constant circ

Unknown

Unless you use really jazzy thermostats with PWM, then outdoor feedback will offer much more comfort with its longer cycle times and less off times. Efficiency, well that depends a bit on the heat source I suppose and whether it is being reset, more than the radiant temp itself.

Worried about a circulator? If leaving a light bulb on in a closet would make a noticeable difference in comfort, would that be worth it? Cause that's about the power usage you're looking at.

Warmboard offers a conundrum for efficiency, since you're probably only operating over a 20 degree water temp range (70-90 or so). The stuff does its job really well. So even if you're using a condensing boiler, I can't believe there is a huge difference in efficiency either way. However, for comfort I can very easily believe there is a difference. With the power of warmboard, if you don't control it with at least PWM or even better OR with indoor feedback, the stuff will be off more than it's on for a good chunk of the season.

"That's my opinion, we welcome yours" :D

Simply Rad_2

Constant Circulation-to be or not to be!

Something we are all going for but why. Is it just for comfort or its it truly more efficient. One of my contractors was putting me on the spot and now I am seeking answers. Does any one know of information discussing this subject. He did have a few valid concerns about the amount of energy needed to circ 24/7. What is the true amount of energy saved vs on/off systems.Any input would be appreiciated
Thanks Jeffrey

GMcD

Depends...

Standard engineering answer, but, the short summary is that constant circulation is best with these conditions:

High mass/slow response radiant systems like slab systems.

High, fast acting heat loads with high heating fluid temperature requirements (the bang-bang operation will result in noise from pipe and radiant surface expansion/contraction)

The general case for constant (or semi-constant) circulation is to modulate the heating fluid temperature to match the ambient heating load - you get a much more stable, steady state comfort condition with minimal radiant temperature fluctuations in the room. You can also cycle the circ pump based on feedback from a radiant surface temperature sensor, like a slab temperature sensor, or a sensor in the floor structure of a wood frame staple up system in the spring and fall and then only use the constant circ during the winter periods to maintain the stable comfort setting.

Mike T., Swampeast MO

Difficult if not impossible to give a "true amount of energy saved" as it all depends on the system itself.

At one end of the scale you have a low-mass baseboard system without any form of boiler temp reset and control via t-stat(s). In that case, constant circulation won't do much if any good and energy savings should be negative.

At the other end of the scale you have a proportional, fully reset boiler operating a system with proportional flow control devices (TRVs or FHVs) and variable speed circulator(s). In that case constant circulation is a completely integral part of the system operation (and its efficiency). Remove the constant circulation and you'll reduce efficiency of the ENTIRE system and comfort will suffer.

In the middle ground where you have boiler temp reset but no proportional flow control (wall t-stats still controlling). Add constant circulation and the comfort level should increase proportionally to the mass of the system and how closely the reset curve matches loss. Calculating energy saved (if any) will be extremely difficult. How many and how powerful the pumps REALLY comes into play.

Simply Rad_2

What about low mass and low temps

I am using warmboard on a few projects and wondering if constant circ is the best solution-low mass and low supply temps. Or should I set it up for design and just leave it for fast reaction time.. I feel the outdoor feed back offers more comfort than on/off. What are your feeling
Thanks Jeffrey