Hey Dave, Since the BumbleBee is a variable speed circulator based upon Delta-T, can we consider this to be “Indoor Reset?” – Anthony, NY
Great question Anthony, ya know I was thinking the same thing the other day when I was doing a training class on some of the benefits of the BumbleBee. When you look at the Universal Hydronics Formula (and if ya don’t know it by heart, get it tattooed on the inside of your forearm or check it out here).
GPM = BTUh ÷ (Delta-T x 500) where;
GPM = gallons per minute flow rate required at any given point in time.
BTUH = heat required at that given point in time.
Delta-T = designed-for fluid temperature drop.
500= constant for 100% water.
So when you look at the formula, it always has to be correct on both sides of the equals sign. That’s the law! The BTU’s are constantly fluctuating based upon the temperature fluctuating inside and outside. If the BTU’s change and the Delta-T remained the same, then the GPM has to change. This is what the BumbleBee does. We need to make the math right. Again, it’s the law. I see where you are coming from in thinking that the BumbleBee can be considered Indoor Reset. An Outdoor Reset Controller utilizes an outdoor sensor to make any calculations for the component. The BumbleBee is reading the heat that is delivered indoors (Delta-T), varies the gallons per minute and therefor can be considered Indoor Reset. What I have experienced in my own home is that my thermostat does not overshoot its target indoor temperature anymore. The system now delivers the heat that is lost at that moment of time and it makes my home more comfortable.
Hey Dave, I just finished watching the Bumble Bee Video. Is dead heading the pump a problem, assuming no zones are calling for heat? And the answer in the video was; “The bumble bee sensing no delta T would ramp down to a minimum”. So I have a follow up question, If the system sits idle for an extended period of time with no noticeable delta T, are we assuming the supply and return piping must cool at the same rate to eliminate the potential for the bumble bee to start ramping back up? – Dave, AK
First of all, thanks for watching TacoWorld and for those of you that missed it live and want to watch the recording, check it out here. This is a great question and the answer is “Yup, kinda?!” However, it is best to connect the BumbleBee to a circulator relay and turn it off when the call for heat stops. The most efficient pump is the one that is OFF! When the call for heating returns, there is one feature built into the logic of the controller that the circulator will ramp up to full speed for 3 minutes in order to start moving the water around and have an established Delta-T. Then it applies the calculations needed to control the speed of the circulator. It is not looking for nor calculating the rate of cooling for a given system, just the Delta-T.
Excellent gents, keep ‘em coming. You can either leave a comment here or email me here
dhblogtaco.wordpress.com 
Hey Dave, Why the 3 minute start time? The good ole VDT used a 30 second. Any talk about adding a feature allowing installers to adjust the start time in the field? Any talk about 0-10VDC for communication with let’s say I-Worx?
Chris, The 3 minute run time on start up to make sure that there is enough of a temperature drop before adjusting the speed. We also don’t know what type of system it would be connected to, it could be connected to a RFH system will real small pipe (=low flow) or large hydro systems, we just never know. We may come in the middle with future circs. I don’t think it would be a field adjustable item. 0-10v is a possibility that the engineers are looking into. Thanks
I’m curious about the BumbleBee’s operation with TRV’s. My thought is that if the TRV were to reduce flow to the radiator wouldn’t that result in increasing the dT, so if a BumbleBee were installed wouldn’t it simply speed up to overcome the restriction caused by the TRV and thereby negate (or at least reduce) the TRV’s designed effect?
Nevermind, found the answer in http://jbblog.flopro.taco-hvac.com/rock-the-boat/ and http://jbblog.flopro.taco-hvac.com/clap-for-the-wolfman/
Your thermostatic valve itself should have built in bypass thus negating that problem. As the thermostatic opens and closes the pump will react to the changing delta-t.
Tyler, you beat me to finding your answer!
Enjoy