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Mono Flow Issues

Hank07974Hank07974 Member Posts: 7
I just replaced my BG circulator pump with a Taco.  The BG was the 100 series and the Taco I bought was the S10.  I put the new pump in and filled the boiler and bled the radiators until water came out the valve.  I start the boiler and the hot water is not being sent around the house.  The feed line gets hot and there is a really loud banging noise coming from the steel tank up in the rafters.  This is a mono flow with two 1 1/4 copper loops going around the basement.  There are 1/2 inch pipes with mono flow tees (1 1/4 x 1 1/4 x 1/2) going to radiators on the 1st and 2nd floors.  I did get water to each radiator.  I tried bleeing air with a hose from the boiler drain near the bottom of the boiler, and it looked like the air was out.  After running the boiler and trying to bleed will hot, it seems that steam is being sent out the hose.

What is causing the problem?  Circulator pump not strong enough?  I was told the scrap the BG and go with Taco.  Should I get another BG instead of Taco?  Is the boiler or a pipe clogged?  If clogged how did the water get all the way to the radiators, even on the 2nd floor?  Why is the boiler making steam? Is there air in boiler?  There is no vent on boiler, only relief valve.  I do not have picture of boiler, but is it an American Standard from 1956. 



  • icesailoricesailor Member Posts: 7,265
    Monoflow Issues:

    Whatever possessed you to (or where did you read) to replace a B&G Series 100 circulator with a Taco S10, a high head, high velocity circulator that is way to big (and expensive) for your application? A 007 would have worked and been a whole lot cheaper.

    Mono-flow systems will work on gravity without a circulator running. Not well, but will run. Mono-flow systems work well with the properly sized pump to move the water through the system at a designed and reasonable speed and volume. They will work poorly or not at all if they are pumped too hard and/or too fast.

    I hope you used the black square cut O-Rings for flange gaskets instead of the POS red rubber ones that some wholesale counter people will try to sell you that are in the shape of the flange. Those red flat gaskets don't fit into the square groove machined into the circulator body by Taco and the other manufacturers. The gasket will dry out and leak.
  • smklinsmklin Member Posts: 46

    Where can you read or find that info on monflow. HAVE 4 350000 BTU Systems that were put in about 1984 that never really worked real great from day 1
  • icesailoricesailor Member Posts: 7,265
    edited March 2014
    Mono-Flow Systems:

    I lost all my good technical stuff when I moved.

    There's a good piece on Mono-flow systems here on Heatinghelp,com. I'm sure that someone will post a link to it.

    The first thing that I think of is are the mains large enough to carry 350,000 BTU's? Is it a 2" main or does it leave the boiler as 2" or 2 1/2" and split?

    The old Yellow IBR design book had excellent information on designing Mono-Flow/One Pipe systems. The new advanced manual doesn't have that information because so few systems are designed and installed now. Mostly all wrong anyway.

    If the pipe sizing is correct, it is probably pumped too hard.

    Here's an interesting article I just found. You have to understand and read behind the lines. But flow rate is critical.

    Here's another good article. Get to the part about radiators seeming to have an issue with air. But it isn't air, it's improper flow.
  • Paul48Paul48 Member Posts: 4,256

    I can't find any info for a Taco S10.
  • Pughie1Pughie1 Member Posts: 116
    How Come

    Dan's book titled "How Come?" goes into monoflo systems in great depth, a wonderful explanation on design & Trouble shooting. It can be found in the shop section here at this web site. For the money a wealth of information.

    John Pughe
  • Pughie1Pughie1 Member Posts: 116

    I should have added that Sailor is right. If you check taco's cross reference guide it recommends an 006, 007, 008, or a 110 as the appreciate replacement for a B&G Series 100 circ.

    John Pughe
  • icesailoricesailor Member Posts: 7,265
    edited March 2014
    S-10/2400-10 Taco Circulators:

    I found it this AM on the Taco web site.

    Maybe they changed the # since this AM. I think that this might be it.

    A lot more money than a 007 and a whole bushel basket full of squirrel nuts more.

    Taco # 110 was always the choice of alternates until they came out with the 007 wet rotors.
  • Hank07974Hank07974 Member Posts: 7
    Mono Flow Issues

    I believe it is the 110.

    So I placed the order for the book it will be a good reference since I just moved into this house.  I did use the Taco gaskets that fits in the Taco.

    Any other tips for getting the water to circulate? 

    My boiler is a 105,000 BTU system.  The unit was working fine until a contractor came in to "dewinterize" the home for the closing.  It was dewinterized by someone else for the inspection, but then winterized until the closing.  So the 2nd guy ran the boiler then tried to get the air out by pumping cold street water into the system.  Well the pumped burned out and I could smell burnt rubber and water was leaking.  We shutdown the system and I closed on a house with a broken boiler.  Long story short, noone is looking to cover the costs, so I am trying to get this thing kick started until summer.  I attached the new Taco pump, but that is where I am at.
  • unclejohnunclejohn Member Posts: 909
    Is the

    Pump installed correctly? Is it pumping the right direction?
  • Hank07974Hank07974 Member Posts: 7
    Mono Flow Issues

    I think so. The arrow on the new pump is in the same direction as the old pump.  I connected the black and white cables the same way.  Would flipping the power cables make it spin in reverse and flow the wrong way?
  • Mark EathertonMark Eatherton Member Posts: 5,584
    edited March 2014
    Probably air bound….

    What the plumber tried to do is called forced purging, and unfortunately, it is not effective with a one pipe monoflow system. With the pump in the OFF position, you must go through the whole house, removing the end caps of the convectors, and manually bleed the free air out of the system. It may even be necessary to lift the ends of the convector to cause the air to go toward the highpoint manual vent. If you don't get any air, you are done. If you don't get any water, the pressure in the system is too low. You need 1/2 PSI per vertical foot of system elevation, plus 5 PSI under normal operating conditions.

    Once you have manually bled the system you might have to raise the operating pressure to near its maximum (27 PSI for a 30 pound relief valve). This causes any residual large air bubbles to compress, and shrink and when the pump starts moving water, it will carry the air back down to the boiler, and either eliminate it through the air scoop/auto vent or take it back to the expansion tank cushion.

    I'd also suggest you turn the burner to the pilot only position while doing this to avoid any other "issues". It might be necessary to do this numerous times until you get complete circulation through all of the baseboards, Air moves around, hence the reason for manually bleeding wit the pump in the off position. Otherwise, you are chasing your tail.

    Regards wiring, no it won't change the direction of flow.

    It sucks that you are being stuck with the bill based on someone else's incompetence…

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • You Could Try

    Burping air out at the circulator flange, by loosening the bolts until air or water comes out, when the boiler is cold of course. I had a taco 007 once that was cast metal across the pump opening, I couldn't get that on to bleed, and spent a lot of time figuring out that one.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Paul48Paul48 Member Posts: 4,256

    Can you get some pictures of the near-boiler piping. Try to stand back far enough to get it all in. If you're getting steam, you have air trapped in the boiler.
  • icesailoricesailor Member Posts: 7,265
    edited March 2014
    First Photo:

    In the first photo, why does the Tridicator show that there is less than 5# PSIG in the system and the boiler is cold? The boiler may be off and cold, but if the feed to the boiler is working and in the "ON" position, there should be at least 12#+ PSIG in the system.

    Is it a "Cold Start" with only that strap on control on the supply to shut it off if the boiler is overheating? Looks like a potential bomb to me. If you're n ot pumping water and the burner is running, the boiler can only turn to steam without something sensing the water temperature.

    What is that 3/4" black pipe that is coming out the front with the tag on it?

    Our advice is free here. For whatever that's worth.

    There are some serious safety issues with that. It wouldn't be approved now without modifications. I sometimes worry about liability with free advice.

    Here's some free advice. Find someone listed here that works near you and get them to fix that. It isn't safe. It may have been safe for as long as it has been installed. Now, it isn't running properly. You take your car in for repair. You need to have that professionally repaired or replaced..

    That combination 1/2" fill and pressure relief is a place to start. It won't relieve properly, and the fill valve isn't working.
  • Hank07974Hank07974 Member Posts: 7
    Mono Flow Issues

    I actuallydo have someone coming over to look at it later today.  The feed to the system is turned off.  When the system was on, the pressure was about 14 and the water made it all the way up to the second floor radiators.  Also when we bled the system, the feed did kick on and I could hear the water being fed into the system.

    I know this is free advice, but would like to have as much background as possible when I deal with the local guys.

    One of my choices will be to leave the Mono Flow or conver to baseboards.  I like the sytem a lot but would welcome any advice on keeping it or switching.

    The 3/4 in on front is the pressure relief valve, looks they added the pipe since the gas valve was in the way if it was pointed straight down.

    At this point, the only change was the pump.  I am hoping the tech can get the air out and heat the house until I decide what the future sytem will look like.

    thanks again
  • SWEISWEI Member Posts: 7,356
    Advice for the future

    Don't trade cast iron radiators for fin-tube baseboard -- you will regret that one.

    Some day, you should install a properly sized fire-tube mod/con boiler running outdoor reset.  When you do that, you should be able to re-pipe the mains and eliminate the monoflow tees using either a reverse return or home-run manifold arrangement.

  • Robert_HRobert_H Member Posts: 135
    "I actually do have someone coming over to look at it later today."

    Im curious what were the results of the inspection?
  • Hank07974Hank07974 Member Posts: 7
    Mono Flow Issues

    He wasn't ready to troubleshoot, so he will be back Friday morning at 11pm.  He was just planning on lighting pilot and bleeding the radiators.

    Also I asked him about adding some radiators to the system and bumping up the BTUs to account for an additional 300sq ft.

    What are my options?  1700 sqft up to 2000sq ft.  I have two 1 1/4 loops around the house feeding 12 radiators.  Can the piping support 4 more radiators?  Can more BTUs or higher temp setting take care of the additional sq footage and radiators?  He will have an answer to that also.
  • RobGRobG Member Posts: 1,850

    If you had a contractor out to work on your system he should have been prepared to troubleshoot it. Since he was not, I would find another company! Unless I am giving an estimate on a new system I always have my service truck (and even then I am usually in it). Where are you located? Use the "Find a Contractor" section on the site to find someone in your area.

    You really should get that boiler replaced come Summer. Just don't have the guy who showed up without the equipment to do it.

  • Hank07974Hank07974 Member Posts: 7
    Mono Flow Issues

    He showed up in a car with his wife.  He was recommended by my real estate agent.

    Anyway, he went back with a coworker and they got everything working fine.  I was able to get into the house at a balmy 70 degrees.  I was not there when they fired it up, but it is working great.  No leads or anything.  Not sure if we just needed to do a couple more rounds of removing the air but they did it and it is working nice.  Almost 60 years old and the boiler works like a champ.

    We did have the relief valve on backwards, so I don't know if that was letting air in, but he said he had to flip that.

    He is writing up an estimate for the new system and I will probably get another opinion but I am looking to get a HE boiler with indirect hot water tank.  Let me know if that is the way to go or tankless hot water.  I have 2 full baths, washing machine, dish washer, standard setup.

    Thank you all for the advice I learned a lot.  Also just got my book in the mail, HOW COME?  I am sure it will answer some of the lingering questions I have.
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