System Design with Differential Temperature (Delta-T)
North American residential system design is pegged to the temperature differential between the supply and return (Delta-T). It's part of the Universal Hydronics Formula, it's how we size boilers, select pipe size and determine the amount of radiation to put into a room. We also zone our systems and turn them on and off via a thermostat on the wall- all in an effort to deliver comfort.
Smart Delta-T Circulators
If we use a Delta-T based smart circulator in these North American systems, like the Taco Bumble Bee or 00-VDT, it reacts to how many zones are open, which zones are open, and even how cold it is outside, automatically - without an outdoor sensor. These infinitely variable speed Delta-T circulators deliver ONLY the BTU's required to match the actual heating load required by each zone. The entire system runs at peak efficiency, no matter the time of year, accurately providing optimum comfort and real electric and fuel dollar savings.
On the other hand, Delta-P ECM circulators operate best on constant circulation and utilize thermostatic radiator valves (TRV's), instead of thermostats, to control the flow to panel radiators. As the TRV's modulate open and closed, the pressure in the system changes and the Delta-P circulator speeds up and slows down to compensate for the change in pressure.
In North American systems with on-off zone valves, those pumps read the number of zones in the system, assign a fixed speed for each open zone and switch motor speeds depending on which zones are open. It's like having a pump that automatically adjusts itself to the number of zones that are open. It's important to know that if you prefer to zone with circulators, Delta-P pumps never vary their speed - they work just like a single speed pump.
Which to choose?
If comfort delivery and efficiency are your goals than choosing the right circulator based on the system design can make all the difference. Delta-P circulators only adjust to changes in system pressure. Delta-T circulators measure the temperature difference between supply and return and infinitely vary their speed to deliver spot-on efficiency, compatibility, and comfort. Then add Zone Sentry Zone Valves and Taco Controls for the most efficient comfort system available anywhere.
Variable Speed Pumping: Where to Use It, How to Use It, and Why to Use It.
The Universal Hydronics Formula
Steep Curves, Flat Curves, Variable
The Bumble Bee: Out of the Hive and
Into Your Basements
FloPro Variable Speed Delta-T Blogs
00-VDT: What You Should Know
Download this valuable reference tool
Proof of Delta-T's Superior Efficiency
This graphic demonstrates a powerful comparison between Delta-P and Delta-T. (You must have pop-ups turned on.)
Circulator Motors the Game-Changing Power of Delta-T Operation
"Providence Housing Authority: A
Delta-T and Variable Speed Trade Articles
winning combination."- PM Engineer
"Variable Speed Circulation: The Simple
Facts" - PHC News
"The Art of Variable Speed Pumping
to a T" - HPAC Engineering
"Variable Speed Pumping" Feature
Article - HPAC Engineering
"Achieving Pump and System Best
Efficiency Point" - Mechanical Business