Our school district has 4 school buildings with geothermal. 3 of the 4 seem to be grossly short looped, and so far the remedy has been to put a boiler adding heat to the loop.

We'd like to propose a better solution, possibly including putting in more loop, but we're not sure how to decide how much more it needs.

If we had the loads of the building, could a thermal conductivity test be done to find out the capacity of the existing loop? If so, how is a TC test done?

If not a TC test, then is there a way to accurately determine the capacity of an existing loop?

With the loop up and running you should be able to measure its actual capacity - flow times Delta-T

That's basic so I must be missing something - such as perhaps there being no way to measure flow?

How do I get the flow without a flowmeter? This is a 6"-8" main loop line.

In a large commercial application some of the transponder type flow meters for municipal water supply have been used with a degree of success.

I also think that the TC test is more involved than engineer stated.  We gather the data over a 24 hour non stop run and then send it away for disection.

Is there no data for initial install?

Heat load/ initial TC test?

It may be worth the investment to have a new loop drilled to the spec of existing loops and conduct a TC test and try to reverse engineer the capacity of the existing loop field before the school takes a another swag at it.

Hope this helps
Eric

TC test I've read of consists of a water heater of known wattage / btuh heating water which is circulated through a test bore for a day or two. Resulting temp change, known bore length, etc yields thermal characteristic for that bore. No magic to it, though seems like it has to be run in warm weather. No reason one couldn't devise a test in reverse direction (getting heat from ground rather than rejecting it into ground, but measuring heat would be harder. since would have to chill the water in an easily measured fashion. Electric heat Btuh rate being so easy to calculate makes that method quite accurate using cheap equipment

Another poster here or at geoexchange noted availability of an ultrasonic flowmeter for rent. That might be just the ticket - does not require breaking into line.

The biggest problem with using what was initially engineered is that it was designed as short-looped. The boiler was included as an original installation item. The driller, not sure who, couldn't get it drilled, so they put horizontal loops under the football field (drilled horizontal). This was not anywhere near the designed drilled loop, but it's what they did. I'm wondering how to test the capacity of what they did, not what they wanted to do.

If the ultrasonic flowmeter is really available, how accurate might it be? Obviously we'd need a fairly accurate reading.

Clark,
do we know what's there already, what the demand is, heat pump size, ewt, lwt.......
We've seen more than a couple short comings here lately (fortunately not my systems) with extreme weather. Not sure if that is a factor there.
Not sure if i can help without the usual questions answered...load..equipment...demand.
We (as i mentioned are falling short here lately (lot's of aux heat) do to unusual conditions, how do we know it's not the same there?
J

It's not because of unusual conditions. It's been this way from startup, fall of 2003.

Each time I talk to a potential customer that knows of this particular school's situation, they thumb their nose and say "those geothermal things are crap".

Usually, our temps in late Dec. thru late Jan have highs of 20, and lows of -20. This year, though, we've been blessed with warmer weather. You guys are getting the short end this time. Typically, our area's design temp is -10. I'd guess the so-called designer of this one used 0, which is still adequate, IF he would ever use backup electric heat in the heat pump. However, if he had done this, after having short-looped it, it would just be a high electric bill instead of a high propane bill.

I'll see how accurate of numbers to what's actually there I can come up with. I just don't believe they'll tell the truth as to how much loop is really in the ground. I think they sold the school district a bill of goods.....I'm sick of bad word of mouth for geo from this Hack. He continues and continues to get away with this crap. Sorry for venting.......

There are any number of testing companies that could supply the method and test equipment to evaluate your existing loops.
It is unusual to hear of a system of this magnitude that does not have permanent monitoring equipment in place to operate and maintain the system. It would be worthwhile to include this capability in any upgrade you do.

Process industry very commonly measures flows, pressures, temperatures, etc with a high degree of accuracy using standard components. Magnetic flow meters are made by several vendors such as Honeywell or Foxboro. Calibrated orifice plates are somewhat cheaper but with existing piping, mag meters offer greater flexibility in location. Mag meter accuracy is standard at something like 1% of full scale reading and imposes negligible line loss.
Temporary measuring equipment such as ultra-sonic flow meters that clamp on the piping could be used but accuracy is less and the testing incurs more labor charges.

Permanent metering would allow for loop additions in stages if funding must come over time.

Dick

Quoting cnygeo 1/22/2009 4:33 PM in another tread: runtime and sizing:

"We can ... try to predict the aux. use based on degree days and capacity."

Clark, assuming cnygeo is correct, can one predict capacity of the loop, if aux (boiler) output, school's heat load, and degree days are known?

Or consult with school's statistics teacher to establish a correlation between the loop capacity and a decline in ewt for a given amount of extracted heat in a certain period. Get data from a known loop.

Finally, could you pump measured heat out of the loop over a weekend until ewt stabilizes at its min acceptable temp for this time of year? Is a weekend not enough time?

Regards, Masoud

Have you talked to the folks at OK State, they may have some thoughts, and they sure don't want geo to have a bad name.
J

So...I did some finding out. Talk about frustrations!

I'm not sure where to start, so sorry if this is incoherent...

-None of the heat pumps in the schools were installed with any backup/supplemental electric heat.
-The loops were purposefully designed short because of the fallacy of thinking that in our area we can "load share" 365 days/yr.
-The heat pumps don't have enough heating capacity to heat the building when the loop temp. drops below 40 deg. F.
-When the outdoor temp. reaches 10 deg. F., the heat pumps cannot heat the buildings, and the loop temp. drops to 35 deg. F. After determining this, they have set the ground loop pumps to shut off at 40 deg. Then the boiler is feeding warm water, at 55 deg. F., to the building loop for the heat pumps to run and heat the building.
-At outdoor temps. around -10 to +10, the ground loop looses heat, instead of gains...the water entering the ground loop is 44 deg. this morning, and returned from the ground at 42 deg.
-The engineer who sized the heat pumps maintains that they are sufficient to heat the building down to -9 deg. F. outdoor temp. at 35 deg. F. loop temp.
-Experience shows that with the boiler on one of the schools, maintaining the building loop at 55 deg. will allow the heat pumps to have enough capacity of output to heat the building.
-The loop designer (so-called) maintains that the loop is sufficient. Even on the newest school, built 2 years ago, he supposedly designed it with 2 loop fields. It was supposed to be a backup loop field, only needed if outdoor temp. dropped below -9 deg. F. However, even with both loops running, they lose ground fast enough that the building can't maintain temp.
-each building is approx. 360-400 tons installed of geo units.

The solution they want to do is to put enough gas boiler in to maintain the entire building loop at 55 deg. F., when outdoor temp is -30. This translates to about 4 million BTUh of boiler. They're not willing to drill more loop, because they know the loop temp will still drop, and the capacity of the heat pump units is lower than needed at lower loop temps.

After today's meeting, I'm not looking for much of any solution, just needing to vent. What we're left with is a HUGE black eye to geothermal.

The same mechanical engineer has designed a system for our electric co-op's new building. We've seen his loads and design. He has shorted the system on tonnage to cover his own load. He's not including ANY backup heat, AND he's using this so-called loop designer, AGAIN!!! Hook, line, and sinker. We're putting efforts together now to convince the electric co-op to reconsider and re-design. We'll see how that goes. We probably have a snowball's chance...

Joe, do you think the guys at OK state would want to step in with anything here?

I don't have any influence at igshpa, but they are quite the geo flag wavers and would be just as disgusted as us; it's worth an e-mail anyway. They have loop designers that travel to large sites and test soil conductivity to keep from over killing huge designs. Some one like that might be able to head scratch through your questions.
For those out there on the design end take note of this situation. Contractors are often criticized for wasteful/over design, but we know that mother nature does not always behave as expected (we've had a 5 year supply of sub zero here lately). Tight designs have the unfortunate side effect of inadequacy in extreme conditions. In my neck of the woods that means when it's really really cold, you don't have heat (seems like you'd need it eh?). Local experience and accountability matter more than any bin report.
Any one in the load share business should carry an extra liability balloon while they are at it....Soon as usage changes (say 35 instead of 30 kids in a class room + hot day... you're toast). I also never understood the reluctance of some to install aux. coils (heating dominated usage) they are cheap and can mitigate many emergencies (I tell my custs. that they get one if for no other reason than having them wait 'til morning to call me if the heat pump acts up).
Worst case Clark, if you take the data you do have and play with it in reverse on design software you should be able to ball park loop size and could offer graduated repairs (we'll install X feet at a time and stop when performance is satisfactory).
Following a few chuckleheads around here myself, but no huge problems like yours.
Good Luck,
j

I wonder if the school officials are under the impression that heat pumps will multiply the gas boilers' heat output by geothermal heat pump cop!

Regards, Masoud

I've been reminded that running a boiler at lower water temps increases chance of corrosion from condensation - I was cautioned that reducing it by just 20-30 degrees could cause problems.

I can only imagine the condensation in a gas boiler configured to heat water to just 55 deg F!

What kind of geo unit are they running that they can't generate heat with an EWT of 35F? Shouldn’t they run to at least 20F? I understand that the BTU output on the other side would be reduced. Wouldn't supplement heating on the other side of the geo units make more since and let the geo units run until they his say 20F EWT? Couldn't they use the existing gas boilers the way most systems use Aux or resistant heat?

Clark, I would hate to be in your shoes...

The boiler would not necessarly run at that low of a temp. The loop could have a 3 way valve to control the temp. One I ran kept the boiler at 195 degrees and varied the loop temp with an outdoor temp sensor. It would vary from 120 degrees to 195.

Learn something every day! - thanks

Clark,

Have Mclain give me a call or get my number from him. I'll get you in touch with a SDSU professor just got done re-writing the IGSHPA manuals that you may want to talk to about these issues. Sounds like you got a real can of worms.
Dan CGD

Not to sound defeated, but what can/might that guy/IGSHPA do? I'm sure they already know of his situations and they haven't seen the need to do anything yet.

At this point, the school district isn't interested at all in fixing the geothermal to be a geothermal system. Instead, their minds are made up and set on putting in boilers for 100% replacement of the loops--not that they won't use the loops still, but they want a redundant system to be able to handle the loop going down.

My concern, now, is more with future debacles such as this one. I want this to stop. I'm sick of all the maintenance employees, board members, other employees--who see that it doesn't work but don't know the real reasons why--telling me and others that geothermal sucks; that it doesn't work at all; that it costs more to operate than a conventional boiler/chiller, or furnace/air conditioner; laughing at the idea of geothermal; being the bruise of this black eye.

We all know that one "oh crap" wipes out a whole lot of "atta boys". Up to this point, I've mostly ignored all of this, but it's starting to really have an effect on geothermal's image in the area.