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Slow Steam Main Cause?

Hey hoping someone can help trouble shoot my steam heat problem!

In a one-pipe parallel flow steam system I am having a problem with unbalanced heat. The boiler is a Weil McClain PEG 40, and the header feeds 2 mains that run in opposite directions around the basement. Both mains are 50-60 feet long and have brand new big mouth air vents on them. The 60 foot main gets completely emptied of air in about 9 minutes from a cold start. The 50 foot main take about 20 minute to start getting steam at the end even with the big mouth air vent removed!

I installed a 20 ounce pressure gauge, and the pressure at the boiler was about 16 ounces before I got any steam coming out the slow main. I attached a diagram of my system if that is useful.

So what could be preventing steam from getting to the open 3/4 inch pipe at the end of the slow main?

One thought is that the slow main drops quite a bit before it hits the wet return. I think it is still 28 inches above the waterline, but could pressure be building up in the wet return, raising the water level, and preventing the air from escaping? I could hear water gurgling sounds coming out of the pipe when I had the vent removed. What would cause that? Dirty boiler, partially clogged wet return? Hoping it is a relatively easy fix and will not require any re-piping.

Thanks!


Comments

  • JUGHNE
    JUGHNE Member Posts: 8,175
    Could you post pictures of boiler piping, including returns, wet and dry. Vent location pictures also.
    Is your piping insulated?
  • New England SteamWorks
    New England SteamWorks Member Posts: 1,407
    JUGHNE said:

    Could you post pictures of boiler piping, including returns, wet and dry. Vent location pictures also.
    Is your piping insulated?

    Ditto.

    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
    newenglandsteamworks.com
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,425
    If the water level rose high enough to obscure the main vent, you would see the water pouring out, with the vent removed.
    My guess would be a sagging corner in the long main. Air being pushed through a puddle, would account for the gurgling sounds you hear.
    Use a level to check the slope, and see what you have.
    I don’t have my paper available-what is the total EDR of the rads?—NBC
  • ratio
    ratio Member Posts: 2,729
    If you heard water gurgling in the main, there's water obstructing the flow of the steam. If water didn't come out before the steam make it to the end, it's still in there -> a sag in the pipe of greater than the pipe ID. Straighten out the sag, make sure that it pitches the right way.
  • EssexSteam
    EssexSteam Member Posts: 8
    Thanks for all the comments. Tons of great info here!

    I went and checked the pipes with a level. They all appear to be slopping towards the wet return and I didn't see any obvious sags. The piping is all brand new and insulated with 1/2 inch fiberglass. I imagine for a complete obstruction that would block the steam from reaching the main vent, the sag/wrong pitch would be obvious?

    I also double checked the A dimension with a laser level. The end of the main is 30 inches above the center of the sight glass. That should be ok according to the Lost Art of Steam Heat.

    Could a clogged wet return be causing water to backup into the end of the main? If it backed up enough, it would obstruct the main air vent (see the attached photo). After the boiler fires for a while the water level in my sight glass drops a good couple of inches. In the attached picture when the boiler is cold the water is up to the tape on the sight glass. That picture was taken right after steam started to push its way out of the main vent. Does that look normal to you?

    See the attached photos of the near boiler piping and main vents.






  • EssexSteam
    EssexSteam Member Posts: 8
    @nbc the total EDR of the radiators is 275. The boiler is rated up to 325. So that is about 20% over-sized. It does cycle on high pressure when trying to raise the temperature of the house after a large setback.
  • gfrbrookline
    gfrbrookline Member Posts: 638
    I'm not a pro but your near boiler piping is wrong and the copper pipes should be replaced with black pipes.

    Since you do not have an equalizer the steam is going to the better vented main.

    The water in the site glass is cruddy at best so the boiler should be flushed and skimmed until it is clear. Clean water will make better quality steam.
  • Steamhead
    Steamhead Member Posts: 14,338
    I'd flush it first. We've had cases where boiler water was in such bad shape that it didn't boil properly, causing problems similar to this.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • EssexSteam
    EssexSteam Member Posts: 8
    @gfr the problem main is the one headed off to the right. There is an equilizer. It's the copper pipe behind the gas line.

    The other main (heading off to the left) is actually counter flow, so the pipe you see there is a drip collecting the condensate that is running back to the boiler. Piping is a little unusual in that it has both parallel and counter flow, but looked ok from the manual.

    @steamhead Let me try flushing. I guess if water is splashing up into the main, that would cause a big problem on the parallel flow path, where it would get pushed along and presumably slow things down. On the counter flow, it would just head back to the boiler. I don't have a skim port, but a regular flushing should be sufficient?
  • EssexSteam
    EssexSteam Member Posts: 8
    Flushing the boiler seemed to help a lot. Need to do more testing tomorrow, but there are no more gurgling sounds.

    I have a valve at the boiler end of my wet return. I was taking water out of there too when I flushed the boiler. The water came out at a pretty slow trickle. What is a typical flow rate for a wet return?

    We are about to wall in all the pipes in a renovation, and I want to make sure I deal with any potential issues with the return first.
  • BobC
    BobC Member Posts: 5,182
    With the system off you could try flushing that wet return by feeding water into a removed air vent with a hose and see how the water comes out. Is there a drain on that wet return near the boiler?

    If the water comes out very slow that return has to be snaked to get the crud out and if that doesn't help the wet return has to be replaced. This is the one place copper pipe can be used.

    After doing the above you probably have to flush the boiler again because of what came back from the wet turn while flushing it. Then you can put the main vent back on and bring the system up to steam to drive off any oxygen in the water.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Danny Scully
    Danny Scully Member Posts: 1,319
    edited March 2018
    That 2nd picture is a little concerning. It looks like it’s the end of 2 mains, and copper piping mixed in there. That main on the left looks really low as well. I thought you said you had 1 parallel and 1 counterflow? Maybe take another few pictures of that area. Also leave access for the big mouths. Where are you located?
  • EssexSteam
    EssexSteam Member Posts: 8
    @bobc Thanks. I'll try to flush the return. One question, do I need valves to close off the mains from the wet return when I flush with a hose? If the wet return is clogged, I might get water backing up into the main?

    @Danny Scully I am in northern NJ. I checked the A dimension on the main on the left with a laser level, and it is 30 inches above the waterline. The main on the right (the fast main) is counter flow for the first 3 radiators, then switches to parallel for the last. (It is also copper, which I know is not ideal, but is not worth fixing now.) The configuration of counter flow to parallel allows the main to not be too low by the time it reaches the wet return.

    I'll take a few more pictures tonight, but it is hard to get the whole configuration in perspective with the 2x4 framing there.
  • Danny Scully
    Danny Scully Member Posts: 1,319
    I wouldn’t close up any walls that have steam carrying copper piping.
  • Fred
    Fred Member Posts: 8,515
    If the main running to the right is the problem main, I'd be looking at how each main is vented and how many radiators (with vents are attached to the main on the left). My guess is that the left main is stealing all the steam until it is full and then it begins to flow into the right main. Steam is going to take the path of least resistance and that appears to be the left main. How many more radiator are on the left main than are on the right main? Slow the radiators vents on the left main down and see if that moves steam to the right quicker.If the main running to the right is the problem main, I'd be looking at how each main is vented and how many radiators (with vents are attached to the main on the left). My guess is that the left main is stealing all the steam until it is full and then it begins to flow into the right main. Steam is going to take the path of least resistance and that appears to be the left main. How many more radiator are on the left main than are on the right main? Slow the radiators vents on the left main down and see if that moves steam to the right quicker.
  • EssexSteam
    EssexSteam Member Posts: 8
    I got a around to flushing the wet return this weekend. Got some gunk to come out of it, but nothing crazy. Running a garden hose into the main vent, a pretty good stream was coming out of the wet return at the boiler end, so it seems the wet return is fine.

    While better than before, I am still getting some imbalanced heating accompanied by high pressure in the boiler and bouncing water levels. Since I have ruled out clogged wet returns and the pitch in the pipes looks good, I think @Steamhead was correct. We had some work done on the pipes, and the cutting oil/ solder/ pipe dope must be messing with the water quality in the boiler.

    Will repeated/regular flushing of the boiler will be enough, or do I need it skimmed? If skimmed is that a reasonable DIY project?
  • the_donut
    the_donut Member Posts: 374
    Another thought is that condensate from the counterflow is condensing steam from your other riser. I see it is dripped, but there will be water in that section of pipe until the header warms up you could try insulating the fittings and like others have suggested, skimming and slowing down venting on the fast side. You might try adding a b&j Varivent on another tapping on the slow side or swapping the big mouth for a Varivent and adjusting the vent rate so steam arrives at the end of both mains at the same time.
  • BobC
    BobC Member Posts: 5,182
    At least now you know the wet returns are clear.

    Now for the boiler water, skimming is a great DIY job, smimming is much more effective at removing oils in boiler water than flushing is. You slowly over fill the boiler till water trickles out the skim port. While doing this you fire the boiler often enough to keep the water just below boiling.

    Skimming is best done through a large port, does your boiler have a skim port installed? If not look in the boiler manual, they usually tell you where it should go. If you don't have the manual tell us the boiler model number.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • ratio
    ratio Member Posts: 2,729

    Will repeated/regular flushing of the boiler will be enough, or do I need it skimmed? If skimmed is that a reasonable DIY project?

    The oils float on top of the water, so flushing really wouldn't help much with that, although it isn't necessarily a bad idea, esp. if you think there might be crap laying on the bottom.

    Skimming is very much a DIY kind of thing. There are numerous threads here about skimming; I'm quite sure there are internet videos of the process as well. Basically, you open a port above the normal water line, on the side of the boiler (hopefully there's something there!), then raise the water level manually until it just starts to trickle out, then let it run like that for as long as you can stand it. The flow will carry the oils out of the boiler. Several 2-3 hour sessions should make a noticeable difference. More may be required, and you can't over-skim, so if you think it needs more, go for it.

  • SteamingatMohawk
    SteamingatMohawk Member Posts: 396
    Your system seems to not have the dry return like in the attached drawing.

  • EssexSteam
    EssexSteam Member Posts: 8
    So it seems that if you have the time, a slow cold skimming is an effective way to get oil out of the boiler. That seems like an easy/ risk-less procedure.

    One question, if I install a pipe and valve in the skim port (this is a PEG 40), is there any reason not to leave it permanently installed? Manual says to remove it when done cleaning the boiler, but if it does no harm, I'd just as soon leave it in.
  • JUGHNE
    JUGHNE Member Posts: 8,175
    Another skim method I found here on the wall:
    Bring the boiler to a good boil, shut off power, manually add water very slowly until you get a fine steady stream coming out of the skim port. Let the small stream flow until cold. Drain boiler down to normal and then fire to boil again.
    The posting said to not stop the flow once started, let run until cold/cool......or you have to start over again.
    The claim was that one skim like this would be all you need?

    I have tried this and it seems effective and easier than firing to maintain temp. I reduced the 1" down on the vertical with a 1/2" nipple to monitor the small stream easier.
    This could be left in place if you shut off the valve and capped or plugged the outlet.
    BobC
  • Fred
    Fred Member Posts: 8,515
    No problem leaving the skim pipe and valve on but for safety sake, so that no child or unsuspecting sole who might be in the basement while the boiler is running opens that valve and scalds themselves on steam, It is advisable to but a cap or plug on the end of the pipe or valve that is only removed when a skim is required.
  • ratio
    ratio Member Posts: 2,729
    I like the warm skim myself. Heat will only thin the oils & make them easier to carry out.

    I actually have a close nipple, sized to the skim valve (2" in my case—big boiler!) with a half-moon shaped piece of plate stock welded across the opening, with a vee notch in it. Thread it into the valve, turn until the plate is down/level, bring the temp up & shut off boiler, crack the valve to bleed off any steam produced, open the valve fully, crack the feed bypass valve & adjust to as light a trickle through the notch as i can stand, & let it run for a few hours.

  • mikeg2015
    mikeg2015 Member Posts: 1,181
    What do the radiator vents look like? If the radiator venting is too fast, steam can take preferential paths. You need a certain amount of "back pressure" even on a vapor system. I swapped all my Gorton 6, C & D for smaller 4's and some Ventrites and my header pressure actually dropped... and lot and it's more balanced.

    The reason? You want steam to condense in a even and controlled manner, without enough back pressure the system will locally go into vacuum at the laterals and radiators and starts to progress out of control. The reason pressure does not build is that all steam gets condensed as fast as it's generated. Pressure only builds when all steam is "not consumed" or due ro back pressure from pipe size restriction.

    Your slightly longer header may have more total venting and therefore less back pressure and so all you steam goes that way. Total radiator venting needs to basically match the boiler steam capacity minus pickup for the header. Too much from what I've observed is as bad or worse as too little. However, too little will result in noisy vents as radiators initially vent but main vents are closed.
    MilanD
  • steamfitter
    steamfitter Member Posts: 161
    The header should be insulated. All steam piping should be insulated. Uncovered piping condenses 5 times more than covered piping.
    Even a uncovered fitting here and there can produce little pools of condensate which suck the energy out of the steam in the mains, adding even more condensate before the main steam gets to the rads.
  • MilanD
    MilanD Member Posts: 1,159
    edited April 2018
    Fred and Mike are right. One side is stealing all the steam until it's full and rooms warm and rads there slow down their condensing at which point the boiler becomes oversized for the system, pressure starts to rise while at the same time the steam starts heading down the other side, now condensing and taking on more steam, but fighting slow venting and now excess steam.

    Looking at your diagram, your currently fast side has approx 2/3 of the attached edr then the slow side (and 2 extra rads). You need to balance the venting via combination of slower radiator and main vents on that, currently fast side, and faster vents on the currently slow side. It may be as simple as a big mouth on the slow side and Hoffman 75 on the currently fast side. Or you can add a ball valve on the currently fast side's main vent and create back pressure by closing it down some (or quite a bit). Or It will require faster venting on the slow side in addition.

    Are the 2 mains same size? If not, that's an added issue as well that would require even more restricting of the currently fast side and speeding up the other.

    A little trial and error on balancing the venting will get you there. Best of luck and let us know how you did.
  • Dave0176
    Dave0176 Member Posts: 1,171
    The boiler doesn’t appear to piped properly either, Weil-McLain wants a 2-1/2 riser and header, you have what appears in the picture to be 2”
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