Hoffman Boiler Return Trap

Bill Marsh

I have a steam heat system which appears virtually identical to Fig. 56 on p. 266 of D. Holohan's Lost Art of Steam Heating.

Sometime of the years, the cap on the Hoffman Receiver Vent was replaced with a main air vent; currently a Hoffman #75.

The radiators all have recently replaced thermostatic traps and thermostatic radiator valves. I have also replaced the thermostatic elements in the Line Return valves (labeled thermostatic traps in fig. 56).

We have recently had mid cycle water hammer and what my wife describes as "hooting radiators." On startup, at the end of cycle, water shoots out of the main vent.

The pressuretrol is set to cut-in at 1/2 PSI with a differential of 1 PSI. I did not understand what was going on until I stood watching the boiler cycle and saw the gauge pressure go to 5 1/2 PSI. My daughter upstairs told me the water hammer started about the time the gauge hit 3 PSI.

The Hoffman Boiler Return Trap has a watchglass. Even with water shooting out of the main vent on the Hoffman Receiver right above it, there is NO WATER in the Boiler Return Trap.

Does anyone understand how this can be? Does it mean this Boiler Return Trap has failed?

My plan is to replace the pressuretrol with a vaporstat ASAP. I figure this will stop the water hammer and the water leaking from the main vent.

If I run the system as a two pipe gravity return at low pressure with a vaporstat, should I even care if this Boiler Return Trap has failed?

Steamhead

I bet

the check valves on the return where the Return Trap ties in, are clogged. These are essential to proper operation, and if clogged or stuck, water will back up into the dry (overhead) returns.

What type of vent is on the Receiver? If it's a vacuum-type vent, it can contribute to this problem.

The Vaporstat is a good idea, if you use one the Return Trap would then serve as a backup.

If the Return Trap fails, Tunstall can rebuild it.

When you replaced the traps, did you include the "crossover" traps placed between the ends of the steam mains and dry returns in the basement?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Check Valves

Thanks for replying Steamhead, but you lose your bet. I thought the same thing this morning and opened both check valves. Had to drain the wet returns to look inside, but they are not clogged and the brass flaps move freely.

I did replace the elements on the Hoffman #8 Line Return Valves with Tunstall Capsules designed for Hoffman #8 Thermostatic Radiator Traps on Woody Tunstall's advice. These seem to work well.

Woody Tunstall is a wonderful help. Even if the vaporstat solves the problem, I will ask him about this return. I suspect removing it from the system and shipping to him won't be easy and is certainly out of the question until heating season is over.

Any tests on this trap short of removing it and shipping it to Tunstall would be helpful.

Bill Marsh

Check Valves

Thanks for replying Steamhead, but you lose your bet. I thought the same thing this morning and opened both check valves. Had to drain the wet returns to look inside, but they are not clogged and the brass flaps move freely.

The Receiver Vent currently has a Hoffman #75 main air vent on it. Sometime over the years, someone removed the original cap and replaced it with a plug. When we bought the house the steam didn't work at all. A local plumber replaced it with a Vent-Rite #75 which did work. In the hopes of reducing my heating bills, I recently replaced it with a Hoffman #75. Its too soon to judge on the heating bills, but the heat sure gets to the radiatiors faster.

I did replace the elements on the Hoffman #8 Line Return Valves with Tunstall Capsules designed for Hoffman #8 Thermostatic Radiator Traps on Woody Tunstall's advice. These seem to work well.

Woody Tunstall is a wonderful help. Even if the vaporstat solves the problem, I will ask him about this return. I suspect removing it from the system and shipping to him won't be easy and is certainly out of the question until heating season is over.

Any tests on this trap short of removing it and shipping it to Tunstall would be helpful.

Steamhead

OK, how about

the piping between the Receiver and the Return Trap? Have you flushed this out too? If the sight glass is working properly, it would seem the condensate is getting as far as the Receiver Vent but not as far as the Return Trap.

And another possibility- have you checked the sight glass mountings on the Return Trap to see if they are clogged?

To check the Return Trap, start the system up from cold, and feel the pipe between the steam header and the Return Trap. It should not get hot as soon as the boiler starts delivering steam. If it does, the valve in the Return Trap is leaking.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Connecting Pipes?

Thanks Steamhead, you've given me three great ideas.

1) I will check the watchglass fittings on the return trap and see if they are clogged.

2) The only pipe I see (I attached a photo) connecting the receiver vent and the return trap is the one with the check valves in it. Fig. 56 doesn't show any other pipes either, so I don't think I am missing a pipe. I can easily see if this pipe is clogged by reopening the first check valve and pouring water into the receiver vent.

3) I will then feel the steam inlet on the return trap on startup and see if it gets hot (The pipes are well insulated and I don't want to disturb that unless necessary.)

Shouldn't take too long to do these things. Thanks.

gerry gill

I agree with steamhead..

could be that the pressure somehow activated the return trap and it stuck open allowing steam to enter and pressurize the pipe in between the check valves..this would back water up the returns..possible.. do what steamhead suggests and see if it seems like the steam in entering the boiler return trap..I dont know if your return trap has this feature, but at least one hoffman boiler return trap had a cap/plug on top that had a wire hook device inside it to manually ''work'' the float arm..you can check and see..there may even be another cap/plug that has an oil fill tube under it..the plumber would put a couple drops of oil in the tube then work the float up and down a couple times to lubricate the mechanism...dont know if your return trap has this feature tho...hope this helps..

Bill Marsh

tests

Thanks for your help, SteamHead

I pulled off the watchglass. I can blow through both valves easily.

After removing the covers from the check valves, I can pour water into the receiver and see it well up from the check valve. The other end was harder, but if I blow into one watchglass nipple with my thumb over the other, I can easily blow water out the open check valve. So I think the piping is patent.

I wriggled my finger into the insulation around the pipe from the header into the return trap. It remained cold through an entire boiler cycle. I suppose the valve could have failed closed. In that case, shouldn't I see water in the watchglass?

Bill Marsh

plug

Thanks for your help gerry.

I did what SteamHead suggested, see above.

There is no plug on top of this trap, but there is an approx 1/4" square plug to the left of where you pipe the return and from the header. Is this what you remember?

Its too late tonight to pull it off, but I may try your idea tommorrow.

gerry gill

it seems weird that you could

blow the water out by blowing thru a sight tube nipple..I would expect that the exhaled air would have vented itself thru the boiler return traps air pipe over to the dry returns vent..I'd be curious to close the check valves back up, submerge back under water and try that test again..this time see if the exhalation vents from the return pipes vent..you with me so far? if the steam valve inside the BRT is closed and its internal air vent valve open, then you should be able to blow air thru the air vent pipe over to the vented reciever and to atmosphere via the air vent..if you feel some backpressure try taking the airvent off and doing it..keep me posted..interesting..you know I'm going to lay in bed thinking about this now!

gerry gill

seems small,

but try it anyways,,,dont break it tho..if its stuck leave it alone..

gerry gill

here's another thought,,

if the internal air valve of the boiler return trap is stuck closed, and the steam valve is closed in it, then air would be trapped in it..if the boiler pressure goes to high the water would back up the B dimension of the dry return and spew forth from the air vent......but the air trapped in the BRT would keep the sight glass showing no water..see if you can duplicate the senario and the open the gage glass pet cock drain and see if water shots out of it then...you should be running your system under ounces anyhow so then if thats the case the BRT will just sit there as an in place testimonial to the elder's genious.

Bill Marsh

Airlock

I think we figured this out. Steamhead was right about the water not getting to the Return Trap in the first place but maybe he didn't know the reason.

The only air vent on my entire system is the Hoffman #75 on the Receiver. There is no air vent on the dry returns. Maybe there's a plug someplace, I'll look.

It used to be when water moved into the Return trap from the pipe up from the check valves, the air could go out the pipe to the dry returns. Now with repaired traps and new TRVs, the air cannot get from the dry returns to the end of the steam main attached to the receiver (just like fig 56) so now the Boiler Return Trap is airlocked.

Maybe some kind of vent belongs in that 1/4" hole instead of the plug gerry was talking about.

Or maybe I can fund a plug and add another vent at the end of the dry returns. I still have a Vent-Rite #75 unused so that might be easy.

Steamhead

Bill, can you

post a pic of this Receiver and how it fits into the system? I thought it was the usual Float Trap/Air Eliminator but your subsequent description of it has me wondering.

Also, I think Gerry is right about why the Return Trap is air-locked. There were two basic versions of Return Traps; one just had a steam line connected to it with an open vent, and the other had the air line to the dry return instead of the open vent- this version was also known as an Alternating Receiver.

If for some reason the air line is blocked, water won't enter the Return Trap. First thing to do is loosen the union in the line and blow thru it. If the air line is clear, the valve in the Return Trap is bad and should be repaired.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

photo and possible solution

Hi Steamhead!

I already posted a photo of the Hoffman Boiler Return Trap (Its a No. 30)and the Hoffman Receiver Vent yesterday.

The Photo is PB280010.jpg above. The return trap is on the left.

The Return Trap has 3 lines - one down to check valves
- one to header
- one to beginning of the dry returns

The Receiver Vent has two lines and (till now) the only vent. The lines go down to the check valves and to the beginning of the dry returns. Below the vent is a T that attackes to the end of the dry returns.

The steam main loops back and terminates by dropping into the wet return just like in fig 56.

I think you are right that the system could airlock if the line from the receiver vent to the beginning of the dry returns was blocked.

Anyway, I think I solved the problem by adding another vent to the return lines. I looked for a plug, like I told gerry I'd do, but didn't find one. So I went into the crawl space and moved the Hoffman #8 Line Return Valve (labeled Hoffman Thermostatic Trap in fig. 56 and repaired with Tunstall capsules for #8 thermostatic radiator traps)with elbows and added a T on the condensate side where I attached my old Vent-Rite #75 vent. I attached a photo of how I did this.

While this might not be technically correct, I think this was alot less work than pulling apart the pipe from the receiver vent to the beginning of the dry returns.

Anyway, I turned on the steam again and the kids were glad to have heat. Once again it went way above the cut-out for the pressuretrol. Once it hit 2 1/2 PSI I began to see condensate in the Boiler Return Trap. The level maxed out about 80% up the watch glass, and fluctuated some so I think the trap works. Anyway no water hammer, presumably because I didn't get condensate backing into the dry returns. And no water squirting out of air vents.

I might swap the Hoffman #75 Vent with the Vent-Rite #75 Vent as most of the air now seems to be leaving through the Vent Rite Vent. But its really miserable crawling in that crawl space, so I may leave well enough alone.

So I think you were right: the return trap works but the water wasn't getting to it. I thank you and gerry for all your help and hope you learned as much from this as I did.

I did order a vaporstat and paid extra for 2nd day air shipping, so hopefully it will come tommorrow or Wednesday. While this is interesting and very educational, gerry is right I really should be running in ounces not pounds.

Steamhead

That's one way to add a vent

But you now have water appearing in the Return Trap, so it's not the air line that was blocked. Maybe the Receiver Vent is gunked up? BTW, from the pic, I see it's Hoffman's version of the Float Trap/Air Eliminator described in chapter 15 of Lost Art.

I'd go ahead and move the Hoffman to the vent location you just installed. The system will heat faster. You could even get another Hoffman #75 and a tee and elbow to mount it on, or a Gorton #2 which has four times the #75's capacity and doesn't cost more, to make the system heat even faster. If it heats faster, it will burn less fuel.



To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Hoffman Line Return Trap

Hi Steamhead!

I've been thinking carefully about your idea and it has considerable merit.

The limiting factor right now in air getting out of my mains is it has to pass through these Line Return traps. Now I've repaired them with tunstall capsules, which have nipples that fit in the orifices at the base of the traps. Consequently, this makes the orifice the air has to pass through about 1/2 its original size, so air will be slow to leave my main.

In general, I hate to remove something put in by the dead men, but I am not running a vapor/vacume system now so I think I don't really need this connection.

Rather than what you proposed, I think the system would probably work better if I remove this trap and put in its place two of your Groton#2 vents, one on the end of the steam main and one on the end of the dry return.

What do you think? I really appreciate your advice.

BTW, I put the vaporstat in last night and it works very well.

Steamhead

I've done that

where we had steam distribution problems, and it worked well. The reason they used those traps was so there would only be one air-venting point. Since the vents used on these systems could hold vacuum, there was less possibility of a vacuum leak this way.

Obviously this is not a consideration now. But before you buy more vents, measure the length and diameter of your steam mains to see just what is needed.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Sizing Vents

Thanks again for your help Steamhead!

I estimate my main is 3 1/2" without stripping off the insulation. It almost immediately splits into two loops.

The boiler is DOE 240 MBR and I have 721 sq ft EDR in radiators, so this is consistent with the table in Dan's Lost Art book p. 86.

The total length of each loop (main and dry return)is 80 ft.

My idea was to get 3 more main vents (either Hoffman #75 to match my existing one or the Groton #2 you recommended) which would put one vent on each steam main and on each dry return, replacing the old Hoffman Line Returns.

I would put my old Vent-Rite #75 back on the Hoffman Receiver.

The best part is I would never again have to crawl into that crawl space to maintain thermostatic traps.

Tell me what you think.

Steamhead

> Thanks again for your help Steamhead!

>

> I

> estimate my main is 3 1/2" without stripping off

> the insulation. It almost immediately splits into

> two loops.

>

> The boiler is DOE 240 MBR and I

> have 721 sq ft EDR in radiators, so this is

> consistent with the table in Dan's Lost Art book

> p. 86.

>

> The total length of each loop (main and

> dry return)is 80 ft.

>

> My idea was to get 3 more

> main vents (either Hoffman #75 to match my

> existing one or the Groton #2 you recommended)

> which would put one vent on each steam main and

> on each dry return, replacing the old Hoffman

> Line Returns.

>

> I would put my old Vent-Rite #75

> back on the Hoffman Receiver.

>

> The best part

> is I would never again have to crawl into that

> crawl space to maintain thermostatic

> traps.

>

> Tell me what you think.





To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steamhead

So

after the split, you have two 3-1/2" steam mains each running 40 feet, and two dry returns that are also 40 feet each?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Size

Steamhead, I guess I didn't explain it well.

The main is 3 1/2 inches before the split.

The total length of each loop (think circumference of circle) is 80 ft. both for Main and dry returns. They run as parallel pipes around the perimeter of the house and the addition. Most is crawl space, so its hard to get to.

You are probably right about not enough vents. The radiators heat sequentially around the loops. And now the pressure is lower with the vaporstat, the boiler cycles on and off some.

Bill Marsh

Steamhead

OK, what sizes

are the pipes after the split?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

main sizes

Steamhead, I'd love to give you an accurate response. They're in a part of the crawl space that's impossible for me to fit in and they are well insulated. I really don't want to remove the insulation mostly because I don't know what it is and don't want to get into it.

My best guess is 2 1/2 or 3 inches.

Bill Marsh

Sizing Main Vents

If anyone is interested after reading the above thread, Bell & Gossett have a table for sizing main vents published on the web.

Here is the link.
http://www.bellgossett.com/literature/MISCELIT/Fhd-207.pdf

It seems sufficient to size my vents.

I thank everyone for all their help. My house is warm, my system is silent, and it will take awhile to judge if I am burning less oil.

Steamhead

No need to remove the insulation

It was almost always 1-inch thick. The pipe's walls are 1/8-inch thick, so if you measure the outside diameter of the insulation and subtract 2-1/4 inches, that's almost certainly your pipe size.

Assuming 3-inch mains, I'd use 2 Gorton #2 vents at the end of each main. If they're 2-1/2-inch, one on each main should be enough.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Vents

Thanks Steamhead!

With insulation, the mains measure 3 3/4 inches after the split, so I'll go with your suggestion of one Gorton #2 on each main. If radiators remain slow to heat, I can always add another. This symptom is more obvious with the vaporstat running system at cutout 12 oz., cutin 4 oz.

I'll put the old vents (Hoffman #75 and Vent Rite #75) on the dry return and the Receiver so the air can get out of radiators once the main vents close.

Thank you so much; you've been a tremendous help.

I tried to find a professional to fix up this old system 5 years ago and only began to work on it myself when the problems became intolerable. In northern NH the pickings are slim, everyone wants to do new installations, and the people who have actually looked at my system seem put off by its being two pipe rather than one pipe steam.

Steamhead

Let us know

how well it works when they're installed! You can "bookmark" this thread from the main Wall page, to hold it on your PC so you can still access it even though it's over 3 days old. This way you can just continue the thread when you're ready and it will go to the top of the Wall.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steamhead

They make good equipment

but in many cases, their vents just aren't big enough for good results, especially with today's boilers.

For example, the Gorton #2 that you are going to use has about 4-times the capacity of Hoffman's biggest vent, the #75. And it costs about the same.

Now if Hoffman would bring back their #10 vent from the 1920s, they'd give Gorton a run for their money. But I don't see that happening.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Gorton Vents

If anyone is interested, Gorton has info about their vents too.

http://www.gorton-valves.com/specify.htm

I was impressed by Steamheads experience. See this link too.

http://www.heatinghelp.com/newsletter.cfm/?Id=116

Too bad he doesn't live in northern NH, but I'm sure there's more work in Baltimore.

Bill Marsh

It already works better.

I did alot.

Repaired all the radiator traps with Tunstall capsules. Old traps had mfg. date of 4/1937.

Installed Macon thermostatic radiator valves.

Replaced defective Pressuretrol with vaporstat, getting system down to 12 oz. from 6 PSI. Maybe I can go lower after the new vents are in.

Replaced the leaking blow-down valve on the boler.

Replaced thermostat with a timed one to turn system down at night.

As soon as I get the Gorton Vents, I will remove the thermostatic traps that are acting as main air vents. I remeasured, decided it was marginal, so I ordered 4 Gorton #2 (2 for each main). Probably its better to get the air out of the mains faster. (I had already replaced the single Vent-Rite #75 on the system with a Hoffman #75. maybe this wasn't the best choice but it improved things.)

All in all I figure almost $2000 in parts. Probably would have spent less if I had known what I was doing. I did some silly things -- like repairing the thermostatic traps before removing them. You pay for your education in life.

Last year I burned approx 1500 gal fuel oil. If I can get 40% reduction, at current prices this should pay for itself in 2 years. If I do better than that, I'll be very impressed, but I won't know for a while.

I tried to find a local professional to do this for me 5 years ago, but failed. I tried again this fall when the little kids radiator went cold due to a trap failed closed. My wife was lobbying to yank the system and put in hot water. In the middle of the project when the water hammer started, she really pointed this out. Took awhile to educate myself, and cold children to get me moving.

Thanks again for your help.

Steamhead

That was a good idea

more venting is better than less. And you've spent far less money than you would have for a tear-out, plus the house has not been disrupted as it would have been in a tear-out.

As they say "your mileage may vary", but we've had reports of steam system owners saving up to 70% on their fuel consumption just by fixing the obvious problems. The 40% you hope for will pay you back even sooner as fuel prices rise- which they will.

Keep us posted.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bill Marsh

Fuel Savings

In case anyone is interested, I filled the oil tank at the beginning of June. Usually it is quite empty at the end of the year. Had 400 gals. residual fuel oil!

I forgot how much I spent, but the way oil has gone up, I think my project just paid for itself.

Thanks everyone!

Steamhead (in transit)

And with oil at $2.50/gallon and rising

you'll be smiling all the way to the bank. Thanks for the update!