As we head into the chilly portions of our Colorado fall season, and eventually winter, I look forward to performing operating tests on the hydronic and radiant window systems serving Hydronicahh.
Most people with common sense shut down their summer homes and return to the comfort of the city during the winter, except those people who relish long traffic jams caused by the people who drive like they ski, and people, like me, with a mission to research and develop out-of-the-ordinary comfort systems. Now that I have all the comforts of home, I can safely spend the night, avoid long, slow traffic lanes of the ski resort masses headed back to the city, and have a quick, safe comfortable drive home come Monday morning.
What normally is more than an hour commute between Hydronicahh and Denver can easily turn into a three to eight hour trip, depending upon road conditions, and the driving habits of those on the highway. Now that I have a reliable, comfortable, efficient comfort system intact, I can avoid the rush of homeward bound skiers, and do some research on these wonderful systems I have installed.
In particular, the radiant windows, which other than generating comfort beyond belief, hold the greatest potential in my mind for significantly reducing energy consumption of the dwellings we are trying to keep comfortable. Only time will tell, and I have numerous scenarios where I can monitor the operating characteristics of the windows and the auxiliary heating systems to see the net-efficiency results of everything that has been applied.
The title of this column is “Hydronicahh — everything in modulation.” The reason I make this statement is that I have incorporated as much state-of-the-art controls and equipment to allow me to modulate not only the flame strength on the modulating boiler, but also the pressure and flow capacity of the pumps for distribution, as well as the on/off cycles of the radiant windows.
Theoretically, the only time that everything would be running at maximum capacity would be at design condition, which for this area of Colorado is -20°F. Does it get colder than that in this region? You can bet your bottom dollar it will, and hopefully, I will be there to monitor exactly what is going on in real time.
As it pertains to circulator modulation, the space heating system will be done with a circulator that will maintain a given pressure differential (constant head). This is because the dynamics of the three zones of hydronic heating will continuously change, based on solar input. As the solar input increases through either the radiant windows, solar thermal or passive solar aspects, the need for auxiliary pumping power will decrease.
On the solar thermal side of things, with the solar thermal being a drain back system, I will initially need a lot of head capacity to overcome the vertical height of the system, raising the water to the top of the collectors and filing the collectors, but once I have established a siphon on the downcomer, my need for energy consumption to maintain good flow drops significantly. I will incorporate a variable speed pump based on temperature differential.
The ground source heat pumps' loop field circulator will also not need to run at full capacity all the time, especially if I go with the five headed beast, and even if I get the opportunity to install a variable speed compressor, the need for a fixed constant flow is not there. I will want to maintain a given differential temperature across this loop, and I will want to consume only the wattage necessary to do so.
The hydronic wood pit will also require a variable speed delta T pump for it's efficient operation. If there is a roaring fire, then the pump's speed will be high, but the net-energy benefits will also be high, so the parasitic costs are justifiable. But as the fire burns down, maintaining a high rate of flow is not beneficial, and in fact could be detrimental to the copper heat exchanger due to the potential of hydraulic erosion corrosion. This is typical of the use of a variable speed pump, and one of the benefits that is commonly overlooked.
Maintaining high flow rates regardless of the demand potential creates a lot of excess wear and tear on system components that really needn't be. Here in Colorado, and especially at that altitude, design conditions occur for less than 4% of the time (normally 2% at the lower Denver altitude), so why should we run our circulators at full strength when the load and/or demand is not there?
Bear in mind that this home will have an active solar photovoltaic generation system on it, and every watt becomes extremely precious. Waste not, want not. Hence, everything in modulation.
This completes my series on the construction of Hydronicahh.
I will have update columns in the future as more time and exposure passes, and will keep you updated on the progress of the installation of the heat sources.
Tune in next month as we delve into the new and upcoming world of air source heat pumps and their application to our hydronic world.
Until then, hug your loved ones, and happy holiday season hydroncing!
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/936-7606.
All Mark Eatherton material in print and on Contractor's Web site is protected by Copyright 2009. Any reuse of this material (print or electronic) must first have the expressed written permission of Mark Eatherton and CONTRACTOR magazine. Please contact via email at: [email protected].