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Monoflo System will not heat after drained for service.
I have encountered this many times after I drained a system for some type of service. When the system was refilled all the radiators or convector's heated except maybe one or two.
This type of system requires the run out pipes (piping between the main around the basement to the radiation) must always go uphill gradually. The problem is usually due to homes settling through the years and the piping now has a high point. This means it is not a gradual uphill slope from the main piping to the radiation. The high point will trap air and when bleeding you get air than water. Since more bleeding only produces 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.
The problem is this The water will go up the pipe that is not air locked 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 and sometime not at all without manually solving the problem. The best way to resolve the problem is either re-pipe the radiation removing the high point trap, if you can't get to or find the high spot you have to install purge valves. A positive purge will eliminate the air in this piping and get the radiation to heat again. Since heat output is related to flow removing the air will get us proper flow through the radiation providing the pump is sized properly. This is how the Water will flow when purged Once the radiation and piping is purged it will get rid of the air and the unit will heat fine. Also verify all the radiation piping slopes uphill so the air can move into the radiation. For cabinet convector's and baseboard the radiation should slope toward the vent side of the radiation so the air can move to the highpoint and get vented out. Heat Loss Info Tech Menu Q&A Forum Contact Us
