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Converted 2 pipe steam to hot water

Hello all,

Ok so We took on that job that many have warned against, we took a 2 pipe steam system system and converted it to a 4 zone hot water system with 2 natural gas condensing boilers. Zones are 1- basement (new baseboard) 2-1st floor, 3-2nd floor and 4th-3rd floor (existing CI Radiadtors)

After going on "The Wall" and talking with other heating guys for the best practice on the how to run the piping for the cast iron radiator zones, we chose to run separate 1" supply and returns with 1"x3/4" mono flow tees connecting to all the individual risers that go to each radiator. We installed ball valves and a purge set up on every branch to every radiator as to be able to purge through the radiator supply and purge out the entire return pipe. It seems to work pretty well.



Long story short after a lot of work and repiping all the new zones its up and running.

We are having some issues getting all the radiators hot.



I've been consulted by a heating expert that there can only be 2 things causing this issue,

Air in the system or a flow issue.



It has been challenging getting all the air out and believe this could be the issue.

A couple of suggestions to get air out were to set the temp in the system lower and raise the pressure up which will help get the air out.

They also said that a few ounces of liquid soap put into the system can help remove air. That's a pretty unique idea.



I have not tried either yet but was wondering if anyone else has any other suggestions or ideas to get air out or have had a similar situation like this and have had any luck in correcting this problem.



Any suggestions would be appreciated!



Thank you,

Comments

  • Ironman
    Ironman Member Posts: 7,367
    Water temp

    Raising the water temp will cause it to release entrained air into the top of the rads. You want to purge with cold, but set the system hot.



    Don't expect an air separator in the basement to remove the air that's in the rads. You need to manually bleed it from the top of each rad. The columns in the rads operate on gravity and the velocity in them is too slow to carry air back down to the return.



    The soap (Dawn) is a good idea, but it only helps where there's forced flow - in the the piping - not the columns of the rads.



    Personally, in think the choice of a monoflo with c.i. rads was the worst one, but what's done is done.



    Did you follow the guidelines for monoflo piping? You can find them on site.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • icesailor
    icesailor Member Posts: 7,265
    Aie elimination:

    Raise the system pressure as high as practical and keep the system temperature hot. Both increase absorption of the air. Sometimes, there might be a place in the piping where air will be trapped and you can't really purge it out or vent it out. If you raise the pressure, you compress the air enough to make the "bubble" smaller and get water flow. Then, like FM, it starts to flow.

    I've seen it happen on a lot of air problems.

    If in fact, you did use Monoflows, double check again and make sure that each and every radiator had a supply and return with a mono-flow. You can get hot water out of a radiator when venting and purging, but it will get cold an hour later if there is no Monoflow.

    Its probably too late now, but the ideal way to do a conversion is to have a purge system on each radiator return before it goes back into the main.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    edited September 2014
    it may

    Not be an air problem but instead a pump/piping problem. The monoflow setup was a bad move and your 3/4 branches to rads oversized unless you have a rad capable of putting out over 15,000 btu...large monflow branches can create exasperating air problems.



    A manifold with 1/2" home runs to the rads would have been mint.



    what do you have for pumping? Assuming all monoflows are on return facing correctly and reg t's are on supply?
  • icesailor
    icesailor Member Posts: 7,265
    Hot/Cold Water Pressure:

    Ironman:

    In the recent past, I had an old 2 story antique house that had a old gravity system with one zone for the whole house. 4" mains, 1 1/2" feeds. Years before, the owner had all the second floor radiators disconnected. It was done in the cellar. Some radiators had been piped with circuits to both floors. One such circuit was under one side of the house and ran between floor joist with little to no pitch to the other side of the house. The second floor radiator probably would vent the circuit. The genius that disconnected it left a huge air trap in the 1" copper going from the Main to the Radiators. The old circuit was steel screw pipe. I was asked to remove some first floor radiators so they could remove old wallpaper behind the radiators. I drained the system, and removed the radiators. Later, when I came back to re-install the radiators, I couldn't get the one working radiator to flow. No matter what I did. The whole house worked except this one radiator in the dining room. I found the 1" copper line. I figured I would have to put some sort of vent into it. It was after 5:00 PM. I had to catch the plane home. Before I left, I raised the system pressure to 25#, just because I did. When I came back the next morning to fix the problem, it was working. The higher pressures squished the air enough to start flow. The air was all absorbed.



    Never underestimate the effect of higher system pressures on trapped air.

    A case of Spirovents, lined up in a row wouldn't get that air out of that pipe.

    I never met a Cast Iron Radiator that had air in it that wasn't suffering from a lack of proper pressure. I never saw a radiator with air in it that had proper pressure that kept the pressure and level well above the highest floor. If I got air and the air stopped without water coming, I raised the pressure accordingly, and never went back.  
  • j a_2
    j a_2 Member Posts: 1,801
    Rads

    What kind of c/i rads do you have tube or column ? And how did you retrofit them…Pics are great
  • Paul48
    Paul48 Member Posts: 4,469
    Flow

              Reading through old documents about monoflo systems was rather confusing, to say the least. For me, it was like trying to figure out a Stephen Hawking calculation. Beyond placement of the tees to create flow, there is orientation of the tees to assist with more or less flow to any given radiator. Each configuration changes required head for circulator selection.

              There have been many postings here, where people have removed series 100 circs from their monoflow systems, and replaced them with Taco 007 circs. They want to know why their system doesn't work right. It's because the 100 has a much greater flow, at similar head to the 007.

             If I were you, I'd get the air out, then gauge the circ inlet and outlet to determine the head, and use the curve to determine the flow.
  • Ironman
    Ironman Member Posts: 7,367
    Agreed

    Raise the pressure.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • icesailor
    icesailor Member Posts: 7,265
    Flows:

    It gets back to my favorite leisure pastime. Sailing.

    Sailing and sails work like airplane wings. If the flow is too low, it stalls. If the flow is too high, it stalls. If the flow for the conditions (shape) is just right, it sails or flies.

    That said, I haven't quite had it explained to me how a 20,000 BTY radiator, that needed to be piped with 3/4" copper tube on a Monoflow  or reverse return. And run it 1/2" PEX to and from the radiator with manifolds.  If one radiator is 10' away and the other is 20' away, one has twice the restriction.

    Why should I worry. Why do I think about it.
    Charlie from wmass
  • JEFF5255
    JEFF5255 Member Posts: 9
    Thank you all for your comments and ideas.....
    We did install ball valves and purge station on every branch line to the radiators. I raised the pressure like you all said and purged the heck out of each one and bingo! We finally have every radiator hot. Some were actually much hotter than others so we used the ball valves to balance the system and that worked too. the ones that weren't so hot started cooking nicely.

    But.......we are not out of the woods yet!!!
    We have a new problem.....will it ever end....lol
    I can't make this stuff up!
    The customer was outside gardening and smelled gas.
    He stated it was coming from the exhaust pipe.
    So I grabbed my combustible gas tester and he was right.
    We now have raw natural gas coming out of the exhaust piping.
    We installed 2 Navien NCB-240 natural has condensing Combi boilers.
    I've had the local Navien rep out who is telling me this is a normal occurrence during pre and post purging and there also is some un-burned gas during combustion that will be present.

    We'll the gas company has been out twice now and red tagged the units stating there is too much gas in the exhaust. I was present during the last visit and witnessed his gas test meter and it showed 20% reading. He explained that it means out of 100% of the exhaust being pulled into his tester 20 % is natural gas.

    The Navien support staff said they thought we had too high of an incoming gas pressure which would possibly cause this to happen. Unfortunately the gas pressure tested out at 8" WC.

    Now I'm stuck.

    Anyone heard of this situation? Any ideas?
    I would appreciate any help you can offer.

    Thanks,
    Jeff
  • Paul48
    Paul48 Member Posts: 4,469
    You might want to move this to the Gas Heating section. Tim would have an answer. I can't see how that is even possible. If it's not excess gas, it has to be lack of air.
    Ironman
  • Ironman
    Ironman Member Posts: 7,367
    If the gas man's readings are correct - and that's a big IF - then the gas valves in the Naviens are the culprits and the burden is upon their back to correct it. This assumes there's adequate post purge, proper ignition and your co2 is correct.

    Did you properly set them to factory specs with a digital combustion analyzer?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • icesailor
    icesailor Member Posts: 7,265
    Two things:

    #1: You're sure that the Navien is set up for Nat. Gas and not LP, and are you sure that it has the correct orifice for Nat Gas and not LP. You need to ask Tim. He's the man.

    #2: If some of your radiators are hotter than others, it may be a flow issue. I don't know who many radiators you have on the 1" circuit, but most all Monoflow systems I've seen used a 1 1/4" "One Pipe" Main to keep the flow restriction down. An often overlooked facet of One Pipe Piping.

    IMO, the current piping trend of using hydraulic mining pumps in heating systems to overcome resistance in undersized heating systems raise hell with old systems.

    So, here's a test that might show it. Someone posted something I said that I forgot about. With the boiler maintaining temperature with the circulator disconnected, open the flow valve and let it flow on gravity. Every radiator in the circuit should get equally hot after a while. If the radiators at the end don't get hot, the restriction of too small mains is keeping the flow high enough. If the mains are all 1 1/4" or 1 1/2" and split back to 1 1/4" and work, the gravity flow is high enough. That's why the 007's worked where the Series 100 worked. The Series 100 was way oversized for most applications. With the current rage of undersized piping, you need those big hydraulic pumps to force the water through the system.