issue wih mono flo syetem

zepfan

I replaced a relief valve on cast iron boiler that has one pump, one thermostat , and no zone valves, I filled the system back up opened the vent on the air purger near the boiler, and checked the first floor radiators, and made sure they were hot. After about two hours there is still a section on the top floor of this house that the radiators are not getting hot. The highest radiator is 17' above the boiler, and the boiler is running at 22 psi. While the other radiators on the top floor are hot to touch, this one section that is on the same level is ice cold. I opened the air vents on each one and get nothing but ice cold water. This is a mono flo system from what I can tell. I can't believe that by replacing the relief valve it has caused a major flow issue, and am looking for any suggestions on what to do next. Any advice would be greatly appreciated. Thanks to all

Alan (California Radiant) Forbes

Monoflow systems are notoriously difficult to purge. Things I would do:
- Increase the pressure to 30 psi. This will make the air bubbles smaller and easier to evacuate.
- Add an ounce or two of dishwashing detergent the the heating water to reduce the viscosity of the air bubbles, allowing them to release their grip and be purged.

Good luck!

zepfan

Thanks for the response, what is the best way to add the dishwashing liquid to the system if the boiler is full of water? Do I need to drain the boiler down, and refill it? Thanks again

Leon82

You could drain a little and inject some from the airvent.

Leon82

Or if you have a hose connection nearby you can put detergent in the hose and connect it to a fitting on the boiler. Open the valve Then turn the water on slow and force it in. Don't go full open or you will fill way too fast.

You may need a double female hose to accomplish it.

This will inject some air too but you said there is a vent near the boiler where you can purge it again.

billtwocase

Ah, good ole monoflow. Was it working before you drained water? Are you bleeding with the circulator pumping? Is there a butterfly or radiator valve on the end that might be closed or bad? Have you tried to trace the piping from the basement? Is it baseboard, wall convector, radiator? Pics will help. If it is baseboard or wall convector, with the pump off, lift the bleeder end as high as you can get it, and open the bleeder slowly. Long runs trap air, and can be a **** to get out. Your pressure, if accurate, is sufficient. Good luck, and let us know your findings

zepfan

I can't say for sure if it was working before or not. This is the first that I had worked on the system, and the people have only owned the house two years. I was venting with the circulator off. Most of the ceiling where the piping is located is finished, and untraceable. The units are more small radiators then baseboard. They are Crane, and stand about 12" off the floor. Thanks for the advice

billtwocase

Cast wall convectors maybe? You should bleed them with the circ running if there is a reason not to otherwise. If there is a valve at the radiator, that can help in bleeding air out. Generally it should be on a supply. Good luck, and post some pics if you get back there

zepfan

I have attached pictures of this job. It has been almost a month, and everywhere in the home is heating with not even the slighest sound of air. I went by there today and opened the quick fill until the pressure got right to 30 psi. No luck. I then, as suggested, added dishwashing liquid to the boiler loop, and let it circulate. No luck. When I open the air vents on these units you get nothing but cold water, no signs of air. I welcome any, and all suggestions. I am out of I ideas to resolve this issue. I can only see the piping so far in the basement, the ceiling is finished. I can tell the the supply wraps around the permiter of the house, and it is hot all the way around. Somhow the water is completely flowing around these units. Thanks to all.

john walsh_2

Can you attach a small diameter tube to the bleeder of the Baseboard radiators that aren't heating and bleed them until you feel the tube getting warm? If they were working before, it has to be trapped air.

Jamie Hall

The problem with monoflo is that it really shouldn't work at all... and even a very slight restriction in one radiator or one loop -- such as might be a little trapped air -- can make the water, which is terminally lazy, go somewhere else. As several have said, if there is a bleeder, open it -- and leave it open (maintaining system pressure!) until you start getting hot water out of it. You are effectively making that the low resistance path, rather than the run between the monoflow T's...

Solid_Fuel_Man

I can't tell from the boiler picture, but I have has sucess with valving out the circulator (with system off and cold) and attaching a garden hose on supply and draining from somewhere on the return or the boiler drain itself. This effectively makes the flow through the primary loop an open system. If there is DHW available for the garden hose even better. Think of it as power purging but with the garden hose as your supply.

After a few minutes of full flow purging, close both hose bibs, and raise system pressure to 30. Try bleeding those cast baseboards again. If you were using hot water to power purge then you may notice some warm radiators. I've had good luck with this method.

If all else fails, I pull a vacuum on empty systems. That would require lots of time as there is water in the system which would need to be boiled off in the vacuum.