Laying of Radiant pipe

SpeyFitter · April 2010

I'm curious about how you guys lay your radiant pipe. The company I work for seems to spend a lot of time doing "reverse returns," the term that we have bastardized to describe trying to evenly distribute the piping to maximize/even out heat distribution. For example, instead of running back/forth/back/forth accross a room, we'd backforth then run a big loop and run the opposite direction. But I seem to think this is a waste of time. If your average design floor temp is 120, and your delta T is 20, you're going to send 130 to the floors and in theory get 110 back. Not enough to make a difference. Besides, if you send the hottest water to the areas with the most heat loss, then it'll also help even it out. I also speculate personally, that by running from hot to cold, instead of having hot/supply pipes beside cooler/return pipes, you'll more easily achieve delta t's instead of having the hotter pipes warming the cooler pipes beside them before they return to the boiler.

And of course there is the venerable cinnamon bun or rosebud layout you often seem pictures of, and I could see that offering benefit at the Taj-mahal, but is even temperature distribution THAT critical when you think of the fact that the Delta T's are often no where near 20 even though we design them that way often times, and will customers notice 20 degrees THAT much, in theory, especially when you consider systems with sleepers where you wouldn't do this, nor systems with staple up, where you wouldn't do this either? Thoughts?

I'm not averse to doing things right, I want my systems to be as best as they can be and provide good comfort, but at the same time I wonder if just running back/forth accross a room makes a difference compared to trying to plan out and implement a more even loop layout?

Devan · April 2010

counter flow patterns

Scott, Using either extruded plates below subfloor or a panelized systems,(QT, WB) I don't get into much counter flow patterns. And if a slab job, I still mostly do serpertine layouts. I don't see much benefit in a slab to use other patterns, but I always go 9" o.c in a slab, and adjust fluid temps accordingly.

Residential installs usually a 5* to 10* design. except QT panels which are 20* drop.

No one has complained yet about uneven floors.

Mark Eatherton · April 2010

Different strokes for different folks...

I've done it every way that can be done, and I have found that no one has ever complained. In fact, I have intentionally left tubing out of the middle of a floor, and walked the homeowner thru, explaining to them that in the very middle of the house, that the heat loss is so low, that it does not matter, but that if they find themselves walking across the floor, and their foot comes across a some what cooler spot, that it is not a concern. Never heard back from that customer either.

Did a super insulated straw bales house one time, that the rookie apprentice I had working with me somehow ended up crossing the supply with the return mains between the mechanical room in the basement and the 2nd floor bedrooms, thereby rending my serpentine patterns completely backwards from normal protocal, dumping the hottest fluid in the interior of the home, and working its way outward to the outer walls, and it was too late by the time I had discovered the mistake. I only mentioned it to my business partner just in case the consumer complained, and they never did.

I really don't think the consumer pays that much attention to detail so long as they are comfortable. We, as an industry, have a tendency to oversell the benefits of "warm floors", when in reality, we should be focusing on the overall concept of radiant comfort, regardless of the radiant emitter.

In super insulated homes with radiant floors, the floor never even gets above tepid. The smart hydronic heating contractors are going to realize that they really don't need to cover every square foot of floor/ceiling/wall surface in order to deliver good human comfort, and they will stay in business when super insulated homes becomes the standard. In fact, floors are the WORST place to put a good heat emitter because the consumers LIKE to put rugs down to control noise. If the heat is coming from another surface, so long as they are comfy, they really don't care WHERE the heat is coming from...

A funny story about reverse return patterns. When I first got started in snowmelt, I had a friend who owned a wholesale outlet who hired me to do the tubing in his driveway. Thinking I was smarter than the tubing, I stretched the tubing out to it's maximum recommended length, then marked the very middle of the tube. I then took the middle of the tube into the center of my first grid, and started walking backwards, paying out the tubing, tying the two parallel loops as I worked my way back to the manifold. I thought I was pretty smart, until I got about 10 feet away from the manifold and ran out of tubing...

In theoretics, reverse return counter flow makes sense. In the real world, I think it burns up more grey matter than what it is worth in the way of benefits to the end user. Sure, you might be able to convince the consumer that doing it that way is better than the competitions way, but bottom line, it costs the consumer more than its really worth, and if they don't notice a difference, what is it worth?.

My $0.02 worth. Keep the change :-)

ME

Gordy · April 2010

Mark

I'm not so sure the reverse way of thinking is not a better way. I see some benefits in my mind.

Gordy

Mark Eatherton · April 2010

Tell me what you're feeling Gordy :-)

I am not completely dissing that method. I am just saying that the end benefits don't justify the means.

In fact, nearer the beginning of the circuit, you CAN feel a big difference between the supply and return. (assuming tube 12" o.c. with one foot directly over each circuit)

The biggest loss of grey matter is having to figure out how to get into the grid, fill and leave a path back out to get back to the manifold. It is tough enough doing conventional zig zagging, and maintaining proper and balanced tubing circuits. Throw in needing to have to think doubly ahead, and you can see a headache coming right at you.

Now, maybe if the consumer were walking around with a $300.00 flux sensor glued to the bottoms of their feet, and a digital micro volt meter in front of them they MIGHT be able to see the difference, but really, how far do we think we ought to take it in the name of comfort? Bear in mind, I have NEVER had ANYONE complain about the conventional serpentine manner.

Snow melting manufacturers use to say the same things about the use of reverse return counter flow patterns, and you CAN se a difference there, but again, no one complains. It melts snow just fine...

Just sayin'... ;-) It's your brain power. Use it wisely.

ME

Gordy · April 2010

My feelings

1. Why run the hottest part of the loop along the perimeter where most furniture usually occupies, and where we usually do not traffic. Plus by giving up that hottest part of the loop to the perimeter we allow a cooler temp to the middle of the room in that loop.

2. If we run the hottest part of the loop in the central portion of the room letting cooler return temp part of loop occupy the perimeter then a larger delta t could be utilised going unnoticed by the occupants. Thus benefiting condensing with a mod/con boiler.

3. By decreasing the delta t at the exterior wall you decrease heat loss.

These are probably gray matter idealism also, but why not think in reverse.

With the ideas comes subjectiveness to types of rooms their layout, and foot traffic patterns with RFH. Ceiling radiant is another story let the reverse theory rip, no one walks up there any way.

Gordy

Mark Eatherton · April 2010

Points well taken...

But as houses get even more efficient, it will be that much more irrelevant.

I agree. Do the ceiling and let them throw WHAT ever they want on their floors. ;-)

ME

heatboy · April 2010

Depends on room layout.......

.... more or less. I'm not sure, when using Delta T's of 10°, how much it really matters. It does take an awful lot more layout to get it correct, for sure.

paul_79 · April 2010

reverse return

i like using the reverse return it is easy for me to lay out and the bends are a little easier to make

Laying of Radiant pipe

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