System Piping

Alan(CaliforniaRadiant)Forbes

People have been showing pictures of their Munchkin installations here on The Wall; radiator systems and radiant systems and all kinds of system piping; injection, mixing valves, straight boiler feed, etc. and it seems to me that people are not paying enough attention to the minimum requirements of the boiler in order to make it condense. After all, why pay so much for a condensing boiler when you've designed a system that has return water temperatures above 140*.

So far, I have only used a Munchkin when there's a radiant heating system connected. That keeps the return water temperatures down. But what about reset controls? We should not be using an injection system or a 4-way mixing valve since they will provide high return water temperatures; instead, we should be using boiler reset or 3-way mixing valves. Or, if it's a budget system, setpoint control, i.e. set the boiler operating limit for design temperature operation.

Am I way off here?





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Mike T., Swampeast MO

Not off at all

The idea of using an inherently low temperature heat source on a system of high temperature requirement seems really strange. Stranger still when the piping is arranged to keep return temps UP!

I can understand using a modulating burner on a micro-zoned system that requires temps above condensing as long as it is controlled so the burner actually modulates. As I understand the current Munchkin, you get either modulation OR reset. Trying to reset such a system (high-temp, micro-zoned) you'll be back at square one regarding short-cycling.

This probably has a lot to do with the upcoming control changes to the Munchkin. As I've heard it described, it should be able to handle modulation, micro-zoning and reset simultaneously without regard to return temperature or rate of flow through the boiler. This is quite a tall order, so hope that the programming is up to the task.

Remember that many (most) old systems with cast iron rads are EASILY satisfied with return temps well below condensing at all times.