Can I get help Setting up a system for Radiant infloor heat?

NeedHeat

I want to add in floor radiant heat.I have a raised ranch home with 2 car garage in the basement. I want to do in floor heat over the garage for now and do the rest of the home later. I will still keep my forced air heater in place but once the whole home has radiant heat this will just be a back up and serve as a blower for the A/C.



The area I want to do for now if 42' by 25'



My plan was to run 1/2" pex 2 runs per joist space with aluminum 4' plates. and then fiberglass insulation. Then run plastic under the joists (vapor barrier) and then dry wall. On top of the floor we have carpet, I will soon change the carpet and pad to a more radiant friendly pad and carpeting (lower R-value).



I was thinking of doing it with a AO smith vertex 100,000 btu lp



Taco pump ect...

No heat exchanger, The water heater would do in floor heat and our hot water needs.

I currently use a 40,000 BTU water heater that works great for just the hot water needs.



I need to figure out what pump I need, how long of runs I need, what water temp I need to run Ect......



Any constructive information good or bad about my plan Would be greatly appreciated!!   Thank you!

Alan (California Radiant) Forbes

Open System

You're talking about installing an open system, something that is not looked upon  favorably here.  But to answer your question, you could set up a manifold for your tubing and use a Taco 007 pump with 1/2" PEX loop lengths not longer than 300'.  Your components (pump, expansion tank, etc.) will have to be bronze or stainless steel.  And I would pay the extra price for PEX with an oxygen barrier.



You don't say which part of the country you're from, but I'd start at 110F to see if it heats the rooms.  If not, increase the water temperature.  I'd put a good tempering valve on the domestic side in case you have to turn up the water heater over 125F.

DJS

What your doing

is a very unsafe idea. You want to run heated water through tubing during the winter. Than let this water sit stagnant for several months growing all sorts of bad things. Than when winter comes, reintroduce this water back into your potable water. I would rather drink out of a toilet. Do your family a huge favor, and stay away from this type of installation. It can only end badly.

I would go with a mod/con boiler so you get the eff with outdoor reset. your not heating a huge tank of water that will just sit there when no call for heat, and will most likly out last any waterheater (depending on where you live).

It may cost more upfront, but I never had anyone complain when the system was installed right from the start, only when people try to save money to get the same great comfort with short cuts.

NeedHeat

bad water

I was planning on valving it so that during the off heating season the cold water going into the water heater would go through the pex in floor heat first, that way its constantly circulated.



If this is still a bad idea, I can add a heat exchanger, but that would also require a second pump.

Ironman

Still a Bad Idea

You're designing the perfect breeding ground for legionella. As Alan stated, you're looking at 100 - 120* water temps in the floor, that's ideal temp for breeding. Using a mod/con with an indirect would be the best and most efficient system. If however, you're bent on doing this on the cheap, then look at using Taco's X pump block to isolate the floor from the tank. It also has built in reset with variable speed injection. Your appliance will still only be about 70% efficient, but you get what you pay for.



And please, don't even consider a tankless as your heat source: they are not designed for space heating (except a "combi" unit) and you'll have nothing but misery.

NeedHeat

closed system

So this water heater is 96% efficient at heating potable water but only 70% efficient heating the floor?



OK point taken on the open system. I will do a Closed system.

NRT_Rob

it won't drop to 70%

but it will drop since you aren't feeding it 50 degree water anymore which is, presumably, the incoming water temp its efficiency is rated at. the Vertex and a few others are not typical water heaters... typical water heaters are about 75% efficient in heating mode.



thirding the don't do an open system advice here... and I'd also recommend variable speed mixing through the heat exchanger to improve comfort.

NeedHeat

variable speed

How do I make it variable speed?

Ironman

96% Efficiency ?

I missed that you stated it was a Vertex. You'll probably hit at least the high 80's in efficiency, depending on water temp.



If you'll use the X pump block, it will give you variable speed injection based on outdoor reset. It will also isolate the floor from the tank so that the floor will be a closed loop. The only limitation with it is the btu output; I believe it's somewhere around 50 -60k btu's.

NeedHeat

X pump block

The x pump sounds great.



If I understand it has 2 pumps, controller,  and heat exchanger all in one?

NeedHeat

efficancy rating?

I'm trying to understand this?



So on a water heater the efficiency will go down with hotter water coming into it?



Dose that mean this water heater if used just as a regular water heater, say we don't use hot water for a day or two and the water in the heater cools and the water heater runs to warm the water back up to set point, that its only running about 80% efficient during that cycle because the water is already warm?

NRT_Rob

efficiency can mean a lot of things

depends on what they are rating. "thermal efficiency" could mean almost anything they want. the water heaters "energy factor" is efficiency, including standby loss, on a 40 gallon/day domestic usage, so there are a few real "cold water in" draws and a couple of maintenance demands in there problem.



generally on water heaters efficiency goes UP for heating, because that energy factor is shifted about 10-15% because the draw is so small that standby losses are a significant percentage of the energy used. With heating that goes away in relevance to the much larger heating load, so effective efficiency is better.



however water heaters like the vertex, polaris, and phoenix are condensing water heaters. they get extra efficiency using cold water. and the numbers they quote for efficiency are typically not energy factors, they are "combustion efficiency" or "thermal efficiency" so more akin to a "no standby loss" number.



it gets confusing.

NeedHeat

Hmmmm

Ok that is confusing.



So on the vortex what ever the actual efficiency is it will be higher during winter because of the in floor heat?  But still low compared to a good boiler?

WarmboardRep

Have NRT Radiant design your mechanical system

If you want an excellent radiant system have Rob @ NRT Radiant design your system for you.  Hiring anyone with great radiant design knowledge is well worth every penny.  That way you know you are getting a quality system that is efficient, safe & heats your home.  Good luck on your project.