Does the Hartford Loop actually do anything today?

ethicalpaul

I've been thinking about the Hartford Loop for a few weeks and I propose that it doesn't do anything useful in modern residential steam boiler applications.

I wonder if I'm wrong. Convince me! I might be missing something.

My case:
- It's designed to prevent all the boiler water from running out onto the floor due to a leak in the wet return causing a dry fire of the boiler
- But what does that actually get you? A typical boiler is steaming like 1 gallon per minute, right?
- So the boiler is going to dry itself out in a matter of minutes anyway. Is the thinking that the homeowner is going to happen to go look at the boiler during this time period and shut it down?

ChrisJ

The equalizer prevents pressure from pushing water out of the boiler.

I don't think this should happen in a proper home heating system due to the low pressures.

Aside from that, I've wondered the same thing for many years now.

How often do wet returns have a catastrophic failure?

I recall there being a huge drop in explosions after the loop was implemented. But why, and this was obviously the days of coal with zero controls on the system.

@DanHolohan @Steamhead Can we have some history and input on this? Many consider the Hartford loop to be an extremely important item. But, is it still?

ethicalpaul

@ChrisJ I like your point about the equalizer. Is it part of the Hartford Loop? I have been confused about the "loop" part of the term because people seem to refer to the Hartford Loop as just the raised part where the return goes into the boiler.

Prior to the "Hartford Loop" was there no equalizer?

I was under the impression that the purpose of the Hartford Loop was to prevent dry fire from drained boiler due to return leak, but maybe that is only part of it.

STEAM DOCTOR

There are really two different things. Equalizer is there to prevent water from being pushed out into return. The loop is there to prevent boiler from drying out in the event that the wet return springs a leak. You can have an equalizer without having a Hartford Loop

Jamie Hall

As I understand it -- and hopefully @DanHolohan will come in here with the right answer! -- it was intended to prevent dry firing. The equalizer part is an incidental benefit (though an important one). And you are quite right -- if no one is paying attention, a boiler can dry fire remarkably quickly anyway -- but not as fast as it would without the loop.

DanHolohan

Yes, that’s exactly right @Jamie Hall Thanks.

ChrisJ

Ok.

How exactly does it make it take longer because I'm not understanding. What does it do that a modern hot water boiler doesn't need?

DanHolohan

It’s for steam boilers.

Jamie Hall

ChrisJ said:

Ok.



How exactly does it make it take longer because I'm not understanding. What does it do that a modern hot water boiler doesn't need?

We need to use our time machine, @ChrisJ , and wander back a hundred years or so. Then we had boilers with lots of water in them -- which were coal fired. They didn't boil water that much faster than the modern ones. In the event of a wet return failure, and assuming that someone was paying attention (which you were -- someone had to check the fire!), the Hartford Loop might give you enough time to draw the fire and get out of Dodge, whereas without it you might have only a minute or two. On modern small volume boilers... got to admit that other than being a handy place to tie in the equalizer, it probably doesn't help much.

JUGHNE

IMO, if the lower return piping leaked, even under the floor and drained the wet return dry, you would still have the water level in the boiler down to the bottom of the close nipple on the HL.

As the boiler fired and steamed away the water, the auto fill valve (if any) would maintain some water level. If not then hopefully the LWCO would do it's job.

ChrisJ

> @Jamie Hall said:
> (Quote)
> We need to use our time machine, @ChrisJ , and wander back a hundred years or so. Then we had boilers with lots of water in them -- which were coal fired. They didn't boil water that much faster than the modern ones. In the event of a wet return failure, and assuming that someone was paying attention (which you were -- someone had to check the fire!), the Hartford Loop might give you enough time to draw the fire and get out of Dodge, whereas without it you might have only a minute or two. On modern small volume boilers... got to admit that other than being a handy place to tie in the equalizer, it probably doesn't help much.

So overall, you agree.

@DanHolohan I know it's for steam.

EBEBRATT-Ed

The equalizer drains the header. The Hartford loop keeps water from backing out of the boiler if a wet return leaks.

You need a check valve or a Hartford loop to prevent the water from backing out. Check valves get stuck from muck, a Hartford loop works much better.

When boilers were coal fired there were no low water cutoffs. The boiler had fuseable plugs as a last resort. The Hartford loop help keep boilers from dry firing....it didn't prevent dry firing any more than a defective low water cutoff can.

It's like wearing suspenders and a belt

A old boiler may work without a Hartford loop but try running a modern boiler without one and you will have trouble keeping water in the boiler.

Put it this way. Would you run a boiler without a safety valve? Why not you have a pressure control don't you?

Safety valves fail and pigtails get plugged. Why take a chance. Low water cutoff and a Hartford

STEAM DOCTOR

The typical equalizer drains the header. Inherently, it doesn't need to be that that way. You can have a header drain on one side of the header and the equalizer on the other side. Just saying.

retiredguy

The original question , as to the necessity of the Hartford Loop, my opinion is that if you are using a gravity return, I would always recommend one. In some cases it could be eliminated but with the questionable piping practices being used today, and the poor engineering and service techs out there, why take the chance. Also, if you utilize a pumped return, it isn't needed. Since most of the steam boilers I worked on were large units (think hospitals and universities) , those boilers that utilized a gravity return system, always had a "Hartford Loop" to equalize the inlet and outlet of the boiler to help keep the water in the boiler and not back up into the return piping. Anything that would help keep a boiler from dry firing was a welcome addition. When the systems were updated to a condensate feed system there was no need for the "Hartford Loop", however old habits die slowly and the old time engineers almost always had a "Hartford Loop" installed as part of the boiler installation. In the very early days of steam boilers, most were fired with coal. On every coal fired boiler, utilizing both high or low pressure, the boiler had an alarm whistle that would sound indicating a low or high water condition. That whistle was the only alarm that notified a fireman of a problem. You can't shut off a coal fire quickly so the whistle was the indicator that something was wrong. Also, In the early days of coal boilers there always was a boiler attendant in the boiler room who was supposed to be "on watch", ie, shoveling coal and tending to the fire. . The whistle would allert the fireman of a problem. A boiler that dry fired and melted the fire tubes and "stay bolts", warped the tube sheets and the outer jacket is a scary scene. I have seen too many.

ethicalpaul

Thanks for the history @retiredguy and others!

I'm not sure of the value (today) of suspenders that work for about 10 minutes after the belt has failed, but I feel my understanding of how we got where we are today has been improved!

ChrisJ

https://heatinghelp.com/systems-help-center/a-hartford-loop-q-and-a/


I don't know much about commercial boilers and stay away from talking about them.

But for residential applications it seems like an obsolete item to me. Obviously it still needs to be done because the manufacturers want them as well as local code. There is no question, a Hartford loop MUST be used.


I don't think anyone is suggesting not using them. I believe @ethicalpaul was simply curious about them as was I.

I've thought about it many times and it just didn't seem to make much sense on a modern low water content home heating system. Hot water systems have no such protection. It's not even considered even if a hot water boiler is plumbed primarily in pex below the boiler. Is it?

Seems like a secondary LWCO would be far more beneficial these days.

DanHolohan

I think they are necessary because so many low-water cutoffs are ignored. It’s very cheap insurance.

ChrisJ

DanHolohan said:

I think they are necessary because so many low-water cutoffs are ignored. It’s very cheap insurance.

Hi Dan,
Do many return lines burst / rupture?

I know plenty of people neglect feeding the boiler water and won't do it until they stop getting heat.

DanHolohan

I don’t have any statistics on that, Chris, but I’ve heard many stories over the years. I just think the loop is worth the two extra fittings.

JUGHNE

Also a side benefit I see is a low point for sludge collection on dry returns. Keeping junk out of the boiler. Easy clean out if valves/plugs are added on the low points. IMO

ethicalpaul

DanHolohan said:

I think they are necessary because so many low-water cutoffs are ignored. It’s very cheap insurance.

But don't they just provide insurance for the short time that it takes to steam the content of the boiler to the leaking return?

ethicalpaul

JUGHNE said:

Also a side benefit I see is a low point for sludge collection on dry returns. Keeping junk out of the boiler. Easy clean out if valves/plugs are added on the low points. IMO

Not bad, but the flip side of that is that it's a choke point for sludge to block the return since valves/plugs are often not there or ignored for years.

JUGHNE

And most likely the whole system is ignored.
Easier to clean or replace the "sludge loop" than the boiler.

DanHolohan

@ethicalpaul Yes, it just buys time but that can make all the difference.

AMservices

I've been piping all my boilers with a Gifford loop.
To me, it adds better performing and control over the water line.
I would still pipe it that way even with dry returns because...well, that's just the way we do things.

Fred

@ethicalpaul , also consider that many, if not most newer boiler installations also have auto water feeders. With a Hartford loop, that feeder will keep water in the boiler (even though it may steam away) while eliminating the HL has the potential to allow water to drain faster than the feeder can supply new water.

ChrisJ

Fred said:

@ethicalpaul , also consider that many, if not most newer boiler installations also have auto water feeders. With a Hartford loop, that feeder will keep water in the boiler (even though it may steam away) while eliminating the HL has the potential to allow water to drain faster than the feeder can supply new water.

You do understand that would mean the LWCO must be working in order to activate the autofeed, right?

Fred

ChrisJ said:

Fred said:

@ethicalpaul , also consider that many, if not most newer boiler installations also have auto water feeders. With a Hartford loop, that feeder will keep water in the boiler (even though it may steam away) while eliminating the HL has the potential to allow water to drain faster than the feeder can supply new water.

You do understand that would mean the LWCO must be working in order to activate the autofeed, right?

Good point!

EBEBRATT-Ed

@ethicalpaul

Part of this discussion should consider the type of leak in a wet return. From what I have seen most return lines weep a little with the leak gradually getting worse... rather than a real gusher.

So a boiler without a Hartford will loose water all the time gradually with a weeper.

A boiler with a hartford will loose the water in the wet return but most of the boiler water will stay. the homeowner will have to add water every day and hopefully notice the change and get the leak fixed.

A boiler without a Hartford its a one shot deal. With a Hartford you might get a second chance

ChrisJ

EBEBRATT-Ed said:

@ethicalpaul

Part of this discussion should consider the type of leak in a wet return. From what I have seen most return lines weep a little with the leak gradually getting worse... rather than a real gusher.

So a boiler without a Hartford will loose water all the time gradually with a weeper.

A boiler with a hartford will loose the water in the wet return but most of the boiler water will stay. the homeowner will have to add water every day and hopefully notice the change and get the leak fixed.

A boiler without a Hartford its a one shot deal. With a Hartford you might get a second chance

What about hot water systems?
Why do they not need any sort of "extra" protection against weeps etc? Many of them don't even have a LWCO.

DanHolohan

I believe most boilers that explode are steam boilers, Chris. That’s how the Loop came to be.

ethicalpaul

> @EBEBRATT-Ed said:
> @ethicalpaul
>
> Part of this discussion should consider the type of leak in a wet return. From what I have seen most return lines weep a little with the leak gradually getting worse... rather than a real gusher.
>
> So a boiler without a Hartford will loose water all the time gradually with a weeper.
>
> A boiler with a hartford will loose the water in the wet return but most of the boiler water will stay. the homeowner will have to add water every day and hopefully notice the change and get the leak fixed.
>
> A boiler without a Hartford its a one shot deal. With a Hartford you might get a second chance

Thanks @EBEBRATT-Ed, I can see what you're saying and I agree there's probably never a gusher.

Have any of the technicians here ever seen a boiler saved by the Hartford Loop?

PMJ

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.

acwagner

I assume boilers back in the day contained more water by volume than modern boilers. More water means more time to detect the problem in time.

From my own experience, when we moved into our house our system had a lot of problems. We had a dry return spring a pin hole leak overnight. Although not in the wet return, it functioned effectively like a wet return leak because it interrupted the majority of the return condensate. I only knew there was a problem because I heard the make-up water run twice within a 15 minute period. Keep in mind this was a very tiny hole, yet it didn't take long to drain the system during operation.

From that experience, I agree with @JUGHNE that it's benefit nowadays is more from the maintenance standpoint preventing some of the sediment from getting to the boiler.

EBEBRATT-Ed

@ChrisJ , hot water boilers are under constant pressure from a prv in the city water line. Also even a slight bit of water loss will cause the system to loose pressure and not heat the building making the problem noticeable.

until recently hot water boilers did not even have low water cut offs

ChrisJ

> @EBEBRATT-Ed said:
> @ChrisJ , hot water boilers are under constant pressure from a prv in the city water line. Also even a slight bit of water loss will cause the system to loose pressure and not heat the building making the problem noticeable.
>
> until recently hot water boilers did not even have low water cut offs

The prv seemed like something that wasn't a must. But you got me at the lack of heat. That would cause someone to go check.

Very good points.

Ron Jr._3

> @ChrisJ said:
> (Quote)
> Hi Dan,
> Do many return lines burst / rupture?
>
> I know plenty of people neglect feeding the boiler water and won't do it until they stop getting heat.

I go on 2 or 3 burst return pipes a year. And that's with a shrinking base of homes with steam boilers around here.

In my opinion , the Hartford Loop is a definite plus on every steam system that has a wet return. It's like fire-code sheetrock above a boiler. Just buys ya some time before a catastrophe could happen. And it dont hurt to pipe it like every steam boiler manufacturer states in their literature

DanHolohan

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

Dan Foley

Like Ron, we run into leaking wet returns every year.

Here is a column I wrote several years ago on this subject:

https://www.foleymechanical.com/wp-content/uploads/2016/03/phc_03_2016.pdf

ChrisJ

DanHolohan said:

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

Dan,

Often it's good to ask questions to get a better understanding of why we do things the way we do. When we understand why, we can often do a better job. Rather than those who do things "just because".

To me, this discussion has nothing to do with leaving a Hartford loop out or removing it. Others may have a different opinion, but I'm asking questions because I want to know more and have a better understanding of it's purpose.

I'm sorry of I gave the impression of otherwise.

PMJ

ChrisJ said:

DanHolohan said:

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

Dan,

Often it's good to ask questions to get a better understanding of why we do things the way we do. When we understand why, we can often do a better job. Rather than those who do things "just because".

To me, this discussion has nothing to do with leaving a Hartford loop out or removing it. Others may have a different opinion, but I'm asking questions because I want to know more.

I'm sorry of I gave the impression of otherwise.

Likewise for my comment. I also think the piping specs should be followed.

However, the state of this art with respect to controls at the residential level is well behind. For very little money these setups could be a lot safer. I'm not feeling that it is out of line to bring things like this up while the subject is up but let me know.