Balancing Uponor TruFLO manifold

Tristan

What is the formula to calculate what I need (gpm?, lenght of loop? output? size of pex?) for balancing a manifold and cast iron rads using flow meter?

Gordan

Download the CDAM from the Uponor site

It's all in there. Desired flow through each branch will be based on radiator output and heat loss calculations.

Dave H_2

in struction sheet

is located here for balancing, page 2

http://www.uponorpro.com/~/media/Extranet/Files/manuals/radiant/TruFLOWClassicMfld_IS_06.aspx?sc_lang=en



Dave H

Tristan

Balancing

I can't download the CDAM on Uponor website. How can I determine the flow

(gpm) and pressure drop (ft/hd) for each loop onthe manifold?

heatboy_30

ADS

Without doing the heat loss and radiant design with Uponor's ( or other) software, there is no way of knowing.

Tristan

Help needed

Despite the fancy flow meter gauge. I have no idea how to balance it.

Here is a bit more details. I have 8 loops, feeding 8 cast iron rads with TRVs.  The water is pumped via a single  Alpha circulator.  Most of the literature that I found online refer to floor radiant design.

What I know is that  I should completely open the flow on the loop with the most resistance then slowly decrease the flow from most to least resistant loop.

Also, the fact that I have the Alpha, which modulate the flow constantly, would that put my setting out of whack?

Anyone who has a grasp on this? I need guidance  on the procedure and how to find the data for balancing formula?

Thanks,

Tristan

bob_46

Balance

With trv's on every radiator and an alpha pump the system will constantly balance itself.

Leave the balancing cocks wide open.

heatboy_30

I should read...

...entire post.



Bob is correct. With the Alpha pump and TRVs, it will work. You can check the temperature drop across each radiator, which may or may not be easy depending on water temperature control, and adjust flow. Might be splitting hairs at that point.

Tristan

A few more questions

Very helpful, thank you very much. However, I am still confused about what would happen when all TRVs ask for heat at the same time? Isn't the case that water  always take the least resistance loop, thus favoring one loop over all the others? Could someone explain to me what would happen? What can the Alpha do in that case? pushing more water?

SWEI

constant pressure

As you more TRVs open, the resistance drops, so the flow increases, keeping pressure drop constant.

Gordan

To elaborate...

...upon what the others have said.



Let's say you're starting up the system for the first time or you're coming out of deep setback. All the TRVs are wide open. The "shortest" loop (with the least pressure drop for a given amount of flow) will get the most flow, but others will get some, too. Pressure drop through a branch is not constant; it goes up nearly with the square of the flow through the branch, whereas it only goes up linearly with the length of the branch. So all the flow will never go through the "shortest" branch. Eventually, that zone will start nearing the temperature that's set on its TRV and the TRV will begin throttling flow through it. The other zones will lag behind and their TRVs will not throttle as much, so this will result in a greater amount of flow through them. Eventually, one by one, like dominos, the TRVs for each zone will "settle" on the amount of throttling required to keep their zones at the set temperature and the system will reach a relatively static balance.



Now, it's not necessarily true that one should rely exclusively on the TRVs for all the balancing. For instance, if you're on outdoor reset and your curve proves to be too low for a particular set of circumstances, it could happen that the "shortest" zone or two steal too much of the flow and aggravate the under-heating in other zones. In general, the best thing to do would be to have the flow through your zones roughly balanced without relying on the TRVs. This is especially true if you already have the fancy balancing valves! Then each TRV has best "authority" over the flow through its zone, and affects other zones the least.



One simple thing you could do is balance all branches for equal flow. Longest branch wide open, and then proceed in sequence of branch length to dial down flow until the flow gauges indicate same flow as the longest branch. Do this with all TRVs wide open - highest setting. This is theoretically not ideal unless all zones call for equal flow (based on your heat loss calculations and the emitters in the zones) but it's considerably better than not balancing at all, and in practice may be close enough.

scott markle_2

Self balancing

If the manifold has meters and you want to justify the expense, then go ahead and do some tweaking, it may not have much effect on system performance because the Trv's are such a great automatic balancing device. It's super easy to balance with an alpha on constant head mode because as long as you have some residual pump capacity making one adjustment does not effect another. (Ie restricting one circuit will not force more flow to the others.)



Make sure the Trv's are all wide open and then make some estimations of the design output you expect from each radiator. Using the universal hydronic equation figure your flow rates. (1 gpm moves 10kbtus at delta 20)



I agree with bob that you don't need the balancing manifold but since you have one, and your using an alpha it's fun to see what's going on. Probably the most useful part of having the flow meters is determining how low you can set the constant head setting (the three position ramp icon) on the pump. if your doing full reset and constant circulation (which you really should be with the Trv's).

Tristan

Thank you!

@Gordan and everybody else, kudos to you all to help a newbie figuring out basic balancing with  TRVs. Again, this was a huge help.

Tristan