Posted By docjenser on 28 Aug 2013 02:08 PM
Water to water at lower supply temperatures has higher efficiencies, so we use them as first stage.
Only during cold spans we have sometimes second stage coming on, whether it is supplement forced air, an air handler, etc.
In addition, what is the purpose of radiant if you don't use it most of the time?

Thank you Doc. Reading this statement has helped me to realize what is likely going on. I was told that there was ONE WORD that was holding up the proposal, and that it has been a point of disagreement between the installer and the third party. Bet you that word is "first" followed by "stage".

Update: we had a 2.5 hour meeting with the rep from the installing company and the 3rd party engineer that was hired to evaluate the system.

Based on our loop in the ground (which, it turns out, is undersized for running both geo units EDIT: it is undersized for running more than 5 tons at once, which means we can only run on unit at a time), there are 2 recommendations for heating:

1. Heat is provided via radiator, first stage W-to-W and second stage boiler with an 80 gallon buffer tank. The W-to-W can handle about 1/3 of the load.

2. A coil is installed in the Spacepak, which somehow allows it to create warm air utilizing the hot water that's been created by the W-to-W. Radiators are the secondary heat source.

The report was very clear that most of the piping and ductwork has to be redone, and recommends that a Test and Balance Professional certifies the results once all changes are made.

New and interesting information is that a setback thermostat can be used because the W-to-W will be controlled by outside temps, and it's just the circulation of the heated water or air that will be controlled by the stat.

My head hurts right now, so I'll quit and see if you are interested in more info.

Loop is sized by load, not how many geo units it serves, so if you have a 5 ton WtoW and a 3 ton W to A but the load on the building is 48000 btu's, you wouldn't need 8 tons of loop.
Isn't your space pack currently a split geo, why do they wanna nix that for a hydronic fan coil.........
Yeah I wanna hear the rest of this

I barely understand this myself, so let's see if I can explain it:

"Heating and cooling load calcs were determined using the wrightsoft load short form". Both our basement and our 4 season back porch (which can be shut off from the house during the dead of winter) were considered living space. Based on that our heating load is 108,930 + 15% safety factor = 125,270 BTU (we are fine on the cooling load side, so I'll ignore that for now)

"For the geothermal piping network, the installed 1-1/4 inch supply and reverse return HDPE lines from the geothermal heat exchanger to the mechanical room are adequate to provide the maximum calculated flow of 15 GPM for the system."

With only 15 GPM of flow, both geo units cannot run at the same time. So in the winter, we've got an "either/or" decision. We either shut down the Spacepak and just use hot water heat with geo providing 30% of the need, or we have the Spacepak use the hot water to create hot air, and don't utilize what I've been thinking of as the Water-to-Air geo unit in the basement during the winter, which I now understand is really a Water-to-refrigerant geo.

If we shut down the Spacepak for the winter, we need to add a radiator to our new kitchen which was designed based on the assumption that we'd have first stage air for heat, we lose any heat to our back porch (no radiators there), our airlock between the 2 front doors no longer gets warm air, and the AprilAire humidifier that is paired with the Spacepak may or may not still provide humidity.

With all those concerns, the second option of adding a coil to the Spacepak to allow it to create warm air from hot water was presented.

Those are the options that were presented to us. More loopfield is not an option, based on the analysis. We just don't have enough room.

All this was presented by the 3rd party engineer. The rep from the installing company was silent through most of the meeting. He did say that they could make all the required changes by the end of October, and that he is also said the company is willing to reimburse us for past expenses and more.

Now, after waiting all summer, I have to make quick decision so that we can get the work done before it gets bitterly cold.

With only 15 GPM of flow, both geo units cannot run at the same time.

Yes, but what about increasing it (flow, not loop size) to supply almost all of your >8 ton load? But it could be that the loop itself isn't good for more.

Posted By jonr on 12 Oct 2013 11:06 AM

With only 15 GPM of flow, both geo units cannot run at the same time.

Yes, but what about increasing it (flow, not loop size) to supply almost all of your >8 ton load? But it could be that the loop itself isn't good for more.

Increasing the flow apparently isn't possible, according to the engineer and based on the information he had available. The system wasn't operating when he evaluated it, and there are no historical readings to look at. I don't know if that would have made a difference.

Here's what the evaluation says: "The existing geothermal heat exchanger has the capacity to handle the entire facility cooling load. However, it has the capability to handle approximately 1/3 of the required heating load...it is recommended that the existing geothermal heat exchanger be utilized for system cooling and first stage heating. It should be noted that the existing property does not have sufficient area to provide the quantity of bores necessary for the entire heating requirement for this facility."

Once all the internal pipes are replaced and we have the "existing controls system" set up along with an appropriate stat, maybe we will find something different. In reality, we don't directly heat our basement (there are no radiators in the basement, and there are 3 Spacepak outlets in the basement), so the heating requirement might be less than what calculations are based on (basement is 1400 sq ft).

Bear in mind none of us design geo for 100% of the load, meaning the loopfield wouldn't be sized for 100% of the load either.
I'm not a regular user of HV (space pack) but I don't know that you will find an application where they recommend a hydronic fan coil down stream of the DX coil.
and yes your split system is a WTA. All systems are water to refrigerant and then something else.

Posted By joe.ami on 13 Oct 2013 07:03 AM
Bear in mind none of us design geo for 100% of the load, meaning the loopfield wouldn't be sized for 100% of the load either.
I'm not a regular user of HV (space pack) but I don't know that you will find an application where they recommend a hydronic fan coil down stream of the DX coil.
and yes your split system is a WTA. All systems are water to refrigerant and then something else.

Joe, as always, your input is highly valued. What might be the downside to using a hydronic fan coil downstream of the DX coil?

The engineer spoke to all manufacturers, and in fact that's how it came to be that the Phoenix is being removed (that and it's undersized for the load). The report says: "The existing water heater appears to be utilized as a buffer tank in the existing installation. Phoenix the unit manufacturer does not recommend that their product be utilized in this manner." >

From an engineering standpoint, I have to believe the hydronic fan coil is a feasible option. I acknowledge it wasn't the first option that was recommended. I will ask what negative consequences there might be if we put the fan coil in and then decide not to use it and go with strictly hot water heat. We could maybe delay having a radiator put into our new kitchen by trying this first.

I googled Spacepak and hydronic coil and found this, which looks/sounds like what is being proposed:

http://mesteksa.com/fileuploads/Literature/SpacePak/SpacePak%20F%20Series/HWCII-3.pdf

Any thoughts on this?

EDIT: found this also:

http://www.heatinghelp.com/forum-thread/142986/hydronic-fan-coil-GPM-vs-EWT

Ok, keep an eye on page 2 where it shows out put at different water temps. 120 water cuts the fan coil cap by almost 2/3rds

Posted By joe.ami on 14 Oct 2013 10:00 AM
Ok, keep an eye on page 2 where it shows out put at different water temps. 120 water cuts the fan coil cap by almost 2/3rds

Thanks Joe. I have an appointment with my architect this afternoon to have him dumb down the options for me...he hosted the meeting on Friday and took good notes. I'll make sure he knows about this concern.

I have to remember that its more important to get this right than to get it done, and if it means they don't start work in October because I haven't figured out which option is best, then they'll have to adjust. I had plenty of time to deal with this in August and September while they were dragging their feet. Now I'm really busy.

Edit after meeting with architect: Okay, feeling better about understanding our options. We are going to request a proposal for utilizing the SpacePak for first stage heating by installing a hydronic coil and a variable speed pump. Water temperature will probably be 120 degrees when we are "all geo" to get the better COP from the W-to-W geo. Still TBD is whether it is feasible to feed water from the boiler (when second stage gas is called for) up to the SpacePak and to the radiators at the same time. The reason we are requesting a proposal is so that installer will specify all equipment in writing, as well as other actions to be taken (like remedying the return air issue and adding additional outlets for the SpacePak to meet/exceed the required minimum.

If you need second stage it is likely that the water to water will be overwhelmed. If you can't go WTA I'm confused as to what good it will do take heat from an already overwhelmed WTW.

The "nuts and bolts" are not set in stone yet. Architect was just explaining to me what might happen after we tell installer that using the SpacePak in the winter is our preference (over just radiators).

WTW will maintain an 80 gallon buffer tank...that's for sure.

New to me was the concept that the Gas HW would not feed the buffer tank, but would be separate. I think this is where control strategy and piping get tricky. And where architect says it is up to the installer to research and figure out whether it is desirable (once there is a call for the Gas HW to kick in) to bump up the water temp feeding the SpacePak as well as heating the radiators. If I/we try to dictate how they solve the problem, I/we take responsibility for the outcome.

I'll see if I can post pics of schematics later. Not even sure if they will be helpful but I'll give it a go in case they are.

I would put the gas boiler in the radiation piping downstream of the buffer. In that way it will elevate temperature of already departed water, possibly letting geo continue to contribute.

Posted By joe.ami on 15 Oct 2013 09:57 AM
I would put the gas boiler in the radiation piping downstream of the buffer. In that way it will elevate temperature of already departed water, possibly letting geo continue to contribute.

Nice double post.

Posted By joe.ami on 15 Oct 2013 09:57 AM
I would put the gas boiler in the radiation piping downstream of the buffer. In that way it will elevate temperature of already departed water, possibly letting geo continue to contribute.

Joe I think that's what we have (WILL have).

I am not sure to know where to start here....

1) The load calculations are questionable. A manual J already includes a safety factor, and given your maximun gas usuage of 14.7 therms a day in the previous years, your heatloss is somewhere in the 60,000-70,000 BTU/H range at -20F, which already includes your internal and solar gains. Look at your start of your thread. According to your engineer, you need a 13 ton system, which is unheard of for a 3000sqf house. Yes, I know Minnesota weather, I lived in Rochester for 9 years. 6-7 tons is more reasonable.

2) I have trouble to understand the strategy to do the entire load of the house with the 3 ton and supplement with a 175 BTU/H boiler. First you wanted to get rid of gas, now you been told to heat a large portion of your house with an oversized gas boiler? Second your need an outdoor reset to reduce the load water temperature on warmer days to significantly save you money. Third you have the 175 BTU/H boiler kick in which will increase your temperature to the radiators and the return water to the heatpump significantly, essentially killing the efficiency of the 3 ton heatpump. You will be better off shutting it down and heating with the boiler.

3) Trouble to understand why the loopfield only supports 1/3 of the heating load. My understanding is that you have 6 boreholes with 205 ft depth. In my neck of the woods this supports 9 tons. Ask for the GeoAnalyst report. Do you have any idea how deep they had to drill until they hit bedrock?

4) Having said that why they don't have the radiators and the 3 ton doing the base load, and then supplement it with the 5 split. Yes you can run them together when the piping inside is replaced.

5) To run both heatpumps at the same time, you need about 19-25 gpm of flow. At 19 gpm flow, your system has a pressure drop through the loopfield and the heatpumps of 50 ft of head. A single Wilo Stratos pump can handle that. Even if it drops down to 16-17 gpm, your delta T will go up by 1 degree, not a big deal at this stage of the game.

You need to step back here because the game plan will not serve you too well. I sense a huge amount of over engineering, which will kill the efficiency. Just look at the 2 flowcenters with now 5 circulation pumps in the proposed, each using 230 watts when running. The system will still be very inefficient. Many disclaimers here: "not for construction".

Just to amplify my suspicion, the plans for the loopfield piping to the heatpump now include 5 pumps instead of 3, but after the flowcenter the engineer suggests that flow restrictors are being placed in the lines (keyed notes 2 and 3 in the attachment). To restrict flow in geothermal, which depends on high flow rate to transport heat, makes no sense, especially after the pipes are renewed to increase flow, and more pumps are installed to increase flow. You are setting yourself up for another failure! You can read on the effect of adding flow restrictors to source circuits, e.g. the circuits transporting water from the loopfield to the heatpump, either balance valves or flow setters, in the following link. http://earthsensitivesolutions.blogspot.com/2013/08/is-your-engineer-dumber-than-bag-of.html

1) The load calculations are questionable.

I agree they seem really high. I have asked for the report. The calc included a 1400 sq ft basement and a 150 sq ft 4 season porch that don't get any hot water heat.

2) I have trouble to understand the strategy to do the entire load of the house with the 3 ton and supplement with a 175 BTU/H boiler.

This is based on the premise that the "capacity of the geothermal heat exchanger" and was calculated using Geoanalyst. As the outcome was stated to me, we have enough capacity for cooling but not for heating. We need backup heat, and Xcel gives us favorable rates if the back up can carry 100% of the load, whether or not we ever use it.

3.Trouble to understand why the loopfield only supports 1/3 of the heating load. My understanding is that you have 6 boreholes with 205 ft depth. In my neck of the woods this supports 9 tons.

Could it be 1/3 of the worst case days? Our permit calls for 6 holes, 200 ft, 3/4" piping, anticipated depth to bedrock 147

4) Having said that why they don't have the radiators and the 3 ton doing the base load, and then supplement it with the 5 split. Yes you can run them together when the piping inside is replaced.

3 ton will do the base load, but with 15 GPM the thought is the 3 ton and 5 ton units cannot run at the same time

NEW information, I am now hearing that they hesitated to give me the schematics, which were supposed to be a beginning of sketching out the possibilities and making sure our installer didn't cut corners. NOTHING is going to happen until we have an agreed upon "for construction" version.

Not even shown on schematics is the need to provide 5x the return air to the SpacePak and provide at least 5 more ducts. And, darn it, they're going to give me a welserver monitoring package, if I get my way.

Doc, you haven't steered me wrong yet, so I'm taking everything you give me and figuring out how to ask it sweetly.

Still working this.

17 gpm for a 3 ton on the load side. Dual pump each flowcenter for both the 3 and the 5 ton each? Heat exchanger in the buffer tank? Balance valves on the source and load side for the 3 ton w2w?