Pipe insulation for steamback systems

RyanW

My pops and brother are in the middle of installing gycol based hot water systems that will use steamback to deal with summer overheating and power outage stagnation.    The question is what pipe insulation to use.    Will the high temp elastomeric foams do the trick or would 1" thick fiberglass insulation be better to deal with the super hot temps of steam pushing back in the pipes?    We have a pile of 1" thick fiberglass on hand and a limited amount of solaflex.



Thanks

Ryan

hot_rod

fiberglass

will work, jacket and seal any exterior sections. I like to use the aluminum cover and fitting boots.



Armacell does now offer a Armacell UT/Solaflex 25/50 product designed for Ultra temperature use. They state it stays flexible at 300F operating conditions and has UV protection. I'd use a 1" wall in the cold areas for sure, probably the entire piping.



insualtion is an area where the industry is looking closely to pick up additional performance in ST solar thermal systems, both in the collectors and piping. The additional cost of high temperature and thicker wall will pay off in the long run. The low temperature types will harden and lose their value even though they may look good on the outside.



hr

Kevin_in_Denver_2

No polyethylene

The cheapest foams melt at 180F and drip off the pipe. Ask me how I know.

RyanW

I have melted that cheap stuff too!

So the choice is basically between 1" fiberglass and 1" of the solaflex high temp elastomeric foam.   We located fiberglass at about 1/3 the cost of the foam so that is tempting but longevity is also a concern.   It sounds like both should be protected from the sun for longevity.

Ryan

scott markle_2

steamback

I'm a bit skeptical of all this steamback talk.



The only collector that I'm aware of that seems specifically designed to assist this effect is made by Shuco.



These residential flat plates have no internal header, just a single small diameter serpentine pipe, that gets connected in series to the other collectors (max of three I believe)



Seems to me that the combination of a very low volume of glycol in the collector and no larger diameter header is why these collectors are capable of self evacuating so well in stagnation conditions. I would be wary of assuming that just putting a large expansion tank on any collector will effectively protect the glycol from damage. Even where the collector hydraulics optimize this effect I don't think we want to be to casual about stagnation. My take is that steamback is a last resort failure mode.

RyanW

Last resort

Yes both of them are designing the systems with other heat dumps and are putting in extra large expansion tanks to have steamback as a last resort if the heat dumps fail or if the power goes out.   They have AET panels so lots of 1" headers and 1/2" harps to blow steam out of.   I can see how the serpentine would evacuate better.  



Ryan