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Installing bleeders on old HW convectors

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D107
D107 Member Posts: 1,849
in THE MAIN WALL
1950s Monoflow, constant circ system; when we had system drained to install a new panel rad this summer, upon refill we found a few areas where air was trapped. Contractor was able to thoroughly bleed the system both at the boiler and at the old convectors, but it took quite a long time and from time to time one or two of the rads still don't get as warm as they should. A few rads inexplicably have the bleed valve UNDER the element which of course can't work. So for these emitters and those that may have no bleed valve is it feasible/cost effective to install one or correct the orientation of others?



All this assumes system is not underpumped. 1 inch monoflow system, 150ft run (8ft head?) with Taco 007. prior circ before new boiler install was 008. Heat Loss for Zone is about 40K btu, minus 15K for basement zone with rads always turned off. Runs with Logamatic 2107/G115-21, ST-150. room sensor.

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  • jumper
    jumper Member Posts: 2,248
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    nobody listens to me

    It takes a little bit of planning ahead. Unless it's an overhead distribution, and even then, it is faster to evacuate and fill with degassed water. Raising pressure and trying to "blow through" the air does not guarantee adequate circulation.
  • D107
    D107 Member Posts: 1,849
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    bleeding convectors

    Thanks. What is your method of de-gassifying the water? if you have any literature on this perhaps you could point me to it. I know monoflo systems are more prone to this problem. I also don't know if you mean to say that even if there are problems with piping pitch in the system your method will prevent recurrence of the problem. any more details would be appreciated; don't think I've seen this on the Wall before.
  • icesailor
    icesailor Member Posts: 7,265
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    ???:

    Do you know what you have?

    The convector cabinet that that you show, when connected to forced hot water with mono-flows, it uses the two bottom connections to the elements, 3/4". The vent goes on the top, If the single vent pipe is on the bottom, it could have never worked. Are you sure it worked before the renovation. Even is it was connected as single pipe steam, I don't think it would work that way. It could have worked as a downfeed with both connections in the top with the bottom connection as a drain. NOT as an air vent.

    Post some pictures of what you have.

    I've never heard nor have I ever used "degassed" water in my life. Any system I filled has been with plain old potable tap water. Run up the pressure to 16# to 20# on the initial fill, and when everything is going.eave it alone. If any don't work, I figure out if they ever worked, and act accordingly. If there is no reason for it not to work, I find out why. If it is piped within specifications, it will work.

    It might work for you. I've never needed it to work for me.
  • jumper
    jumper Member Posts: 2,248
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    degas water

    Hot water in a vacuum chamber has no gas. To get the water from the chamber into your system can be a problem. Like I said the system has to be evacuated. The filling station has to be higher than the hydronic system or you need a special low head pump. I offered this procedure forty years ago and clients who paid the bucks ended up with a better hydronic system. One client logged daily fuel consumption relative to degree days and then thought about investing in this business.



    The pressure should be the lowest possible for the height of the system.
  • D107
    D107 Member Posts: 1,849
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    bleed convectors

    Thanks for the replies. Ice Sailor, this is a split level house; for the first part of this run the single pipe 1.25" copper main is below the rads; then the next two rads are--as you sort of guessed--downfed from the same main. So now I realize that being downfed, a vent couldn't work there, and any upside down vent would work as you say as a drain--not sure when you would need it for draining, maybe for bleeding(?). on one of the downfed rads without a vent there is a 3/4" drainpipe with a shutoff valve below the element, which we used to bleed that rad. This was clearly an add-on drain, and does indicate that years ago there were some trouble spots in the system. The system was bled when the new boiler was installed six years ago and seems to have worked well and seems to work well now, though that rad with the drain/valve i may have to re-bleed once in awhile. Back in the 70s four fan-assisted units replaced their respective convectors--not sure why--and two of those units were given direct returns. So it's possible the system was compromised. Now that you've reminded me that you can't have vents on a downfed rad, I'll have to check the rads when I'm out there.



    (As I mentioned the prior circ was the taco 008, which, looking at the pump curves, at 8 ft of head moves about 10gpm vs the 007 which would move around 7gpm. That would seem a high flow to me, but if the head was really 10ft, the Taco would only pump around 2gpm. so perhaps circ choice is an issue.)



    I'm not at the house now so I can't send pictures, but overall the tees in the basement appear to be venturi. Tech did raise pressure to bleed; had to do it at the boiler twice, and we had to bleed some rads two or three times after they initially bled all the air out.
  • icesailor
    icesailor Member Posts: 7,265
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    Drains:

    The boiler drains on the bottom are so you can drain something below the mains. You have to have a low point to get the water out of the piping.

    You said that there were fan coils connected there before. Fan coils can have problems connect as Mono-flows, especially when down fed.

    Something you said makes me think that once, they were connected ad a reverse return or direct return.  You do not EVER need to vent convectors like that that are fed from above. Air rises.

    The only time I have ever seen underfed mono-flow radiators not work is when they were sharing a main with above the main radiation. As I remember from way back when, two mono-flows on the loop solved the problem. If one or both drop isn't starting to get warm, it's not flowing.

    Maybe bigger circulators would do something but I've never seen the need to do it.

    Like so many things I read about, I again ask, did it ever work? Did it work before you got there, and if not, why.

    Customers are not always forthcoming about facts that something hasn't worked for years. You are just the next lucky person to have a crack at it.
  • Paul48
    Paul48 Member Posts: 4,469
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    Monoflow

    "minus 15K for basement zone with rads always turned off"

    ice......Isn't that a problem with monoflow? Like removing radiator and just capping.
  • icesailor
    icesailor Member Posts: 7,265
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    Missing Mono-Flows:

    I've read that here.

    I've never personally seen it but that doesn't mean it doesn't happen. It also makes sense. I'd hate to try to figure out how many accounts I have with Mono-Flow systems with missing radiators and they never have problems. I usually find the missing tees when I'm crawling around in the dirt under a house.

    Whenever I have found a circulation problem with Mono-flows, it was because the circuit piping was too small (1/2") and/or the length for the size was too long, back and forth. I've seen Mono-Flow radiators that were piped both on the same end and the ends never got hot. Radiators that were connected diagonally and heated in a diagonal. But the #1 reason I have seen them not work was ones that were below the mains and down fed. They HAD to be piped with 3/4" and use two Mono-flows.

    As far as circulator types, where I work is rather provincial, isolated. The only circulators I ever saw were Series 100's and Taco 110's. When 007's came along, they were a direct replacement for anything we saw. It was what was mostly available. I've seen whole large two story houses on one zone of Mono-flows with a Series 100, replaced with a 007 and never a complaint. I've split up the same houses with one 007. As far as I knew, they worked and are still working.

    I have an account that was built in the 1990's. There are all 007's except one where the installer installed 15 small Runtal radiators that were 1/2". They were connected with 1'2" series looped through the heaters with the supply and return being 3/4" and pumped with a Taco 010. The loop started in the kitchen and ended up in the living room where the thermostat was. The kitchen was always too hot. That was a piping problem, not a circulator problem.

    Ya' just have to get in there, look at it and figure it out. That's my take and experience.
  • D107
    D107 Member Posts: 1,849
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    photos

    I dug out some photos from earlier this year. Photo 1 shows the supply to the basement rad from the main; not sure if that is a venturi T or not. Photo 1 also on the right shows the supply going up to the first main floor rad. Photo 2 shows the return from the basement rad to the main line.  That appears to be a venturi. Basement rad was likely added to system in the 1960s.



    Thanks for your input; I'll have to keep monitoring this; if it's just a matter of one rad needing to bled once in awhile, no big deal. 2000 sq. ft house LI, using 700 gal oil a year for heat and hot water. Not too bad.



    Zone 2 which is baseboard does heat up slower--cold floor porch, less insulated. I was confused when the tech said you don't bleed baseboard circuits---that zone is above the boiler. I'll check next time if there's a vent at the end of the run.
  • Paul48
    Paul48 Member Posts: 4,469
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    Knowledge,or lack there of

    The way I understand monoflow tees, is they create a restriction and cause the water to flow in a different direction. If you close a radiator, all your left with is the restriction and no alternate means of flow. It creates very high restriction.Even if a radiator is removed from a monoflow system, you either remove the tees, or pipe a bypass. I'd open the radiators to the basement, and see how everything else functions. Usually it takes 2 monoflow tees for down flow.
  • D107
    D107 Member Posts: 1,849
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    thanks

    My only concern with turning on the basement rads --aside from heating a room that's not really cold--is that when the tech bled the system those basement rads were closed--mistake I know--so if there's air in there I'd be adding that to the system which could magnify the problem.
  • Paul48
    Paul48 Member Posts: 4,469
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    Ahhh Memories

    Remember driving your folks crazy blowing bubbles with a straw in a glass of soda? I'd say, it's not likely there's air down there. This would just be a test. If the system works better, you might have to look at piping a bypass for the basement.
  • icesailor
    icesailor Member Posts: 7,265
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    Venturi/Monoflow tees:

    Like I said before, down fed Mono-Flows should have two and should be piped in 3/4" to cut down on friction loss.

    I'm not the resident engineer. If it wasn't for the calculator in my cellphone, I would be up the creek.

    The reason I was so surprised at the issue of disconnected Mono-Flows is because I have seen so many of them that didn't seem to create any problems, it wasn't an issue. But in thinking about it more, there is more to the discussion. The fitting uses a form of The Bernoulli's Effect which among a few things, says that if a fluid is flowing at a certain volume and speed in a confined space, and the fluid is pushed through a restriction, the speed of the fluid increases but the volume through the restriction remains the same. When it leaves the restriction, it returns to the original speed and volume. But at the place where the flow rate changes, there is a drop in pressure. Air flowing into the air horn of a carburetor does this and the drop in atmospheric pressure forces fuel through the jet and into the air flow.

    In the case of the Mono-Flow, when the pump pushes the fluid through the main, and through the orifice, the lateral connects at the place where the speed of the fluid reverts to normal or where it speeds up. Or both in the case of down feds or very long laterals that need a higher flow. Depending on whether the tee is on the supply or return, the pressure is equalized through the lateral. The pump provides the initiative to do so. There isn't all that much vacuum pressure developed. I once tried to suck the water out of a water filter using the branch of a Mono-Flow. It didn't work.

    Mono-Flows are more of an improvement over gravity flow than anything else. They work well when the heated/lighter water wants to go up. It does NOT like to go down.



    That's why all the normal rules for Mono-Flow installations go out the window when you pipe and connect down. Most of the old systems I ever saw with radiators or convectors below the main were on a separate zone. The problems were usually when someone tried to pipe a radiator that had radiators above the main and the new ones were below the main.

    If I ever wanted an example of a Mono-Flow that didn't work, I'd use yours.
  • Paul48
    Paul48 Member Posts: 4,469
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    "00"

    The 008 is a much higher head circulator than the 007. Did the 007 come with the new boiler?
  • D107
    D107 Member Posts: 1,849
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    008

    Yes, old, way oversized boiler had a 008. new 007s were installed for both zones and DHW. I'm wondering what year the 008 first came out. The prior boiler was a replacement boiler probably installed in the early 1970s in this 1956 house. But I doubt the 008 was around then. So I'm thinking that the 008 was installed later on --quite a while after those four fan-assisted heat/ac combo units-- to try to solve the air problem. While I never heard of a heating complaint growing up, it seems possible that many homes could have air issues and never know it if they're not severe; but certainly oil bills would be higher than they should be. before we had the Buderus installed 6 years ago, oil usage was 1200 gal/yr. though some of that might have been due to an unmaintained burner etc.  Usage now 700 which still seems high considering large rear porch Zone 2 is always kept at 60, and basement rads are off. 700 gal/yr to heat about 24K heat loss for the main house, (out of 47K for the entire house inc. basement & porch) hot water, (one resident), fairly new windows, standard old fiberglass insulation plus quarter-inch styrofoam boards.
  • icesailor
    icesailor Member Posts: 7,265
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    007's

    What circulator came with a package boiler isn't part of the equation.

    Back in an earlier era, you had a salesperson come and measure the building. They shipped the materials to you and you installed what they gave you. In 1965, before 007's were available you got a B&G Series 100 or sometimes, a Taco 110. When 007's were introduced, we were told that it was a cheaper direct replacement for a Series 100 or a 110. The price of the three piece circulators became so high that 007's were the only ones used.

    Swapping a Series 100 on a working mono flow system with a 007 never created a problem. Every package boiler that I ever installed came with a 007, in a color that matched the boiler's color scheme.

    The only high head circulator I remember was a B&G P-3 high head high flow circulator.

    It wasn't until "they" started coming out with all these Gucci circulators with multiple ratings to cover all the bad/cheap undersized piping and the need to overcome resistance from bad piping installs.
  • Paul48
    Paul48 Member Posts: 4,469
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    four fan-assisted heat/ac combo units?

    And monoflow to boot. The 008 may have been the only thing they got right with the old system.It was probably installed later, but not to combat air....to combat high head.
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