Loops, more short ones vs fewer longs ones?

Dan R_2

I've got a question, it's not exactly an Earth shattering one but I've been going around with a friend about it so I figured I'd put it out here and hope for some feedback.



He and I are going back and forth on whether the potential benefit of more, shorter floor loops make sense vs. the extra fitting cost and labor associated with making it happen. In particular this is for an underfloor retrofit with open basement access using Joist Trak and 1/2" PEX but I suppose the question is probably more general than that.



Here's how I see it:



I think that the flexibility of more, shorter loops is worthwhile. The positives are that a smaller circulator is required, both because I've got more parallel branches for lower total resistance and also because my shorter loops will show less delta T even with a smaller flow. The smaller circulator will give me lower operating costs and the shorter loops with smaller delta T will probably give me better temperature consistency or at least equal with a much smaller flow. I think that lacing 100-150' loops with the manifold located right at the loop location is actually easier on the labor side than lacing up a 250-300' loop with a pull at both ends back to the boiler room even with having to get the manifold installed out where the loops are. I also think that with more short loops piped in a good reverse return you can get a lot closer to balancing the whole panel by design and avoid the "with flow meters and balancing valves" part of the description when you order or build the manifold.



Here's how he sees it:



Breaking the system up into more than the absolute minimum of loops is a pain in the butt and the extra fitting costs (manifold with two or more times as many outlets, etc...) and labor costs will never been gotten back in circulator electricity savings or fitting costs. You'll also wish that you had balancing valves to make the system work the way that you want when it's actually up and running no matter how well you think that you designed it (he might have added a "you dummy" at the end of that but I can't remember for sure, we were talking about this with mugs in hand).



Now I know that this stuff is rarely a one answer for all things kind of business so the answers above are both correct and both wrong at times. But, having said that, I'd sure like to know what you all think about it.

mor

Result=correct heat output

if all thing are equal then what one prefers is correct. You can be creative in staging the heat output with both methods. I usually opt for fewer parts to break and fewer point of service.

CMadatMe

I'm a little puzzled

Your talking about saving dollars because of labor and loop lengths but you are using 1/2" tubing and plates. How about 3/8" tubing and plates since 1/2" doesn't give you any more btus than 3/8" cost less and  is heck of alot easier to pull. We try to keep out loop lengths even across the floor.  Makes balancing a heck of alot easier.

Dan R_2

puzzling...

I think that you're bringing oranges to my apples discussion... Not totally sure about that so please correct me if I'm wrong. I guess that won't stop me from asking questions about it anyway though ;')



I probably don't have a good handle on the pricing but I had thought that 3/8" PEX was only 10-15% cheaper than 1/2" and that the plates were about the same for either size. Is that right or do I have bad pricing information? I might also have brand blinders on as I've been working with HePEX and Joist Trak.



I can totally see where pulling the 3/8" would be a lot easier but I think that my real beef with it would come from the head that it generates relative to the 1/2" . I'm probably only going to get about 60% of the flow (for a similar configuration) with 3/8" . That doesn't seem like a good trade-off to me.



Sorry if I totally missed your point, but those are my first thoughts anyway.

CMadatMe

I've been dealing with Wirsbo

since 1990. In the 20 plus yrs of doing radiant in residential applications I have never used a pump other than a Taco 007 or a Grundfos UPS15-58 for any application. Your pump does not need to overcome the total head loss of all the loops only the highest head. If it can overcome the highest it can overcome all.

I had thought in your original post cost of labor was some what of an issue. I can pull 3/8" a heck of alot faster, meaning less time and more money in my pocket. So that 12% turns into 25%. As for price of plates they I sell them for the same price.

Dan R_2

labor lost...

Yeah, sorry about that. If it sounded like I was asking about labor in the first post then I wrote it badly.



Mostly I just started thinking about doing it a different way than what he was used to doing and trying to discuss the pros and cons with him. His answer was short and pretty clear as far as his opinion was concerned so I wanted to bring it up here to see what folks thought.



I'm waving my hands a bit about cutting loop length down but moving loop count up as a way of changing system flow characteristics and whether the trade-offs might be worth it primarily based on being able to use a lower power circ. Of course there are so many variables that no blanket statement is possible so maybe it's really not worth bringing up?



Those 007s pull something like 85 watts don't they and the 15-58s are 60/80/90 depending on speed. I know that there have been a fair number of threads here about cost of circulator power, particularly on the constant or near-constant circulation systems over a whole heating season so I don't want to beat that horse any more than necessary but that's really what I was thinking about, regardless of how badly I wrote it...



So, maybe a better way to put it would be to ask if anybody here has moved in the direction of trying to lower overall system resistance by making any given radiant panel up out of more shorter loops or if they generally consider the extra work and materials involved to be more of a pain than it's worth? My buddy definitely says "no way" but he tends toward the conservative end of things ;')



Thanks for the response, I enjoy talking about this stuff.