Hydronic Pipe Layout

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Kengie

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Hi there,

I am looking for some second opinion from the wonderful community here.

Previously I was using an oil based boiler and recently converted to a Naiven combi boiler NCB240-130H with a 3 zone smart thermostat and aluminum fin baseboard. While looking at the primary loop of the pipe layout, i notice it seems to be different from what the oil based boiler pipe layout to be. It seems now with the Naiven setup, the heating supply side connects / loops directly into the return side. If I remember correctly, in the oil based boiler setup, the heating supply side would go directly to the baseboard and after completing the loop through the baseboard. It would then return back to the boiler.

In regards to what I'm describe is in the second photo highlighted in the red rectangle.

Things I notice.
1. When previously using the oil based boiler, I would heard the baseboard stretching as I understand the boiler is sending 180F of hot water. Now with the combi boiler, that doesn't happen anymore. With this been said, are there setting to output at 180F with an outdoor sensor?
2. I know that the combi boiler is a mod condensing boiler with a outdoor sensor, but even in single digit temperature. The supply temperature hardly read 180F, it is mostly 155F - 165F.
3. This isn't accurate but placing a thermometer on the baseboard itself, it read 127F on the copper pipe. With supply temperature output of 165F, is it normal that there is a 38F temperature drop? There is about approx. 18 feet of vertical piping as I took the baseboard temperature on the second floor.
4. Another thing I notice is that previously the values was on the supply side when I was using the oil base boiler, while the pumps are located on the return side. The pumps are Grundos Alpha1 with variable 3 speed.

Attached Images:
20220117_134146L.jpg


20220117_134153.jpg


Thank you for your time and input.
 

fitter30

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Anybody's condensing boiler is 95% efficient with return water temp 130° or lower. Above 130° 86%. Boiler side should be piped with primary/ secondary loop with back to back tees or the Navien manifold system.
problems with your piping like to see spring check valves on the pumps keep water flowing backwards thru pumps that are off. Is the fin tube 1/2" or 3 /4" piping looks 1 /2" . Oiled fired boiler has very little head plus has a lot of water volume compared to a combi.
 

John Gayewski

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The "effeciancy" everyone is so happy to get has costs. Mostly related to comfort. Hot things feel nice. Efficient things aren't as hot so they save you money but don't feel as nice.

The secondary loops would generally return right next to the boilers inlet to keep the water as cold as possible as it enters the boiler, there by giving it longer run times and less cycling. I would have to have a whole lot of very specific info to be sure your system is functioning as designed. It looks to me like your supply lines should be where the return lines are and vice versa. However boiler manufacturers change their piping schematics frequently lately. And I don't think even with them in reverse as yours seem be to would effect the performance all that much, but like I said there's too mitch specific info I'd need to give a fully informed answer.

Do you have the schematic that came with the boiler?
 

Kengie

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Thank you fitter30 and John.

As mentioned from fitter30, in the middle of the schematic. It shows a dotted rectangle and if I'm reading the schematic right. It seems Naiven schematic is showing that the return is mixing / entering to the supply direction.

Which in my current setup based on my photo. It seems that my supply is mixing / entering to the return direction. Also based on the schematics, the pumps are placed on the supply side, while mines was installed on the return side. My pumps are Grundos Alpha1

Also with Naiven recommended manifold, it shows that the direction is return to supply direction.

Link to the Naiven manifold
Naiven Official Manifold Doc
 

Dana

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Thank you fitter30 and John.

As mentioned from fitter30, in the middle of the schematic. It shows a dotted rectangle and if I'm reading the schematic right. It seems Naiven schematic is showing that the return is mixing / entering to the supply direction.

Which in my current setup based on my photo. It seems that my supply is mixing / entering to the return direction. Also based on the schematics, the pumps are placed on the supply side, while mines was installed on the return side. My pumps are Grundos Alpha1

Also with Naiven recommended manifold, it shows that the direction is return to supply direction.

Link to the Naiven manifold
Naiven Official Manifold Doc

The Navien manifold is a hydraulic separator, necessary to guarantee minimum flow through the boiler no matter what the zone radiation flows are doing. The way your system is plumbed doesn't have a hydraulic separation feature, and the radiation flows interact with both the boiler flow and the flows from other zones.

With a high mass high flow/low head 180F cast iron beastie you got away with it, but ideally in a big primary loop system like that the supplies & returns from individual zones would need to attach at nearly the same location with closely spaced tees, each set of tees providing hydraulic separation between the zone flows and the boiler flow. As-plumbed the returns and supplies are well away from one another generating pressure differentials on other zones as well as on the boiler, affecting flow.

If the boiler were a low head higher mass type that would tolerate both high and low flows one could just break the loop (in the red rectangle) where the supply & return manifolds come together, capping each manifold off. But that will not work with the high-head Navien water tube heat exchanger, unless you inserted a hydraulic separator (such as the pre-made manifold) near the boiler, before the manifold connections.
 

Kengie

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Thank you for your reply Dana and very much appreciated.

nearly the same location with closely spaced tees
I took a measurement as it seems that the supply side are 5 inches apart and the return side are 6 inches apart.

At the current setup, is there any problems with it? Should I ask the plumber to redo it with the pre-made manifold (not the preferred option, as it basically criticize his work).

Any ideas as to why the Naiven doesn't keep a steady 180F (or near 175F) even in single digit outside temperature? I check the settings on the Naiven and there is a boost mode of 185F but after a boost of a while. The supply temperature would only hover around 156F ~ 165F. Can the Naiven output at 180F if there is extreme cold temperature? Reasoning for this is (sorry but comparisons with the oil based boiler), with 3 zones calling for heat. I notice the baseboard of the longest loop isn't generating much heat, rather it is almost just warm to the point i can rest my hand there for a long period of time. Compared to when the oil boiler, it seems to be much more heat generated then.

Something I also notice and curious about with a pump versus value setup (i'm a curious person). Then in a value system, any zone that wasn't open / on, the baseboard is cold. While in a pump system, it seems that even though the zone wasn't on all night, the baseboard would be a bit warm. Is it because in a pump system, there is possible water flow? While in a value system, water flow is completely shut down until the value is open?
 

John Gayewski

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The tees are spaced. The problem is that thr return water is before the supply. Your supply lines are always taking in return water.

You should have the option of running whatever temp you want at whatever frequency you want, but that would be tough with the pumps receiving mostly return water. You'd need a much faster primary pump to overcome the cold return water coming into the secondary pumps. That's not really a good solution though.

As far as it being an actual problem? Is your thermostat keeping up?

How does the system when it's really cold? Not what temperature are the pipes. What does the thermostat say?
 

Kengie

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Thanks fitter30.

Is the fin tube 1/2" or 3 /4" piping looks 1 /2"
Based on your first post reply, the aluminum fins are 3/4"

As far as it being an actual problem?
I wouldn't say there is a problem. Just getting an second opinion as I remember the piping of the oil based setup was that the supply loop never connects back to the return. The only way the heating water returns to the boiler is after it completes the loop. Then again I don't know anything about heating systems.

Is your thermostat keeping up?
I would say yes, but at single digit outside temperature. It is barely keeping up with all three zones on. E.g. Outside temperature is 8F, thermostat is set to 72F but the thermostat reading is 68F in the morning. With that being said, I wonder if this system will keep up when I add an additional zone.

How does the system when it's really cold? Not what temperature are the pipes. What does the thermostat say?
It's hard to say if it is really cold, I would say it's barely managing. Outside temperature above 20F, then I would say it is fine.
 

fitter30

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Here is slantfin fin tube see if fin size is close to yours. If it is can measure what u have.
Go to the literature down load 2 nd page.
 

jadnashua

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Slant fin radiators' output isn't linear...so making the inlet hotter gets more output faster the higher the inlet temp is.

For maximum comfort, your radiators would be getting heat nearly constantly, and adjusting the inlet temperature to account for the higher load when it's colder out. A well-calibrated curve on the outside reset should help, making the inlet temperature hotter to compensate for the heat losses. Longer cycles are usually more efficient than shorter ones. So, you may be rarely hitting that 180-degree inlet temp you were seeing very often (and maybe never, depending on the outdoor reset and the rest of the setup).

If the system can't hold the thermostat setting (and you aren't using setbacks, as the recovery rate may not be great, depending on the boiler output), you may need to adjust the curve on the outdoor reset to make it hotter when it gets that cold outside.
 

John Gayewski

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Thanks fitter30.


Based on your first post reply, the aluminum fins are 3/4"


I wouldn't say there is a problem. Just getting an second opinion as I remember the piping of the oil based setup was that the supply loop never connects back to the return. The only way the heating water returns to the boiler is after it completes the loop. Then again I don't know anything about heating systems.


I would say yes, but at single digit outside temperature. It is barely keeping up with all three zones on. E.g. Outside temperature is 8F, thermostat is set to 72F but the thermostat reading is 68F in the morning. With that being said, I wonder if this system will keep up when I add an additional zone.


It's hard to say if it is really cold, I would say it's barely managing. Outside temperature above 20F, then I would say it is fine.
You should be able to hit the thermostat setting. If your set at 72 and your only making 68 it should keep climbing until the boiler can't modulate down any further and has to shut off because your at 72.

Your boiler should only be running non stop when it's at or below design temp outside.
 

jadnashua

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How long a boiler can run constantly depends somewhat on how much modulation range it has and how well it is sized for your needs and the current load. The more modulation, the longer it can run, providing more comfort and efficiency.
 

Kengie

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Here is slantfin fin tube see if fin size is close to yours. If it is can measure what u have.
Thank you. I will review the info. It's a good learning experience.

you may need to adjust the curve on the outdoor reset to make it hotter when it gets that cold outside.
The outdoor curve for the low temperature (Outdoor Low Temp Set) is 55F and the high temperature (Outdoor High Temp Set) is set to 80F. The Outdoor Reset Curves is set to Finned Tube baseboard.
Naiven NCB240-130H Manual --- Outdoor Reset Settings are on Page 107.

You should be able to hit the thermostat setting. If your set at 72 and your only making 68 it should keep climbing until the boiler can't modulate down any further and has to shut off because your at 72.
You are totally right. The boiler is running all night, it isn't an issue as it is a mod-condensing boiler. Just seems to have a hard time keeping up. I'm also thinking of adding an additional zone and not sure if the system can keep up.

How long a boiler can run constantly depends somewhat on how much modulation range it has and how well it is sized for your needs and the current load. The more modulation, the longer it can run, providing more comfort and efficiency.
I see and that does make sense. I was just wondering how come the system doesn't output the max supply temperature (or at least closer to 175F) during extreme outdoor temperature especially when my area hits single digit temperature.
 

jadnashua

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I think you need to change your low-temp value on the outdoor reset control. Default is 14F, and depending on where in NE you are, that may be too high.

The longer the individual loop(s) are, the less even the overall heat will be as the water cools off along the way. It can be helpful to route your loop(s) such that the hottest water runs by the coldest area (often the walls) before it goes to the warmer areas, that can also help even things out.
 
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