Suppling two different water temps to different radiant systems?

ALH_4

First of all you're changing the heat load significantly. You'll need a new heat loss calculation. It is important to remember that the heat loss number is at one instant of time, the coldest outdoor temperature at which you would like to maintain a given indoor temperature.

I would look at some of the new modulating wall-hung boilers. You might not be condensing all the time, but they do have outdoor reset built in, are sealed combustion, and you can add mixing valves to limit the temperature of the radiant zones. Be careful of the 75C high limit on some models. I like the safety of sealed combustion appliances. I'm partial to Viessmann boilers. The <a href="http://www.viessmann.ca/web/canada/ca_publish.nsf/Content/Vitodens200_ca_english">Vitodens 200</a> is as good as it gets if you can work with 167F as your high limit.

-Andrew

DeirdreLouisville

How to supply two different water temps?

I have a staple up radiant floor heat in about 800 square feet of my first floor (yes, I know it is sub-par, but it is what I've got). I am currently putting in a kitchen and remodeling two baths and am planning a concrete floor with embedded radiant heat. My staple up system need high temperature water to work effectively (a minimum of 170 degrees), but my kitchen system will probably operate at a much lower temperature (105-130 is what I am hearing). I would also like to add water baseboard on my second floor, if possible.
How can I most effeciently supply water to these different systems? Can it be done at all?

Unknown

staple up and baseboard on a high-temp primary circuit, hopefully w/outdoor reset.

Mix down off of that circuit with either a mixing valve or injection pumping to a secondary, low temp circuit. mixing should also be controlled w/outdoor reset at least, and with slab, you might even want indoor feedback.

Easy Peasy!

Brad White_9

I second that....

When you have a higher temperature of primary water (170 or whatever) and you need lesser temperatures in the 100-130 range you have lots of room to mix it down, make as many flavors (temperatures) as you need. Just keep in mind that each will have it's own control, whether responding to outdoor temperature reset, to maintain a constant temperature in the secondary loop or respond to room temperature. All things are possible!

Mike T., Swampeast MO

And Also Keep In Mind...

...that your overall system efficiency will be most influenced by the highest temperature used in the system.

DeirdreLouisville

Thanks guys.....but

Are you saying that I should heat all the boiler water up to 170 and then cool some of that down to whatever temp is best for the concrete floor? I was afraid of that!


So, what is the best boiler for feeding these systems? We would be heating about 3,000 square feet in Louisville, KY.

Ron Schroeder

Look into

added baseboard to decrease water temp to 2nd floor or panel radiators

http://www.runtalnorthamerica.com/radiant-heating/

Mike T., Swampeast MO

Yes, the boiler will have to heat the water to the temperature required by the "neediest" source--in your case, this is almost certain to the be "staple-up". I'm presuming this is bare-tube staple-up, correct?

There's nothing at all wrong with mixing down for multiple temperatures. In the world of condensing boilers however, LOWER IS BETTER and radiant floors are usually considered the "low temperature" requirement with radiators of some form the high.

Again, if using a high-efficiency condensing boiler its' efficiency will be most influenced by the HIGHEST temperature requirement in the system. If the staple-up needs at least 170F to operate effectively, you will have little to gain from condensing technology and a traditional boiler may be better.

In ANY case, you are contemplating a system of significant complexity. Complexity adds to costs in EVERY way: materials, labor AND maintenance. To get the most for ANY boiler you need a true pro! The modulating ability of most condensing boilers MIGHT be able to significantly increase your efficiency above a standard boiler, but such will require especial attention to design and control details. I rather doubt that you'll be able to find any "pro" in Louisville, KY with the required experience and skills to do this. STUDY, STUDY, STUDY (including CAREFUL observation of your current system) and you should be able to make your own design to specify to any decent contractor.

Mike T., Swampeast MO

Yes, the boiler will have to heat the water to the temperature required by the "neediest" source--in your case, this is almost certain to the be "staple-up". I'm presuming this is bare-tube staple-up, correct?

There's nothing at all wrong with mixing down for multiple temperatures. In the world of condensing boilers however, LOWER IS BETTER and radiant floors are usually considered the "low temperature" requirement with radiators of some form the high.

Again, if using a high-efficiency condensing boiler its' efficiency will be most influenced by the HIGHEST temperature requirement in the system. If the staple-up needs at least 170F to operate effectively, you will have little to gain from condensing technology and a traditional boiler may be better.

In ANY case, you are contemplating a system of significant complexity. Complexity adds to costs in EVERY way: materials, labor AND maintenance. To get the most for ANY boiler you need a true pro! The modulating ability of most condensing boilers MIGHT be able to significantly increase your efficiency above a standard boiler, but such will require especial attention to design and control details. I rather doubt that you'll be able to find any "pro" in Louisville, KY with the required experience and skills to do this. STUDY, STUDY, STUDY (including CAREFUL observation of your current system) and you should be able to make your own design to specify to any decent contractor.