- Residential Market
- Light Commercial Market
- Commercial Market
- Indoor Air Quality
- Components & Accessories
- Residential Controls
- Commercial Controls
- Testing, Monitoring, Tools
- Services, Apps & Software
- Standards & Legislation
- EXTRA EDITION
Articles by John Siegenthaler, PE
The following formula has been around the North American hydronics industry for a long time: Btuh = 500 x gpm x delta T. It can be used to estimate the rate of heat transfer into or out of a device that has a stream of water flowing through it at a known flow rate, and with a measured temperature change between the inlet and outlet of that water stream.
In newer modulating/condensing boilers, many of their heat exchangers had to sacrifice two very desirable qualities in the interest of being small and light.
A cool concrete slab is like a black hole for Btus. It gobbles up any heat that dares to get close. The solution is to install a mixing assembly operated by a controller that measures the boiler’s inlet temperature, as well as the water temperature supplied to the distribution system.
When it comes to the difference between energy and power, our industry tends to get sloppy with its terminology.
A tradeoff has always existed between the water temperature at which hydronic heat emitters are sized and their cost. The higher the supply water temperature assumed by the designer, the smaller the required heat emitters and the lower their installed cost.
While I agree that heat pumps do move heat from one location to another, I strongly disagree with the premise that air-source and geothermal heat pumps are not renewable-energy heat sources.