Split zone, 90º tee restricting flow to one side?

fiehlsport · November 2023

Problem: The left side of my house has baseboards that are slightly cooler than the right side. Measured with an IR temp gun, roughly 5-8ºF less at all points when comparing each side of the split zone.

It is fed from a 1"-piped zone that drops down to two 3/4" sections to the left and right side of my house. Single feed, dual return. Both sides of the house have roughly the same baseboard length.

My fear is that since the left side of the house is fed with the yellow arrow, it is not getting as much flow as the side with the purple arrow. Does it make sense that the water would shoot past the sharp 90º bend and tend to flow more to the purple arrow?

Pic in the next post...

fiehlsport · November 2023

Jamie Hall · November 2023

Indeed it would. The flow resistance in a straight line is... just the resistance in a half inch or so of pipe. The resistance in the leg of the T is much greater -- quite enough to make that sort of difference.

fiehlsport · November 2023

Thanks Jamie, reassuring that this might be my smoking gun. Finally found it in the basement ceiling behind some tiles.

Now, to solve this, I'll have to reduce down to 3/4" a little further back and implement some sort of U-Joint or "Wye,", correct? Not sure what the best way to plumb this would be to maintain flow equally on both sides in the limited space I've got up there between joists and drop-ceiling.

PeteA · November 2023

@fiehlsport
do you have valves on the 3/4 lines that can be played with a little to vary the flow and force a little more hot water to your cooler side to make it more balanced? I have a very similar setup and I learned a ton on one of my other posts asking questions about how that type of system works.

fiehlsport · November 2023

@PeteA I have valves on the returns where they enter the boiler at the very end of the lines. I have tried modulating the flow of the "purple" zone down to 50% with this method but noticed no change, unfortunately.

If that worked, I was going to get some Caleffi balancing valves on the returns to match the flow of each one perfectly, but my ball-valve balancing test didn't do much, so I didn't want to take the leap.

Jamie Hall · November 2023

Ball valves, due to their design, don't actually restrict the flow all that much until you get them a good bit more than half closed. Might try it again.

EBEBRATT-Ed · November 2023

@fiehlsport

You can fool with changing the piping but that is a useless attempt.

The best way is to install two balancing valves but if you can't get the temperature to change with the valves you have what are balancing valves going to do.

You could just install 1 balancing valve on the purple line to restrict it a little that might make the difference even with it wide open. 5-8 deg your not going to have to change the flow much to balance those.

The purple line goes down in temp 2 1/2-4 degrees and the yellow goes up 2 1/2-4 degrees and your there

fiehlsport · November 2023

Appreciate the insight from everyone.

Aren't balancing valves just ball valves that don't have big handles on them, with a flow gauge in GPM? Or are they "better" at balancing due to a unique design consideration?

My thought from the last year of considering this, was that fiddling with the ball valves on the returns was essentially doing the same thing, but blind with no actual flow data.

https://www.supplyhouse.com/Caleffi-132559AFC-3-4-Sweat-QuickSetter-Balancing-Valve-w-Flow-Meter-2-0-to-7-0-GPM-Lead-Free

Jamie Hall · November 2023

Valves valves valves... there are so many different types. Ball valves (and the related eccentric plugs) have a simple straight passage through them when they are open, and as you turn them closed the hole in the ball (hence the name) gradually loses alignment with the ports. Thing is, you have to get that alignment quite a ways off before the head loss starts to really increase.

A true balancing valve will be designed (there are several ways to do it) so that the change in flow resistance is much more linear from all the way open to all the way closed. Some are surprisingly linear, in fact. Globe type valves are really pretty good balancing valves. Depending on the geometry of the ports, some slide type valves (including the "ceramic" ones on many modern plumbing fixtures) can also be surprisingly good.

hot_rod · November 2023

Ball type balance valves work fine.
Pull the ring on the Quicksetter, put a wrench on the valve and immediately as you start moving it you will witness the flow change

Like any valve selected to be used as a control valve, sizing is important

I would not crank a ball type valve more than 70- 80% The flow path is not so smooth when shut down that much

But if you are cranking it down that much you probably have the wrong size valve and a grossly oversized circ

Look at a balance valve as a fine tuning device, it is not intended to make large flow corrections

With fixed and variable orifice type, the fine thread hand wheel allows you to make very precise adjustments , fractions of a gallon. If you need to be that accurate

Engineers tend to focus on a type of valve they are familiar with, and spec that valve their entire career 😉

I take 5 different types of balancing valves to an engineers office for training, explain the features and benefits of the different technologies

Variable orifice, fixed orifice, ball, PIC, and thermal balance valve

fiehlsport · November 2023

Good stuff… I’ve been tinkering in the basement all night, and have found that once I get the ball valve restricted to the point where the return temps start to balance out, the noise from the valve is unbearable.

And this is with a B&G ecocirc 20-18 pump, turned way down. Even at its slowest setting, way too much noise out of the valve.

Would a Quicksetter still behave like this, or is it quiet when reducing flow?

Though I agree, I don’t really want to go too low when the real fix is probably just to split the tee’d side of the zone into its own zone entirely.

hot_rod · November 2023

My first question would be what flow rate are you tying to balance down to?

Pros and cons to splitting into two separate zones. Better temperature control. But possibly more boiler cycling, or short cycling. Balancing the two circuits is the correct approach. Noise is from excessive flow against a cranked down valve, not a good operating condition.
At some point you could be inducing cavitation.
It's possible even on low setting you are over pumping the loops? Are you on fixed speed 1? That should be a fairly low flow position.

If one side is over-heating, you could close down the damper a bit. That reduces output on that loop and may boost the other split just enough. Easy enough to try if the baseboard has adjustable dampers.

fiehlsport · November 2023

Yes, I used the lowest constant setting on the pump for testing with the ball valve cranked down about 75%. I use proportional curve "A" normally, which is a bit faster at all times.

I suppose I'm not sure what flow rate I really need at this point. Some math is likely in order. If I slap two Caleffi balancing valves on the returns, will these valves create noise when the high side is balanced down a bit?

Hadn't thought about the dampers, yes, that should be an option for sure to keep some heat in there.

Another item of note, maybe helpful, maybe not, is that my return temps are only about 3-4F lower than the supply. I am running outdoor reset and supply temps have been in the 115-135F range the last few days. Outdoor temps ranging from 28-55F. Lowering the pump speed has had little to no effect on increasing the supply/return Delta T - I really want a 5-10 degree delta, at least, for max condensing potential until it's just not possible anymore in December/January... If I blast the pump up to a higher setting, the return delta is even smaller, at around 1-3 degrees. I don't understand how that's possible with 50 feet of baseboard heating my first floor.

EBEBRATT-Ed · November 2023

If your return temps are only 3-4 degrees lower than the supply temp then it is possible you are over pumping and your pump is too large.

Depending on what you have for baseboard the 16.5 foot side would be 9075 btu/hour or.9 gallons/min flow. The 32.5 foot side would be 17875 btu/hour 1.8 gpm.

That is very low flow and not much baseboard. Is that the entire house or just one floor.

Your probably way over pumping based on that.

fiehlsport · November 2023

@EBEBRATT-Ed I have a correction... both sides have exactly 24.5' of finned baseboard area on them. I screwed up calculating earlier and will edit the initial post.

Am I still over-pumping based on that data or does it change anything? This system initially had a Taco 007 on it, so that was definitely way too much. Just swapped the pump a few days ago.

This is the first floor of the home. ~1200sqft. The second floor is electric minisplits only, and the basement has a zone for around ~800sqft but it isn't used much.

Is there even a smaller pump that would fit my application? Maybe I should crank the B&G down to the fixed low setting? (Curves attached above in hot-rod's post)

I am thinking now that since both sides have the same amount of fin-tube, this 90º is more of my issue than anything. There has to be a measurable reduction in flow to the colder zone because of this, and the return temp would drop if there was more heat being transferred.

EBEBRATT-Ed · November 2023

You only need 1.34gpm for each side so 2.7 gpm total that is very low flow for the pipe size you have. 3/4" can flow about 4 gpm so 1.34 for each side is well below that.

bburd · November 2023

Balancing valves are probably the best way to solve this, but it looks from the photograph like that is a reducing tee and splits into larger pipe in the yellow direction than in the purple direction. If that's true, it's probably the main reason for your flow imbalance. There are probably elbows elsewhere in the loops that reduce the effect of the tee that Jamie mentioned above.

hot_rod · November 2023

If 2.7 is the required flow, that Eco on fixed speed 1 is not a bad choice.

If you do use a Caleffi Quicksetter it would be the 1/2". the 3/4 is a 2- 7 gpm range
1/2" is .5- 1.75 gpm range

fiehlsport · November 2023

Thanks - I think I will throw a Quicksetter or two on the returns where they enter the boiler room soon with a few 3/4" sweat --> 1/2" threaded reducers. Installing a Tekmar 400 control next week and need to save my pennies after that endeavor!

Couple more questions:

1) The 50' of baseboard on the primary zone likely pales in comparison to the length of pipe used to complete the loops around the house - does that have any bearing on what the pump speed should be? The circuits are easily 100'+ I'm sure.

2) Would the fixed setting 1 on the Ecocirc be too slow once the basement zone is activated? There's roughly 20-25' of baseboard on that zone. I'm going back and forth between using fixed speed 1, and the slowest Delta P setting on the pump - The pressure setting ramps up the pump very slightly when the basement zone calls for heat, which is a good thing I assume.

EBEBRATT-Ed · November 2023

You either sit down and calculate every fitting and piece of pipe but where will that get you? Try it and see.

fiehlsport · November 2023

😆 if only I could…. Drywall ceiling in most of the basement. Yeah, finned baseboard length works for me.

hot_rod · November 2023

It’s easy enough to boost the speed one notch if the system doesn’t keep up this cold season.

Split zone, 90º tee restricting flow to one side?

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