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mnicholet 4/14/10 12:58 AM

hydronic radiant floor heat on hot water tanks
 
3 Attachment(s)
Most hydronic in floor heating systems I see are on boilers. Your advice regarding this set up would be appreciated. Two hot water tanks providing in floor radiant heat. TPR valve was stamped for 15 PSI (looks like boiler TPR) on the HW tank. The TPR valve was leaking. Thanks.

mcyr 4/14/10 9:19 AM

Re: hydronic radiant floor heat on hot water tanks
 
Here you go Mark.

Open System

The open system uses one heat source, your domestic water heater, to provide both floor heating and domestic hot water. The two systems are basically tied together.
The same water that ends up in your hot shower or dishwasher, for example, has passed through the floor first.

This is a very efficient system because one heat source is doing all the work. As long as the water heater is sized appropriately and matches your heating and domestic needs, the need for a separate heating system is eliminated.

Closed System

This approach utilizes a dedicated heat source for the radiant floor. The fluid in a closed system is re-circulated around and around in a completely closed loop. There is no connection whatsoever to the domestic water supply.
The main advantage to this system lies in the fact that, being closed, anti-freeze instead of water can be used as the heat transfer medium. If freeze protection is an issue, than a closed system with anti-freeze is a good idea.

Now whether or not that is the right kind of TPR, some plumbers might chime in.
Hope this helps.:)


mlarson 4/14/10 9:46 AM

Re: hydronic radiant floor heat on hot water tanks
 
Mark,

No matter the heat source ,you still have a closed system as long as the water in it is not used for teh potable water system.

The pressure relief at 15-20 psi is right for a dedicated system depending on the elevation of the highest radiator.

mnicholet 4/14/10 5:03 PM

Re: hydronic radiant floor heat on hot water tanks
 
Update:

I talked to John Wood Canada and they said :

The hot water tanks providing radiant heat have to be an open system providing hot water to atleast one fixture or faucet. The TPR valves are improperly rated for pressure and heat and should be replaced.

mgratton 4/14/10 6:11 PM

Re: hydronic radiant floor heat on hot water tanks
 
Electric water heater...not much heat!

Was it heating the whole house or just parts and how large was the house?

mlarson 4/14/10 6:24 PM

Re: hydronic radiant floor heat on hot water tanks
 
Quote:

Originally Posted by mnicholet (Post 645667)
Update:

I talked to John Wood Canada and they said :

The hot water tanks providing radiant heat have to be an open system providing hot water to atleast one fixture or faucet. The TPR valves are improperly rated for pressure and heat and should be replaced.

Does it supply water to any faucet?

If not it's a closed system and the pressure relief is correct.

mcyr 4/14/10 6:46 PM

Re: hydronic radiant floor heat on hot water tanks
 
Types of Radiant Heat Systems - Open, Closed and Indirect

A "closed" system is most often refers to a situation where your heat source is dedicated solely to the task of heating water for the radiant heating system. The term "closed" refers to the fact that the water in the radiant heat system re circulates continuously from the heat source through the tubing or radiators and back to the heater again.

The "open" system uses one heat source, your domestic water heater, to provide both floor heating and domestic hot water. The two systems are basically tied together. The same water that ends up in your hot shower or dishwasher, for example, has passed through the floor first. This is a very efficient system because one heat source is doing all the work. As long as the water heater is sized appropriately and matches your heating and domestic needs, the need for a "separate" heating system is eliminated. An open system using a tank type heater such as the "Phoenix" is the most efficient and simplest radiant system you can use and can be ordered with an internal solar coil.

An "open" system refers to a situation where the heat source - typically a water heater - provides hot water both for domestic use and to the radiant heating system.
When there is a call for heat, water is drawn out of the water heat tank, it circulates through the heating system, and then returns back to the water heater. That same water mixes with the water in the tank which is also the direct source of the domestic hot water. So, when a faucet is turned on, water that has been through the heating system is furnished for showers, dishwashers, etc.
While the Universal Plumbing Code does allow for open systems, some local building inspectors do not. Before deciding on or committing to a particular type of system, you should understand what is allowed in you area.

An "indirect " system allows you to separate your domestic/potable water from the water in your heating system and still use a single heat source. By pacing a heat exchanger between the water heater and the radiant heat system, separating the heating system water from the potable water.
Rather than sending water directly into the heating system from the water heater, a pump pushes water from the tank through the heat exchanger which has series of plates inside. At the same time, the water in radiant system is being circulated on the other side of these same plates in the heat exchanger. Heat from the water heater is transferred through the plates to the heating system water. Hence, the heating system water is heated "indirectly" from the water heater. Indirect systems are "closed" systems.

A tank type heater such as the Phoenix combined with a flatplate heat exchanger works best.


CLOSED INDIRECT SYSTEM, SINGLE MANIFOLD


http://www.radiantdesigninstitute.com/img12.gif
Well if anything, its a good schematic. :mrgreen:

mlarson 4/14/10 6:48 PM

Re: hydronic radiant floor heat on hot water tanks
 
I think we can reasonably sure that Mark has encountered a closed system.

A 15 psi pressure relief would not hold on a domestic water system.


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