Air Bound Monoflo Convector
Monoflo systems work well as long as there are no air pockets in either the supply or return pipes to the convectors. This type of system requires the run-out pipes (piping between the main around the basement to the radiation) to always go uphill gradually from the cellar to the convector. The convector element could be cast from copper or steel pipe. The element should be installed so that the component of the cabinet has a vent on the high side, which would be the return side piping. This convector is correctly piped. I encountered a problem after draining a system for service, which was initially baffling. When the system was refilled, all the radiators and convector heaters heated up, except for maybe one or two, even though they had all heated up before the service. This problem is usually due to homes settling over time, and the piping now has a high point. This means there is not a gradual uphill slope from the main piping to the radiation. The high point traps air, and when bleeding, you get air before water. Since more bleeding only produces more water, you believe the problem is not related to air, but in this situation, it is air-related. Bleed all day if you want, and you will not get the air out of the pipe with a high spot. The problem is that the water will go up the pipe that is not airlocked, and you believe there is no air, so we want to blame something else. Mounting the pump on the supply and pumping away from the expansion tank may help the system work over time by adding pressure. I have seen it take two weeks and sometimes not at all, without manually solving the problem.Monoflo System will not heat after being drained for service.
Monoflo systems work well as long as there are no air pockets in either the supply or return pipes to the convectors. This type of system requires the run-out pipes (piping between the main around the basement to the radiation) to always go uphill gradually from the basement to the convector. The convector element could be made of cast copper or steel pipe. The element should be installed so that the element in the cabinet has a vent on the high side, which would be the return side piping. This convector is correctly piped.
I had a problem after I drained a system for some service, which was baffling at first. When the system was refilled, all radiators and convector heaters heated up, except for one or two, despite having heated up before the service. This problem is usually due to homes settling over time, and the piping now has a high point. This means there is not a gradual uphill slope from the main piping to the radiation. The high point traps air, and when bleeding, you get air before water. Since more bleeding only produces more water, you believe the problem is not related to air, but in this situation, it is air-related. Bleed all day if you want, and you will not get the air out of the pipe with a high spot.
The problem is this
The water will go up the pipe that is not airlocked, and you believe there is no air, so we want to blame something else.
Having the pump mounted on the supply pumping away from the expansion tank and adding pressure to the system may help in getting this system to work over time. I have seen it take two weeks and sometimes not at all, without manually solving the problem.
This is how the Water will flow when purged
Once the radiation and piping are purged, it will get rid of the air, and the unit will heat fine.
For cabinet convectors and baseboard, the radiation should slope slightly toward the vent side of the radiation so the air can move to the high point and get vented out.
Disclaimer: The information found on this website is for informational purposes only. All preventive maintenance, service, and installations should be reviewed on a per-job basis. Any work performed on your heating system should be performed by qualified and experienced personnel only. Comfort-Calc or its personnel accepts no responsibility for improper information, application, damage to property, or bodily injury from applied information found on this website, as a professional should review it.