TACO Bumble Bee

[Coal Reaper]

no, and i dont know that i will mess with it. all i am trying to do is send the coolest water back to storage that i can and still be able to satisfy heat damands in the house. essentially sending return water away after the usable BTUs have been removed. currently i am sending 100*F water back to storage regardless of supply temp. BB adjusts it speed to bring the primary loop up to operating temp and then dials back in order to maintain the set point temp. this is working well right now but i may need to increase set point temp as we enter winter months.
i did find a blog on tacos website that discusses BB with regards to deltaT that may or may not be of some use. every post argues why deltaT (specifically the bee) is better than deltaP so take that FWIW. there is a link at the bottom to the previous and next post.
(broken link removed)

 

[ewdudley]

no, and i dont know that i will mess with it. all i am trying to do is send the coolest water back to storage that i can and still be able to satisfy heat damands in the house. essentially sending return water away after the usable BTUs have been removed. currently i am sending 100*F water back to storage regardless of supply temp. BB adjusts it speed to bring the primary loop up to operating temp and then dials back in order to maintain the set point temp. this is working well right now but i may need to increase set point temp as we enter winter months.

As you're seeing already this works nicely for controlling and minimizing return temperature to storage. Like you say, as conditions change you can adjust the return temperature so it's high enough.

i did find a blog on tacos website that discusses BB with regards to deltaT that may or may not be of some use. every post argues why deltaT (specifically the bee) is better than deltaP so take that FWIW. there is a link at the bottom to the previous and next post.
(broken link removed)

As for delta T, that poor Taco guy is all over the map. Here's an example of his reasoning:

The Universal Hydronics Formula expresses this analogy mathematically:

GPM = BTUH ÷ (ΔT × 500)

BTUH is the heating load, which changes all winter long depending on a whole bunch of factors, including the weather. GPM is the flow rate required to deliver the BTUH. That flow rate changes in lock step with the BTUH heating load. The greater the heating load, the more GPM is needed, and vice-versa.

He says over and over that if the required heat goes from say 40,000 BTU/h to 20,000 BTU/h then just hold deltaT constant and the HEC-2 will adjust flow to give just the right amount of heat.

This would make sense if you put your emitters on your roof, buy they're inside and they see about the same temperature all winter long. When it gets colder outside the deltaT of the emitters changes very little, so there's very little for the HEC-2 to react to.

So no, flow rate does not "change in lock step with the BTUH heating load". To model the physical world he needs a lot more than a simple algebraic definition.

Now if you have multiple zones then deltaT would change as zones go active and then go inactive, and then the HEC-2 would flow more for more zones and less for fewer zones, same as a constant head pump.

 

[Coal Reaper]

While i agree with you, my take away was that deltap circs work good. Perhaps too good. Says they overpump in most situations. And that deltat would accont for this and only provide the min flow that is required in order to maintain that deltat. Now i have zero experience with deltat circs, but couldnt somebody that mildly knows what they are doing size it correctly such that it would react very similar to deltat? Seams to me that they both can perform the same function. I am struggling to see why one is better than the other in different applications for multiple zones.

 

[ewdudley]

While i agree with you, my take away was that deltap circs work good. Perhaps too good. Says they overpump in most situations. And that deltat would accont for this and only provide the min flow that is required in order to maintain that deltat.

Again, he keeps saying that deltaT will go down as outside temperature goes up. This is true only to the small extent that the emitters will see slightly higher temperatures because it's warmer near the floor, convection flows up past the emitters will be slightly slower, and the warmer walls will absorb less direct radiation. By and large, if you pump 180 degF water into an emitter sitting in a 70 degF room, the deltaT will not change all that much as outside temperature increases. Therefore his claim that a deltaT pump will slow down significantly in response to increases in outside air temperature is plain old flim-flam hand-waving.

Now i have zero experience with deltat circs, but couldnt somebody that mildly knows what they are doing size it correctly such that it would react very similar to deltat? Seams to me that they both can perform the same function. I am struggling to see why one is better than the other in different applications for multiple zones.

For the situation of needing more flow for more zones and less flow for fewer zones either deltaT or deltaP will both generally tend do the right thing. DeltaP is simpler and should be preferred for that reason.

But for controlling a temperature according to flow like you're doing with your return to storage temperature control then a temperature controlled ECM pump is just the ticket.

 

[Coal Reaper]

Gotchyah