Small Radiant System Question
etherhuffer
| Posted in Energy, Heating & Insulation on
I am rehabbing a small area, about 400 square feet, and its adjacent to my furnace room. I was considering getting an AO Smith ProMax SL which has two extra ports, and doing an open system. A closed system with an exchanger would drive up the cost to 3k minimum for tank, exchanger, pump, etc.
Anyone have ideas on open systems? Radiantec has a large site describing the various layouts. Legionella questions seem to pop up a lot. I can’t see how a loop of small dimension would turn into a bacteria farm. Any thoughts?
Replies
This'll probably draw a lot of posts decrying closed systems, and a lot of posts saying the others are full of bunk. I think the bottom line is that nobody really knows.
That said, if you have budget issues, I figure it's cheap enough to just use a HW heater as a closed system boiler & you'll get the best (well, maybe not the BEST) of both worlds. Of course, this means that you'll dedicate the new HW heater to radiant, leaving your existing HW heater to serve the home's HW needs.
You're still gonna need controls, pump, tank, etc., either way.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.
I was going to use the house hot water tank for both. There are only two of us, and we have gas heated water. A non glycol loop would need a pump and tank and a few valves. No?
Well, then that's an open system which many say isn't a good idea. I know I've personally run into trouble with them -- the water getting stagnant in the heating loop, then spraying you with black water when you take a shower when the heater kicks on -- fun stuff like that. There are workarounds, but you have to know what you're doing.
Personally, I think spending a couple of hundred bucks on a separate WH for the radiant is cheap insurance against this sort of problem. Also, if you do use the same WH for radiant and potable, you'll want to upsize it to carry both during heating season, and then you're oversized in the summer, wasting energy.
I've also seen very compact electric boiler systems that aren't too expensive that seem to work well in small installations. You may wanna give that some thought.
Maybe give NTRob who posts here on occasion a shout. He's "da man" on all things radiant. You could also try searching for older posts on this topic -- I seem to remember it coming up before.
Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.
Contact Rob here: http://www.nrtradiant.com/
I had a friend do the open loop system. In the summer, he runs the water through the radiant loop to keep it 'fresh'.
As far as legionella ... I don't think I would worry. Legionella requires a fairly specific set of conditions that are somewhat similar to many household applications (e.g. showers and evaporative swamp coolers) non of which have issues associated with supporting legionella. I did a bunch of research once on this and while I didn't retain the details (CRS?), I retained that common hot water use applications do not support legionella ... but I can't recite WHY that is the case. Cooling towers are prime candidates for legionella, yet swamp coolers are not ... otherwise they simply wouldn't exist or be allowed.
That's my two cents.
Always found a lot of good info @ Heatinghelp.com- the wall. I would use a heat exchange in that type of setup, spend a little more, save a lot of headaches later.
Have you really priced the difference for going from open to closed as an additional $3K?
To add a small closed system to an existing system, you need a HX, a circulating pump, and an expansion tank. A few hundred instead of a few thousand dollars in materials, plus better domestic hot water performance and better radiant heat performance as you'd get the heat when you need it.
I will say I'm biased and not a fan of open systems. I just think they are so unnecessary.
mongo, I can't source a heat exchanger and pump set up for less than a couple grand. The prefab AO Smith exchanger is 1500 bucks. Can you educate me a little more?
http://www.patriot-supply.com/products/showitem.cfm/66702
I don't know if this will help or not... BUT.. :) in a copy of mother earth news i picked up somewhere... the people used a "cold plate" as a heat exchanger with reported good results... for a small room such as yoursit's a bit of information that i filled away since i had several cold plates...so... what is the cold plate? it's the alum. plate that sits in the bottom of an ice bin that the soft drinks run through before they are dispensed... ie it's a heat exchanger... so the drink comes out cold... since i had installed quite a few and never really thought of them as such... I retained the idea...I don't remember exactly how they used it... but I do remember them stating it worked well and saved them a ton of money...Keep us posted on your install... I think there is a lot of interest... there was an artical in FHB just this past year about different systems... seems march of 2009? maybe?
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rich linked to a copper heat exchanger, here are some more stainless ones for a little more $$. You have a very small system so you can stay below a couple hundred here.
Here's an expansion tank for $25.
Pumps, I usually use Taco but you can choose any. A pump can be had for $50-$75.
You'll need other items as well depending on how your system is set up. a $10 air trap, a 12psi refill valve for $15, etc. Maybe a control module/relay to link the pump to the t-stat. Depends on the design, but you're still far far away from even $1000, never mind $3000.
I'm not advocating this company, they were the first hit on a google search so I used them as the example.
Dude! You rock! At that point I become a plumber, but its not rocket plumbing science.
Are folks using stainless exchangers for corrosion reasons? And I wonder if you use glycol on a closed loop if you need an approved exchanger so that you don't get toxicity issues?
I got a bid for 6k to do this from a contractor. When I got done laughing, I had to wonder if he just didn't want the job or what. And perhaps he buys the Radiantec and AOSmith stuff off the shelf and bolts em up, explaining the higher cost.
I am trying not to cross that line from sheer genius to absolute stupidity!
Hey, I used to be a rocket scientist. RFH and rocket science? They both include a little plumbing, a little soldering, and fuel gets turned into heat. They're pretty similar when you break things down into the essentials. Although I think Taco makes better pumps then the "lowest bidder" stuff we used to use.<g>
I've never heard of toxicity issues with glycol and plumbing. Realize that glycol is used in closed non-HX systems with copper, brass, and pex, with no worries. I'm not aware of any negative issues with glycol and either copper or stainless HXers. Someone better versed might know, but I've never heard of any problems. Someone else might have better info on that, or you could ask over on The Wall.