DIY Hydronic Floor Heating - Page 46

Mikesolar · 09-29-14, 05:38 PM

The standard is to put cuts about 1" deep in slabs of 400ft2 or larger. We get a corrugated plastic tube over the pex about 12" long and this bridges the gap. Most of the time we put the breaks under partition walls. That is way more important for big commercial slabs than homes and the slab is way more stable if you are running a weather compensation (outdoor reset) on the floor but it's not super important.

buffalobillpatrick · 11-24-14, 12:20 PM

I have a neighbor that had me do system design & the copper near boiler manifold work on a large home system.
As he tends to drink a lot, when he rented the compactor for basement floor, he didn't get one corner area compacted properly. over the years that 8' corner has cracked off & sunk down about 3" in very corner, & about 1/8" at the big crack at the pivot area.
6 months ago he poured a self-levelng top layer to hide the problem.
I keep expecting that the 1/2" PEX will spring a leak, but so far no leak, pex is amazingly strong stuff!

Drake · 02-09-15, 03:35 PM

Is there a reason that pex should not cross itself in the heat distribution floor loop within a slab floor? All of the research I have come across clearly shows great designing of patterns to not cross but within a 4" slab there should at least be enough depth to physically do so. Fluid loops of HDP for geo heat pumps seem to be OK with crossing.

I like the spiraling pattern of exterior to interior center had keeps hottest fluid along outer heat loss walls but can't see the need of having to chase itself back around out to exterior to get back to manifold without crossing was a loss. Within 4" and midway in slab being the recommended depth of pex there should be plenty of room to run the colder return from center of floor loop back under loop pattern to start point and manifold.

Mikesolar · 02-09-15, 05:44 PM

It shows poor loops planning to have tubes cross. If someone else after comes to service it, after the fact, the crossed tubes would mess up understanding the design. In the 1,000,000+ ft of tubing I have put in over 25 years, I have never had to cross tubes.

The concentric spirals give a very nice heat distribution but do take a lot of planning. Most people don't do them.

Drake · 02-09-15, 09:30 PM

I have no problem laying out a non crossing spiral pattern as I have only two identical side by side floor loops. Just having the hottest and cool fluid in the loop flow past each other doesn't seem to be the most efficient but maybe the delta between the two is not enough to lose much. What about a serpentine "u" shaped pattern exterior to center with the two loops open "tops" facing each other? That would have no crosses. Thanks for all your input.

AC_Hacker · 02-10-15, 07:10 AM

Quote:

Originally Posted by Drake

I have no problem laying out a non crossing spiral pattern as I have only two identical side by side floor loops...

If you track back in this glorious thread, you'll find some lovely illustrations of temperature gradients from a thermal computer model of various hydronic slab layout schemes.

You'd learn a lot in just a glance.

-AC

Drake · 02-10-15, 10:29 AM

I have read this entire post several times(and surprisingly find something I didn't recall each time) but have not read anything about WHY pex should not be crossed nor what might be the best recommended pattern for using the hydronic loop to redistribute solar gain within a floor slab as well as standard radiant heating. The comment you highlighted was to point out that the crossing of pex wasn't because I couldn't lay it out without doing so. I have reviewed those illustrations and did learn a lot but I don't see how they aid in determining a loop pattern that could move passive solar heat gain in a slab floor as well as supply greater heating along exterior walls. Which is what I am working on and inquiring about.

buffalobillpatrick · 02-10-15, 12:10 PM

For houses that I have seen, the Delta-T between hot water entering a 200' loop and the cooler water leaving seems to range 10-15*F Many factors can effect this.

I have never seen pex layed out so that it crosses itself. As I said pex is very tough stuff & I don't think it would get damaged.

AC_Hacker · 02-10-15, 07:39 PM

Quote:

Originally Posted by buffalobillpatrick

..I have never seen pex layed out so that it crosses itself...

Yeah, I think that PEX that crosses itself is a sign that the layout was poorly planned.

-AC

Drake · 02-10-15, 11:21 PM

I guess I can't see how letting pex cross itself constutes "Poor" planning if a valid reason for not having it cross is not presented(I haven't found one yet). THe illustrations on pg 16 clearly show what I consider poor planning in heat distribution from what I have read as by most the ideal. That of having the most heat along exterior walls and less in center.One pattern is clearly most heat to least across progression. The other two are fairly equal across loop with the return of loop much cooler(which must be a heating loss from adjacent hotter tubes). A better loop pattern I would think ought to hotter on the outsides and cooler in the middle. Don't see that from any of these plans. Varying the tube spacing could maybe do it but that isn't shown. Have planned out a few different patterns that better run hottest fluid along exterior but a concentric spiral to center is the shortest loop and has zero return bends(just 90's) that are more difficult with narrow tube spacing.

11-24-14, 12:20 PM	#452
buffalobillpatrick Master EcoRenovator Join Date: Mar 2014 Location: Florissant, Colorado Posts: 599 Thanks: 814 Thanked 59 Times in 55 Posts	I have a neighbor that had me do system design & the copper near boiler manifold work on a large home system. As he tends to drink a lot, when he rented the compactor for basement floor, he didn't get one corner area compacted properly. over the years that 8' corner has cracked off & sunk down about 3" in very corner, & about 1/8" at the big crack at the pivot area. 6 months ago he poured a self-levelng top layer to hide the problem. I keep expecting that the 1/2" PEX will spring a leak, but so far no leak, pex is amazingly strong stuff! Last edited by buffalobillpatrick; 11-24-14 at 12:23 PM..

09-29-14, 05:38 PM	#451
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	The standard is to put cuts about 1" deep in slabs of 400ft2 or larger. We get a corrugated plastic tube over the pex about 12" long and this bridges the gap. Most of the time we put the breaks under partition walls. That is way more important for big commercial slabs than homes and the slab is way more stable if you are running a weather compensation (outdoor reset) on the floor but it's not super important.

02-09-15, 03:35 PM	#453
Drake DIY Guy Join Date: Jan 2011 Location: Mpls,MN Posts: 315 Thanks: 2 Thanked 17 Times in 17 Posts	Is there a reason that pex should not cross itself in the heat distribution floor loop within a slab floor? All of the research I have come across clearly shows great designing of patterns to not cross but within a 4" slab there should at least be enough depth to physically do so. Fluid loops of HDP for geo heat pumps seem to be OK with crossing. I like the spiraling pattern of exterior to interior center had keeps hottest fluid along outer heat loss walls but can't see the need of having to chase itself back around out to exterior to get back to manifold without crossing was a loss. Within 4" and midway in slab being the recommended depth of pex there should be plenty of room to run the colder return from center of floor loop back under loop pattern to start point and manifold.

02-09-15, 05:44 PM	#454
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	It shows poor loops planning to have tubes cross. If someone else after comes to service it, after the fact, the crossed tubes would mess up understanding the design. In the 1,000,000+ ft of tubing I have put in over 25 years, I have never had to cross tubes. The concentric spirals give a very nice heat distribution but do take a lot of planning. Most people don't do them.

02-09-15, 09:30 PM	#455
Drake DIY Guy Join Date: Jan 2011 Location: Mpls,MN Posts: 315 Thanks: 2 Thanked 17 Times in 17 Posts	I have no problem laying out a non crossing spiral pattern as I have only two identical side by side floor loops. Just having the hottest and cool fluid in the loop flow past each other doesn't seem to be the most efficient but maybe the delta between the two is not enough to lose much. What about a serpentine "u" shaped pattern exterior to center with the two loops open "tops" facing each other? That would have no crosses. Thanks for all your input.

02-10-15, 10:29 AM	#457
Drake DIY Guy Join Date: Jan 2011 Location: Mpls,MN Posts: 315 Thanks: 2 Thanked 17 Times in 17 Posts	I have read this entire post several times(and surprisingly find something I didn't recall each time) but have not read anything about WHY pex should not be crossed nor what might be the best recommended pattern for using the hydronic loop to redistribute solar gain within a floor slab as well as standard radiant heating. The comment you highlighted was to point out that the crossing of pex wasn't because I couldn't lay it out without doing so. I have reviewed those illustrations and did learn a lot but I don't see how they aid in determining a loop pattern that could move passive solar heat gain in a slab floor as well as supply greater heating along exterior walls. Which is what I am working on and inquiring about.

02-10-15, 12:10 PM	#458
buffalobillpatrick Master EcoRenovator Join Date: Mar 2014 Location: Florissant, Colorado Posts: 599 Thanks: 814 Thanked 59 Times in 55 Posts	For houses that I have seen, the Delta-T between hot water entering a 200' loop and the cooler water leaving seems to range 10-15*F Many factors can effect this. I have never seen pex layed out so that it crosses itself. As I said pex is very tough stuff & I don't think it would get damaged.

02-10-15, 11:21 PM	#460
Drake DIY Guy Join Date: Jan 2011 Location: Mpls,MN Posts: 315 Thanks: 2 Thanked 17 Times in 17 Posts	I guess I can't see how letting pex cross itself constutes "Poor" planning if a valid reason for not having it cross is not presented(I haven't found one yet). THe illustrations on pg 16 clearly show what I consider poor planning in heat distribution from what I have read as by most the ideal. That of having the most heat along exterior walls and less in center.One pattern is clearly most heat to least across progression. The other two are fairly equal across loop with the return of loop much cooler(which must be a heating loss from adjacent hotter tubes). A better loop pattern I would think ought to hotter on the outsides and cooler in the middle. Don't see that from any of these plans. Varying the tube spacing could maybe do it but that isn't shown. Have planned out a few different patterns that better run hottest fluid along exterior but a concentric spiral to center is the shortest loop and has zero return bends(just 90's) that are more difficult with narrow tube spacing.