Which fluid for my pex?

[Burl]

Down to the fluid part, 1000 feet of pex in my garage floor, well insulated, etc. Its down to a pick betweem Dowtherm SR-1 and green automotive antifreeze w/deionized water. I know the difference in price, and I haven't skimped on anything else, why should I start here. Any hard facts for the Dowtherm? Thanks.

 

[chevelle67]

We use SR1 in alot of equipment at work. The one thing most people dont know about a glycol solution is if using standard antifreeze it has a potential to get bacterial growth. SR1 is inhibited to prevent it which is reflected in the cost.

 

[nate379]

Are you not going to heat the shop all the time?

 

[malibu101]

On alge growth and antifreeze- A buddy of mine got a Miller TIG torch cooler a few years ago. Miller sells a Miller branded coolant for it at a price higher than normal green antifreeze. Buddy say what the heck and runs auto antifreeze. Worked perfectly fine. After less than a year there was a green (alge) slime all over the resiviour. He ended up cleaning the whole thing out, buying the Miller coolant and it is still fine today.

I've seen it in a different application, not with radiant heat, but, I'd head the advice given on alge growth in auto antifreeze used out of it's application.

 

[Burl]

Are you not going to heat the shop all the time?

I live in northern West Virginia, the garage will get heat probably 6 months out of the year. I figure about 55 to 60 deg. normally. The guy who will sell me the Dow never mentioned a bacteria issue. This is a closed system, maybe thats why.

 

[chevelle67]

Nope closed or not can get bacterial growth, algea is different. Numerous times I have had customers call about low glycol levels on chilled water loops but they cant find the leak or where it is going but also never tell that sytem pressure also has climbed over time. Long and the short of it is bacteria was growing, giving off gas (thats why system pressure was up) and consuming some of the glycol. The bigger problem comes when the bacteria starts to produce ammonia and corrodes the brass and copper in the system.

 

[chevelle67]

heating loops are more prone to Baterial growth due to the higher operating temps

 

[Burl]

Alright, I'm convinced about the bacteria stuff, anybody have any facts about heat transfer?

 

[ScaldedDog]

Before we leave the bacteria conversation, is there an anti-bacterial additive for hydronic heating systems? I googled for it, but didn't come up with anything.

Mark

 

[nate379]

So it's going to be heated in the winter all the time correct?

What is the reason for the antifreeze? Most places around here that are heated all winter just run water. That's all I have for my house and garage.

I know a few guys that don't heat all winter and they use reg automotive antifreeze. One way or another you need to flush it out every couple years. Auto antifreeze is less than 1/2 the cost.

I live in northern West Virginia, the garage will get heat probably 6 months out of the year.

 

[chevelle67]

Glycol @ 20% heat transfer loss is about 6% total, @ 40% its 14.5%.

 

[Burl]

Glycol meaning auto antifreeze? If so, any numbers for the SR-1? Nate, the reason for the antifreeze is in case of a power outage, which happens nearly every time the wind blows in my area.

 

[Ezzie]

You should not use ethylene glycol in a hydronic system. You should use propylene glycol mixed with water (50/50) for areas that dip below freezing. This is the same stuff that is used to winterize pool pumps, RV's, summer cottages, etc. since it does not have the same environmental issues as ethylene glycol (common automotive coolant).

 

[chevelle67]

SR1 is ethylene glycol based so the HT loss is the same as above. SR1 and ethylene is used extensively used for hydronic sytems. Propylene has some advantages but the reason it is not used extensively is the heat transfer rate is quite a bit worse.

 

[nate379]

Yeah, that is something I have worried about as well, which was part of the reason for me asking.

I am estimating it would take 2-3 days for the slab and building to cool down to the point of freezing, does that sound right?
I was told by the plumber that the Pex would survive freezing.... not true? I'm not it's not ideal, but even if you are on forced air heat and you loose power, all your domestic water pipes would freeze. No way to protect those.

The main reason I haven't looked much into it was the lowered heat transfer and the cost of the antifreeze. Also having to install in injection system.

Glycol meaning auto antifreeze? If so, any numbers for the SR-1? Nate, the reason for the antifreeze is in case of a power outage, which happens nearly every time the wind blows in my area.

 

[Burl]

I'm really not worried about the pex in my slab freezing, just the parts ABOVE the slab (water tank, manifolds, all copper piping, etc.). As for my house, as I said, the electricity goes off quite often, and a generator has been the backup plan for a few years. I also can drain about 90% of the water in my pipes throughout my house. The rate of heat transfer of the different fluids was what I was getting at, and Chevelle took care of that.

 

[tdkkart]

I'm really not worried about the pex in my slab freezing, just the parts ABOVE the slab (water tank, manifolds, all copper piping, etc.). As for my house, as I said, the electricity goes off quite often, and a generator has been the backup plan for a few years. I also can drain about 90% of the water in my pipes throughout my house. The rate of heat transfer of the different fluids was what I was getting at, and Chevelle took care of that.

The handy part is, because you are using radiant heat, and because you are heating using a concrete slab as your heat storage/source, assuming you are normally keeping the room temperature at a normal level, it will take several days before your system drops below freezing even in below zero temps.

At the price we pay for electricity these days, there should be no excuse for being out for more than a few hours except in the case of an ice storm of the century.

Which remeinds me, I've gotta call my power company to fix the street light across the road, we use it to tell when the grid comes back on when we are on gen power. That time of year is coming.

 

[5wndwcpe]

Good info here, especially on page 8.

http://www.dow.com/PublishedLiterat...rans/pdfs/noreg/180-01332.pdf&fromPage=GetDoc