an hour or two, maybe even more if you consider the boiler will only run, maybe 30 minutes per hour, if that much.

That boiler is still on its pallet in my garage 😅

I’m running the Utica PEG 112 (Dunkirk design) one more season, but I’m super impressed that you know my boiler model!!

And I’m really surprised the Peerless holds that much more water—it’s barely more EDR

ChrisJ

ethicalpaul said:

> @Fred said:

> (Quote)

> According to Peerless, the 63-03L steam boiler has holds 9.3 gallons. You'll get an hour or two, maybe even more if you consider the boiler will only run, maybe 30 minutes per hour, if that much.



That boiler is still on its palette in my garage 😅



I’m running the Utica PEG 112 (Dunkirk design) one more season, but I’m super impressed that you know my boiler model!!



And I’m really surprised the Peerless holds that much more water—it’s barely more EDR

I don't know.
Impressed, or concerned you have a stalker.

@Fred Why don't you know the water content of my boiler!?

Fred

ChrisJ said:

ethicalpaul said:

> @Fred said:

> (Quote)

> According to Peerless, the 63-03L steam boiler has holds 9.3 gallons. You'll get an hour or two, maybe even more if you consider the boiler will only run, maybe 30 minutes per hour, if that much.



That boiler is still on its palette in my garage 😅



I’m running the Utica PEG 112 (Dunkirk design) one more season, but I’m super impressed that you know my boiler model!!



And I’m really surprised the Peerless holds that much more water—it’s barely more EDR

I don't know.
Impressed, or concerned you have a stalker.

@Fred Why don't you know the water content of my boiler!?

@ChrisJ , I don't like hanging out in Jersey, peeping in windows.

HGifford

Henry Gifford here, inventor of the Gifford Loop as a replacement for the Hartford Loop.
I agree with the comments above about how little the Hartford Loop accomplishes. Many years before I was born it became common knowledge that the Hartford Loop accomplished 3 things, which if I remember correctly are:
1 - separates water from the steam
2 - equalizes pressure between top and bottom of boiler, so pressure can't push water back out the return
3 - prevents dry firing if a return leaks
As to separating water from the steam, proper header piping will do this, and drain the water down the equalizer, or the Hartford Loop, depending on what part of the pipe is called what. But connecting the return above the floor will not separate the water, thus the Hartford Loop does not do number 1.
As for equalizing the pressure, it definitely does this. But, the pressure between the top and bottom of the boiler is already equal (neglecting the weight of the water). Connecting a pipe between the top and bottom of the boiler equalizes the pressure as much as hollowing out the handle of a beer mug equalizes the pressure between the top and bottom of the mug. So, I see this "function" as useless. What prevents the steam from pushing water back out the return (much) is the (almost) equal steam pressure applied to the returns at the drips.
As for preventing dry firing, I agree with those above who say it delays the inevitable for a few minutes at best. But, in most cases it won't even do that, because nobody knows (or says) how high to pipe the Hartford Loop. Boiler instructions say to pipe it 2" or 4" below the water line, but I've never seen one which says if that below is the normal water line or the lowest water line. And, as the pipe generally has an inside diameter of at least 2", measuring to the top or bottom or middle of the pipe can make a difference of 4", which is never specified. So, usually the Hartford Loop is too low to prevent the water in the boiler from getting below the lowest permissible water line, therefore the idea of extending the life of the boiler for a few minutes is, I think, doubtful.
I have no doubt that long after I am dead many people will think the Hartford Loop performs these three functions, but I'm glad to see that so many people aren't buying the story.
I think the Gifford Loop is very beneficial, and I always pipe gravity returns with it. Anyone interested can find more information in the link someone left above, or google the (long expired) patent: US6,349,677.

ChrisJ

HGifford said:

Henry Gifford here, inventor of the Gifford Loop as a replacement for the Hartford Loop.
I agree with the comments above about how little the Hartford Loop accomplishes. Many years before I was born it became common knowledge that the Hartford Loop accomplished 3 things, which if I remember correctly are:
1 - separates water from the steam
2 - equalizes pressure between top and bottom of boiler, so pressure can't push water back out the return
3 - prevents dry firing if a return leaks
As to separating water from the steam, proper header piping will do this, and drain the water down the equalizer, or the Hartford Loop, depending on what part of the pipe is called what. But connecting the return above the floor will not separate the water, thus the Hartford Loop does not do number 1.
As for equalizing the pressure, it definitely does this. But, the pressure between the top and bottom of the boiler is already equal (neglecting the weight of the water). Connecting a pipe between the top and bottom of the boiler equalizes the pressure as much as hollowing out the handle of a beer mug equalizes the pressure between the top and bottom of the mug. So, I see this "function" as useless. What prevents the steam from pushing water back out the return (much) is the (almost) equal steam pressure applied to the returns at the drips.
As for preventing dry firing, I agree with those above who say it delays the inevitable for a few minutes at best. But, in most cases it won't even do that, because nobody knows (or says) how high to pipe the Hartford Loop. Boiler instructions say to pipe it 2" or 4" below the water line, but I've never seen one which says if that below is the normal water line or the lowest water line. And, as the pipe generally has an inside diameter of at least 2", measuring to the top or bottom or middle of the pipe can make a difference of 4", which is never specified. So, usually the Hartford Loop is too low to prevent the water in the boiler from getting below the lowest permissible water line, therefore the idea of extending the life of the boiler for a few minutes is, I think, doubtful.
I have no doubt that long after I am dead many people will think the Hartford Loop performs these three functions, but I'm glad to see that so many people aren't buying the story.
I think the Gifford Loop is very beneficial, and I always pipe gravity returns with it. Anyone interested can find more information in the link someone left above, or google the (long expired) patent: US6,349,677.

Thank you Mr Gifford.

ethicalpaul

Thank you for the informational reply. I'm going to pipe my boiler with the Gifford Loop

Voyager

DanHolohan said:

Let's ask this another way: What is to be gained by leaving it out?

A little cost as with leaving almost anything out. Many of the issues I saw during my engineering career were caused by things left out during a redesign by someone who didn’t understand fully the original design and thought a few bucks could be saved.

That does not imply that things don’t become obsolete and should be removed, but we should do as was done here and first truly understand the purpose of a component before deciding to remove it.

Fred

@HGifford , I don't think most of us believe the Hartford Loop even remotely does point 1 or 2, in your comments. Those who do simply don't understand the intent of the Hartford loop.
I even think most of us would certainly agree that the Gifford loop is a design improvement over the Hartford loop. Having said that, I'd be interested in further explanation on your point #3. If, in fact, the Hartford loop has little value in helping to prevent a dry fire, why did you not simply suggest/recommend total elimination, rather than redesign, which, I think was the impetus of this thread?

ChrisJ

Fred said:

@HGifford , I don't think most of us believe the Hartford Loop even remotely does point 1 or 2, in your comments. Those who do simply don't understand the intent of the Hartford loop.
I even think most of us would certainly agree that the Gifford loop is a design improvement over the Hartford loop. Having said that, I'd be interested in further explanation on your point #3. If, in fact, the Hartford loop has little value in helping to prevent a dry fire, why did you not simply suggest/recommend total elimination, rather than redesign, which, I think was the impetus of this thread?

@Fred,

Many absolutely do believe #1 and #2 especially since #2 I believe is mentioned in the Hartford document, I know it's written somewhere.

As far as why he did what he did, did you read his patent? It explains all of it. Google Patents.

Fred

ChrisJ said:

Fred said:

@HGifford , I don't think most of us believe the Hartford Loop even remotely does point 1 or 2, in your comments. Those who do simply don't understand the intent of the Hartford loop.
I even think most of us would certainly agree that the Gifford loop is a design improvement over the Hartford loop. Having said that, I'd be interested in further explanation on your point #3. If, in fact, the Hartford loop has little value in helping to prevent a dry fire, why did you not simply suggest/recommend total elimination, rather than redesign, which, I think was the impetus of this thread?

@Fred,

Many absolutely do believe #1 and #2 especially since #2 I believe is mentioned in the Hartford document, I know it's written somewhere.

As far as why he did what he did, did you read his patent? It explains all of it. Google Patents.

Chris, as I said in my post, I don't doubt what "many believe" truth or otherwise. Also, my question is still valid. I have read why he redesigned the loop and I know it creates a more stable water line, in contract to the Hartford loop . My question remains; Why did he not recommend eliminating the loop, in total ?

HGifford

As to number 3 above, no, neither a Hartford Loop nor a Gifford Loop will prevent dry firing - the water in the boiler will get too low if the boiler is steaming and a leak starts leaking water faster than the feeder feeds new water into the boiler (and all the Low Water Cutoffs don't work).
To those above who ask why I don't simply remove the Hartford Loop, one reason is that too many inspectors and other people would ask for it. Another reason is that the Gifford Loop (like a Hartford Loop but with the inside of the horizontal nipple 1/2" above the height where the feeder starts feeding water) will stabilize the water line, like some people above have mentioned. Water sloshing around between the boiler and the returns causes the water level in the boiler to fluctuate. In modern boilers the surface area of the water in the boiler is smaller than in an old boiler of the same firing capacity, therefore the height of the sloshing in the boiler is greater than in older boilers (compared to the height of the sloshing in the returns - see drawings in article someone linked to above - thank you). Some manufacturers now build time delays into LWCO/Feeder controls to prevent boiler flooding, which I don't like - I don't want the fire on with the water dipping low many times per minute. So, instead, the Gifford Loop prevents sloshing below the level where the feeder feeds water, preventing flooding (from the feeder feeding water in response to sloshing) and greatly stabilizing the water line - it can get so rock steady it's hard to know the boiler is steaming without looking at the pressure gauge. I use a "line level" (a bubble level with two hooks to attach it to a piece of string - like masons use) to get the Gifford Loop at just the right height: the inside of the horizontal nipple 1/2" above where the feeder starts feeding. 1" is also OK, but don't install it too high or there will be a buzzing noise when condensate is coming back. Nobody asks any questions when they see it, and it stops a lot of problems with boiler flooding, banging radiators, spitting air vents, etc. It costs nothing and can't do any harm, thus is worth doing anytime a steam boiler is being installed or nearby piping work is being done. And, yes, you can repair or replace condensate pipes without draining the boiler or turning it off - very handy to not have to turn off the hot water to an apartment house while repiping returns.

dopey27177

The Hartford loop is the cheapest insurance policy against a dry fire known to boiler installers. this followed by installing a low water cut off, a mechanical device that usually is not drained periodically by the home owner.

Let us look at why wet returns are used in steam heating systems.

when a dry return is used in a one pipe heating system in excess of 100,000 btuh building the dry return depending on length and pitch the dry return can be 1-1/2" pipe.

Looking at return sizing tables a 1" pipe can be used for some of the buildings up to 200,000 btuh.

So we can save money on pipe installation by using a wet return therefore the Hartford loop is necessary.

Many buildings had wet returns installed and often they ran down the center of the basement (shorts run to the boiler.)

In my day (25 years ago and before) I replaced the underground piping with type K copper with silver brazed fittings. Did not reinstall underground but ran the pipe around the perimeter of the unfinished basement.

Some buildings had finished basements where several wood panels had to be removed to allow the new pipe to be installed.
More often then not 2X4s had to be notched and the pipe was supported by copper J hooks.

One important thing to remember is some times a dry return gets water logged and some banging can occur for a short period of time where in a wet return it never gets water logged,

Also when a wet return is reinstalled clean out ts should be installed to allow the wet return to be flushed from time to time.

Jacob Myron

luketheplumber

JUGHNE said:

How about this, almost fail safe:
Commercial range hoods have spring loaded melt-able fuse links, which in addition to activating the fire extinguishers, will release the normally closed gas line fire valve......no power needed.....all simple mechanical devices.

This would also cover the stuck open gas valve that causes runaway overheating.

have you ever seen or dealt with a stuck open gas valve before

JUGHNE

Luke, yes this happens.
My most memorable one was on an ancient furnace. (furnace or boiler would have the same results). The house was overheating. The elderly lady shut off the power at the circuit breaker. Then the furnace keep firing with no blower air flow. Came close to melting the flex duct connected directly to the air supply plenum. Slumlord, very bad install, used furnace that was rescued from the landfill.

Had a couple others in the past 40 years. (I cover a very small area, this is more common than people imagine.)
That is why any valve that has been submerged or subject to dirty/wet gas must be changed.....they may not close completely.
Also if subjected to high pressure, that could have the same effect.

Larger commercial boilers have 2 gas valves in series. Both would have to fail for over firing.
Some of these have a normally open solenoid valve between the main valves, piped to the outside, this valve closes when the main valves are called to open. So if the first valve was stuck open the gas would be passed outside and hopefully someone would smell it.

PMJ

I have two gas valves in series. I bought my flue damper 25 years ago from an engineering school classmate who is in the commercial boiler business. At the same time I did that he told me to put in a second valve for the added safety. Made sense to me - didn't cost that much.

Jamie Hall

It can happen with oil, too. Some of you may recall that I experienced a fused closed contact in a relay in Cedric's burner control, which meant that none of the safeties would shut the system off (killing the power did, of course). There another misunderstood and sometimes despised safety with no moving parts saved the day: the Hoffman Differential Loop operated as designed, and as a result the system differential pressure never got over half a pound or so and condensate could return more or less normally (the total system pressure did get well up into the silly range, though).

ChrisJ

@dopey27177
Probe type LWCOs are preferred. If it's a float style LWCO it must be drained weekly with the burner firing to ensure the LWCO operates and shuts it down. This isn't optional.

That said, did you read the posts by @HGifford? I highl
> @Jamie Hall said:
> It can happen with oil, too. Some of you may recall that I experienced a fused closed contact in a relay in Cedric's burner control, which meant that none of the safeties would shut the system off (killing the power did, of course). There another misunderstood and sometimes despised safety with no moving parts saved the day: the Hoffman Differential Loop operated as designed, and as a result the system differential pressure never got over half a pound or so and condensate could return more or less normally (the total system pressure did get well up into the silly range, though).

And what would've happened in your case Jamie if you had a substantial leak in a return and no feeder?

Would the Hartford loop have saved the boiler?

Jamie Hall

In a word, in that particular circumstance, no, @ChrisJ . In fact, I'm not exactly sure what would have -- if anything. Perhaps the Fireomatic overhead might have shut things off before they got really pear shaped.

I've thought a good deal about that incident (i really don't like that level of excitement) and haven't come up with a really good solution. The best approach, which I haven't implemented yet and which does have some drawbacks, would probably be yet another pressuretrol and LWCO (wretched excess!), both manual reset and set to rather extreme values, in the main power feed to the boiler, rather than in the burner control circuit. They'd have to take the full starting current of burner, which is probably manageable, and interrupt the full running current -- which might be more problematic. Or possibly they could power a fail/spring closed solenoid valve on the oil feed (though I'm none too keen on always on solenoids... they can stick).

Thoughts?