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Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
reply to Tex

Re: [HVAC] Manual J and heat pump sizing

Sure does Tex. That would be great but I wonder if it's really going to be worth the cost?

I have a 16i 2-stage condenser and variable air handling unit and that was very expensive.


Tex
Dave's not here
Premium
join:2012-10-20
kudos:2
I don't know what they cost, but I'm sure they are very proud of them. Of course, two-speeds aren't cheap, either. Who knows how many years it would take to reach a break even point.


Hvac tech

@rr.com
reply to Ken
Sizing heat pumps 150% of the cooling load..28500+28500+14250=71250btu/hr old school
Water source heat pumps are very efficient,but as you gas has gone crazy expensive $800 for 192 gallons.If I were you I would by a 5 ton air handler with 20 kW strips and two water coils one for a/c and one for heat,,,,first water from the ground is at about 50, pipe that to the cooling coil evap temp at 50 degrees instead of 40 as with refrigerant. For heat I would put in solar hot water for heat through the other hot water coil in the air handler as well as my hot water tank, with back up gas fired water heater. The a/c part works good did it last year at my brothers in North Carolina..check with local solar water contractor...I'm going to use baseboard heat(hot water).


Hvac tech

@rr.com
reply to Ken
Don't forget you can possibly right off the total investment thru solar and renewable energy program state and utility.


Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to robbin
said by robbin:

You may want to research units that use inverter technology.

I am looking at that right now as my #1 choice. The Water Furnace 7 Series looks amazing, but the price might be out of my budget.

tons             cooling           heating
3          13,000 -  38,000   14,000  -  41,000
4          19,200 -  49,000   19,000  -  55,000
5          23,200 -  60,000   23,000  -  65,000
 

The 4 ton unit would be perfect for me, I'm trying to find out prices on any scratch and dent models they might have. The other model I'm looking at is a Daikin Mcquay with variable speed compressor.

tons             cooling           heating
3          15,900 -  38,900    9,900  -  30,100
4          17,200 -  50,900   18,800  -  40,700
 

The heating max btu's are a little deceiving. I believe Water Furnace uses the top capacity possible, such as 118%, as the max number. Daikin on the other hand uses 100% as the max number, even though the unit can go above that. I found a chart that showed the Daikin 4 ton with an actual top of around 53,000, inline with the Water Furnace numbers.

mj3431

join:2003-04-21
STL, MO
reply to Tex
I had a Greenspeed 3 ton unit priced for me 2 years ago. They wanted nearly 10k just for the equipment. We do have a 4 ton Greenspeed in one of the offices at work though and it works really well, and is very quiet.

prairiesky

join:2008-12-08
canada
kudos:2
reply to Ken
Do not grossly oversize your AC load, it's the wrong thing to do. You don't want the unit to short cycle, that's when premature failure occurs. It's better for it to be slightly undersized and run longer.

Can you do 2 three ton units in parallel? I take it these are water to water?

Have you considered using an air source? They're simple and not much more expensive than a normal A/C unit.

I have no idea what your climate conditions are like, but up here closed loop geo thermal systems tend to not produce enough heat 8-10 years down the line. The reason being that we need more heat than cooling. The earth temps slowly get drawn down to the point where we're making a big block of ice in the ground that never really thaws.


Cho Baka
Premium,MVM
join:2000-11-23
there
kudos:2
Reviews:
·TekSavvy DSL
said by prairiesky:

The earth temps slowly get drawn down to the point where we're making a big block of ice in the ground that never really thaws.

I've wondered about that.
Either the loop needs to be deep and ma$$ive, or what's the point...
--

garys_2k
Premium
join:2004-05-07
Farmington, MI
I suppose that the loop should extend to beneath the water table depth. That would help keep the temps stable around the pipes.


Tex
Dave's not here
Premium
join:2012-10-20
kudos:2
reply to Cho Baka
said by Cho Baka:

said by prairiesky:

The earth temps slowly get drawn down to the point where we're making a big block of ice in the ground that never really thaws.

I've wondered about that.
Either the loop needs to be deep and ma$$ive, or what's the point...

It just goes to show that no technology is perfect. Inevitably, there will be tradeoffs.


Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to prairiesky
said by prairiesky:

I have no idea what your climate conditions are like, but up here closed loop geo thermal systems tend to not produce enough heat 8-10 years down the line. The reason being that we need more heat than cooling. The earth temps slowly get drawn down to the point where we're making a big block of ice in the ground that never really thaws.

I can't speak for what your conditions are, but that simply can not happen here with a properly sized loop.

prairiesky

join:2008-12-08
canada
kudos:2
unless your summer inputs and winter outputs are the same, something won't align unless you have some other source to make up the extra capacity. here we have an average of 5777 heating degree days vs 186 cooling degree days. They're so unbalanced that it's a deep negative


Ken
Premium,MVM
join:2003-06-16
Markle, IN
The earth itself is what provides the extra capacity. If you make the loop big enough and at the proper depth you should never freeze the ground. It would be like dumping cold water in the ocean and worrying about the ocean freezing. Even in Antarctica if you dig deep enough you will find warm ground, granted it might be 20 miles deep. It's all just a matter of sizing everything correctly for the local environment.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse
reply to Cho Baka
You do not want to have the loop too deep, deeper does not give you more heat (unless you go very very deep). The loop should recover from the summer sun. Some frozen ground is not a problem if the loop recovers during the warm period.

The issues people have run into is that loops where sized for 75-80% of total heat load and aux heat did the rest. 10 years later when aux heat get more expensive a bigger heatpump is installed. Now the new heatpump put a larger load on the loop and the loop get too cold, outside what it was designed to handle.

You can construct loops that are design to work below freezing. It is not as efficient but can be done if space is at a premium.

Basically it is all about correct loop sizing and it is much better to oversize the loop that will last 50+ years and buy a cheaper heatpump, which will be replaced at some point, than the other way around.

prairiesky

join:2008-12-08
canada
kudos:2
reply to Ken
said by Ken:

The earth itself is what provides the extra capacity. If you make the loop big enough and at the proper depth you should never freeze the ground. It would be like dumping cold water in the ocean and worrying about the ocean freezing. Even in Antarctica if you dig deep enough you will find warm ground, granted it might be 20 miles deep. It's all just a matter of sizing everything correctly for the local environment.

radiation only goes so far down. Most loops are 20 ft plus. For reference, our frost line is ~8-9 feet deep. The frost comes out naturally by mid July usually. That doesn't leave much time to replenish anything lower. Some of the loops go to 20 feet which will not see much replenishment and if it does get some, it's no where near enough. The ocean is a different story, it's a fluid which moves around and can you don't see the same water twice. pulling water out a lake does make more sense than the ground for precisely that reason, it's a bigger body and it's motion allows you to access it. The motion also allows natural convection in the summer which allows it to gain back more heat.

You have to answer the question, where does the replacement energy come from and how does it get there.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse
I am surprised that loop depth are so deep in your area. In Scandinavia loops are normally 1 - 1.5 meter down and the loop has a 1 meter distance to itself side ways. At that depth the loop get the replacement energy from the sun.

The medium in the loop is an ethanol - water mix that can handle temperatures down to -30 Celsius. A good loop might have a minim temperature of -1 Celsius or better.


Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to prairiesky
The earth itself is warm. Yes, the soil near the surface is heated and cooled by the air temperature based on the season, but below that soil, is soil that remains a constant temperature year round. If you put your loop in that soil, and size the loop correctly, geothermal will work indefinitely. This is the principle behind vertical loops.

scooper

join:2000-07-11
Youngsville, NC
kudos:2
reply to Ken
I'm sort of surprised by that as well - only 1-1.5 meters ? that's only about 10 feet - you can almost dig that with hand equipment, although I can see contractors using a backhoe for that.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
More like 5 feet

iknow_t

join:2012-05-03
reply to Hagar
said by Hagar:

I am surprised that loop depth are so deep in your area. In Scandinavia loops are normally 1 - 1.5 meter down and the loop has a 1 meter distance to itself side ways. At that depth the loop get the replacement energy from the sun.

The medium in the loop is an ethanol - water mix that can handle temperatures down to -30 Celsius. A good loop might have a minim temperature of -1 Celsius or better.

Scandinavia is very far away from the U.S. as a matter of fact, it's in another country.. it has a different climate too. even comparing the climate of Canada and Florida there is a HUGE difference.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse
reply to scooper
scooper,

They have a special plow like thing that get the loop hose down and seal it up in one shot if the soil is good. With a backhoe you dig one 1+ meter wide ditch half the loop length and put the loop hose on one side and return on the other side.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse

1 recommendation

reply to iknow_t
Iknowit,
I am confused of the purpose of your post?
I know Scandinavia is far away from the US. Your post implies that my knowledge/experience of Scandinavia has no bearing on the discussion.
Ken is is Markle, IN average yearly temp 50.19°F, Stockholm Sweden average yearly temp 43.9 °F. I think that is close enough.

I replied to prairisky, his profile says Canada which has similar climate to Scandinavia.

I am surprised at the loop depth prairisky mentioned. Physics works the same regardless of county and I do not see the economic gains of a loop depth of 20 feet but I sure there is a reason for it, just trying to learns something.

iknow_t

join:2012-05-03
said by Hagar:

Iknowit,
I am confused of the purpose of your post?
I know Scandinavia is far away from the US. Your post implies that my knowledge/experience of Scandinavia has no bearing on the discussion.
Ken is is Markle, IN average yearly temp 50.19°F, Stockholm Sweden average yearly temp 43.9 °F. I think that is close enough.

I replied to prairisky, his profile says Canada which has similar climate to Scandinavia.

I am surprised at the loop depth prairisky mentioned. Physics works the same regardless of county and I do not see the economic gains of a loop depth of 20 feet but I sure there is a reason for it, just trying to learns something.

the type of soil and underground temperatures would make a big difference. above ground temperatures are a smaller part of it.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse
Sorry for going off topic but I am curious about loop depth.

I agree that type of soil matters since heat transfer in different soils are quite different, strongly correlated to the water content of the soil. But that tends to effect how long loop length you have not how deep you put the loop.

Underground temperatures are usually correlated to average yearly air temperature unless you have an other heat transfer medium like moving ground water.

It is expensive to dig 20 feet down. It would be less expensive to dig less deep and have a longer loop. If the loop is divided in two or more parallel loops the flow resistance stay low and does not require a huge pump. I would have guessed that you put the loop at/just below the frost line but I am not a professional in the field.

prairiesky

join:2008-12-08
canada
kudos:2
reply to Ken
20 feet is actually quite shallow here. I don't design the loops, just the capacities needed. 50 feet is common, and I've read up to 300, but haven't heard of it in person. I've done well to well which has gone 250 before, but never closed loop.

For reference, we need a LOT of heat here. As I mentioned before 5777 degree days of heating and ~170 cooling. Aswell, the frost goes to ~8 feet, call it 9 to be safe, that means the ground at 9 feet deep is frozen solid, therefore below 0C. To be able to get heat out of a heat pump, your loop temp needs to be ~7c(45f). Which means you need to go down further. Then you need to factor in how much capacity you need over a heating season or many. That tells you how many holes you need and how deep you have to go in order to have enough capacity. The problem we run into is that the earth is supposed to act as a sink, absorbing heat in the summer and withdrawing it in the winter. But, our seasons are so lopsided that the ratios are way off.

You have to treat the area of influence as a black box. It has inputs and outputs. If they don't match, then in the long run you're gonna run into trouble, it's not a matter of if, but when. The large the loop, the more time you have.

We had a project a few years back with the opposite issue. The company was using well water for cooling their plant. Over 10-15 years, they overheated the well to the point where it couldn't provide the capacity they needed because the aquifer wasn't flowing through fast enough.

That being said, every single situation is different and the climate is a HUGE factor.