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Posted by HeatPro on January 26, 2011 at 15:36:45:
In Reply to: tankless coil leak and boiler pressure posted by Dan on January 26, 2011 at 11:41:17:
That would be VERY unusual. It would be more possible if your water pressure at the tap was very low, as domestic water house pressure is usually over 40 psig and boiler relief valves are under 30 psig.
The usual is that when you have a leak in the tankless coil in the boiler, water comes out of the relief valve and the fuel bill goes up because of the cold water passing through the coil into the boiler.
If you do use a great amount of cold water heating in the coil, the pressure might drop simply because the water in the boiler system is shrinking with the cooler temperature as the cold water passes through the coil.
You would check for a leak in the boiler by turning off the feed water to the boiler pressure reducing valve and closing the valve to the cold water line entering the tankless coil in the boiler. If the boiler pressure doesn't drop below 10 psig there probably is no leak.
You won't get hot water while you watch it with those valves closed, but you would have heat.