Radiators not getting hot

MonofloMad1

HELP! No one can figure out how to get my radiators hot... I am not a plumber so bare with me. When I bought my home everything worked beautifully. Had some work done and dry walled basement ceiling (I know really dumb) my main feed and return were literally cut out and moved to a central beam in the middle of the house. I have a Monoflo setup with a plain t on the intake for each radiator and a Monoflo on the return. All the original plumber did was move in the main leaving all t’s To the radiators where there were and simply cutting out length in the main. At the same time each intake and return to each radiator increased in length by like 10ft and on top of it he use 1/2” pex instead of 1/2” cooper..... no one can figure out how to get my radiators hot again! Do I have to cut out our ceiling and replace all the 1/2” pex with 1/2” copper? OR can we replace all the t’a on the supplies with Monoflo as well as keeping the Monoflo on the return? OR can we somehow install a valve on the main between each intake and return to slow down the flow on the main and force the water through each radiator? PLEASE HELP!!

Jamie Hall

My first thought is air... although others with far more experience on Monoflow systems will have better thoughts. But that said, a Monoflow system can, by the nature of the beast, be a real bear to get all the air out of (purged, not just bled).

Gordy

I'm thinking air too. mono flow systems are kind of a bear to purge.

However that extra distance added to the branches by moving the main piping to the middle of the basement could play a role too. Most mono flows used perimeter piped mains with mono flow Ts , and covectors are directly above the mains.

MonofloMad1

We think it’s air too especially since the non working radiators bounce around. For instance at the end of last winter we had 3 not getting hot - beginning of this season we had 5 not getting hot - now today after Plumber was here earlier trying to force air out we have a total of 7 not working!! How can we force the air out?

Gordy

Is the plumber bleeding with the pump off?

What is the system pressure? You may need to raise it to like 25 while bleeding, and make sure you maintain that pressure while the bleeding process is being done.

Start with the radiators on the top floor farthest from the boiler, and work your way down to the one closest to the boiler.

Then start the system with higher than normal pressure for a bit. This compresses any residual air bubbles so they can get back to the air removal device.

You might have to repeat this process several times. Once everything is working drop the system pressure down to normal. 12-15 psi for a two story home.

Gordy

You can do a search on this site to pull up some mono flow system issues other people had.

Gordy

The distance between the t's is very important. Also was there a change in circulator size. Flow rates are important too.

MonofloMad1

We have a ranch with 2 giant radiators in basement and baseboards in a first floor addition which was added to the system in the 50’s. The distance between t’s is width of the each radiator. I’ve had about 5 plumbers most out multiple times and all have purged the system.... every time the same 3 never get going and every once in a while another one with stop getting hot (current count is 7!)

MonofloMad1

Can we install a valve in the main between each intake and return branch to slow down the force of the flow through the main forcing it through each radiator?

MonofloMad1

Or install another Monoflo replacing the regular t on each brach so there will now be 2 Monoflo for each radiator

HVACNUT

Monoflo means older so my question is, is there a purge station at the boiler for the loop? That would help. Or better, is the loop getting hot?

About 20 years ago an old timer showed me this. Right or wrong, it's worked for me over the years.
If the main loop is hot then try increasing the pressure on the boiler to NEAR 30 psi.
This works better with 2 people.
Crank the heat to 90°.
Keeping high pressure, go around and bleed each rad until the air is gone and the water is hot at the rads.
It might take a while but be patient.
If and when all is good, bleed one rad until the pressure drops to 12-15 pounds.

Long branch runs can be a nightmare. A hex on the Cape Cod homes.

If they need it, nows the time to replace all the vents too.

MonofloMad1

Run is boiling hot. There is a purge at the boiler and we tried getting the air out like 20 times.... I myself helped the guy yesterday watching the psi stay under 30. Would something in between each t to slow the flow on the main and force it through the feed branches work?

Jamie Hall

MonofloMad1 said:

Can we install a valve in the main between each intake and return branch to slow down the force of the flow through the main forcing it through each radiator?

Yes, it would. At that point you would have converted the system into a series system -- and the radiators farthest from the beginning would be getting pretty chilly water. However, it might help for the purging, and then you could try reopening various valves...

but, if you start cutting pipes and putting in valves, have you considered the possibility of repiping the whole thing as a reverse return? All your new branches could stay as is, and the main line would stay as the main as far as the last radiator. You would need one new return line starting at the return from the first radiator and picking up the rest of the returns as it went along, then cutting into the existing return line at the last radiator. Only slightly more work than cutting in valves would be.

MonofloMad1

Really trying to avoid repiping because ceiling is finished....

MonofloMad1

Also the guy made all these connections to utilize the existing main... I’m guessing all these ups and down piping on the branches aren’t helping the water flow either.... in the picture you can see a return from a below ground radiator

MonofloMad1

In this photo you can see the source pipe for that same basement radiator... it does a big U around an existing waste line. Again are all these turns messing up the flow to each radiator? If so wi

MonofloMad1

MonofloMad1

Will choking down the main between each source and return branch help force the flow through?

Jamie Hall

Monoflows work -- when they work at all -- because the monoflow T creates a slight low pressure on the return, which causes water to flow in the radiator loop rather than the main loop. The combination of the longer runs and the somewhat convoluted piping probably has put enough head loss in the branches that the pressure difference isn't enough to induce much flow.

Will choking it down -- as you mentioned earlier with your valve idea -- force flow? Yes. Use valves which can be adjusted, though, as you are going to have a very delicate balance between enough flow through the radiators -- and poor balance. My own thought -- again -- is to repipe as a reverse return system; if you do it in PEX you will need one access at each return location -- unless you are so unfortunate that the return has to run through a joist instead of parallel... You'll need that access to put in a valve at each location, anyway.

Gordy

From what i see the repipe is most of the issue. Someone wasn’t familiar with how a mono flow system functions. More importantly the piping.

MonofloMad1

I don’t understand the reverse return system thing and to be honest the sound of it scares me lol.... I spoke with my plumber and told him the idea I had to install the valves and he said he liked the idea so we are going to try that. At least I finally have a guy that comes back lol the rest stopped returning my calls after the 3rd or 4th visit.

I will let you know how it works! Thanks for helping me think things through!!

Gordy

It’s to bad the system wasn’t tested before the ceiling was installed. I’d be a bit upset right now.

MonofloMad1

You are 100% correct! I was dumb and naïve. This is my first home and I had a general contractor that was **** all of his subs were **** and I found out when I went to close the permits out that the plumber and Electrican weren’t even the guys listed on the permits. Oh and I didn’t even want to drywall the ceiling the contractor talked me into it... apparently it would have been a lot more work for him to do drop ceiling. So basically I had too much trust in the wrong guy. I learned a big lesson from him.

But yes it was very very dumb of me to not test the radiators before they closed ceiling and to close the ceiling all together.

Zman

Water is lazy and will take the easiest path. With the old monoflow, the extra resistance on the return tee was enough to make some water go through the radiator. The extra resistance of the pex and turns on the radiator side has made that path less desirable.
Do you have bleeder on the rads?
Can you post a picture of the boiler room piping?
The model of the circulator would be helpful as well.

HVACNUT

@MonofloMad1
Dont beat yourself up.
You paid for a job that was supposed to involve people who actually knew what they were doing. They probably tried to purge, gave up, told you it was working, and bolted outta there.
Will the contractor do right by you or is he giving you a hard time about coming back?

MonofloMad1

No way I wouldn’t let him or any of his subs back in the house! I’d rather pay someone who I trust then have him come back.

Gordy

You can use the find a contractor on this site see if someone is close to you. Maybe they can help.

You may not like the suggestions however.

I would also see your contractor, and sub in court! That’s none sense to leave someone with a disfunctional heating system!

Alan (California Radiant) Forbes

As I see it, the air is stuck in the branches to the radiators. I've never done this, but if you could find someone with a pipe freezing setup that could freeze the water in the main, between the tees, that would allow the air to be purged.
Monoflow systems saved on installation costs, but they sure are a pain to deal with.

STEVEusaPA

Alan (California Radiant) Forbes said:

As I see it, the air is stuck in the branches to the radiators. I've never done this, but if you could find someone with a pipe freezing setup that could freeze the water in the main, between the tees, that would allow the air to be purged.
Monoflow systems saved on installation costs, but they sure are a pain to deal with.

Ice Ice baby! Pretty clever Alan.

EBEBRATT-Ed

Nothing wrong with monoflow. The extra length in the branch piping may make the radiators & bleeding a little more difficult but with 10' added to the branches I don't think this is enough to restrict the flow. A lot of monoflow systems used 3/8 tubing for the branches and it still works.. Chances are air is trapped in the pex if the piping is not pitched uphill from the mains to the radiators and has sloppy up and down bends.

1 You could put valves between the tees in the mains.

2. The other possibility would be to install 1 valve on each radiator in the supply or return to stop the flow and force water through the other rads. May or may not be easier that basement valves in the mains.
3. 3. The other idea is to just put valve on any branch radiator line that you can access. You may only have to shut down 1 or 2 rads to get the other rads to get flo the you can open valves
4. Install a larger pump may get the flow moving

Gordy

I won’t interject beyond how it is suppose to work. The way I see it the OP is a victim of another take the money, and run contractor that should be dragged through the court system by the nap of their neck.

If nothing else they’ll maybe learn touching something they know nothing about will cost them money, instead of taking the money. Not making sure the system was functional before the ceiling was installed just shows the lack of caring about their work.
I don’t know if all these call backs of other people trying to get the system going is out of pocket, if it is it’s out of the wrong pocket.

billtheplmbr3845

In one of the first post wasn't it said they took the main and relocated it. Maybe they turned it and the tee's are facing the wrong direction. Direction of flow matters. I install quite a few in older homes, they work if installed correctly

Gordy

MonofloMad1 said:

You are 100% correct! I was dumb and naïve. This is my first home and I had a general contractor that was **** all of his subs were **** and I found out when I went to close the permits out that the plumber and Electrican weren’t even the guys listed on the permits. Oh and I didn’t even want to drywall the ceiling the contractor talked me into it... apparently it would have been a lot more work for him to do drop ceiling. So basically I had too much trust in the wrong guy. I learned a big lesson from him.

But yes it was very very dumb of me to not test the radiators before they closed ceiling and to close the ceiling all together.

Don’t beat yourself up. You were not the dumb one. Obviously they were. No it’s not up to you to test the radiators it’s up to the clown that modified the system.

We see this kind of jack leg crap all the time here, and it’s a bloody shame people do this kind of work. May as well steal money, because that’s what it amounts to.

delta T

@Alan (California Radiant) Forbes I have a freeze kit and I would never have thought of that......thanks for the tip, I like it!!

rick in Alaska

Did they bleed the air at each baseboard, or just at the boiler? This type of system has to be bled at the radiators to do it properly. Generally, you make sure the pressure is up in the system, and then bleed the air out of each individual baseboard until water comes out. One thing I try to do is raise up the end of the baseboard that has the bleeder on it in order to get the air up to the highest point in the baseboard Sometimes you can get them to raise up, sometimes not. If you can, put a wedge under that end and leave it until you have bled all the baseboards. Then go back and do it again.
Rick

Alan (California Radiant) Forbes

As a last resort, you could add 2-3 tablespoons of dishwashing detergent to the system, increase the pressure to just under 30 psi and turn the system on.

The detergent will alleviate the surface tension of the water and the increased pressure will make the bubbles smaller, making it easier for them to start moving around.

If you have an air eliminator at the boiler, it will remove any air that comes strolling by. If you don't have any air elimination devices, purge the system with as high a pressure as you can after running the heating for an hour or so. You may have to do this multiple times, but you will be able to tell if it's doing any good by the sound the air bubbles make when they move around.

Introducing the detergent into the system can be a challenge. You might need to find someone with a transfer pump or someone here can chime in with a better idea.

duffy_4

If you can get a contractor with a good thermal imagining camera he might be able to “see” where and which lines are air bound . If all the supply and return connections are accessible you could convert it to a home rum system with pap tubing ,which makes for simp,e system to purge

Steamhead

@MonofloMad1 , where are you located?

JohnNY

I haven't read all the replies here but if the resistance to flow is greater from the tees (typical and monoflow on the main) to the radiators than the resistance to flow on the main between those two tees, then the water will have no reason to move through the branches to the radiators. What you've got there has to be redone to comply with the laws of physics rather than hope to wish them away. Get a proper heating plumber in there next and he will straighten it out.
Or she.
Sorry.
All good.

Brewbeer

Is there a way to bleed the air at each radiator? Can you take some photos of the radiators to show us what type they are?

MonofloMad1

So the valve idea worked like a charm!! All of the rads that never got hot are on fire. It works beautifully I can even open up the flow all the way to the rooms that get too hot or close the valve a little for the rooms that feel colder. Still have 2 not hot but those 2 aren’t 2 that the plumber put valves on today. We wanted to try a few to make sure they would work before we made a bunch of holes In the ceiling. On to a new post about this damn Nest thermostat I installed 🙄