Balancing a reverse return system with different emitters?

delcrossv

I recall reading that with a reverse return system, it's best/necessary (?) for the emitters to me of the same "type" so as to have similar resistance to flow. Issue is, no one lists "drag per section" for these.

So, if I have, say, a loop with varying sizes of CI rads in the bedrooms(based on room size / heat loss) and put a baseray in the bathroom am I asking for trouble? Or do I have to install some balancing valves on the smaller- less drag emitters and do pressure drop measurements?

Also, does it make sense to reduce main size as I get to the end of the supply line or just go with constant size based on total emitter load for the loop?

Lastly, any recommendations for hydronic system design books-with calculations?

Teemok

I reduce pipe size at the ends based on flow needs but mirrored manifolds works fine. If you have the luxury of time balancing can be done with simple valves. Tuning each by measuring the delta T of emitter. Or do the math for GPM and install fixed flow device like Caleffi flowcal. (X) ft of emitter at (Y) SWT = BTU. Find the total capacity of emitter via per ft or section rating. GPM x 500 x DeltaT= BTU. Solve for GPM for each emitter

Big Ed_4

You need to size the radiators to what is needed per room . Balance the system with TRV's if you can. Adding an outdoor reset would balance it further ....

hot_rod

Ideally the radiator is matched to the room load, if not a balance valve or the wheel type angle valve could be used.
A TRV would give you temperature control and balance.
A delta P circ would also help balance if you go with TRVs

A lot to learn about the various balance valves

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_8_NA_Hydronic balancing.pdf

Teemok

If balancing/tuning using the delta T method, the rooms air should be at temperature. I do a rough tune to make sure all emitters are getting decent flow heating up then I wait for the structure to stabilize at 68-70F then with the boiler system at full operating temperature measure delta T's for each emitter and tune for desired drop. Note: If some emitters are in series the delta T is across both or all of them.

EBEBRATT-Ed

@delcrossv

Resistance to flow is not the main issue. It is the type of radiation on the zone. Cat iron rad heat slowly and hold heat longer and cool slowly. Finn tube baseboards heats fast and cools fast that is why they should not me mixed on the same zone.

Teemok

Agreed. It seemed the mix was already done. It would be balancing more than just delta T's. Different cycles and outputs make it ill advised and yet people balance poor setups the best they can all the time. Thanks for clarifying that it's not that easy.
Living in north CA, problems with mixed emitters aren't as pronounced as I imagine they would be where it is continuously deeply cold. It's definitely playing on an easier setting here. There's more less than ideal set ups that pass as working good.

delcrossv

@EBEBRATT-Ed CI radiators and baseray. No copper fin tube. Question is the different "drag" between the baseray and the upright rads.

Good to know about mixing fintube and rads!