PRODUCT ADVICE FOR NEW INSTALL WHAT WOULD U DO??

HEAT

thanks for info. if i go with in direct water heater then i will have to have a mixing valve of some kind cause i cant run indirect with 120 degree boiler temp. what exactly is a mod con boiler? ive never installed one can it be pvc vented? thanks for any advice also what brand of boiler would u use?also what would u use to regulate water temp going to in floor?are the advanced outdoor temp and water temp sensing controls the most efficient way??

Dana


If you have never installed a modulating/condensing boiler, I would recommend that you find someone that has. These are NOT like anything you have installed before and require digital combustion testing equipment for proper start-up.

That being said, most mod/con boilers vent with PVC although there are a few that do not. They require special venting material available through the manufacturer.

You would not need a mixing valve to lower your radiant supply water temps(assuming all zones require the same temp) since the mod/cons will prioritize the domestic water heating zone on a call for heat. Once the domestic is satisfied, the mod/con returns to space heating mode and what little high temp water is left will be cooled very quickly. No adverse affects on the radiant zones.

Also, most mod/cons come with some form of reset built in. This means you can program a heating curve into the "brains" of the boiler and it will adjust the temperature of the water going out to the radiant zones. This prevents "over-shoot" of the temperature in the space and it lowers your fuel consumption. Much better than thermostatic mixing valves!

The "mod" part maens that the boiler modulates it's firing rate according to what is needed. This is different from the "on/off" boilers you are used to. Again, this lowers your fuel consumption.

The "con" part means that the boiler is condensing. It will condense when the water temps required stay below 130° for LP. You are pulling more heat out of the flue gas rather than letting it go out the exhaust.

I doubt that your slab zone will ever need the same temp water as the Onix staple up so you may experience some over-shoot in that zone. You could use a TMV for the basement zone set to limit the water temp to say 80°.

I have used both the Onix and the aluminum plates. The plates raise the initial cost a bit, but they work like a champ. Not that Onix doesn't work, I have it in my house. But if you are doing the install yourself, spend the money and go with the plates. We use Uponor's plates with 3/8" HePex. Goes up faster than you might think.

Regardless of which boiler you decide to use, it is VERY important that it be tested with digital testing equipment upon start-up. it is the ONLY way you will know if the boiler is burning properly AND safely.

Hope this helps!

Mark H

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Dana - Make sure you put the proper insulation under the concrete slab before you pour the concrete or you will be trying to heat the whole world. Big waste of energy.

Typically use 2 inches of Styrofoam extruded polystyrene foam. Do not use polystyrene bead foam because it absorbs water and loses it's insulating value.

reply

thanks for advice but looks as if i'll be going at it alone.the company i'll be buying the boiler from will do the sizing and there pretty trustworthy.i didnt really realize combustion tests for propane have become or are so important other than checking the gas pressure ive never heard of anyone doing a combustion test on gas r propane or is that just for the newer mod con boilers?thanks for any future advice you can give me on this matter it is greatly appreciated

Doug

That works where you are, but we can't use it here. We have termite problems and the extruded polystyrene is like a super-highway for them, complete with an engraved invitation...