Help restoring Hoffman System

OatKing

Hello all!
We moved into a 90 year old house in 2016 in Eastern Iowa. Just now getting around to understanding the steam system and my goal is to restore as much as possible throughout the house. Thank you all for the information posted here and on YouTube. Learning about this community was incredibly helpful to undertake this home restoration. My system has issues and I'm asking for advice on what needs to be done and improvements possible. I own and read LAOSH, "We Have Steam Heat" and spend many hours on "The Wall" reading and thinking. Thank you all again!

Issues:
#1 Cycles on low water - condensate returns about 1-2 mins after shut down.
#2 Occasional mild water hammer - random occurrence.
#3 Hearing a strange sound, similar - but not the same as - air bubbles entering the office water cooler coming from the pipes
#4 Strange piping arrangement on wet returns [see top down photo]
#5 Wet return drains only a trickle from bib, Boiler drain doesn't drain any water.

More about my system:
2 pipe Hoffman vapor heat, with differential loop
Venting: Main: Hoffman #15 and 2x #18 crossover traps, 1 air vent on rad. on 2F BR (I understand this is covering up some other issue).
mostly #18 traps. various working condition
mostly #7 valves. various working condition
16 total radiators and in-wall convectors. (no EDR calculation yet, waiting on E.D.R. book),
Boiler: WM EG-65 approx. 20+ years old
Insulation: Asbestos w/ a little fiberglass
P-troll: in: .5 / out: 1.5psi
LWCO: Safgard 400
Auto feed: VXT-24 on 2min delay/2 gallon feed

Please let me know if you have any follow up questions, I tried to start out with the basics first.

ethicalpaul

I think your near boiler piping is horrible, but I can't tell for sure, because, frankly, your photos are kind of bad.

Can you take some where the boiler itself is in the center of the photo and far enough away that the floor and ceiling below and above the boiler appear? And from like 3 angles?

Like image#1 is close, but I can't see the whole boiler and the immediate pipes around it.

dopey27177

Here is what the system should look like.

It appears that some one worked on the system worked on the piping and may have removed something.

Need better pictures.

The devices shown in the drawing may look different from the Hoffman equipment but all the parts are basically the same.

What may be problematic is the lack of check valves at the bottom of the return system or defective or missing steam traps.

I believe you may have a modified vapor steam system. They usually operate at 1 lb steam pressure or less.

Enclosed is a drawing from my book.

Zipper13

I'm a novice myself. But like you, I had the same problem draining my boiler at first. I was shocked to find that my original 100 year old Hoffmanvent still holds a vacuum. Early on I found the easiest way to break the vacuum and allow the water to drain was to remove the vent from the differential loop before opening the drain. I have since added a valve and skim port which I can open to break the vacuum before I drain.

I'm sure you will have a vaporstat recommended. I thought about upgrading from my pressuretrol to a vaporstat but found that my system never exceeded 3 oz of pressure anyway so decided I don't need to cycle on pressure.

I have found that my Burnham boiler is very sensitive to the fill level. My boiler guy fills it 2/3 to top of the sight glass after cleaning each season, but the boiler bangs there, so I drain it an inch lower and it's silent.

Just my ameture two cents.

You're going to get some great feedback here. Several helpful Hoffman fans are on this board!

Jamie Hall

As @ethicalpaul says... hard to see what's what.

To add to the photos he suggested, can you come up with one (or several? which clearly show the piping from the header to the Hoffman Differential Loop, and the way the dry returns are linked to the top of the Loop (with the vent(s)), and the way the wet return from the Loop connects to the main wet return?

A few other comments.

First, the Hoffman Equipped system such as yours must have one, and only one, venting location, and that venting location must be at the end of the dry return(s) after they have hooked together and immediately before they drop into the Hoffman Differential Loop. There could be multiple vents there on an antler arrangement, but that's it. You may need more main venting at that location, but the existing Hoffman #15, assuming it is working, may be quite adequate. You will need a low pressure gauge to verify that.

Vents anywhere else on the system will defeat the purpose of the Hoffman Differential Loop and cause odd results, depending on where they got stuck on. Get rid of them. The vent on the radiator may be covering up for a failed closed trap or for a return line which is pitched incorrectly and holding water. Or just a mistake...

For better or worse, a Hoffman Equipped system must be controlled with a vapourstat (like most other vapour systems). The cutout must be set at no more than 7 ounces, with a cutout usually around 3 to 4 ounces. Any pressure over that will trip the Differential Loop and result in variations on poor to no heating. I suggest you keep the pressuretrol, but mount a vapourstat and low pressure gauge somewhere handy.

Your comment on draining from the boiler drain and the wet return -- plus the slow condensate return -- suggests very strongly that it is past time the wet returns were flushed out, as well as the boiler drain.

Weil-McClains are moderately forgiving on near boiler piping, but what little I can make out is not encouraging. I'm particularly concerned that the line from the header to the Differential Loop may not be done properly.

OatKing

Thanks and sorry for the small photos! They were 5MP on my phone so I reduced the size. Late tonight, when I return home, I'll take some better, larger and labelled photos. There's a hydronic loop and DHW heater that are completely separate, but physically close to the boiler, adding to the obstructions. I can understand why it's hard for others to see what's going on.

Jamie Hall

That should be "cutout at no more than 7 ounces and cutin usually at 3 to 4 ounces..." in my post above.

Steamhead

@OatKing , where in Iowa?

OatKing

@Steamhead Cedar Rapids, City of Five Seasons.

EBEBRATT-Ed

@OatKing

Near boiler piping the "header" is too close to the water line. Should be 24" minimum above the water line. Lots of issues but if you read the LAOSH you already know that.

You going to have to start from scratch and pick your way through it......You can save it and you should.

I would start with edr calculation to see if you should keep the existing boiler.

Fix near boiler piping

go through all the traps and venting.

Thatt's enough to get started

OatKing

@ethicalpaul - kindly see images 6, 7, 8

@dopey27177 - thanks for the docs. There are a few terminated connections, (one original, one later added). The diagram looked complex, so maybe previous modifications removed multiple items.

@Zipper13 - thanks for the suggestion about breaking the vacuum to drain. Will try tomorrow.

@Jamie Hall - kindly see images 9, 10 for the Hoffman connections. There supply to the differential loop doesn't directly connect to the header, it comes off the main steam line, near the ceiling.
The overflow connection to the wet return is the pipe running right below the draft good.
Because the Hartford loop is so tall (36" tall and 20" above waterline, I wonder if the installers placed the rad vent because the current configuration doesn't allow air on that leg to reach main vent.
The Hoffman #15 appears to still work. I let you know the pressure when I replace the pressure gauge.
Will remove and plug the rad. vent, pick up a vaporstat, install a low pressure gauge and let you know.
@EBEBRATT-Ed - Correct, the header is about 6" too low. I will calculate the EDR for the entire system.then decide what to do with the boiler.

ethicalpaul

Thanks, those are nice photos! As others said, I don’t like the low header. I also don’t like how the tee off the header comes off horizontally.

Also that’s a big boiler for just one steam supply pipe.

It’s my opinion that for these reasons, this near boiler piping will carry a lot of water into your main.

There is good height up to the main, but the water will get carried up there like an old coffee percolator. Ilike @EBEBRATT-Ed ‘s advice

Jamie Hall

So long as all the dry returns tie together above the top of the Hoffman Differential Loop, you don't need any other venting on the system -- and don't want it. The connection of the steam line to the loop from the main isn't ideal, but it is one way of doing it and quite valid.

dopey27177

Look at my drawing again.

it appears that there is no air separator in the system.
Find the 1/2" radiator trap on the system. It should be on your dry return piping (some times there are 2 or three of them) that depends on the piping configuration.

Also look for the the air check, that can be clogged or stuck .

These parts can be disassembled and cleaned.

Check the heights where shown. These are minimum dimensions. If grater its OK. These dimensions are to assure that the dry returns do not get water in them where they connect to the wet return.

Getting back to the steam traps on the system. Barnes and Jones manufactures internals for all your steam traps. Purchasing new traps and installing them can get real expensive.

Getting back to to steam pressure settings. Maximum steam pressure should not exceed 12 oz. with a differential of 4 oz.

You may need to reset the vaporstat or replace it.

EDR calculations are not needed. Vapor systems have larger radiators than steam systems operating at at pressure. Example,
1 pound pressure steam is 215 degrees. 3/4 pound pressure is about 213 degrees, but your system can operate at in a vacuum up to 15" That is steam at a temperature of 182 degrees.

The heating system when tight will normally operate in a vacuum.

Hoffman accounted for the lower steam temperature by installing larger radiators.

The lower temperatures emanating from the radiators kept the air from drying out and as a result the heat was more comfortable. ( less dry nose conditions)

Check the radiator valves to see if they are adjustable or have orifice plates in them)

Jake

Jamie Hall

I'm sorry, but I have to differ, @dopey27177 . The Hoffman Differential Loop -- any size -- is calibrated to trip at between 7 ounces per square inch and 8 ounces. No more. The cutin should be around 3 ounces. Any higher pressure differential will trip the loop, and that is -- at best -- undesirable.

If that Hoffman #15 is operating properly and the radiator and crossover traps are operating properly and the pressure never rises above 8 ounces, it will never see steam. It should, however, close on a vacuum.

I'm not sure to what you are referring by an "air separator", nor an "air check". Possibly you are referring to what I term a crossover trap? In most cases those are standard Hoffman radiator traps and yes, if they are malfunctioning, they can be disassembled and the internals replaced.

dopey27177

Just noticed you have an air valve on one radiator. Remove it. It is affecting the vacuum in the system.

you have a blown steam trap some where in the piping system.

Plug off the vent valve tapping. This will allow the system to go into a deeper vacuum.

See if the problem on the radiator is (does not get hot enough)

Jake

OatKing

@dopey27177 : Thanks for the advice. I agree that there is one (likely several) traps that need to be replaced. I will wait until spring to tackle the traps when I can tear into the system, but I will put the air vent from the rad. to check see if that rad. alone is cold or the entire loop. I will get a vaporstat and low press. gauge once I loosen the old fittings. Just about every valve or fitting is either plugged or seized.

@Jamie Hall : can you explain your comment a bit differently about "as all the dry returns tie together above the top of the Hoffman Differential Loop...", I am trying to understand the path air takes getting back to the main vent.

@EBEBRATT-Ed: I received E.D.R. and began compiling my radiators - Thankfully they are listed. Since the 8 convectors are in the wall, covered by plaster I'm trying to estimate based on size and enclosure height. Since EDR assumes 215F and 1PSI, how would running vapor system on less pressure and possible lower temps effect the calculation?

For the group, since the NBP is poor and the boiler is likely 20+ years old, should I look into replacing the boiler with the piping?

EBEBRATT-Ed

@OatKing

The change in btu's from 1psi to vapor will not change the output enough to make a difference.

Once you get your radiation total compare it to the boiler nameplate.

I would get the system running as best you can with traps, venting check piping pitch etc and see how it goes.

Then make a decision about the boiler later based on the edr you need and the boiler needing to be repiped.

I would not repipe until the boiler is changed

Jamie Hall

On dry returns (oh no, here we go again) for vapour steam systems. The dry returns for a vapour steam system -- indeed, any two pipe steam system -- carry the air and condensate from the steam mains and from the radiators. The air and condensate from the radiators gets there through the radiator outlets -- which in many vapour systems, such as the Hoffman Equipped systems, have steam traps which prevent the passage of steam, but allow air and condensate to pass (some other vapour systems use a combination of orifices or interesting static widgets to ensure that only air or condensate reach the dry returns; the effect is the same). Almost all such systems originally had crossover traps from the ends of the steam mains to the dry returns. These are essentially identical to radiator traps (in fact, the air capacity of a radiator trap is high enough that most systems used the same traps as the radiators). They are placed above the steam mains, and so allow only air to pass. Condensate from the steam mains in parallel flow systems (the vast majority) was handled either by a drip to a wet return or, more rarely, by a water loop seal arrangement which established a water seal between the steam main and the dry return, allowing condensate to pass but neither water nor air.

So. Summary. Air and condensate from the radiators passes through the radiator traps into the dry return. Air from the steam main passes through the crossover traps into the dry return, and sometimes condensate passes through a water seal into the dry return (rather rare, actually).

Note that steam is never present in the dry returns (under normal operation, but see below).

Further, the air pressure in the dry returns is very close to atmospheric (again under normal operation -- again, see below).

Now. The air has to get out of the dry returns somewhere. Since neither radiator traps nor operators are goof proof, almost all vapour systems employ air vents to exhaust the air (a few earlier systems were simply open to the atmosphere). The simplest place for the air vents was and is at the boiler. Thus all the dry returns can tie together at the boiler and share a single vent (in more modern systems, it's usually two or more vents -- but they are all in the same place). Any condensate in the dry returns at that location is allowed to drain down to the boiler wet return to join the condensate from various system drips.

It should be noted that many vapour systems used vapour vacuum vents, such as the Hoffman #76 or #15, rather than our now standard vents. These vents allowed air to pass out, but sealed against a vacuum, thus placing the entire system under vacuum and allowing it to operate at lower temperatures when the fire (in the case of coal) was damped, or when the burner (in the case of oil or gas) was turned off and the system was cooling. There are some advantages to this; whether they are worth the additional cost of the vacuum vents is debatable.

At this point, it is well to note that there is a complication in many vapour systems: devices intended to keep the differential pressure between the steam mains and the dry returns to some low level. Keeping this differential low serves to prevent -- in most cases -- the water from being forced out of the boiler by high steam pressures (high is relatively speaking here) and from blowing the various water seals. These devices -- of which the Hoffman Differential Loop is perhaps the most common -- function by introducing steam from the header into the dry returns and, at the same time, closing the vents so that pressure will increase in the dry return if the differential pressure is too great (typically about 8 ounces per square inch). This is the only time in these systems when the vents will close, unlike ordinary two pipe and all one pipe systems where the main vents on the steam mains will close frequently and on every cycle. But, in order for this to work, the vents must be at the same location as the device in question, or very close, so that the steam can reach them immediately and the pressure can build as needed in the dry returns. Thus all the dry returns in these systems must be joined together at one location, and the only vents in these systems must be located at that location which is also where the device is located and which is, of necessity, at the boiler.

A bit long-winded, but I hope that helps.

dopey27177

Jamiehall made a perfect description of the operation of vapor vacuum systems.

Without a drawing of the system words do not help much. Jamie hall works on these systems which come in various configurations. See the attachment for a picture of a one of the expensive installations of its time. follow his words to the picture
and you get a better understanding of your system.

As far as the heating elements go they were sized to provide the
BTUs needed at steam temperatures as low as 180 degrees f.

Today if your system was working correctly you might find the house to hot because storm windows, new weather stripping and a tighter house than originally built.

Additionally if the steam mains are not insulated the steam will condense into water and you will lose the steam volume needed to fill the piping system. You need cubic feet of steam to fill the piping and radiators.

Jake

OatKing

@EBEBRATT-Ed : the EDR of my system is 738.2 sq ft - without adding the pickup factor. I realize my boiler(WM EG 65) can only supply 654sq ft. Adding the PU factor of 33%, would take EDR up to 981. I will post my specific rads and conv. to show my work a little later, but an undersized boiler was not a conclusion I suspected.

@Jamie Hall : thank you so much for the indepth explanation about venting. It finally sunk once I realized that once air passed the crossover trap, it move against the condensate flow in the dry returns to the main vent.

@dopey27177 : I removed the air vent on the radiator and installed a plug. The system still cycles on low water but the condensate returns faster and noticably more of it.

I haven't checked the line pitch yet. I'll wait until spring when the asbestos insulation removed. Right now I am still processing all the information gathered. I am so thankful for this community as I go along with this process. Just yesterday, I found in the library, information on Trane Concealed Heaters and able to get exact calculations on my system EDR. Thanks again, everyone!

OatKing

Attached is my EDR calculation. I made an error earlier, so the actual EDR is 702.55 - about 35 sq ft less. There is also a discrepancy in my boiler's capacity, the manufacturer's document states the EG-65 supplies 654 sq ft, but the data plate and IBR certification states it only supplies 633 sq ft of steam.

Jamie Hall

The boiler is big enough. You don't add anything for the "pickup" when calculating your EDR, and the boiler manufacturer does -- 33%. So there's enough capacity. Only thing -- insulate your steam mains if you haven't.

OatKing

Thanks @Jamie Hall. Currently, the steam mains are insulation with asbestos. There are a few spots where the radiator take offs approach the foundation and floor joists that are uninsulated but I plan to correct that when I re-insulate in the spring.

Jamie Hall

You can also encapsulate the asbestos in place, if you don't disturb it it's not really a hazard. On the other hand, if you go to sell the place someday, the buyer likely won't be happy...

OatKing

Happy Memorial Day, everyone! I wanted to give an update on my progress and ask a few questions.

- got a quote on asbestos removal. Wasn't terribly shocked, just adequately shocked.

- pulled all guts from the traps. Have 8 trap covers that are out of round. [Previous Knuckleheads used a pipe wrench instead of a socket]

- discovered a couple of replacement traps put a significant bend on return lines. See the picture with the trap and line disconnected for reference.

- pulled the Hoffman #7s and will ship to @Gordo for restoration.

- moved some "small" radiators.

- checked the pitch on some condensate lines. Discovered some settling and incorrectly pitched lines.

QUESTIONS:
- should I be concerned about the out-of-covers?

- what is the best starting spot to adjust pipe pitch?

- The main vent line coming off the differential loop slopes up slightly as it goes away from the DL. It's the line I am pointing to with a pipe wrench handle. Is this correct or should I raise the differential loop up so the line slopes down?

Jamie Hall

That line -- the main dry return -- should slope slightly down towards the inlet to the differential loop. All the way to the end(s). I think that you are saying that it does -- and if so, don't fix it.

OatKing

Thanks @Jamie Hall . That's what I was trying to say so I won't mess with that.

I forgot the other photos. On the one you can see the "small" rads (along with original dark yellow paint.)

In the other, you can see how far a previous installer had to bend the return line down to attach to the trap.

Jamie Hall

That mismatched bit of pipe and elbow? That was connected? It's a wonder that radiator worked at all. Did it? Is there any way to correct that mess so the return can drain properly? There does exist the Hoffman 8C and 17C Straightaway trap. The outlet of those is horizontal -- not a vertical drop -- but they are a little hard to find. I think just judging by eye, though, that substituting one of those for the angle type which is there that that pipe would just about line up. Probably the best approach (pick 8C or 17C to match what's there in the angle pattern). There is the minor detail of getting the old spud out of the radiator... but what's a little hard work from time to time?

Steamhead

The Barnes & Jones #122S is another good choice. The union nut thread on these traps is the same as on the Trane B-1, so you might get away with not changing the tailpiece.

dopey27177

Does your Hoffman Vapor System Look like this.

Well any way you need a master vent to allow air to be removed from the system. That vent valve will need a built in air check or a check valve installed before the vent valve. The check valve prevents loss of vacuum.

See attachment, sorry for the black shading.


Jake

Jamie Hall

Indeed, if the system is a Hoffman Equipped system -- and, I hope, still has the Differential Loop attached -- it will operate with slightly greater efficiency with the ability for the main vent to seal and hold a vacuum. Slightly greater. The Hoffman 76, still made, is such a vent (the Hoffman 15 is no longer made -- it was bigger, so you probably would need two 76s). Problem. The 76 is not cheap. Second problem. The cracking pressure of most outboard check valves, such as you might be tempted to put in before the vent, is higher than the design operating system pressure -- so the vent will not operate at design pressure (typically around 2 ounces until the radiator traps are all closed), and you need it to -- as @dopey27177 says, you have to get the air out...

Solution. Accept a slightly lower efficiency, and use one or two Gorton #2s as your main vent. No, they won't hold a vacuum. Yes, they will be open when you need them open. Yes, they will close when you want them to (when the Loop operates).

OatKing

yes, it was connected and somewhat worked, surprisingly. You can't tell in the photos since it shows mismatched height, but the alignment is worse for the length. My plan is to replace the steam and condensate pipes with different lengths so the trap isn't directly under a floor joist and there isn't any unnecessary strain.

I still have the differential loop and the original Hoffman No. 15 - both appear to work just fine so I plan on leaving them alone.

Jamie Hall

OatKing said:

I still have the differential loop and the original Hoffman No. 15 - both appear to work just fine so I plan on leaving them alone.

Lucky man. Keep that No. 15 as your one and only vent. It's all you'll ever need. I'm jealous.

OatKing

New question: I saw @Gordo 's critique of the Hoffman 18 trap. Before I lay down (more of) my money, should I replace some of my Hoffman 18 with a different style trap?

Here are my thoughts and I welcome yours:
- on radiators with Hoffman #7s, I can keep the Hoffman 18s and just replace the guts since the steam trap may never see steam if the modulating valve is properly adjusted.

- on the Trane Concealed Heater, with steam traps in the basement, I can install 122As maybe with super trap cages, since the convectors may/will see steam every cycle.

- replacing cross over traps with either 122 super traps or bigmouths. The challenge with big mouths is getting 1/2" size.

What would you do?

Jamie Hall

Whoa. A BigMouth is a vent, unless you pipe it as a crossover trap -- in which case, why not leave the crossover trap? As I've said before, you want one, and only one, vent on your system -- and that #15 is exactly what you want. Leave it alone.

If the crossover traps are not working, replace the guts. Otherwise leave them alone.

Gordo

B&J does make a non internal O ring "big-mouth" trap which we use to replace the #18 (or #8) poorly venting cross-over traps. It is in essence a 3/4" Mepco trap with a 3/4" by 1/2" face bushing and 1/2" x 3/4" spud adapter.

Jamie Hall

Gordo said:

B&J does make a non internal O ring "big-mouth" trap which we use to replace the #18 (or #8) poorly venting cross-over traps. It is in essence a 3/4" Mepco trap with a 3/4" by 1/2" face bushing and 1/2" x 3/4" spud adapter.

There you go. That will work nicely.

OatKing

Some updates (good and bad)
- installed BJ super traps, big mouths, and replaced all ST guts with new BJ cage units.

- The ST covers are also accessable for future cage unit replacement. (See attached photos)

- all rads & convectors now work! 

- unfortunately, all other issues remain and new ones appeared

- boiler still cutting out on low water during heating cycle and auto fill unit adds water once every day or so.

- can't seem to find where steam could be escaping. No visible plaster bulging, paint discoloration, or wet spots. Even used a thermal camera to find leaks without success

- getting more water hammer, ticking and other sounds than before. 

- any help is greatly appreciated.

Jamie Hall

Well... let's see. The ticking noise is almost certainly expansion. Hard to track down. Harder to correct. Sometimes it is simply where a pipe rubs against the floor or a joist -- or a hanger. Sometimes it is in the radiator itself. Sometimes...

The hammer is a little more problematic. If you localise it, so much the better. It is almost always a section of pipe which doesn't have quite enough slope (or even a reverse slope!). The worst offenders usually are radiator runouts --even short lengths of sort of horizontal pipe can be quite problematic, particularly if they are relatively small. If the hammering occurs at or near the beginning of a cycle, one trick to help find the problem children is to notice where the steam has -- or has not -- gotten to. A problematic horizontal section of runout, for instance, may hammer as it is heating up, and stop once it is hot.

On the cutting out on low water during a cycle. I assume you have already checked that the wet returns really are wet. Otherwise, have you flushed them out? They may just be incredibly gunked up. And all the dry returns slope to drips adequately? It is remotely possible that the system is big enough that the boiler water volume is just not enough. There are ways and means of addressing that in a very simple and straightforward manner -- but let's check those wet returns first.

On losing water once a day or so... not good, but you know that. It's extremely unlikely that the radiator valves are the culprits, if they are Hoffmans. However, it is surprising how much water a simple little drip can add up to, and so checking all the threaded joints, particularly on dry returns, for any sign of dripping or leaking (for example -- one drip every ten seconds works out to about half a gallon a day...) is well worth the effort.

ethicalpaul

Are you losing the water, or is it temporarily going somewhere and then returning after awhile? This is an important distinction.

And to add to @Jamie Hall 's good information above, if you have a suspect banging radiator, you can rotate the vent upside down to prevent steam from entering its suppy. If the hammer goes away and then comes back after you un-rotate the vent, then you've found your problem child. Edit: sorry that would be advice for a 1-pipe system.