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Re: Replace or repipe this boiler?

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Posted by HeatPro on October 23, 2005 at 14:23:42:

In Reply to: Replace or repipe this boiler? posted by Dave on October 23, 2005 at 12:55:18:

We communicated with email pictures last winter. Your problem comes from whizzing very little water content around in a circle while heating it with 240,000 btuh of burner. Instead of having sufficient water mass to allow a 20-degree rise, the boiler heats up the water in the loop immediately. Even low fire will still be heating little water too fast. This flashes bubbles in the main, makes noise, and kills your circulator. This type of installation error comes about due to inadequate education in the field, thus assuming that engineering 'magic' like a high-tech-sounding zero-balance piping will solve all problems. A zaro-balance primary-secondary piping circuit works well with large-mass boilers where the burner has to heat water over a longer period. It doesn not work well in an instantaneous-water-heating application such as yours.

You can install an 80-gallon tank at the main where the TACO 0010 (you have a 0012, which is over-pumping) is so a larger water mass is available to let the boiler heat it over about 20 minutes of firing. That is what the repairman is suggesting when he recommends installing a Buderus instead. The tank to make the same larger mass is less expensive and can be used as a hot water preheater as well if it is a tank with a copper coil in it to use the heat in the tank for hot water. There is such a tank manufacturer in NJ. It requires few changes and less expense, and you arrive at the same solution as in paying more for a new boiler. There is nothing functionally wrong with the boiler, the primary loop, the zero-balance design, nor the circulator. The installation is just missing the water mass to temper the heat-up speed.

An outdoor-reset control like the Tekmar would be good for your system AFTER you give it sufficient storage mass. You can't depend on the control to rapidly turn the burner off before the water gets too hot from too much too fast.

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