How to handle two floors 9 zones each.

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Old 01-15-14, 06:34 PM
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How to handle two floors 9 zones each.

Let me draw a picture first and then ask my questions.
I have two floors. One concrete finished basement and then a second floor above. All radiant floor on both levels using 1/2” plex. I believe I will run one 1” line in from an outside boiler (run a second parallel 1” line if needed for more volume) and one 10zone manifold for upstairs and one 10 zone manifold for the basement (concrete). Each floor having around 2,400 feet of ˝” plex (near 5k total)

The advice I was given and what confuses me was to run the full temperature (180 degrees) threw the top manifold and install the ˝ plex a few inches below the sub floor (hang on joyces). Not to put the plex on the bottom of the subfloor (because high temp and no mixing valve) and to insulate bellow that.
Then take the return upstairs manifold (temp less than 180 at this point) and run to the basement concrete manifold and use a mixing valve to set around 110 maybe a bit higher.

My questions are:
1)should I run to parallel 1” lines in from the boiler and one line go upstairs and one line down. Use a mixing valve on each and put the 1/2” plex ON the bottom of the subfloor upstairs?
2) should I do only one 1” inline in but split it on the two levels?
3) should I do as advised above?
4)something completely different?
 
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Old 01-15-14, 07:03 PM
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First off, it's not 'plex', it's PEX .

We can't design the system for you... obviously... only offer advice. The best advice I can offer is that since it will be VERY costly to get this WRONG, that you might do well to HIRE a competent designer to put together the details of the design. You will get more than you pay for here, but there is no substitute for having a design done by a pro.

You need to know a LOT more than you think you do in order to get this right.

For example, do you know how many BTUH you need for EACH ROOM in the home?

Have you done the calculations to determine if you will be able to get the required BTUH output from the floors to heat the rooms?

The size of the tubing you need to run to/from the boiler depends on how many BTUH you need to heat the home, and how long the run.

ONE INCH tubing is good for about 75K BTUH maximum.

Is this NEW CONSTRUCTION?

Is the PEX floor tubing already installed?

If the tubing is already in the concrete, I hope that you have good insulation under the slab and that the tubing is not buried too deep in the concrete.

When you say NINE ZONES, do you really mean 'zones'? A 'zone' is defined as an individually controlled heating loop... in other words, NINE THERMOSTATS and zone valves? If that's what you're thinking there, get it out of your mind.

Do you mean LOOPS? In other words, 9 loops of tubing connected to a single manifold?

If you are thinking 2400' of tubing in 9 loops, that's not a good idea. That's 266' of tubing per loop and you will have trouble pumping that with a reasonable sized pump. All the design manuals will tell you not to exceed 200' on a loop of 1/2" PEX and even that is pushing in in my opinion, and keep the loops as close as humanly possible so that you don't have to mess with flow meters and balancing valves in order to get proper flow through each of the loops. If you mix short and long loops on one manifold, you are going to have more flow in the shorter ones and less in the longer.

The advice I was given and what confuses me was to run the full temperature (180 degrees) threw the top manifold and install the ˝ plex a few inches below the sub floor (hang on joyces). Not to put the plex on the bottom of the subfloor (because high temp and no mixing valve) and to insulate bellow that.
I don't agree with this advice. (Where did it come from?) While it is a possible installation method, one must take great pains to make absolutely certain that the space between the joists with the hanging PEX is as AIRTIGHT as possible. This is a major pain. IMHO you are MUCH better off with the staple up and aluminum transfer plates.
 
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Old 01-16-14, 10:26 AM
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Yes. Loops not zones. 9 loops on a zone in basement and 9 loops on another zone for second floor.
Well Im not hiring anyone. Thats why Im here. I want to soak up as much information as I can and then mistakes will probably happen still.

Each loop is between 200 and 230 feet. Sounds as if from your post I will need two parrallel 1" lines coming from the boiler. One for each floor. A mixing valve for each floor and put the pex on the bottom of the sub floor on the second floor. There maybe better tricks for simplification but at lest what I described here I cant go wrong with right? Please feed back..

is the longer than 200 feet what causes higher head pressure? If not what causes high head pressure?
 
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Old 01-16-14, 04:34 PM
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I want to soak up as much information as I can and then mistakes will probably happen still.
You better HOPE that mistakes are not made when that tubing gets set in stone (or concrete!) because short of a jackhammer, there's no fixing that.

So, how about some answers to my questions then? You have to help us help you!

do you know how many BTUH you need for EACH ROOM in the home?
Have you done the calculations to determine if you will be able to get the required BTUH output from the floors to heat the rooms?
Is this NEW CONSTRUCTION?

Is the PEX floor tubing already installed?
Do you have good insulation under the slab and the tubing is not buried too deep in the concrete?
at lest what I described here I cant go wrong with right?
I wouldn't say that. If the system is properly designed for the correct flow and outputs the proper heat output to heat the home, then you'll be fine. There's LOTS of ways to 'go wrong'!

is the longer than 200 feet what causes higher head pressure? If not what causes high head pressure?
Yes, basically it's about 'system head'. Every piece of tubing, fitting, valve, etc, all add RESISTANCE TO FLOW (AKA 'HEAD') into the system.

Circulator pumps operate on a 'curve'. They can only pump just so much water. The maximum they can pump would be with an open discharge pipe... ZERO HEAD... the minimum that they can pump is with the discharge blocked off, INFINITE HEAD (also known as 'CUTOFF HEAD' which isn't exactly a blocked off discharge, but for discussion purposes we can consider it so)... at all points in between the two extremes, they will pump according to the point on the curve that the PUMP CURVE intersects the SYSTEM CURVE.

If you design a system with excessive head, you would need a humongous power hungry pump to move the required amount of water you need to move.
 
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Old 01-16-14, 06:01 PM
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do you know how many BTUH you need for EACH ROOM in the home?
no.. No idea how to calculate that. Thought that spacing 8 to 10" covering every space possible would put enough pex in the concrete and after I could control with temperature and a thermostat.

Have you done the calculations to determine if you will be able to get the required BTUH output from the floors to heat the rooms?
I wouldnt know how.

s this NEW CONSTRUCTION?
Is the PEX floor tubing already installed?

Yes new construction and Im responsible for installing the pex

Do you have good insulation under the slab and the tubing is not buried too deep in the concrete?

Going to use 2" blueboard Styrofoam. Cant commit on depth. Havent installed it yet. Im less than four weeks away from have to do so.
 
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Old 01-16-14, 06:30 PM
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at least what I described here I cant go wrong with right?
I wouldn't say that. If the system is properly designed for the correct flow and outputs the proper heat output to heat the home, then you'll be fine. There's LOTS of ways to 'go wrong'!
Here are a couple good examples of how you can go wrong...

no.. No idea how to calculate that.
I wouldnt know how.
Cant commit on depth. Havent installed it yet.
You see, there is a LOT of room for error!

You need to have an estimate of the projected heat loss of the building in order to properly size the boiler, how much tubing to install, what spacing to use, the proper methods for routing the tubing so that the floors heat evenly, how deep in the concrete to set the tubing..........

You can start by running a heat loss estimate.

Go here and download the program. Spend a few hours inputting the data.

http://www.doityourself.com/forum/bo...alculator.html

Going to use 2" blueboard Styrofoam.
Do you know how to treat the perimeter of the slab properly with the insulation? Perimeter insulation is perhaps MORE important than the insulation underneath the slab (but that is also VERY important). You need to create a 'thermal break' between the slab and the foundation walls.

You still have a lot of homework to do in a short time if you are planning your pour that soon!

Under-slab Insulation

From the following URL:

New Construction

Perimeter Insulation

The perimeter of a radiant slab accounts for the majority of the slab heat loss. In fact, an un-insulated radiant slab operating at 80° F. with an outside temperature of 10° F., can lose as much as 150 BTU/Hr for each lineal foot of slab perimeter. It is recommended with the relatively low cost and tremendous benefit of perimeter insulation that it be installed for all radiant slab applications.
There's tons more... I found these by googling this:

Let me google "radiant slab perimeter insulation" for you
 
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Old 01-16-14, 06:37 PM
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Then, you need to know how many BTU you can expect to get out of a radiant floor system.

TYPICALLY this is not more than 25 BTUH, but in some cases you can get slightly more, in many, depending on floor coverings, furniture placement, you will get less.

What this means:

Let's use an example of a 20 x 15 living room. That's 300 sq ft.

Let's say that your heat loss estimate comes up with a heat loss of ohhhh, let's go with 8000 BTUH.

Let's say that you can cover the entire floor with radiant tubing and achieve 25 BTUH/SQ FT of heat output from the floor. 25 x 300 is only 7500 BTU... what do you suppose is going to happen if the room LOSES MORE HEAT than you put INTO IT?
 
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Old 01-17-14, 10:19 AM
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The house isnt built.. Im going to put as much in the floor as I can. Hit it with higher temp and more flow if needed (Tennessee doesn't have that cold of winters) and if its short then my gas heat can pickup the extra.

Back to design. help me minimize big mistakes. Again I have three weeks.
If you want me to respect the complexity of the system? You have my attention.
 
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Old 01-17-14, 10:51 AM
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if its short then my gas heat can pickup the extra.
I don't think you let on previously that you will have supplemental heat available.

When you say 'gas heat', what do you mean? forced hot air?

Yes, designing heating systems is more complex than meets the eye...
 
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Old 01-17-14, 03:12 PM
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Yes, forced hot air via gas. radiant floor is just a luxury but I would rather it be done correctly and work well enough that the gas heat will not need to come on except for extreme cold.
 
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Old 01-17-14, 03:31 PM
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one of the links you provided said this:
" In milder climates, the use of insulation under the slab is generally not required nor recommended."

How would I know what southern climate in Tennessee quality for this? Maybe I should do 1" thick insulation instead of my original thought of 2" over doing none..

None is a heck of a lot easier and cheaper. It is a below grade slab in a basement on a hill side walk out for the rear of the house.
 

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Old 01-17-14, 04:15 PM
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OK, good... knowing that you will have supplemental heat should the need arise is a good thing!

You might want to do a little more thinking, because having two heat sources available may mean that you can make each of them SMALLER because of the fact that working together, they can heat the entire home properly.

Look at it this way...

With ONE heating system, it MUST be designed to be able to provide 100% of the heat needed on the coldest days, the 'design conditions'.

This means that for the vast majority of the heating season that system will be OVERSIZED for the heat load on the home, because those 'design conditions' only occur typically for a week or so during the entire heating season.

Over sizing a boiler means it won't be running at top efficiency for the majority of the heating season.

With TWO heating systems, they can be 'staged' such that when one can't keep up, the other one kicks in and makes up the difference.

NEITHER ONE has to be sized for 100% of the load!

When the weather is warmer, you only need to run one SMALLER system and it will run at a higher efficiency.

When you are done with your heat loss estimate, you might decide that you want the radiant to be the primary heat source, and design it so that it can provide ... ohhhh, let's say 75% of the total capacity needed to heat the home.

Let's say that your heat loss estimate comes out to 50K BTUH.

In this example then, your radiant heating could be designed for about 38K BTUH and the hot air could be designed for 12K BTUH (although you will probably be hard pressed to find a furnace that small).

Maybe you would be better off with 50/50 ? which means that you could end up with the smallest boiler AND the smallest furnace that you can find.

The overall efficiency of the system would be increased substantially.

There are 2 stage thermostats available that would make setting this up fairly easy control wise.
 
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Old 01-17-14, 04:27 PM
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As for the under-slab insulation... I wouldn't go less than 2" in any case.

How much cheaper really?

A 4x8 sheet of 2" EPS is about $28 around here. I could do my whole crawlspace for a little under $700 or so.

Extra insulation is NEVER a 'waste' of money.

That amount of cash is a drop in the bucket compared to what you're spending building the home...

Think of it this way too: Once the slab is poured, there is no going back for a re-do. It's DONE.

If you need to cut expenses, cut them on SOMETHING ELSE that you can easily re-do at a later time without too much extra effort or expense.

Keep in mind too that it's not only the CLIMATE, but the GROUND CONDITIONS that dictate the need for insulation under the slab. Depending on the moisture content of the soil under the slab, the heat loss could be greatly increased. Ground moisture will suck the heat right out of a slab.

If you HAD to save money on insulating the slab, at the VERY LEAST, you MUST insulate the perimeter, and I would go with 2" EPS UNDER the slab at LEAST 4 feet in from the perimeter. If you wanted to 'skimp' on the insulation, do it in the CENTER of the slab.
 
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Old 01-18-14, 08:08 AM
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I cant undersize the gas forced air. The home needs to be 100% sustainable without the boiler. Down the road my wife might be left in this world alone and she wont need to be outside playing with a boiler.

This is the boiler I already have waiting on standby. I also would like the radiant system to be able to carry as close to 100% of my heating needs as possible. Might as well maximize on savings.
Central Boiler - E-Classic® Models

I hear you on the insulation. Why save that little of money. I just didnt understand at what level that statement from that website was relevant to me in my area.

How will a load bearing wall be handled on the interior where a footing is pored, insulation is laid, slab is pored, and then the load wall on top of that? My question is with the insulation sandwiched in this scenario will it not affect the over all support? Will or could it crush?
 
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Old 01-18-14, 08:51 AM
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How will a load bearing wall be handled
Aren't the footings and piers laid in before the slab is poured? I'm not a structural engineer, but my gut tells me that you don't want insulation in the path of a 'point load'. Obviously you will have to sacrifice a few square feet of insulation in this case. I don't think it will make much of a difference.
 
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Old 01-18-14, 10:33 AM
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Obviously you will have to sacrifice a few square feet of insulation in this case. I don't think it will make much of a difference

So there is going to be a heat sink to earth? A lot of trouble to insulate under and from exterior walls to allow this.. Any options?

Also why are you the only one sounding off here? this place crawling with people like me and none in the know?
 
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Old 01-18-14, 11:30 AM
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So there is going to be a heat sink to earth?
Insulate around the pier and footing when you pour. Create a thermal break between the slab and the pier/footing.

It's only going to be a small amount of sq footage... isn't going to kill ya as far as heat loss goes.

Also why are you the only one sounding off here?
Because I'm the one with the biggest mouth!

How many different opinions do you want anyway? Am I not answering all your questions to your satisfaction? I guess you get what you pay for?

Anybody else want to chime in and tell him the same thing?

"Say something once, why say it again?" (Talking Heads)
 
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Old 01-18-14, 11:41 AM
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MUCH APPRECIATED.. Your a Trooper

Im doing all the reading I can.. Ordered a few book and my eyes are bleeding from this glowing monitor. Just thought that more ideas is always good.
 
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Old 01-18-14, 12:10 PM
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Just thought that more ideas is always good.
Yeah, it's always good ... and I'm actually a bit surprised that no one else has come in.

I guess they figured old BigMouthBass has said it all?
 
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Old 01-18-14, 01:46 PM
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Another thing I need help on...
The room that has the manifold is having a hard time getting all these loops out of the room. I have everything spaced out nicely except four loops are very close together for about 10 feet trying to get out of the room before they can space out and go their own way. My thought it these fresh off the manifold loops close together (within inches) are going to put a ton of heat in this one 10 feet. I want or need some kind of sleeve to cover the out lines for insulation until they can be spaced.
 
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Old 01-18-14, 02:19 PM
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how to handle two floors 9

How close are you laying the pex tubing to the footings and are you delivering the hottest water next to the footings first or vice versa ? How big is the storage tank or home for the heat from the outside boiler?
 
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Old 01-19-14, 12:36 PM
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Was not planning on running an inside storage tank.
I get the lines to along side the outside walls (within a few inches) as possible so to put the most heat in the outer edges. Then work my way in towards the center of the slab. I have three, towards the center of house, load bearing walls. I suppose I will insulate and separate the slab from the footing and slab these walls have to set on.. its going to bring some coolness into the house.. Any ideas?
 
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Old 01-21-14, 06:38 PM
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cricket, cricket, cricket...
So Im good to go?
 
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