by 'Q' on Thu Apr 05, 2007 5:27 pm Trying to come up with an answer that is easily explained on here is tough.
Basically, assuming that the existing pressure in the tank is the result of steam (which is water in another form) and not compressed air, the introduction of more water will not alter the functioning of the boiler.
Three things to consider:
1) Increasing the temperature of the water will cause it to evaporate and produce steam which will increase pressure in the tank.
2) Increasing pressure in the tank results in a higher required temperature for water to evaporate and produce more steam. Also, the temperature which the steam will condense back to water goes up (called the dew point).
3) Lowering temperature will result in condensation of the steam back into water, which will lower the pressure in the tank.
By introducing more water into the tank, you will increase pressure (and lower the temp a little). Increasing the pressure will raise the evaporative point of the water, not allowing more steam to be produced unless the water increases in temperature (not going to happen if the pressurestat is doing its job) and raising the point that the steam will condense back to water. This will effectively balance things back out so that the pressure regulation performed by the pressurestat will maintain the desired temperature.
Hope this makes sense.
