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Weak baseboard radiator

Mr_TAMr_TA Member Posts: 40
Hi all,
I have a weak baseboard radiator that was untouched for years. It's the last one (I think) in the loop, and also the biggest one. I troubleshot the following:

1. Loose carpeting (hardwoods)
2. Closed air/vent cover (these radiators don't have closing vents)
3. Dirt between metal fins (clean)
4. Closed shut off valve (doesn't seem to have them, just air vents with a flat-head screw)
5. Air trapped in the system (this is probably the culprit - read below)

So i was trying to bleed the radiator in question. Turned thermostat on, verified that the system works, all other radiators are hot, the pump works, all good. Unscrewed the manual vent. Some water poured out, first with a pressure, shot up 6-7" (the hole is upward pointing), also made farting sounds - which I think is the air coming out. Then it slowed down to eventually no water coming out at all! As if the system is completely empty. I thought, ok, maybe give it some time to push the air along, so I closed the screw, came back in 15 minutes, repeated - same thing happened.

Am I doing it right? How can it run out of water when the system is on?


  • unclejohnunclejohn Member Posts: 1,525
    Where is this baseboard locate? Top floor or basement.
  • icesailoricesailor Member Posts: 7,265
    edited December 2014
    A common occurrence with a system that has a tired Pressure Reducing Valve/feed valve on the boiler. And not enough system pressure. Is this heater on the second floor?

    You mentioned Carpet. When the baseboard was first installed, was it set on a hardwood floor? And later, someone added wall to wall carpet? Carpet Butchers slide the carpet under the bottom baseboard openings which restrict the airflow through the baseboard and element. Properly, the baseboard heaters should all be raised up 3/4" and a 2 1/4" wide wood strip installed so the carpet butchers can put tack strips in front of the baseboard and finish the carpet in front of the baseboard,

    With cast iron baseboard, you always put down the wood strip if the baseboard was going on carpet. So the legs didn't sink into the carpet.

    Its like kitchen floor installers never telling you that you really need to raise your cabinets or countertops because once they have the new floor down, you might have to cut the legs off the old dishwasher to get it out, and a new one might not go back in.

    And it might kill the sale.
  • Mr_TAMr_TA Member Posts: 40
    edited December 2014
    It's the top floor. Unfortunately there's no pressure gauge in the loop so i don't even know what the pressure is (I read people talking about 25-30 psi being optimal). The system is very old, I know that because the boiler is a pilot light driven one (SlantFin brand) with minimal insulation and virtually no electric circuitry, literally just the thermocouple, pump relay, the gas valve, done. I'm guessing 70s-80s.

    I'm assuming the solution to the weak feeder valve problem would be to 1) turn heat off, 2) drain the system, 3) cut the copper pipes, 4) solder in a new valve, 5) fill the system with water, and turn it back on?

    Sorry i meant carpeting was one of the things that people suggest to check - I wrote hardwoods in brackets meaning it's hardwood floors, so carpet is not an issue here. Basically airflow through the radiator is fine - it's definitely lack of water pressure.
  • Mr_TAMr_TA Member Posts: 40
    Just read that backflow preventer valves can be fixed, is that true? Do I need a repair kit or an adjustment can be made? For an older valve, are kits available or it's only for newer ones? Thanks.
  • icesailoricesailor Member Posts: 7,265
    The "backflow" part is separate from the Fill Valve part. There are no repair kits for fill valves. Other than new valves.

    I don't remember ever seeing a 1970''s to 1980's boiler without a pressure/temperature Tridicator gauge. Perhaps it leaked and some one removed it rather than buy a new one.

    Post some photo's of the boiler. Especially the front. And a photo of the fill valve.
  • Mr_TAMr_TA Member Posts: 40
    See attached pictures. I did find the gauge, it was hidden behind the pipes. Is 20psi enough? The apartment is on the 3rd floor, the boiler is on the 1st (so about ~18 feet below the radiators).




  • icesailoricesailor Member Posts: 7,265
    That Watts S1156F is a definite candidate for replacement. It has been leaking through the adjustment nut.

    If you're lucky enough to move the bypass lever, it might not ever stop filling. Don't futz with it at 5:00 PM. You might be there until midnight. Have a new one with you. A brass one.

    That blue tag with the stamping on the tag has a easily readable date code. Make sure that you get a brass one. NOT a cast iron one.

    As far as the pressure on the gauge. it says 20#, and the check is in the mail.
  • Mr_TAMr_TA Member Posts: 40
    Looks like it's a threaded coupling? Should be replaceable without cutting/soldering?
  • RobGRobG Member Posts: 1,850
    You can replace it without sweating any joints if you have room to unscrew the valve from the male adaptor. I would buy another tridicator at the same time to ensure the pressure is accurate.
  • Mr_TAMr_TA Member Posts: 40
    Thanks guys. I'll try it on the weekend.
  • icesailoricesailor Member Posts: 7,265

    That isn't a coupling, it is a union nut. If you're extremely lucky, and do well with scratch off tickets, it might be a direct swap.

    If you count on it being a direct swap, it won't. If you plan that it isn't, it will be.

    If you're experienced and a risk taker, you can loosen the union nut, and with two wrenches, undo the valve from the nipple. If the threads on the end of the nipple aren't South of the Equator.
  • Mr_TAMr_TA Member Posts: 40
    Found the same valve, swapped the contents but now seems like air trapped because I had to drain. Am I correct in thinking that leaving it on without bleeding is a bad idea, even for one night?
  • Mr_TAMr_TA Member Posts: 40
    Going to bleed this morning. 22 psi pressure. Should I flip the lever up for bleeding?
  • Mr_TAMr_TA Member Posts: 40
    Ok small problem just became huge. All radiators are stone cold. Supply at the boiler is hot. Pump works. Return is just warm. I bled a couple of gallons out at 3 radiators and all I get is water, not a single bubble. The gauge reads normal temperature and 20 psi pressure. To bleed I briefly lifted the fast fill lever to bring pressure up to 30-35 psi and then returned the lever back down.

    Any suggestions would be much appreciated :)
  • kcoppkcopp Member Posts: 3,463
    Are you sure the circ pump works? How about the expansion tank? Water logged?
  • Mr_TAMr_TA Member Posts: 40
    Hi kcopp,
    It makes the sound that it always made, not sure if functions properly. For what it's worth, the return line at the boiler is warm but not hot. That may be the heat traveling the other way given that water doesn't move.
    The expansion tank is horizontal. Does that mean it's the old style, without a diaphragm? If so, it could theoretically be filled with water. Does that mean I need to drain the whole system and refill? How do I ensure there's no water left in the tank before filling it?
    Not sure what your question about water being "logged" means.
  • RobGRobG Member Posts: 1,850
    It sure sounds like the circulator is not working. If you have pressure at the top floor and no air in the system you need to check the pump.
  • Mr_TAMr_TA Member Posts: 40

    What would cause it to break? It worked before. Or it's just hell of a bad luck?
    How can I be sure there's no air in the system?
  • RobGRobG Member Posts: 1,850
    Can you post a photo of the pump and piping?
  • icesailoricesailor Member Posts: 7,265
    I might suggest that if the OP changed the fitting by "Catching it on the fly" and didn't completely drain the system, that vacuum held the water above the main piping, which might have filled with air, while the upper radiation stayed full. And when the OP filled the system, he compressed the air between like an air sandwich, and the upper floor vents are opened, the air sandwich is pushing water out. Is the boiler supply into the system hot? The return is only warm near the boiler. Were the air vents opened at and above the boiler? I've seen where the entire boiler was full of air and the circulator is running.

    They don't teach you these tricks on the YouseTubes.

    Stick the back of a finger onto any spot of iron on the boiler near the bottom. Is it hot? Put it near the top, Is it cooler? If it is, the boiler is full of air and the control is shutting it off. If it is an oil boiler and has an internal tankless coil, turn on the hot water, then off the power to the boiler. If the water comes out hot, run it until it is cold to cool down the boiler, Then, vent the air out.
  • Mr_TAMr_TA Member Posts: 40
    Pics of the piping attached. It is a gas heating boiler only (no tankless hot water).

    Today, I drained the system entirely, by opening the lowermost drain valve (hardly visible on the 1st pic, under the pump and the pipe), and opening the vents in the apartment. Then, I closed the return valve (yellow valve in the middle), opened the top drain valve (red valve, above the yellow), and filled the system (by opening the green feeder valve, on the right), making sure that water runs through the entire circuit before coming back to the boiler. A whole bunch of air did come out of the red valve, then when pure water started coming without any "bubbles" (by that point, I drained 6-7 buckets), I closed the red drain valve, opened the yellow return valve, and turned it on.
    The only improvement has been that the return line is now hot, not just warm. So it seems the water does circulate, and the pump works. All of the radiators, including their supply and return pipes, are still dead cold. The flame shuts off correctly when the temperature reaches the threshold, and pump continues working, as expected.
    A plumber stopped by who was there to help another tenant with their problem. When I asked him about it, he suggested I drain a lot more water, he said it should literally be a bath tubful, and suggested I just run a garden hose outside and leave it with the pressure regulator's lever in top position for a while to ensure there's no air the system. He said if that didn't help, then it's probably a faulty pump.
    My theory is that there is a "parallel" pipe for each radiator that runs under the floor, and it carries the hot water, and all of the radiators are solidly air-bound. I'll go back there and bleed the radiators some more tonight, see if that makes a difference.



  • icesailoricesailor Member Posts: 7,265
    edited December 2014
    The yellow handled valve above the circulator must be closed. Put a hose on the red boiler drain above the yellow gate valve. Open the boiler drain with the hose. As soon as the water starts to flow out of the hose, open the fast fill feature in the 1156F fast fill pressure reducing valve, The water in the boiler should be hot, and the burner should be on.

    Get that "plumber" that gave you that advice and put the hose in the back of his truck and see if you can fill it up with nasty boiler water. Put your hand around the return pipe above the red handle boiler drain where the hose is connected. You might get water at first, Then, air, water and air, then water. The water coming back might get very cold. It might not. But it will start to get noticeably warmer. Maybe more air, The sound of the water will become VERY quiet, then the pipe/hose will start to get really hot. Shut off the fast fill on the 1156F and shut off the hose. With your hand still on the return pipe, open the yellow valve handle. You should feel the water temperature inside the pipe changing while you hold it. So hot that you can't hold on to it.

    If it doesn't get hot after that, either the circulator isn't working now (unlikely if it was working before) or the valve stem on the yellow valve is rotted off and the valve is stuck closed.

    In the unlikely case that there is a parallel flow set up like with Mono-flows, the main would still get hot and some portion of some radiator would get hot.

    The boiler is perfectly set up for proper purging of air. If it is a series looped baseboard system, there is no need to ever go upstairs to vent the baseboards.

    I see it is a gas boiler.

    """ Any possibility that this boiler had a tankless coil and the control that goes with it, and someone raised up the Low Limit "LO" to the same as the "HI" or above? That will make the circulator not run. """

    That circulator is older than dirt. I've seen some so old that they were turning into stone that still ran.
  • MikeL_2MikeL_2 Member Posts: 247
    Mr ta,
    The connection for the feed valve is in the least desirable location, and, the expansion tank should NEVER be installed horizontally. Air will get into the tank and corrode the exposed steel.
    Are you sure that the gate valve is open ; they can break in the closed position. I would run some water through the drain cock with the gate valve open, it is possible to have a slug of air in that section of pipe between the closed gate valve and the drain cock.........
  • icesailoricesailor Member Posts: 7,265

    There are differing opinions on that location for the fill valve. Some of us prefer that the cold water entering the system go first through the boiler, where it gets heated as it goes into the system to be purged. If you feed into the supply, and only cold fresh water is fed into the system, it is very easy for the boiler to not fill with water and the water is only going into the piping. Cold water into a hot boiler is a very bad thing.

    Some of us old dogs were taught to feed the boiler first. Then, the system.

    Its my understanding that codes etc. say that if a heating system/piping is below a boiler, all the boiler piping must first rise above the boiler so that in case of a break in piping below the boiler, the boiler will stay full of water, and the feed water valve will continue to add water to the boiler (if the feed water valve is left open).

    It will definitely get the adrenaline flowing when you have a hot boiler with little or no water in it and the system is full of cold water that has been purged, and you lower the pressure by trying to purge some system that isn't set up for proper purging, and the boiler starts dancing on the floor from the boiling water inside. What do you do in the instant? Time to hit the service switch on the boiler? Where's the remote electrical disconnect? If I go to the coffee shop, how many cups of coffee and donuts will it take to cool down enough so it won't it won't blow up when I get back and figure out what's wrong? ( They had a Flow Check, and an air scrubber device, fed the fill into the bottom of the air scrubber with the Extrol hanging off the bottom, and the flow check being closed wouldn't fill the system until the circuits were filled. And the ball valve on the return below the purge drain ensures that the boiler won't fill first.

    The instructions are always right. Mostly.
  • Mr_TAMr_TA Member Posts: 40
    Good news! The radiators are slightly warm now after me purging through the hose for about 10 minutes. The return line is boiling hot and the flame turns on repetitively.
    I'll go back and repeat soon for a longer period of time and will report if it's better.
    Thank you.
  • Mr_TAMr_TA Member Posts: 40
    I'm not sure what your question about the boiler having had a tank less coil, means. As in, it was a hot water tank less unit, and then that feature was removed? I don't think so, there are no signs of tampering of that extent. I would expect there to be holes, etc. Also, 2 other boilers just like this one are right next to mine and they don't have hot water, either.
    Having said that, it does have a lo-hi knob, but that wasn't touched forever. I'm pretty sure the pump works or at least tries to because it makes an electric motor sound.
    I'm purging the system according to your instructions but neither the return (drained by hose) nor the supply are getting warm. I'm thinking it's not powerful enough to heat this much cold water so quickly.

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  • Mr_TAMr_TA Member Posts: 40
    PS. Is it worth it to install auto vents on the radiators?
  • RobGRobG Member Posts: 1,850
    Just because the pump motor is spinning does not mean the impellor is not shot. With the age of the pump as is, I would just replace it. If you have the knowledge and tools you could confirm it but it's not worth the effort compared to the price of a pump. If the system is purged of air and the rads are not hot, the pump is not moving the water. Is there a valve closed somewhere? If not, it's the pump.
  • icesailoricesailor Member Posts: 7,265
    edited December 2014
    When I posted my post, I noticed it was a gas boiler. In Quotation Marks ("" ""), I noted that. You have the correct control for that boiler. Whenever there is a call for heat, the circulator runs.

    You said that the system was working fine until you got into it. My question in that case is always "What Changed"?

    I'm not a "trial & Error Mechanic". I like to be sure of what's wrong before I start changing things. Maybe the circulator IS bad. Maybe it isn't.

    Did you carefully follow my instructions on how to properly purge the system? Did you completely close the yellow handled gate valve, connect a hose to the red handled boiler drain, and let it drain. No matter what, the water in the supply side of the main will get hot, and the water at the hose will get hot. It HAS to get hot. Once the purge hose gets hot, open the yellow valve. The pipe should be hot and it should heat. cool down, and heat up again. It bothers me that you say the return is getting hot but that some of the emitters are warm. It wasn't working like that before you started.

    Do you have an old dark green Thrush Flow Check with the lever on the side that can be put in a closed position and the system can't be pumped through the boiler supply side?

    There's a reason that the return is getting hot. And it isn't supposed to. The only way that can he happening is if the supply side is closed.
  • MikeL_2MikeL_2 Member Posts: 247
    I respect you and your experiences, however, the PONPC is not an opinion, it is a scientific fact. People a lot smarter than I have proven the benefits of pumping away, and boiler manufacturers recognize the benefits as well - they include diagrams of this preferred near boiler piping strategy with their Installation instructions.
    You and I are a lot alike, I am the owner / operator of a small business; I started in this trade in 1968. I guess I am an " old dog " in some ways, however, I choose to adopt new tricks.
  • icesailoricesailor Member Posts: 7,265
    Where did the PONC come from in this problem?

    As I understood this problem, the boiler worked before the Op did something to it, afterwards, he can't get it to work.

    Some might tell the OP that he needs a new heating system. Package boilers come with a new circulator. If the circulator is bad, you can fix the bad circulator with a new boiler.

    If the fill valve is filling the boiler. You have the return valved off and a hose on the purge drain, draining. The boiler water is hot with the burner running. The return at the boiler is hot, but there is no hot water coming back to the return. Wherever the PONC is, has nothing to do with this problem.

    Most of the people that I had to compete against thought that a PNOC had something o do with a Ping Pong game.

    I'm not denigrating any PONC's. I read about it long ago on old Taco and other heating books. It isn't a new concept. But Prior to 1994, when Weil McLain came out with their WGO series of oil package boilers, all circulators I ever saw were mounted on the returns. So although the concept wasn't new, the location was moved.

    Its a good thing they don't pipe them like they used to.
  • Mr_TAMr_TA Member Posts: 40
    Fair point. It turned out to be air - 30 minutes of purging water solved the problem. I didn't realize initially how much air can get clogged in a hydronic system.

    Your diagnosis was correct - I didn't drain the system fully when replacing (repairing) the pressure regulator, and introduced a whole bunch of air into the system.
    "Did you carefully follow my instructions on how to properly purge the system? Did you completely close the yellow handled gate valve, connect a hose to the red handled boiler drain, and let it drain. No matter what, the water in the supply side of the main will get hot, and the water at the hose will get hot. It HAS to get hot."
    Did, and no, it didn't get hot. The pump functioning or not didn't matter, because I was forcing the water through the circuit under street pressure since the lever was up. The supply never got hot, let alone the return. I think it's because of this boiler being old and not powerful/efficient enough - but that's just my half-educated guess.
    "It bothers me that you say the return is getting hot but that some of the emitters are warm. It wasn't working like that before you started. "
    When I had opened the yellow valve and had closed the red one, it did that yesterday (after doing what you suggested for >30 minutes today, everything appears to work now, hooray). That's why I kept thinking that the only explanation would be a parallel flow. If the radiator's main line is clogged, then water wouldn't circulate at all. However, the return at the boiler was getting warm, so at least some amount of water was making it around. So if radiators were cold, meaning they were air-bound, then water could only go through the parallels - or it's magic.
    "There's a reason that the return is getting hot. And it isn't supposed to. The only way that can he happening is if the supply side is closed. "
    Not sure what you mean by "supply side is closed".

    One day, either the floors will be replaced or the building will be demolished. At that point, if we are still around, I'll make it a point to make it to the building and check if it has a parallel flow and post the answer here.
  • icesailoricesailor Member Posts: 7,265
    It doesn't have any parallel flow.

    Regardless of how much or how long you had the by-pass lever up, it won't pass more water through the valve than is running out of the purge hose. The PRV is connected BELOW the yellow handled ball valve. Any water going through the system to be purged, must first go through the boiler. If the water in the boiler is hot when you start, the returning water to the purge hose has to get warm and hot.

    If you didn't get warm or hot water through the purge hose, you purged it anyway if it is now working. If it is now working, the circulator is fine. The reason the return started getting hot is because of expanding air pressure in the system. That boiler/system is perfectly piped for easy purging and draining.

  • Mr_TAMr_TA Member Posts: 40
    In any case, it works now - THANK YOU!!
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