Gravity system with Honeywell Heat Generator

Mike T., Swampeast MO

Expansion tank outlet was cut off below the roof. Was it capped?

"Explosion like" noise does sound ominous. The Heat Generator system was able to produce gravity circulation through smaller than normal piping by producing higher than open atmosphere boiling temperatures--kind of a closed system with an open safety...

Likely time to convert to forced circulation and remove the Heat Generator. Even with a "blow out" the mercury should have settled back down in the lowest point (the Heat Generator). Consult local authority for proper disposal.

Dave K

Gravity system with Honeywell Heat Generator

I have been asked to provide options on replacement of an American Radiator boiler that has failed. The cause of the failure is unknown - although the homeonwer indicated that there was an "explosion like" sound that woke them up in the middle of the night. We inspected the system (the fire department had responded and removed the top of the boiler). The interior of the boiler was clean (no soot). The homeowner also indicated that the attic access was jarred. Upon viewing the expansion tank, we noticed the sight glass missing and the vent pipe cut-off in the attic (probably by the roofing contractor that repalced the roof). The gravity system has a Honeywell Heat Generator. My concerns are that if the boiler is replaced and the system remains a gravity system - is there someting wrong with the heat generator (how can we diagnose this? mercury concerns?) and is the expansion tank compromised? What are the pitfalls or concerns of removing the Heat Generator. Also, can the expansion tank in the attic be eliminated and replaced with a conventional expansion tank near the boiler and a vent in the attic?
Does it just make sense to convert the system - taking into consideration all of the additional work (and costs) and deal with potential balancing problems. I understand the restrictor plates need to be relocated to the first floor rads - is there any risks in doing this as far as leaks? Does the piping system need to be flushed while the system is accessible?

gerry gill

be careful

the last system i took apart had the mercury blown thru the piping system all the way thru the first floor piping..i asked an old timer how this can happen.. he said some ''duffus'' turned the water on full blast when filling the system..the generator probably hadn't worked right for years, if ever, because of this..you can tap off a pipe and put a diaphram tank next to the boiler..a big one..a real big one..cap the tank pipes in the attic and bury them under insulation..best if you can pull them into the floor below..remove the generator..carefully cap its inlet and outlet..your all set then..system will still function on gravity..if your converting to pumped..around here a orifice plate with 3/8th inch hole in it will get put in every radiator to auto balance the system..hope this helps answer your questions.

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Paul Pollets

You'd be wise

to replace the boiler at this time!! Gravity replacements are converted to forced circulation when installing the new appliance. We usually install a thermal bypass or a 4 way mixing valve to prevent thermal shock. Installing a bypass is often required by most boiler manufactures, if the warranty is to be honored. Yes, the piping systems should be cleaned and flushed with special chemicals prior to commisioning the new boiler.

We also revalve all of the radiators when the system is dry and use "Thermostatic radiator valves" (TRV's) in place of the handwheel valves. This allows precise temperature control. The attic expansion tank is removed and riser capped with an auto air vent. A new pre-charged exp. tank is relocated at the boiler.

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