Baseboard not working after bleeding it, but others do.

[Theodore]

Hi,
I have hydronic heat system at home. One zone. Boiler in basement with loop around the basement ceiling perimeter, with a set of venturis and Tees going to each baseboard upstairs and even to the 2nd floor. One baseboard unit on 2nd floor doesn't heat up. When i bleed the one bleed valve on it, water immediately comes out. So, no apparent air lock in the pipes. I'm at a loss as to what else it could be. The system has performed perfectly for years.

I suppose it's possible that some corrosion or chunk of crap may have broken off and clogged the incoming/outgoing pipe to this one unit?? Worst case scenario would be to wait for warmer temps and then de-solder both ends of the baseboard and use a wet/dry vac to make sure both pipes run free and clear. But I'm no expert at this sort of thing and would appreciate advice from more experienced folks, especially if it keeps me from doing that worst case scenario I just mentioned!
Thanks
Theodore.

 

[Dana]

It's unlikely to be a blockage.

But if the system has been running 50+ years there can be enough erosion on the mono-flow tee to the point where it no longer induces enough pressure to get adequate flow through the branch.

^^^think of what this looks like^^^ when the conical constrictor on the monoflow tee (on the right) eventually erodes to a more wide-open condition. There eventually isn't enough back pressure to force much flow into the radiation, especially for longer loop runs from the basement to the second floor, which requires a bit more back pressure than short loops to first floor radiators.

How big are the tees and many loop plumbing?

How big is the branch plumbing?

Since the failed side loop is a second floor room there may be some place to cut in a small circulation pump into the supply or return path back to the main loop in the basement to force that flow, operating the pump via a thermostat in that room. That is sometimes easier/less risky than trying to hack in a brand new monoflow tee, with more risk of breaking pipes & fittings that could bring the entire heating system down.

 

[Sponsor]

 

[Theodore]

Thanks, Dana. Here's some responses to your questions:

>How big are the tees and many loop plumbing?
The main loop pipes and associated tees in the basement are 1-1/4" diameter brass. There are 13 radiators in the house (mixture of convectors and baseboards), so 13 venturis, and 13 tees.

>How big is the branch plumbing?
Each venturi and tee in basement reduce to 1/2" vertical branch services to each baseboard and convector.

>Since the failed side loop is a second floor room there may be some place to cut in a small circulation pump into the supply or return path back to the main loop in the basement to force that flow, operating the pump via a thermostat in that room.
Not sure that would be practical. Such a stand-alone pump would, ideally, need to be interlocked with the main thermostat so there's no pointless pumping of this one interior loop while the rest of the system is off. Not to mention would be a bit wonky to have a stand-alone circulator somehow exposed in my son's room. It's a recipe for disaster, if you know what I mean! I really do appreciate the suggestion, though.

 

[Dana]

If the loop plumbing and mono-flow tees are brass/bronze rather than the more often seen iron, it's likely that you would be able to replace the tee without destroying things. (Rusty-crusty threaded iron fittings have much greater tendency to bind-up with corrosion after 50 years making it impossible to take apart without breaking things.

You may have to cut the pipes and install couplings to put it all back together.

There may be room in the basement or the plumbing chase to the second floor to install a pump solution. Cutting into only the side loop plumbing. Installing it exposed in finished room isn't anything I would suggest. Without knowing how the plumbing is routed between floors makes it hard to come up with a guaranteed workable approach.

The interlock for a second pump doesn't have to be complicated. A zone relay for the micro-zone pump powered from the output of whatever conrtols are switching power is powering the main pump makes a pretty simple interlock. When the main pump is powered & running there is power to the second pump only if the micro-zone's thermostat is calling for heat. When the main pump isn't running there is no power to the second pump.

 

[WorthFlorida]

.... So, no apparent air lock in the pipes. I'm at a loss as to what else it could be. The system has performed perfectly for years.....Theodore.

Let the water flow for about a minute or two to be sure that there is no air in the loop. Also, open it as wide as you can get it that might flush out any debris, otherwise, follow Dana's suggestions.

 

[Dana]

Thanks for mentioning that! It can sometimes take a lot of bleeding to get the air bubble out of a second floor baseboard if the bleeder is on the far end from the bubble. Do it without the pump running, and don't call it "done" until it's bled a quart or three of water out of it. If it's possible to isolate the main loop upstream of the tees it will help drive a bit of back-flow through the loop due to the mono-flow tee, if flow direction is keeping it from purging a bubble.

 

[Theodore]

As suggested, without the circulator pump running, I bled the baseboard until about 2cups of water came out. This is way more than any other baseboard needs in the house before you can hear the telltale sounds of air bubbles. I then turned up the heat, and waited for all other baseboards to get hot. This one still didn't. So I bled this one again, while the circulator was running. After several more cups of water, the pipe on the side with the venturi started to get warm. The pipe on the "supply" side, remained room temp. I have an infrared thermometer gun and confirmed the same. So, now, my guess is that something is clogging the supply side. Has anyone had to deal with a similar clog in the radiator plumbing? Certainly a concern in my mind that trying to remove the baseboard will be very difficult as the joints are almost flush with the finished floor, and then, if I try to blast the one branch line with air pressure, it may cause whatever is clogging it to travel to another location.
Suggestions appreciated.

 

[Dana]

As suggested, without the circulator pump running, I bled the baseboard until about 2cups of water came out. This is way more than any other baseboard needs in the house before you can hear the telltale sounds of air bubbles. I then turned up the heat, and waited for all other baseboards to get hot. This one still didn't. So I bled this one again, while the circulator was running. After several more cups of water, the pipe on the side with the venturi started to get warm. The pipe on the "supply" side, remained room temp. I have an infrared thermometer gun and confirmed the same. So, now, my guess is that something is clogging the supply side. Has anyone had to deal with a similar clog in the radiator plumbing? Certainly a concern in my mind that trying to remove the baseboard will be very difficult as the joints are almost flush with the finished floor, and then, if I try to blast the one branch line with air pressure, it may cause whatever is clogging it to travel to another location.
Suggestions appreciated.

Are there shut-off valves on both sides of that baseboard? If yes, pulling the baseboard and cracking open the valve on the supply side may blow out the plug, if it's in the pipe. With the baseboard out you may be able to back-flush the radiator to push any accumulated crud back out the supply end.

If not valves, are there at least unions on those stubs coming up through the floor?

 

[Theodore]

Are there shut-off valves on both sides of that baseboard? If yes, pulling the baseboard and cracking open the valve on the supply side may blow out the plug, if it's in the pipe. With the baseboard out you may be able to back-flush the radiator to push any accumulated crud back out the supply end.

If not valves, are there at least unions on those stubs coming up through the floor?

No shutoffs on either side of baseboard.
These fittings *look* like unions, but I'm not too familiar with them. Please take a look at photos from both ends of baseboard, attached.

 

[WorthFlorida]

T=You do not have to open the union fitting. There is a plug that can be removed to really the loop. Before doing so, get a nipple of the same size, turn off the water, insert the nipple so you a can fit on a nylon hose to bring the water to a pail. On the other side you can also removed the bleed valve to flush from their but be sure to have new one should the original one is bad.

 

[Dana]

Yes, those large hex nut type rings are union type connections, integrated into the ell on the left side, integrated into what looks like valve body on the right side (indicated by red box in WorthFlorida's response), which would allow you to remove the baseboard if need be.

It also looks like you have bleeder valves (of different types and vintage) on both ells. Have you tried bleeding separately it on each end, with and without the pump running?

 

[WorthFlorida]

The air bleed and fitting on the left looks to be higher above the floor than does the right side. If bleeding only from the right side, it is not at the highest point. That is what it looks like in the pictures.

 

[Dana]

The air bleed and fitting on the left looks to be higher above the floor than does the right side. If bleeding only from the right side, it is not at the highest point. That is what it looks like in the pictures.

I agree, it looks that way to me too. But pictures or even in-person inspection can be deceptive- floors aren't always level, walls aren't always vertical. Bleeding it at both ends would be the right thing to do before cracking the system open.

 

[Theodore]

I agree, it looks that way to me too. But pictures or even in-person inspection can be deceptive- floors aren't always level, walls aren't always vertical. Bleeding it at both ends would be the right thing to do before cracking the system open.

Agree, the left plug is slightly higher than the right side air bleed valve. But, when I was bleeding the right side for 10 minutes straight, the left is where the pipe started getting warm. And, based on inspection in the basement, the left side has the venturi, and the right side is the regular tee. So, I can't imagine it's a case of air lock within this branch of the system.