Variable Output Circulators. Delta-P Vs. Delta-T

When considering between the Grundfos Alpha and the Taco Bumblebee circulators, what are the advantages (and disadvantages) of one type over another when used in a zone valve and single circulator environment?

Specs are about the same. I have been using the Bumblebees because the price was promotional. Grundfos is excellent also, so kinda a personal decision. Both will work on your zone or single circ situation. The proper answer is as Sting says: Depends. Some folks like a Besseme(Mercer/BMW), some like a Chevy/Dodge/Ford.......they all get you where you want to go, reliably.

After doing some research I came across the Taco argument that Delta-P is not to be found anywhere within the standard hydronics formula which states that:

GPM's required = BTU's/( 500 x Delta-T)

And obviously Delta -T is found within this formula.

Based on this, along with whistlenut's success with them, I'm now starting to lean toward the Bumblebee as opposed to the Alpha.

Only one issue (question) remains. When the system gets a zone T-Stat call for heat and the zone valve opens and the circulator starts up, if the zone has been sitting idle for a log time and the water within it has thereby gotten as cold as it can get, under these conditions the initially returning water may be only perhaps 60 degrees, vs. the supply at say 180 degrees. This means an initial Delta-T of 120 degrees between supply and return. if the Bumblebee circulator is set up to deliver a Delta-T of the ideal 20 degrees acorss supply and return, what on earth will it do if it sees a Delta-T of 120 degrees?

120* Delta T is bad no matter what the pump...you would have a bigger problem to solve than what pump to select.

Where's Sting?

Since my differential pressure bypass valve allows for some degree of hot water going directly from the supply to the return manifold I don't think I ever actually see this extreme degree of Delta-T, but it must still approach 50-60 degrees for brief periods of time. Also, my individual zones have only 4 to at most 5 gallons of water within each loop.

That said, I was considering removing the DPBV if I ever install a variable speed pump, believing that the two will fight against each other.

lsayre wrote:After doing some research I came across the Taco argument that Delta-P is not to be found anywhere within the standard hydronics formula which states that:

GPM's required = BTU's/( 500 x Delta-T)

This formula is only an approximation it makes an assumption the pumped water is 60 deg F. Not at all the case in a hydronic heating system. When you use this formula rather rather than a much more complicated design formulas that take into consideration more realistic boiler supply and return water temperatures you over design. That is, you choose a larger pump than what's needed. My memory may not be correct on the 60 deg number but it is considerably lower that typical boiler water temperatures.

I'm not familiar with Taco's control logic and how they use the measured temperature difference to vary the water flow. It may not make any difference at all because after some initial flow is established supply and return temperatures will be considerably different than at initial startup.

My longest single zone loop is not more than 140 feet. For 3/4" Type-M copper pipe, that would equate to 3.75 gallons. All of my zones summed together have a bit less than 13 gallons of water within them.

If you want to go Bee, wait a while because they are currently working on version either 2 or 3. They have been working the bugs out.
There has been some problems with excessive noise and programming issues. They're right on it though, also, the new ones are not yellow anymore.
I don't know what to say about the P/T debate........I used the Grundfos for one reason-to stop Honeywell ZV banging and to quiet velocity noise. It works........but I can't tell you how! Even the Grundfos reps have trouble.......it's very...shall we say weird how it operates. But, I have had zero problems with the 6 or 8 I have used so far.
I am interested in the Bee, but I'm going to give it another year or so first.
Wilo and B&G also have similar units.

Sometimes the price of admission AIN'T worth the 'ride'. I have had good luck with the Taco's and have used two Alpha's. Both brands were in higher end situations that had multiple systems, radiant all through plate exchangers, some antifreeze protected, some not, conventional radiation, even water to air ex-changers. In any event, we were not the first guys on the job, but after 7 other firms, we got it working as the heat engineers specked, and there were no 'Bee's' or Alpha's when these places were built. Re-piping and the Bee's made the system work VERY well and made for a happy homeowner.

EACH APPLICATION IS DIFFERENT, so never assume a canned response will solve the problem. Especially when some really good folks preceded you; folks you respect a great deal.
Thinking outside the box will NOT work for everyone, and many times a simple tweak will allow you to sleep for a few more nights.....until the next 'mind-twister' comes along..

Larry, are you trying to make your system do calculus for you, too? Close only counts in................... horseshoes and hand grenades.

McGiever wrote:.

Where's Sting?

The whipping boy is in the building laying near his dish
let me drop everything and take care of you right now!

This is not information that is relevant to my zone valve setup, but for those of you using zone circulators, Taco claims that the Bumblebee is the only variable speed circulator that will in fact vary its speed if used as a zone circulator.

From the Taco literature it seems that in order to get past the surge of cold water at first startup (I.E., my main concern as seen above) the Bumblebee always runs at full rated speed for the first 3 minutes. That could mean that with only one zone valve open the GPM's of flow being forced through the single 3/4" pipe for the first 3 minutes will be very high indeed. That could lead to velocity noise. To avoid the potential for such a water rushing noise when only one zone valve is open would lead me to believe that leaving the DPBV in place is perhaps a wise idea. It also means that the pump is obviously not monitoring Delta-T for the first 3 minutes after it starts running.

When set in “dE” or “SP” variable speed operating modes, the circulator will always run at full speed for the first 3 minutes to ensure consistent water temperature for the sensors.

If (as for me) the zones quite often only run for about 8-10 minutes, that means the Bumblebee is not doing what it is supposed to do for up to 30-40% of the time. That to me greatly decreases its value.

you are making so many wrong assumptions above - either you have not read what I write or you have chosen to ignore it

too much to refute from this access point = sky is dancing soomn that will kill my concentration

ill get back to you = tomorrow if you will listen

Kind Regards
Sting

I emailed my concern to Taco, and they promise a response within 24 hours.

Well then

lets see what the experts have to say

keep us posted - have your people contact my people -- Do Lunch???