November 8, 2011
The thing about installing a radiant hydronic system for one of your customers is that sooner or later that customer is going to expect the thing to produce heat. Look, all sarcasm and funny business aside, the simple fact is if you're installing radiant hydronic heating or cooling systems in either a residential or commercial environment, the heart of that system is going to be a boiler.
You can add solar and you can add geothermal but it's going to be a boiler that will be doing the actual work of keeping the system in balance, making sure water going into the system is neither too hot nor too cold, and generally watching over the system to make sure it remains happily operating at optimal temperatures, no matter where the currently circulating heat may have been generated or whether it will be used for household or commercial purposes.
In a non-condensing boiler, fuel is burned, heat is passed through a heat exchanger to warm up your water and then all those exhaust gases go up the stack and into the environment. A condensing boiler collects some of the exhaust gas headed up the stack-namely water vapor-and removes its latent heat by condensing the water vapor.
Condensing boilers sold in the U.S. are equipped with a miniature onboard computer that varies the unit's output according to demand. Conventional wisdom has it that conventional boilers operate in the neighborhood of 80 percent efficiency, but nearly all residential modulating/condensing boilers on the market run at efficiencies approaching 98 percent or more.
An example would be the big Rheos + models from Laars in the photo opener. Rheos boilers, a part of many commercial systems, start up at low fire (50 percent) rate, and then increase the firing rate up to 100 percent depending on the load. Couple this with efficiency up to 90 percent and a high density copper heat exchanger that maximizes heating surface and you've got yourself the beginnings of a very efficient building.
On the more residential front, the company recently introduced to market the Mascot II, a compact, 95 percent efficient wall-hung unit with zero-clearance installation.
The boiler is designed for ease of installation and serviceability, with built-in condensate trap and auto air-elimination vent. Setup is easier with full access to both the gas valve and control panel at the same time. Also included is a sealed condensate trap that doesn't need to be primed at startup.
Changes are coming down the pike for the familiar XFyre modulating/condensing commercial boilers from Raypak. Introduced in 2009, the XFyre boiler line was expanded in 2010 to include five models ranging between 300- and 850 MBtu with up to 99 percent efficiency.
"In November we will be announcing a first for North America, initially on XFyre," said Raypak marketing consultant Stan Young. "This is an all-new, integrated control platform that is modular, scalable, and will allow software upgrades. This new control system will be incorporated into all Raypak product lines by the end of 2012."
At Lochinvar, suppliers of the popular Knight-branded boilers, the Knight FT modulating/condensing units represent the company's newest in radiant boilers.
Lochinvar Knight Wall Mount fire tube boilers are available in seven models with inputs from 55,000 to 399,000 Btu/h. The company's Smart System control features a built-in cascading sequencer that allows up to eight units to be installed, delivering up to 3.2 million Btu/h. Again, these wall-mount units offer up to 99 percent thermal efficiency and low-NOx emissions.
A.O. Smith's newest line of commercial boilers for both domestic hot water and radiant hydronic use are the XP and XP Automatic Circulating Water Heaters.
XP represents the latest in high-efficiency fully condensing boilers from the company, offering outputs ranging between 920,000 and 3.4 million Btu/hr. XP models have control features with a touch screen user interface. The control operates each of the burners as a separate boiler, which means it's able to send error messages about problems with one burner while activating another-thus preventing system shutdowns.