would like to add radiant floor heat to an existing baseboard setup

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Old 02-06-14, 10:02 AM
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would like to add radiant floor heat to an existing baseboard setup

hello everyone!
i come to seek guidance on a project for spring time. this will be done by myself when warmer weather comes around.
background:
4 year old gas boiler system installed by myself.
weil mclain CGs gold boiler kit

4 zone taco ZVC 404

3 zones current
zone 1: basement
zone 2: main floor
zone 3: upstairs

all ran by a single taco pump that came with the boiler.


my question:
once i get a heat loss done,
what do i use to temper the water down?
i have seen a 3 way valve that tempers the water down, but where do i get the cold water from in a closed system?
i have more questions coming later.
any good reading material for free?
 
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Old 02-06-14, 11:00 AM
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what do i use to temper the water down?
i have seen a 3 way valve that tempers the water down, but where do i get the cold water from in a closed system?
Yes, a mixing valve.

The 'tempering' isn't done so much by adding COOL to the hot, but rather only adding enough hot to the already circulating water in the tubing... only enough to bring it to temperature.

Look for an article by John Siegenthaler called " A Little Floor Warming Please " (Google that title) and read that article... good stuff there. Piping diagrams show how the mixing valve is connected.

you do realize that you need a pump on the outlet of the mixing valve, right?
 
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Old 02-06-14, 12:04 PM
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thanks! exactly what i was looking for.


how does this look?
black triangle: manual mixing valve
white circle: circulator pump
black arrow: new zone valve
black lines: new pipe
red line: new feed line
blue line: mixed cool line
orange line: pex radiant tube
 
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Old 02-06-14, 12:29 PM
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Pex-Al-Pex or Pex with aluminum transfer plates at about an 8" spacing can use the same temperature water as your baseboards keeping things simple. And if the loops are kept short enough, you may be able to do it with just the existing pump.

I added that to an existing baseboard/monoflo set up for the kitchen and bath floors and still only used just the internal pump of my boiler. Have to do some math...

And all one zone. One T-stat... uniform house temp. Firm believer in KISS.
 
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Old 02-06-14, 12:50 PM
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You can tee that blue line into the orange return, you don't have to run them both back to the manifold.

Of course you can do as Who mentions, but some flooring materials don't appreciate being heated to 180F (or nearly so) and if the floor surface is over 85F or so it gets uncomfortable to the feeties if you spend much time with feet on the floor.

This is 'supplemental heat' as I understand it... you aren't looking for MAX output.

You want to try and keep a 1/2" loop of PEX below say 200' in length, but IMHO even that is a bit too long. If you need longer length it's better to feed multiple loops in parallel and connect to a manifold.
 
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Old 02-06-14, 12:51 PM
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I added that to an existing baseboard/monoflo set up for the kitchen and bath floors and still only used just the internal pump of my boiler. Have to do some math
funny you should say that. exactly what i am going to do. i have an addition of our kitchen being done this year and i want to do this very thing. right now i have a old steam radiator (converted to water) heating my kitchen/dining room.

this is just "T'ed" off the same floors line. i wonder if i can just replace the radiator with the radiant pex? i am not very good at figuring head loss/pump sizes though...
 
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Old 02-06-14, 01:04 PM
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Of course you can do as Who mentions, but some flooring materials don't appreciate being heated to 180F (or nearly so) and if the floor surface is over 85F or so it gets uncomfortable to the feeties if you spend much time with feet on the floor.

This is 'supplemental heat' as I understand it... you aren't looking for MAX output.

You want to try and keep a 1/2" loop of PEX below say 200' in length, but IMHO even that is a bit too long. If you need longer length it's better to feed multiple loops in parallel and connect to a manifold.
doing a quick square footage of the new kitchen/dining room and bathroom, it looks like right around 300 square feet. pexsupply's web site says around 500 feet of pex. i guess ill will be running 2 lines.

does this mean 2 pumps?

i imagine i can still stick with one zone valve?
 
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Old 02-06-14, 01:20 PM
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500' of tubing total? You probably want to run THREE loops.

You can still use just one pump, the outlet of the pump would feed into a MANIFOLD from which the tubes to the floor would emerge and into the floor... same thing on the return side, out of the floor into a manifold, into a single tube.

The COMMON tubing, that is, the tubing that all the flow runs through before splitting off to the separate tubes should be 'up-sized' to at least 3/4" ... it's all about flow and minimizing restriction.

If you run tubing too long you need a humongous pump to be able to pump any water through it. Keeping the runs shorter minimizes the restriction that the tubing imposes.

Another advantage to running multiple loops in a given floor assembly is that you can 'distribute' the heat more evenly.

Water starts cooling in the tubing once it starts flowing. By the time it gets to the end of the tubing it will be significantly cooler than when it entered. If you loop this long run of tubing around the room you are bound to have some areas that are cooler than others.

With multiple loops you can minimize that effect...
 
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Old 02-06-14, 03:31 PM
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honestly, i would not trust the quick guide calculator from pexsupply's website but it did say just shy of 500'. slant fin will be used once i get to that point. i see what you are saying about running SEPARATE manifolds fed from a single new line off the existing manifolds for the feed and return (pictured on first post).
great idea! thank you very much for that.

next question:

once i do get this all plumbed up, it needs wired. the main existing pump is turned on from the boilers PC board. the boiler' PC board is powered through the TACO ZVC404's main end switch. is anyone familiar with this? the manual is available online. i was not able to attach it since the size of the file is larger than allowed (PDF file).
i know how to wire up a new thermostat and zone valve to this unit. i do not understand how to wire a secondary pump using the TACO ZVC404?
 
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Old 02-06-14, 04:07 PM
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Before we go too much farther...

I asked earlier if this was SUPPLEMENTAL heat... to an area that was already heated, and I'm not sure that has been answered directly.

You said, and I bolded "new":

the new kitchen/dining room and bathroom
What I'm looking for is if you are heating an ADDITION to the home strictly with the radiant?

Have you done a HEAT LOSS ESTIMATE for the NEW space?

Have you determined that you can actually heat that new space adequately with the radiant floor heat?

Is this new space frame construction? Will you be 'stapling up' the tubing to the underside of a frame construction floor with heat transfer plates? Or will this new addition be on a SLAB?

If it's on a SLAB, you MUST insulate the perimeter of the slab, AND UNDERNEATH it with EPS foam insulation.

You're talking about 300 square feet... about the best you can really hope for as far as heat OUTPUT from the floor is about 25 BTUH / SQ FT. This does not include areas that are covered by cabinets, furniture, or appliances.

So, bottom line is this:

Before continuing with the project, be absolutely certain that you are going to have enough heat in the new addition. You MUST know HOW MUCH heat you need for the space, and be CERTAIN that your new radiant system can actually OUTPUT that amount of heat.

Let's stop here before continuing, because if you don't know the answers to this, going forward is pointless until you do.
 
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Old 02-06-14, 04:11 PM
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I just scrolled back and see that I missed a few of your posts...

Need to re-scan the whole thing to see what else I might have missed... you might have answered some questions that I asked already.
 
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Old 02-06-14, 04:25 PM
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OK, let's take a few steps backward here. You want to get this right the first time.

I think you should do a room by room heat loss estimate.

Download one of the software in this thread:

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

Once you know how much heat you need in each room, and that the in-floor radiant will be able to handle the heat load, then we can go on...

Nothing is ever as easy as it seems!
 
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Old 02-06-14, 04:28 PM
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Looking at the picture you posted of the existing heat setup, it appears that 3/4" pipe is coming to and from the boiler and feeding three existing zones of heat emitters.

It's very likely that 3/4" pipe to and from the boiler is VERY MARGINAL ALREADY. It should probably be 1" pipe... it may be, but in the pics it looks like 3/4".

Do you know what size it is?

Can you show a full pic of the boiler and the piping around it?
 
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Old 02-06-14, 05:59 PM
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the manifolds are in fact 1" pipes. the pex tubing is 3/4". i have not done a heat loss with the new addition yet,no(the rest of the house is). i will do this tomorrow at some point (or within the next few days). this may be the primary heat source depending if it's capable or not.
this floor is above a full heated basement and will be staple up with transfer plates.
 
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Old 02-06-14, 07:18 PM
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the manifolds are in fact 1" pipes.
You're not measuring 'across' the pipes to arrive at that, right? Steel pipe is not measured by the OD of the pipe...
 
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Old 02-06-14, 07:19 PM
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Troop:
180° water (when it even gets that high) inside a plastic tube, slipped into an aluminum transfer plate isn't going to harm a typical plywood or plank subfloor. And the floor temp is more dictated by the room's heatloss - dictating plate spacing - than anything. If the floor needs to be that warm (85°) he needs better insulation. But like we know it all starts with a room by room heatloss.

88:
You aren't planning on using 3/4" pex for flooring I hope... much much much easier to work with 1/2"... there is a LOT of bending/cursing involved.

Also, if you have the space, you might want to consider a buffer tank, could even be an unwanted elec water heater. Use a mixing valve between it and that conventional boiler gets to run long hot cycles like it should should for longevity and economy. Essentially, the buffer tank works like a heat battery. The boiler charges it to an ideal temperature for the home heating system, and the home heating system gets its heat from the buffer tank. Use your current pump between the tank and the boiler and get a fancy ECM pump on the heating side that adjusts to how many zones are open automatically so that a single open zone isn't overpumped. Near continuous circulation with it would make for great comfort.

I would go much shorter with your loops unless you are sticking additional pumps on them. No reason to do long loops. You aren't imbedding it in concrete. My kitchen wasn't that big, and I still split it into parallel loops of around 60' iirc and my system had fairly high head as my fintubes were piped with monoflo and needed the higher flow to work properly.

Got a lot of math to do... but don't let it scare you. Baby steps... room by room heatloss first.
 
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Old 02-07-14, 05:39 AM
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already done one heat loss on the house, another is no biggie! the pic is the first one i did back in 2009.

You're not measuring 'across' the pipes to arrive at that, right? Steel pipe is not measured by the OD of the pipe.
this is standard 1" black pipe for the manifold.

WHO:
no, i will not be using 3/4" for the tubing. when i installed this prior it was like wrestling a snake! lol

a buffer tank is a great idea! i could put this under the kitchen where the existing line runs for the (old steam) radiator. then "T" off of it on the outlet into another manifold split for the radiant floor section?

the ECM pump, i am not sure i understand where this is placed on the setup? could this run the multiple (new radiant) lines split up? sounds like multiple zones require another TACO board?

thank you so much for the help already! I am no hurry yet to get this started so we have lots of time (dont we always think this).
 
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Old 02-07-14, 05:54 AM
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88, I removed your attachment... too much info in that... like your address...

Please clip or obscure that personal info and repost...
 
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Old 02-12-14, 11:12 AM
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well, here is the heatloss...sorry it took so long.
 
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