First Post

Harvey Ramer

Why has the Geo industry not yet started utilizing exp tanks and air separators on closed loop systems? Every Geo contractor that I talk to has air problems with closed loop. They have even gone so far as to make a kind of open tank that is inline with the piping. This lets air out and they pump off the bottom of the tank to ensure they always have water at the pump inlet. But now they are oxygenating the water.

The Hydronic industry has addressed this problem a long time ago. One would think the Geo industry would follow suit?

Harvey

hot_rod

$$$$ They feel it adds too much cost is about all I can gather. But the somehow rationalize the cost of non-ferrous circs on those open tank systems??!!

I did a seminar on air and dirt removal at the IGSHPA expo a few years back, very little interest in changing old habits.

The also use high head circs or circs in series which seems to be a sweet invitation to cavitation in those open systems.

I'm surprised the pump manufacturers are comfortable wit two- four circs bolted flange to flange for high head operation.

Some of the GEO pump stations had two circs in series pushing, two pulling the loop field. Crazy stuff.

don_9

The one i have had this discussion with feel that there enough loop field to handle the expansion n contraction.As for the air that what they have a purge cart for n without any make up water being added they feel they will have no issue with air.One has to remember that the pressure on the guage they see in the summer will not be the same in winter on a closed loop.Truth be told i have never had a issue with air on one.I have had lack of pressure due to a leak in the loop field.

mark o

Thanks Dan for this section !!! What a great topic . The 2 types of systems I've used back and forth because of this issue are pressurized closed and non pressurized closed loop . The expansion tank in my jobs in pressurized is utilized on the suction side of the pump . I don't really care for it as there is no fill valve as we : pump away : which makes no sense . The flush cart is not enough in my opinion to stop all air bubbles and eventually will need more purging as loop pressure drops and air bubbles get larger . I utilize non pressure standing column tanks whenever,possible for flooded suction type pumping . Unfortunately it is more expensive and less jobs / customers accept this .

hot_rod

I'd agree expansion capability may not be needed.

But even the entrained and micro bubbles in the fill fluid never capture and vent out without some sort of device. We are talking under 200 bucks to add a quality micro bubble eliminator?? What's the installed cost of a typical loop field? seems a small price to pay to give a boost in efficiency.

If you use a high head fill pump you do have the potential to churn some air into the fluid, especially with glycol.

Extra tough to scrub air from glycol fluids. Some of those clear, demo air elimination displays, with glycol added, you see at trade shows actually have a chemical added to help entrain air to remove it. It could take hours to purge tiny air from glycol without a little chemical help

Any air on the tube wall or the HX surfaces reduces efficiency, why not scrub it all out?

I used a Discal on my small 3 loop GEO field. I know it worked well as I had to add a small amount additional fluid twice.

Also the loop field give up more air when the temperature rises, so good to check after an entire heating and cooling season.

Harvey Ramer

When I go in to do a repair, I first test the PH of the fluid. Glycol can become nasty stuff. If needed I flush the old fluid out and then add a product like Alpha 11 (Fernox) . I add a Discal air sep. exp tank fill valve and backflow preventer. I will typically leave the fill valve turned on to maintain an acceptable pressure level in the system. Glycol is extremely slippery stuff and there are a few connections where it can slowly weep out, depressurizing the system. Plumbed properly and in an average setting, I see absolutely no need for a flush cart. I have never used one, nor have I had air problems. Typically your fill point will be close to the highest point in the system. As you fill it, the air vents out. The bubbles that are left will be vented through the air sep as the system runs.

My goal is, no callbacks.

Harvey

mark o

Harvey is that fill combo on return from loop field tied in near highest point ,,, so we are pumping away fromloopfield

Harvey Ramer

You got it. Pumping away from the exp tank and into the GEO unit. Guaranteed no air problems and enhanced thermal transfer in the Geo unit due to higher pressure and the absence of any micro bubbles.

You also don't need those lame, Ill conceived pumping stations. Choose the correct circ based on the flow required and the total head loss. The money saved on the pumping station can be used for and efficient circ such as a Viridian or a Magna. Now you just increased the COP of the unit through reduced pumping costs.

Also, those rubber hoses that connect to the unit, are quite restrictive to flow. You can hard pipe right up to the unit and if vibration is a concern, put in a short piece of appropriately sized pex. Depending on the flow requirements, this may allow you to drop a circ size.

Harvey

zac_2

I've been installing expansion tanks on every loop i've installed in the past 5 years or so and it has eliminated any air & pressure related issues. There are geo specific expansion vessels constructed of HDPE and designed to be buried though that would make me nervous, why not install in in an accessible location? Folks in the Geo manufacturing industry are a different breed; always trying to reinvent the wheel & making silly engineering decisions; why 600ft long loops? Wouldn't we want to keep our head low to reduce pumping costs? In Europe they spec max 100 meter (328ft) loops to achieve just that. I've been told we do that here to increase turbulent flow to increase heat exchange, I guess electricity's cheap enough here to get away with it for the time being, oh well. It's high time wetheads took over the design & implementation in this sector.

SWEI

Sounds like the same sort of stuff we come across on outdoor wood boiler and homebrew solar thermal systems.