Water hammer in 2-pipe steam system following work by plumber

Laura

Hi all,

I'm hoping you can help! We have a 2-pipe steam heating system with old radiators (circa 1890)but a new furnace (2001). This is our first winter in the house.

We've had uneven heating in the house - at times it is 15-20 degrees hotter upstairs than downstairs (most often in the middle of the night or when it was very cold) and on very cold nights the 1st floor wasn't even able to heat up to the desired temperature. Several plumbers told us we don't have steam traps and thermostatic valves were suggested. Given that it's hard to sleep when it's 80 degrees, we decided to try that.

We had the work done yesterday and last night we had horrible water hammer all over the house (but hadn't had that problem during the day). We had never had this problem before. It seems to occur early in the heating cycle. I checked the burner & the plumber upped the main pressure to 5psi so I reduced it back to where it was & lowered the differential as well, but am not sure if that could cause all the water hammer. Can anyone offer some insight - could too-high pressure alone cause the water hammer?

Also, has anyone heard of radiators that don't have steam traps? If so, how were they supposed to work?

Thanks & sorry if this question existed in the archives (I couldn't find anything similar)

- Laura

Boilerpro_3

It is very likely you have a vapor system

which means the system is supposed to operate a maximum of 8 Ounces, not lbs., of pressure. The banging is very likely caused by pressure being set too high. The maximum most residential systems need is about 2lbs, which is the pressure the boiler shuts off at.

Before saying much more, however, some pictures, if possible, would be very useful...some of the original radiator valves, some of the radiator outlets, and some of the piping around and above the boiler. This will tell everyone here alot about the type of system you have. Two pipe sysetms comein a number or variations.

Boilerpro

Jamie Hall

bang whang

Several thoughts -- all from the 'been there, done that' school of heating maintenance.

First, when the thermostatic valves (which are new, right?) are closed, more steam will try to go where there are open valves. It is quite possible that the extra velocity is carrying water over into the runouts to those radiators, where the water is making the water hammer. I would be very suspicious indeed of this as a cause, since if I understand you correctly, this didn't happen before the valves were installed. That it is early in the cycle suggests the same... open those thermostatic valves!

There should have been valves on the inlets to the radiators -- the idea is to adjust those so that you get the heat in the room which you want; if this is a vapour system, that shouldn't be hard to do, although it's a little fiddley.

Make sure your pressure is low -- if you have a Vapostat, 12 ounces is as high as you want, and 8 ounces better. If it's an ordinary Pressure switch, set it about as low as it will go -- 1 psi max.

And yes, some vapour and two pipe systems do not have traps on the radiator outlets, but depend on a bewildering array of either special outlet fittings or on calibrated inlet valves to make sure that all the steam fed to the radiator is condensed before it leaves. The Lost Art of Steam Heating has a good section on this.

Laura

ed wallace

2 pipe steam

is the boiler piped to manufacterers specs ?? new install or existing install ???

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patrick linhardt

> Hi all,

>

> I'm hoping you can help! We have a

> 2-pipe steam heating system with old radiators

> (circa 1890)but a new furnace (2001). This is

> our first winter in the house.

>

> We've had

> uneven heating in the house - at times it is

> 15-20 degrees hotter upstairs than downstairs

> (most often in the middle of the night or when it

> was very cold) and on very cold nights the 1st

> floor wasn't even able to heat up to the desired

> temperature. Several plumbers told us we don't

> have steam traps and thermostatic valves were

> suggested. Given that it's hard to sleep when

> it's 80 degrees, we decided to try that.

>

> We

> had the work done yesterday and last night we had

> horrible water hammer all over the house (but

> hadn't had that problem during the day). We had

> never had this problem before. It seems to occur

> early in the heating cycle. I checked the burner

> & the plumber upped the main pressure to 5psi so

> I reduced it back to where it was & lowered the

> differential as well, but am not sure if that

> could cause all the water hammer. Can anyone

> offer some insight - could too-high pressure

> alone cause the water hammer?

>

> Also, has anyone

> heard of radiators that don't have steam traps?

> If so, how were they supposed to work?

>

> Thanks

> & sorry if this question existed in the archives

> (I couldn't find anything similar)

>

> - Laura

patrick linhardt

water hammer

I just spent the Friday PM commute thinking about this. If you confirm that the original radiator valves were removed for the installation of the new thermostatic valves, I will propose this theory. The original valves were internally metered(many manufactureres used many varied methods) to proportion the steam flow to the radiator size.
These were removed in the morning and new thermostatic valves installed in their place. The new valves have no such internal meter, they allow maximum steam flow when wide open. In the mild afternoon the boiler was not on long enough to heat the whole radiator. As it got colder that night, the boiler was on long enough to fill the whole radiator. As soon as a new valve opened wide or stayed open on a warm radiator, steam blows past the vapor device or return elbow into the dry return to cause water hammer.
Let me know some more detail, I'm interested also in the floor to floor imbalance.

Unknown

Great answer

I'll put my poker chips on this bet.

Noel

gerry gill

glad to see you active here Pat,

your book was a great read, and now is a truck companion along with my truck copy of lost art..i'd like to see some pictures of these radiators please, as boilerpro suggested..it would really help us to see what you see..picture of the old valves would help too...thats a good theroy Pat..you've got me thinking now..

DanHolohan

my stack

too!

Laura

Much more detail for you pros

Wow! I didn't expect such quick & solid responses on this. You guys are great! So I'm going to post a bunch more info below as a summary of my issues along with a number of photos of my system, which I'm told is very unusual. I don't have photos of the old valves - but my plumber may still have them (& I think he may be following this thread) So Rich, if you have any info, please feel free to add it.

Below are all the facts I could think to include plus some questions & photos (no one ever said I wasn't thorough):

Preexisting conditions:
- 1st winter in home built in 1890's
- two-pipe steam heat, new furnace 2001
- only 4 radiators in the back of the house had valves that can be turned on/off. The others were stuck (there was a small fire in the back of the house in 1996 so my guess is that these radiators were repaired at the time of the renovation)
- at night, or on very cold days, 2nd floor is 10-20 degrees warmer than 1st floor.
- on nights with outside temps below 0 degrees F sometimes first floor can't even meet temp set on thermostat
- no water hammer, steady water levels, pressuretrol set at around 2psi (main) and less than that for the differential.
- no apparent steam traps, no apparent F&T valves, one main vent

Work done this week by plumbers:
- Pressuretrol upped to 5psi (main) and 3 psi(differential)
- The two "dips" in the pipes at the end of the lines were drained of condensate (see photo of "dips") though each only had a small amount of water.
- Danfoss thermostatic valves added to all but 2 radiators in the home (9 total)
- They will be replaced by valves with remote sensors early next week so the current valves are mounted vertically rather than horizontally as the instructions stated because the remote sensor valves can be mounted vertically. (Didn't realize they had the wrong parts until they had removed the existing valves)

Current problem:
- Water hammer throughout the house - primarily at night. Infrequent during the day.
- Have not verified this - but I think the radiators on the leg with no dip at the end may not be experiencing any water hammer.
- Water Hammer appears to be at the middle to end of heating cycle & I feel like it's in the supply line (?) though that doesn't make sense to me.
- In one instance of water hammer this afternoon I was able to stop it by setting that radiator's thermostatic valve to 5 (high)
- When the furnace turns on, all radiators seem to get hotter than they did prior to the fix and you can hear the steam running through them, which wasn't true before. The 2 just before the "dips" in the pipes still do not heat up as much as the others.
Note: this morning I lowered the pressure to approx 2psi (main) and something lower than that for the differential (no tick marks below 2psi on pressuretrol)

Photos attached:
1&2 are of the Burnham furnace
3 is of the furnace piping & main vent
4 & 5 are of the "dips" at the end of 2 of the piping "legs"
6 is of a typical radiator in the house

QUESTIONS:
- How might I eliminate the water hammer?
- Does anyone know what purpose these "dips" in the piping serve? I don't see any F&T valves - might these serve that purpose?
- Might those "dips" need water in them to function properly? (i.e. the water that was drained from them 2 days ago) Might this cause the water hammer?
- Is there any reason that the Danfoss thermostatic valves might cause or exacerbate water hammer because they are installed vertically rather than horizontally as instructed?
- Does anyone see any issues with the air venting or furnace piping? We have only 1 main vent & no other air vents in the system.

Thank you letting me pick your brains on this one!!

- Laura

Laura's Dad

Clarification of the location of the piping described as \"Dips\"

The piping described by Laura as "Dips" (and shown in the photos) ties the steam output and condensate return lines at the end of each run. They are an apparent short circuit and, we suspect, likely to fill with condensate. We do not understand their function but are concerned that the fact that they were drained during the recent plumbing work has in someway aggrevated the water hammer issue.

Steamhead

You bet it did

I've seen this before. These are "loop seals" which allow the small amount of condensate in the steam main to drain into the dry return. The water in the loops keeps steam from reaching the dry return. You could do the same thing with a float trap, but the loop does it with no moving parts.

Almost all Vapor systems were designed to keep steam out of the dry returns (Kriebel was an exception). If steam reaches the dry returns, it will bang since the pipes are not sized to carry steam.

Too much pressure in the steam mains will blow the water out of the loops, and this will also cause banging. How deep is the water seal in those loops? You need 30 inches depth for each pound of pressure. If you have a Pressuretrol and the loops are 30 inches deep or less, change the Pressuretrol to a Vaporstat that cannot be set higher than 1 pound.

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Boilerpro_3

You're on the right track

those loops must be filled with water for the system to work properly. They are called loop seals. Condensate that forms in the steam mains dribbles into them and fills them until water starts to overflow into the return line. This water prevents steam from traveling from the supply to the return. If the pressure gets too high, it will push the water out of the loop seal and steam will enter the main, causing banging and poor heating. Each 28 inches of water in this loop balances 1 psi of pressure in the boiler. It looks like your loop seals are about 1 psi "tall" .... 28 inches..... so the pressure the boiler shuts off at must be below 1 psi. Also, I would almost bet that the original radiator valves had orifices in them to meter the steam into the radiators so steam could not make it through the radiators to the return elbow and into th return main. If the old valves had them, you'll need to put new ones in the thermostatic valves for the system to function properly.

Also, your main vent is much, much too small, even for the smallest of systems. You probably need something with about 15 to 20 times the venting capacity as that one. Take a look at Gorton Vents... they have lots of capacity.

And, as always, copper is a very poor choice for steam piping (boiler piping) It expands and contracts greatly with the rapid changes in temperature and then the joints leak.

You probably have one of the most efficient heating systems available and with a little knowledgable TLC, it can run incredibly well.

Boilerpro

Boilerpro_3

HI ya Steamhead.....NM

Steamhead

Hi BP

I was going to mention the vent and the copper, but you did it as well as I could. Laura and Dad, that vent is probably the only way for air to escape from the system, so it must have large air passages. The best choice is a Gorton #2 (www.gorton-valves.com) but make sure it isn't placed near anything that will get it hot enough to close prematurely.

The loop depth, however, is a "B" dimension rather than an "A" dimension since there should not be any pressure in the dry return. Therefore we need to use 30 inches per pound.

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gerry gill

those loop seals

are very sensitive to pressure..laura's dad, have you ever used a u-tube manometer? thats essentially what that loop seal is.. take a laser level and shot a dot from the lowest permissible level of water at the boiler over to that loop seal, see how much pipe is left below the ''dot'' before it goes horizontal..divide these inches by 1 3/4 (1.75) and the result is your maximum operating pressure from the boiler in ounces..check both loop seals this way..since its a replacement boiler, you may find these loop seals are no longer under water, that they are in fact higher than the boilers lowest water line..if so have your plumber lower the loop seals..you may have to install orifice valves or orifice discs in your existing valves..steamhead has the orifice sizing chart.

Steamhead

Gerry, that type of loop seal

will still be OK if it's above the new boiler's waterline.

The other common loop-seal arrangement, where a wet return line comes out of the bottom of the seal, is the one that's sensitive to the waterline. A too-low waterline will drain the water from the seal and steam will get thru.

I've used the type of seal in the picture to isolate steam-main drips where a formerly wet return was turned into a dry return when the boiler was changed, and repiping the entire return would have been very difficult.

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gerry gill

opps, yup.yup

i see it now...thank you,,it'll make me look better next time before typing ;-)

john_27

It certainly is a vapor system.....

a Veco or most likely a Broomell.....if you get Dan's book"Lost Art", you will see a picture of your return elbow under his section on Broomell systems. Also, you will see that the supply valves are pictured, and had multiple orifices in them to control the steam to the radiator...they were sized at 80% of the radiator capacity so that steam wouldn't reach through to the return lines. My guess is that you will have to take a look at your supply valves.....it's all in the book...John

Laura's Dad

Some improvement as \"loops\" fill with condensate

The feedback has been terrific!

Current reports from Laura are that the hammer has disappeared with most radiator control valves set at 5 and two set at 2. I suspect that the loop seals, which had been drained, are filling with condensate and are again blocking the steam from the return line. I gave her a way to fill or check that the loops are full. Confirming evidence includes the need to add a bit of water to bring the sight glass to midpoint.

I think the system may still be short cycling so we'll have to confirm that.

It would appear that the next steps are to:

1) Improve the venting and change the Pressuretrol to a Vaporstat. (We’ll contact the boiler manufacturer for recommendations)

2) Check the removed control valves for orifices.

We'll keep you informed. Thanks again!

gerry gill

post a picture

of the original valves,,we'd all love to see them i'm sure.

Laura

Thank you! Thank you!

You can't imagine what a relief it is to finally understand our heating system a little better! Your help was invaluable. I wish I could tell our whole town about this site (many in my Boston-area town, Winchester, have steam heat in their homes &, I'll bet, live with problems they think they can't fix) But at the very least I can put a couple of "Bricks in the Wall" to help grow this site to express my gratitude.

Our plumber, who is hopefully reading all of this, should be able to help us with the 2 items my dad referred to in addition to replacing our current main vent with a larger one (which, to his credit, he had recommended to start with). If I can, I'll report back to let you all know it worked!

Have a wonderful Sunday! And again, thank you!

Sincerely,
Laura

fs

#4a or #75 vent is what you'll need, check to make sure you feed is not pitched back towards heater also, I had a incident similar with the unbalance heating and changed all the main vents and corrected the pitch and it worked great, not saying this is the same problem your having since steam is a very detailed work of art.

john_27

An alternative to a hoffman 4a or a 75 is the gorton #2.....vents at 5.5 cfm versus 1.5 cfm (for the 75).....a 75 is not enough capacity for the main vent....if you search under "gorton" on this site...you'll find their telephone number...also, the Gorton appears to close at 110 degrees...I put mine outsde of the boiler room to forestall this problem...John