How to fix this mono flow rad? (FIXED)

sixplex

Never worked, 70 y/0. 1 monoflo tee, Tees are only 16 inches apart (narrower than the rad), rad is slightly below the main

Easiest fix?

Current thoughts

1) Just remove the rad connect the ends together
2) Add second Monoflow tee
3) Put in a smaller rads, this one has 14 sections, much wider than 16 inches


What do you guys think? Local contractors don't get monoflo, i basically have to tell them what to do.

mattmia2

Do the pipes heat? Are you sure it isn't just flowing through the first section of the radiator and back to the main?

Is the arrow on the return the right way? If it isn't air bound you should get some heat(or has a broken valve that is closed even when it looks open or debris caught in the valve or the tee).

A second monoflow tee, bigger runnouts to the radiator will both give you more flow, but if you have 0 flow something else is going on.

Mad Dog_2

Mono-flow (Venturi) tees are generally placed as wide as the radiator or connector.  That's Black pipe?  Alot harder to add if needed.  Mad Dog 🐕 

Mad Dog_2

Hard to tell from pictures.  Can you make a sketch?  Mad Dog 🐕 

mattmia2

They have another post where they asked this same question that has a few more pictures.

mattmia2

I don't know if you saw this before:
https://heatinghelp.com/systems-help-center/diverter-tee-q-and-a/

You could always add a full port ball valve between the tees if you rework anything to help it, you could close the ball valve just a little until it diverted enough water through the radiator to make it heat if just adding a second tee wasn't enough.

sixplex

Both supply and return go up 6 inches from the main then down as pictured. Arrow is pointing in the right direction. Tried bleeding the rad, water comes out. Not sure what else i can do

Mad Dog_2

Circulator could be crapping out.  Pics of Boiler and Piping?  Mad Dog 

sixplex

There are 25 rads on the circuit, this is the only one that doesnt heat up, circ is fine

Big Ed_4

I agree

Mad Dog_2

Ok, but I have seen that happen when impeller was wearing down...one, then three radiators stopped heating.  Mad Dog 🐕 

hot_rod

Air-locked? Did it ever heat properly?

bburd

IIRC two monoflow tees were specified according to the original designs if a radiator was mounted below the main:  one on the supply and the other on the return. It's important to align the flow arrows correctly.

@mattmia2's suggestion above regarding a full port ball valve in the main where it bypasses that radiator would also work if correctly adjusted.

109A_5

Hello @sixplex,
If you actually want good heat from this radiator, I would do two things. Compare the piping associated with this radiator to the others that work good and change this one to match. And at least move the lower pipe to the other end of the radiator. Otherwise I would not waist the time, money, effort, etc. doing anything else.

ScottSecor

At seventy years old, I would be concerned about the internal condition of the monoflow tees. We have numerous residential and commercial customers that have similar systems with cast iron monoflow tees. On one job in particular that has or had numerous system leaks over time, the tees were in poor condition.

Many of these tees were plugged with rust and sediment (on the bull that feeds the radiator). In some instances the venturi (cone) was missing or in poor condition. On one very large system, the half inch steel pipe that fed the radiator above was clogged for a few feet. If your system has had a leaky boiler or some rotted pipes I would be very concerned that the monoflow tee is not doing what it was designed to do, namely divert water to the radiator.

JohnNY

sixplex said:

circ is fine

How do we know this? What are we calling "fine"?
Also, removing the tees and going full-flow through the radiator will make the rad heat to its full potential at every call for heat....unless there's some kind of ODR logic in place...which may or may not suit your purposes. Be ready for that. With the limited info we have here, it looks to me like there are too many elbows and too long of a run with small pipe to permit flow through that branch. You probably already know this but the TDH through the heat emitter branch can't exceed that of the piping between the supply and return tees, which tends to be not very much and is mostly determined by the Delta-P through the Venturi cone. Is my stream of conciousness helping yet? I find 1-pipe hydronic systems to be pretty darn interesting. I just wish they worked better.

mattmia2

JohnNY said:

is mostly determined by the Delta-P through the Venturi cone.

^^^^ this part, it should stand out more.

I thought the B&G monoflow book was in the library somewhere but I couldn't find it.

109A_5

Maybe the document / charts at the end of this posting will help.
https://forum.heatinghelp.com/discussion/167456/old-monoflo-tee-pressure-drop-ratings-and-calculating-system-pressure-drop

Also a lot of info. here.
https://heatinghelp.com/systems-help-center/diverter-tee-q-and-a/

sixplex

Appreciate all your thoughts.

Based on the Q and A. The rad may not not be optimally piped because:
1) The tees aren't the width of the rad apart. The mitigating factor there is a 90 between the tees which adds some resistance / length.


2) This rad is BELOW in the main, the Q and A, says 2 monoflo tees should be used in such cases, there is only 1. The mitigating factor the run to the rad being short.


Circ was replaced 2 years ago, it's heating up 27 other rads on the loop just fine. Would a higher head circ help that rad, doesn't seem likely to me.


There is 1 other rad on on the loop piped almost identically, but the rad itself is half the size, and is located closer to the end of the loop (cooler water goes down easier), it's the only other rad i had issues with as well, at the end it started working somehow.

mattmia2

I have an idea. i bet there is air trapped in the horizontal section of pipe off of the monoflow tee. looking at the diagram of the monoflow tee, there is a place at the top behind the cone where air can get trapped, if the tee is sideways and there is a pipe attached to it that bubble could be in the pipe.

It may eventually dissolve and work its way out depending on the air elimination in the system, if it has a diaphragm expansion tank and has a microbubble type air scrubber it will probably eventually work out, just an air scoop or a compression tank probably not, especially since there is little to no flow in that section to bring deaerated water in to that section to absorb more air.

sixplex

Intuitively think you may be right. If you look at two horizonal supplies on top of the radiators, those are air bleeder vents, only water ever comes out of those. Do you still think there could be trapped air?

Ironman

Has anyone noticed? There are two mains? Unless that’s one main that makes a U turn where we can’t see it, it may be piped direct return with this one rad piped Monoflo.

@sixplex
Are the rest of the rads piped with monoflo Tees?

mattmia2

sixplex said:

Intuitively think you may be right. If you look at two horizonal supplies on top of the radiators, those are air bleeder vents, only water ever comes out of those. Do you still think there could be trapped air?

I would like some comment from others that know monoflow systems better than I about my theory. I think if the emitter is below the main the outlet has to be on the bottom of the main.

If i am right and there is a pocket of air trapped in the lateral above the cone in the tee, if the bleeders are below it then you will not be able to bleed the air out there, the air will rise above the water and stay in the lateral at the top.

The only ways i can think of to get the air out short of adding a bleeder at the high point of the lateral or using 45's or 30's to angle the lateral down off the tee are:

1. Add some valves on the supply and return at the radiator and a drain between the valves so you can shut off the supply, open the drain, open the fast fill on the boiler, and purge enough velocity through the monofolw tee and lateral to flush the air down and out the drain.

2. Add better air elimination to the system and convert to a diaphragm expansion tank if it isn't already and get enough air out of the system that the air dissolves.

3. Maybe purge enough water through the monoflow loop to draw the air out.

This also could explain why your other radiator started heating, if enough of the bubble dissolved to start flow.

109A_5

Since there is only one monoflow T and I believe the air bleed valves are the highest point in that area how is air trapped ? The UP arrow in the picture is actually UP, correct ?

mattmia2

I think that up arrow you drew is pointing off to the side. The emitter is being fed from above.

109A_5

Looking at the wood structure. A side view as I see it.

sixplex

109A_5 said:

Hello @sixplex,
If you actually want good heat from this radiator, I would do two things. Compare the piping associated with this radiator to the others that work good and change this one to match. And at least move the lower pipe to the other end of the radiator. Otherwise I would not waist the time, money, effort, etc. doing anything else.

hmm. the pipe you're suggesting we change is the return, seems like all we'd be doing is increasing the resistance of this monoflo circuit

sixplex

109A_5 said:

Looking at the wood structure. A side view as I see it.

wow yes, i couldn't manage to draw that. and where the blue x is the pipe is extends travels parallel to the wall a bit

sixplex

Did some more debugging.

1. removed the bushing at the bottom, to cleaned the sludge, there was a bit but not a huge amount.
2. connected a male 1/8 npt with a plastic tube attached to it in place of the air bleeder on the return, ran some water through it, there was flow out of it, not much though

hot_rod

Boosting the system pressure for an hour or so can sometimes free up an airlocked section. Take it to 20-25 psi, keep an eye on pressure so you don’t pop the relief.

The pressure increase will squeeze the air pockets smaller and allow them to flush through. Assuming you have a working air eliminator at the boiler?

109A_5

sixplex said:

hmm. the pipe you're suggesting we change is the return, seems like all we'd be doing is increasing the resistance of this monoflo circuit

The point of moving the pipe is so that heated water flows through the whole radiator, it has to flow across the whole radiator not just across the left end. The whole radiator has a lot more surface area to dissipate heat from. I would think the water in most of the radiator is very stagnate and any gravity flow assistance (cooling of the water) is almost non existent. I guess what I am getting at is, I see it as possible multiple problems. You need good flow to the radiator and fully across it for optimum heat transfer to the area.

The monoflo tap is to the correct pipe ? I see two pipes in the wall void. And the supply and return to the radiator is in the correct orientation too ?

You may have to do this too.

sixplex

Noticed significant corrosion at the top of the 6" section going up from the supply tees. Thinking air must be getting trapped there which is why the rad doesn't heat

sixplex

sixplex

Had an old timer heating guy come by, he suggested putting a valve on the supply, red section, said this would allow to remove air from the rad and make it work.

does that make sense?

mattmia2

no

HomerJSmith

It's simple. When a radiator isn't outputting the expected heat energy only two things can cause it.
1) The temperature of the supply water is too low.
2) Low or no flow thru the radiator. I'm discounting the temperature between the radiator and environment assuming there is a differential.
1) Check the boiler temperature output, other radiator's output looking for irregularities and make comparisons. Adjust as necessary.

2) Take a FLIR camera of the supply piping and radiator, looking for blockages. Temperature changes.
The sys doesn't have a pump, it has a circulator. They are not the same. A circulator can't push
push water thru an air pocket.
There may be corrosion plugging up a pipe opening.
There may be a clogged monoflow tee.
There may be a partially closed valve.
There may be an incorrect piping arrangement.

Since flow or lack thereof is the problem, I would go with the FLIR camera in making a diagnosis. It would be the way to look what is happening with the temperatures in the piping and radiator. Eliminate the guess work!

Big Ed_4

Your problem is not air ( the two bleeders were enough ), your problem is lack of flow . Are they any disconnected radiators on that loop ? Is the loop piped full size ? Is there a dictated circulator for the monoflow loop ? What changes has been done to that system in the last 70 years is where you will find the problem ..

sixplex

Big Ed_4 said:

Your problem is not air ( the two bleeders were enough ), your problem is lack of flow . Are they any disconnected radiators on that loop ? Is the loop piped full size ? Is there a dictated circulator for the monoflow loop ? What changes has been done to that system in the last 70 years is where you will find the problem ..

No changes, nothing is disconnected, circ size, fine.
Neighbour has an identical building her rad (same as mine) is piped differently (bottom supply possible other differences) and works great. I'm thinking at this point they piped it wrong 70 years ago, or used a monster pump. Makes no sense for me to have a much stronger pump for this one rad if the other 35 rads work fine

sixplex

So plumber put in a valve on the supply. Air problem and blockages are ruled out i guess,
water comes of of every bleeder with the valve closed.

It's 25C out, i jacked up the temp on the boiler to check, this is what it looks like.

The return is ice cold.

EdTheHeaterMan

Has anyone asked where the problem radiator is located in the overall system? This slide from a class I taught may help to understand why I ask.
I can see from the IR picture that there is some flow but not enough.

I could also make a Gil Carlson type suggestion. Add a pump

sixplex

It's not the last rad in the loop. 

Is there a small pump that's designed for such a purpose ?   It's a common hallway, a typical circular would look ridiculous there