Problem with Monoflo System after Conversion

[Neil]

I recently converted from oil to gas, hot water monoflo system. I have convectors throughout the house and 3 baseboard heaters (recently purchase the home). After we fire the system up all the convectors heated up, however the 3 baseboards didnt and there is no where to bleed them. Do I have to add bleeders to the 3 baseboards? I also raised the boiler temperature from 175 to 182 and noticed two of the 3 baseboards heated up. Is there anything I can do or my best course of action in to

install bleeders on the baseboards? Boiler pressure is at 15 PSI, this is a split level ranch and the 3 baseboards are on the 3rd floor.

Thanks, Neil P

[John Gilmer]

It's "nice" to have vents in the high spots in a hot water system.

BUT if you have a air trap in the system at the exit of the boiler you can eventually get the air out. But you have to have one or the other.

(The physics/chemistry is that air will dissolve in cooler water and go out of solution when it gets hot. An air trap in a hot part of the system will "pump" air out of the cooler parts.)

[Neil]

John:

Thanks for your input, I have noticed that 2 of the 3 baseboards are now running ok (hot) but the third unit in the bathroom is still cold. All the remaining convectors are nice and hot and the system is running great. I have the original installer returing on Monday to install bleeders on all 3 baseboards. Would cooler water idea work by me turning down the boiler temp to the lowest and running the system. By doing so would the circulator cause more air bubbles? I am all new to heating system, however I am an Electro-Mechanical Engineer, so I am not intimidated to fix the problem if I can. It looks like air is trapped in the one baseboard which is on the 3rd floor and above the supply line.

Thanks again, Neil P

John Gilmer wrote:

[John Gilmer]

Might. If you have a way of taking air out of the system.

Some of it will happen just by running the system. In the loops where there is a air block, the reduced flow will cause the supply to cool and thus air will diffuse back to the hotter parts of the system. The air will tend to stay in solution in the working radiators because they are also cooling the water.

That's why an air trap is so effective (and so necessary.)

If you have an air trap you can force a flow thru the air blocked part of the system by shutting off the supply to to other parts. But you STILL have to get the air out.