what do i need to install a hydronic pex underfloor radiant system

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Old 02-28-14, 09:41 PM
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what do i need to install a hydronic pex underfloor radiant system

I am planning on installing radiant pex heating under my tile floor in the kitchen. I will be using warmboard and 1/2" alum pex . Its not a large run .Only about 200ft so i would like to only do one loop on one zone. Do i need a manifold if only one loop? I read up on the internet but most info is for multiloop systems.

The way my boiler is set up now is i have two zones on the supply side.One zone for downstairs baseboard and another zone for upstairs baseboard. The radiant pex i would like on a third zone. My boiler is set up basically honeywell zone valves on the supply side and single circulator pump on the return side.

Do i need another circulator pump for the radiant pex or can i just tap into the existing circulator pump like the other two zones are doing?

What do i need for the boiler to add the radiant pex system exactly and how do i set it up ? BTW the radiant pex loop will be right next to the boiler room and both on the first floor.

Here is a few pics of my boiler setup to go off of




 
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Old 03-01-14, 04:13 AM
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Height, patience, lots of math, and still more patience. I would do two parallel shorter loops. In case you are two warm, or you don't get the flow...
 
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Old 03-01-14, 08:16 AM
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Ditto two loops. While most sources say that you can run up to 200' loops of 1/2" PEX, I personally feel that it's bad practice. Run two loops for easier pumping and more even heat distribution.

Do i need another circulator pump for the radiant pex or can i just tap into the existing circulator pump like the other two zones are doing?
Yes, you do.

You also need a 'mixing valve' that will limit the temperature to the floor heating loops. You don't want to run 180F water through them, it needs limiting to [usually] not more than 120F. In your case with warmboard and tile floor, probably even less than that. You don't want the floor surface temperature above 85F.

Is that a NEW boiler after the storm? What happened to it? Looks 'aged' already...

Who did that beautiful neat wiring job?

Read this article for some insight in what you are wanting to accomplish:

You'll have to register to see the article, but it's free:

A Little Floor Warming Please John Siegenthaler
 
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Old 03-01-14, 07:33 PM
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Yes its a brand new boiler put in by rapid repair(city run) after the storm . Its just dust from the house being renovated and the contractor who we fired not putting up something so the dust wont get all over it. Wiring is also rapid repair.Funny how the city is allowed to pass crappy work as long as its them who does it. lol.I cant really complain though as they gave us a brand new boiler for free and its not a bad boiler either.

So where on the boiler should the new circulator pump go? Can it go on the return side next to the other circulator pump or does it have to be on the supply side next to the zone valve for radiant heat? Also what circulator should i go with?

I know i need a mixing valve on it but where on the boiler do i install that? There is a mixing valve on it now for the potable hot water but im assuming you cant tap into that one?

So if i run 2 loops then i will go with a 2 port manifold. Say the loop was 100' or less ,would it still be better to go with 2 loops. Why doesnt anyone ever run 1 loop like a baseboard heat system? I am not sure how many feet of pex i will need yet but i know its a pretty small amount . We have a lot of cabinets and a island so it really will just be in walkways which is like half of a 12x15' room.
 
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Old 03-02-14, 08:48 AM
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Most of the questions you've asked can be answered by accessing that article I posted link to.

Study the included diagrams and come back with questions after viewing it.

There is a mixing valve on it now for the potable hot water but im assuming you cant tap into that one?
Correct.

if i run 2 loops then i will go with a 2 port manifold.
Right, a few tees and some PEX adapters.

Say the loop was 100' or less ,would it still be better to go with 2 loops.
No, you could do that with a single run.

Why doesnt anyone ever run 1 loop like a baseboard heat system?
Flow issues mostly, and 'balance'. You need to keep the flow up in order that the water doesn't cool too much as it passes through the loop. Trying to pump long lengths of PEX is going to require a much larger pump than you need. Using parallel loops, you minimize the flow restriction and can use a smaller pump. You also keep the AVERAGE temperature in the length of the run more consistent, and this helps to balance the heat delivered to the floor.

it really will just be in walkways which is like half of a 12x15' room.
That's a pretty small area. I believe this is not the primary heat in the area? Just want to warm up the tiles a bit? You won't need 200' of tubing for that I don't think.

If this IS only supplemental heat to warm the floor, I personally might consider an electric solution.
 
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Old 03-02-14, 05:29 PM
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i did read the article . There are a few different options in the article though . Yes this wont be the primary heat in the room .The baseboard around all the walls which is the primary heat. This is just for making the tiles a bit more comfortable on the feet. I have used electric radiant before but never been a fan of it, pouring the slc and all then hoping you dont break a line when tiling ect.

So if theres a chance i will be running say 100' and keep it to one loop how would i pipe that without a manifold. Would it just be like a regular baseboard piping but with mixing valve added in? Also with that little of a run would i still need another circulator pump? In the article there is a option without a need for a extra circulator.Does that depend on the size of the circulator i have now and how much its pumping for the two existing baseboard loops on it? The radiant loop will be on its own zone valve. Or maybe even run 2 loops still with 50' per loop. Would that need a extra circulator?
 

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Old 03-02-14, 10:40 PM
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Also just wanted to add to my last post .

Trying to put it all together. Let me know if this sounds good. I tap into the pipe on my boiler with the 2 existing zone valves and add a third zone valve to it. From the new zone valve (3/4") piping goes straight to the supply (in) side of mixing valve and return side of boiler.From the supply side of the mixing valve (out) goes to a circulator (listed below) . Out of the circulator goes to the supply manifold for the two loops of pex . On the return of the pex it goes into the return side of the mixing valve and supply (in ) of mixing valve/return to boiler.

(possibly this one 007-F5-7IFC - Taco 007-F5-7IFC - 007 Cast Iron Circulator with Integral Flow Check, 1/25 HP)

Does any of that sound correct?
 
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Old 03-03-14, 03:50 PM
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So if theres a chance i will be running say 100' and keep it to one loop how would i pipe that without a manifold. Would it just be like a regular baseboard piping but with mixing valve added in?
Yes, simple.

Also with that little of a run would i still need another circulator pump?
I would use a pump.

In the article there is a option without a need for a extra circulator.Does that depend on the size of the circulator i have now and how much its pumping for the two existing baseboard loops on it?
Note that the solution shown without a pump is for a HIGH TEMPERATURE installation, you won't be doing that, unless of course you have access to the underside of the floor. HIGH TEMP installations actually hang, or suspend, the tubing an inch or so below the underside of the floor, then the space between the joists needs to be carefully insulated and made AIRTIGHT to create a 'chamber' through which the tubing passes. It's a PITA actually.

The radiant loop will be on its own zone valve. Or maybe even run 2 loops still with 50' per loop. Would that need a extra circulator?
How will you control that zone valve? Since this is going to be supplemental floor warming and not the primary heat for the room, if you use a room thermostat, and the primary heat satisfies the thermostat, you won't have any floor warming. I think what you are going to want is a FLOOR SENSOR to maintain the floor temp at some level, say 75-80F or so.

Yes, you are going to want to use a pump in any case.

Take a look at the 'wild' setup, the one without the zone valve.

What if you piped it up just like that, and wired the pump so that it would come on any time the boiler fired for another zone calling for heat.

To keep the floor from getting too warm, you could install a floor sensor to inhibit the new pump from running if the floor is already warm enough.

You could use one of these:

ETC-111000-000 - Ranco ETC-111000-000 - Single Stage ETC Temperature Control w/ Sensor, 120/240V Input (Includes 8' Cord)

and when you build the floor install a tube that you can insert the sensor into before you lay the tile. You want to make it accessible so that you can change the control if it craps out.

If you wire the floor pump so it runs whenever the boiler fires, you can use the NORMALLY CLOSED contacts of this control to inhibit the pump when the floor comes up to temp.

I've got a couple other ideas for controlling this as well.

For 100' of tube, I'm sure the 007 will be fine. You can also use the Grundfos 15-58.
 
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