How would you control a Bumblebee circulator in a pure TRV situation?

Eastman

not contrived

"Admittedly, I'm using a contrived example to illustrate my point..."



I do not feel it is contrived at all.  Perhaps one is dealing with a significant solar gain issue.  Let's say you have a well balanced home run panel rad system connected to a modulating heat source.  Normally, a tuned ODR curve keeps the system in equilibrium with long cycles infrequently interrupted by the thermostat.  But the southern exposure of this solar orientated home seems to get clobbered.  TRVs are employed on half the rads to solve the problem.  What happens when the sun hits the glass?  The rads on the south side throttle down flow to reduce their AWTs.  The rads on the north side must logically increase their AWTs to balance the bumblebee's fixed delta T enforcement.  North side overheats.  The thermostat, probably located in the center of the house, ends the call for heat.  The same problem, but in reverse, happens for a windchill at night.



Both a fixed speed pump and fixed delta T pump will suffer to a degree from this problem, but a fixed delta P pump will not.  (The optimal ODR curve is different though.)



Suppose a bypass is employed.  This implies one is pumping water that doesn't get used.  And, if the bypass is at the rads, the thermal distribution losses on the returns are being raised unnecessarily.  For a single distribution pump solution at the residential level, surely any possible electrical efficiency gains of a couple ten's of watts are totally offset by these inherent disadvantages when dealing with a system making extensive use of TRVs.



What about a more suitable system?  Gordon's final question really launches this thread into a new subject:  (suggest starting new thread)



"So then, the question is: does it make sense to bump up the supply

temperature in order to obtain a lower return temperature, but at a

lower flow? And to what extent, if any, does it make sense to do that?"



When does it make sense to use a fixed delta T, a fixed delta P, or a fixed speed?  And why are these are only options?  Surely neither of these schemes will produce the optimal solution as a given moment for a given system.  What would?  What hydraulic characteristics should we take note of?  What variables should the pump measure?  What parameters should be adjustable?

knotgrumpy

HR said what I was trying to say...

"There is a point when the heat output from a convector drops quickly at low supply

temperatures. Output charts show this clearly. So if you are running a

system on ODR and forcing a ∆T would you not at some point run out of

"driving temperature" and virtually no heat output from the panel rads

or fin tube? Even in mild weather conditions buildings need some heat."



I would think version 2.0 of the Delta T circs are going to interface with the ODR, or incorporate ODR into the pump itself. It doesn't make sense to enforce the very specific design delta T throughout the entire season's worth of varying heating curves.



I've seen ODR supply temps at 105F.  To reduce return temps to 85 degrees system wide is not going to be efficient.



Having said all of that, I think my current monstrosity of a 5 pump monoflow system would probably buzz along pretty sweetly most times on 5 BumbleBees because each pump would be adjusting to each individual zone's particular efficiencies and deficiencies.



The pressure will not change, so no need of delta P adjustments, but the cast iron convectors on one circuit definitely don't give up the BTU's as fast as the 3 column radiators on another zone.



Be really neat if I could get it down to 4 zones with the Bees mounted to a Caleffi Hydrolink ;-)

CMadatMe

I have to Disagree

A heating system source of heat is predicated on the heat loss at design temp. The water temp from the heat source is designed based on the needed water temp to over come that heat loss based on the delivery of a specific flow rate to deliver the btu/hr needed through a heat emitter. All of this is predicated on the universal hydronic formula of gpm = btuhr/ (delta-t x 500).



If I can deliver the proper btu/hr at design I can deliver it at any given time. The pump will move the btu/hr I need. It doesn't care about a specific water temp. It is the designers responsibility to make sure the emitter can take the btu/hr from the conveyor belt.



This is a heating system and as a friend says, not the space shuttle we are building.

knotgrumpy

Take a picture

Of a mini circulator for me!

Mark Eatherton

Mix-spelled German conference...

It should be called WISH, cause you won't be seeing most of those products on this side of the pond. Too many lawyers.



But you WILL see lots of good free beer :-)



ME

hot_rod

micro circs

already in circulation in Europe.

knotgrumpy

Now that's what I'm talking about, Hot Rod

They make so much sense.



In the picture on the left, do you know what sized pipe that it is attached to for some sense of scale?



On the right it looks like a Wilo display.

SWEI

Wilo display

Geniax is a jaw-dropper http://productfinder.wilo.com/repo/Graphics/00473791_0.pdf

Harvey Ramer

I have used the Bee and

delta-p both and I love them each and every one for who they Bee;) This Bee word is gonna go over big! The only Bee sting I got was when the sensor plug came loose from it's socket, generating a no heat call at 9 pm. on a cold windy night. I put it back in and it hasn't happened since. Probably didn't have it plugged in right in the first place.



Bee cool!

Harvey

knotgrumpy

That is a well developed system already...

Thanks SWEI !



I have always thought that radiant pex manifolds are analogous to electrical panels that are feeding circuits by Romex cable.  Distributing the energy captured in the water.



Looks like an electric distribution system.

tom3holer

Bumblebee issues

I have 2 Bee's to be used in my home heated with an Alpine 80.

I installed the first one on the primary boiler zone in the fixed "CP" mode. I did this as the graph showed speed 2 to fit the requirements of 5' of head and 4.2 GPM. for a D/T of 35* The LED does show 22 Watts which is correct for speed 2 but the GPM shows 9.5GPM. That is over 100% error. Is the accuracy of the GPM readout really that unreliable? I even throttled the ball valve back a bit and the GPM readout actually went up and the wattage went down to 14. I just want to make sure that I am flowing te correct rate on the primary of the P/S plumbed setup.



My plan was to use the two of them on the two larger zones of my three zone house in the D/T mode. There is some repipeing yet to be done to the zones so I  though I'd use one temporarly on the Primary to see how well it worked.



Has anyone had experience with these pumps to see if the PM readout is so error prone?



Thanks for any thoughts,



Tom

SWEI

what's your ∆T on high fire?

can't speak to the display accuracy, but the boiler controls should tell you what the water temps are.  Adjust the pump speed until you get what you want.

tom3holer

D/T's

SWEI,



Yes, thank you I do understand that but am not sure about secondary interference. Will not the zone's effect the the boiler rise? It seems that if I am flowing less than the boiler with one zone on or flowing all zones with more than the primary it will effect the rise. I was going to do as you suggest, as I have a clamp on digital temp meter that reads D/T, but wasn't sure what do do with the zones.

Thanks,



Tom

SWEI

sorry

thought this was on a boiler loop.  Why not just leave the circ in ∆T mode?

tom3holer

D/T

I had thought about that but am not sure of the reliability of the D/T mode with the use of sensors and all. That would be the way to go as it would keep D/T's the same no matter what the output. I just don't think that is a safe way to go in this  new operating mode till its proven. Any thoughts?



Tom

SWEI

∆T circs

have been around long enough.  ECM circs have been around long enough.  No reason not to trust the combination of the two. 

tom3holer

Setting primary flow

I am still a little uncomfortable using D/T as there is no way to set a min flow as a backup. I would like to set it by firing the boiler on high fire and setting the flow to get the 35* D/T as shown in the Alpine manual. My confusion comes with what to do with the secondary zones. Do they all have to be running?  

Tom

ced48

How Can You

ever get a delta t of 35 degrees on the boiler loop alone? The only way this kind of a delta t is possible is when a heating or other load is taking enough energy to get down to this level. Even with a "normal" heating loop, such a delta t is not likely.



I believe this is why boiler makers send such powerful pumps with their boilers. Many situations just don't make for the desired high delta t's.

CMadatMe

They Provide

The pump sizes they do because they are scared of who is installing them. By sizing the boiler pump for a smaller flow rate (large rise) it gives you the best chance of removing the btu/hr created by the boiler to the system side when piped pri/sec. The only time you need the full btu/hr out put of any boiler is when you are at design conditions and every single zone is calling.



The majority of the time the system cannot pull out the flow that carries the made btu/hr out of the boiler. No matter the rise chosen the only time you are going to get the full temp rise no matter a 20,25,30,35 is when you are under total design conditions unless that boiler flow matches what the system side is taking making the system delta-t the same. Its the flow the boiler pump is making that you want to be able to pull out to the system. Because what you can't pull out heads right for the boiler return.



Tom you cannot just open the zones. Use the charts for gpm and head and choose the correct curve. Unless today it's your coldest day of the year and the space needs heat you can't pull out the btu/hr created. You will never see a 35 degree rise!

tom3holer

Design Day

Chris,



Thank you for the reply. I do have a pump that has a curve that matches the required flow for a 30* D/T.



 I don't understand your statement:



 "Unless today it's your coldest day of the year and the space needs heat you can't pull out the btu/hr created"



I don't unerstand what the OAT has to do with it.  If its 60* outside and its 68* inside and I set all 3 Tstats to 72 and manually set the boiler to high fire with a water temp of design day, lets say 160 should I not be able to monitor the boiler rise and confirm my pump is pumping the correct amount? Yes, I realize it will not take very long to satify the Tstats, but it should be long enough to to the test.



You have a far greater understanding of these systems than I, and realize I am probably missing something.



Thanks,



Tom

CMadatMe

Because

There is no way in gods creation the emitter can pull out the btu/hr being delivery through the distribution system. If you don't pull out the btu/hr you don't cool the water so the delta across the zone will be small. Plus the pump is going to tell you how many gpm it's moving. Though not accurate, still a glitch in reading gpm accurately.

ced48

Taco Claims the GPM

readout on the Bumblebee to inaccurate, an estimate at best.



I agree that it is impossible to get the 35 degree drop in any standard heating loop, unless it's so long that the room to room temp difference will be noticeable.

tom3holer

Chris and ced48

Chris,



If all zones are on, and the house is over raidited with 198' of standart BB and 24' of Hicap, why  won't I be able to pull all the btu's from the 80?



ced48,



We are talking aout a D/T on the boiler loop not the zone side.



Tom

ced48

The Boiler Loop

on it's own can't possibly loose 35 degrees as it spins around a 10 foot loop, with nothing but the bare pipe as a heat remover, Can it? Please, someone explain if it can-