geothermal hydronic

Randy Calvi

We are an HVAC contracting co. in the Portland, OR area. Our speciality is geo and radiant/hydronics. We've been doing various mixes of them since 1998 or so. Prior to that, my activities are WAY varied, but always involved mechanical/controls/HVAC in one way or another.

I have quite enjoyed reading some of the posts here (when I've had time) since I discovered the RPA a few years ago. It's fun reading about all the different creative ways people come up with to solve the same problem.

Thanks for the welcome.

RC

realolman

geothermal hydronic

anyone have any ideas, opinions,info about geothermal hydronic heat?

GMcD

I like it

There are a few projects around here with a geo-exchange systems, and a water to water heat pump plant that serves a radiant heating/cooling system along with the coils in the dedicated outdoor air handlers. The photos here are of a local Library project with horizontal slinkies laid under the large underground parkade, serving a radiant slab heating/cooling system.

BC_8

Love it

I think geo and hydronics are a great match if done correctly. In my area (NY) it is about 1/3 the cost of oil or propane, 1/2 the cost of gas. Only wood, coal, or solar can beat it for operating cost. Some things to keep in mind:

-Low hydronic temps are KEY. Efficiency is much better at low temps and most units won't do much over 120F (and that's pushing it for long term durability). I notice Climatemaster has a higher temp capable unit that looks pretty good. Obviously this depends on the envelope and climate, but in my case it pretty much meant radiant was my only option. I have a couple of rooms using panel rads, but they are de-rated to about 30% of their nominal output, so they're pretty big.
-Outdoor reset is almost always a good idea. Again, low water temps=high efficiency. In my case there is about a 30% savings using reset.
-Plan on a buffer tank unless you have a high mass system without much zoning - the heat pump needs a certain flow rate.
-Watch out for energy hogging loop and hydronic pumps. The Grundfos 26-99s and 26-116s that are generally used aren't very efficient - check out the Armstrong E-series. Over the course of a season the savings can be significant.

These comments are specific to hydronic systems - there is lots more to think about on the geo side such as loop sizing etc - lots of good info out there if you look around.

One downside - the ARI doesn't have a rating system for hydronic heat pumps, so they can't be energy star elegible and therefore don't qualify for any of the federal tax credits. >:(

BC_8

wow

Geoff, where is that located? Is it in service yet? I would imagine the heating/cooling loads must be pretty well balanced since the loop field doesn't seem like it will get much solar or groundwater recharge. I've always thought that horizontal loops under buildings/parking lots were a bad idea, but I've seen a few lately that seem to be working.

[Deleted User]

My experience with GEO

Has been less than glamorous. Over half the compressors we have installed in the last 5 years have failed, some more than once (one is on its third compressor).

The biggest problem appears to be the equipments ability to start and stop. The systems are all properly sized as it pertains to buffer, distribution and loop fields, and the loop fields are performing quite well. We've data logged numerous failed systems and were quite suprised with the number of start cycles per hour.

Until which time someone comes out with a soft start compressor (ECM motor) we are backing away from the GSHP market.

As it pertains to the loop field pumps, it would be my recommendation that you go with a Wilo Stratos and set it to operate on Delta T, which will only use as much energy as it needs to. Word of caution. THe GSHP manufacturers ALL depend upon the loop field motors to provide useable BTU's in their performance calculations. In other words, the use of a highly efficient loop pump motor will negatively affect the output performance of the GSHP system.

And as far as being "green" is concerned, until which time every watt comes from a renewable energy, like nuke, or hydro or wind or solar, that particular statement is misleading at best. They're still burning dinosaurs so you can move heat from mother earths feet to her head...

I am not impressed with that particular industry. They have a LONG way to go to be as reliable and competent as the current offering of ultra high efficiency boilers we deal with every day.

Sorry to be a curmudgeon. It is just our experience, and I'm hearing that we are not alone...

ME

BC_7

mark...

I'm very interested in your experience since I've recently been seeing high refrigerant discharge temps on my unit. What info do you have to indicate that the number of cycles was causing the failures? Not doubting you at all, it's just that most of the info I've seen indicates that high compressor discharge temps are what kills them. How many cycles were you seeing per hour?

Interesting about the loop pumping energy - I've been chasing a low performance issue on my unit, I'll have to run some calcs and see if this makes a difference.

GMcD

The Pictures

The photos are of a project that will be in the commissioning stages in a couple months. It's a bit of a hybrid system since the heating energy for the building is coming from a local district energy system, which is supplemented by a large array of solar water heating panels. The geo heat pump system for this particular project is going to be a primarily cooling only system, and the climate it's located in has maybe 30-40 days during the summer where free cooling from the DOAS air supply will need the radiant cooling to be operating from the heat pump plant. We also have bypass valving around the heat pump unit to use direct ground temperature heat exchange for the mid-range cooling for the radiant slab when we only need 18C to 20C water in the slab. The heat pump plant will provide the 16C water when we need it during the July/August period. The predicted EER in cooling will be over 24. Not bad.

The slinkies are buried onto native wet clay soil, and there is a constant flow of ground water through the sub-soil zone there, so we have very good soil conductivity. It's only a 45 ton cooling capacity plant for a 32,000SF building. The energy efficiency is in the building envelope design, keeping much of the solar gains out of the building and using supplemental natural ventilation and the displacement ventilation air supply with 18C (65F) air supply.

There is another building locally (Gleneagles Community Centre) with virtually the same type of systems, except that one has the geo-exchange loops placed 2.5 meters (8 feet) deep under an outdoor gravel parking lot. It's been operating for over 6 years now, with no problems other than a few circ pumps that had to be replaced under warrantee, early on in the project's life.

Another local project - the City of Vancouver National Street Works Yard offices uses a water to water heat pump plant, but with vertical boreholes for the geo field. That building uses DOAS displacement ventilation as well as suspended radiant heating/cooling panels, all served from the heat pump plant. It's been running for 3 years now, no problems.

GMcD

Water to water heat pump problems

I have to agree with your basic issue of electrically powered "stuff" in terms of the source energy issue. We haven't seen the failures of the water to water heat pumps around my area. We've generally been getting the WaterFurnace brand, and getting good local support, and the system operating parameters haven't been "extreme". We're very careful to balance the energy loads, and being up in a heating dominated climate, we always have some supplemental heat to insure that the geo-exchange field loads are balanced.

wethead7_2

two speed

Have you looked into some of the higher end two speed model with the unloading scroll compressors? We have seen improvements longer run times and more efficient and affective
control of the temperature. The use of the correct controls is important.

J Prisby_2

Geothermal Conference in Midwest



I am not sure where you're located but a good start is happening in Dubuque, IA sponsored by the Iowa Heat Pump Association and the Wisconsin Geothermal Association. It's going on this week starting on Tuesday March 18th with a Geothermal Radiant Floor Design and Installation Seminar to kick it off, a trade show March 19 and conference sessions March 19 and 20th. You can check out the details at www.iaheatpump.org. There were still some seats left as of the other day for the seminar on the 18th. I recall someone else mentioning this in an eariler post as well. I'll be planning to see what's going on myself.

Jim Prisby

realolman

a couple questions

My house is partly old and with a couple recent additions. Pretty well insulated. I presently have an oil boiler with baseboard heat. 63,000 btu heat loss.


Would it make any sense for me to pursue converting the house over to radiant, in anticipation of installing geothermal hydronic?

What does the info in the attatchment mean? How does one match the model to the heat load using this chart? I got it from a manufacturers web site. I didn't know if it would be appropriate to post, so I removed any reference to the manufacturer.

[Deleted User]

Not compatible with BBH, unless....

the original installers used the Long Island heat loss calculation method (wall to wall BBR and BBR on the doors with rubber hoses for the hinges :-)

The max temp you MIGHT see from a typical GSHP is around 120 degreesF. I found out that though they do list higher temperatures in their literature, it is not recommended that the units be operated there. Marketing hype overrides engineering department as Ken Secor would say...

As for the attachment, what you are looking at is their performance data. In other words, if your source can provide X GPMS at 32 degrees F, then you can expect the unit to deliver X GPMs of XXX degree F water to the load side.

What these guys (I think) are talking about as it pertains to balanced loads is to make sure your loop field (vertical versus horizontal) has access to enough "energy" to keep from super chilling your loop field.

In otherwords, don't draw more out of a loop field than can reasonably be expected to recover in a short rest period. If you are going with the vertical bore holes, and are in an active aquifier (moving water below ground) you will not have a problem. If you are in a static water basin, or hit dry holes through out, you have an extremely limited amount of free "energy" to tap, and consequently, your loop field could run low on "energy". The same applies to horizontal loop fields in poor conductive soil conditions that depend upon surface moisture for condutivity replenishment. I am suprised to see the slinkys under the parkade. I hope the deisng engineers took everything into consideration. At last check, the GSHP manufacturers association did NOT recognize horizontal slinky beds as viable energy sources, but that was also 5 years ago that I attended their classes. Things change.

There are some studies that have been done on situations whereby there was little to no AC loading (AKA loop field recharging), and static aquifer conditions, and the temperature of the loop field is slowly but surely degrading, and will eventually require "recharging", using either ambient summer air, or possibly even a small solar array attached to the loop field to "boost" the ground temperatures, or eventual abandonement.

To answer some other questiojns, we have lost both recips and scrolls, with and without 2 stage, unloaded starts. We typically do DHW preheat with the GSHP, so consequently, the compressor is typically HARD starting against high residual head pressure loads. Maybe that is our mistake. Attempting to use the equipment for doing something common sensical like DHW pre heat.

We find ourselves going back and putting simple outdoor reset controls in an attempt to get longer life expectancy out of the compressors. Come to think of it, we even had one WITH the ODR fail. Fluke, I'm sure.

We found the compressors starting between 6 and 12 times per hour depending upon the load considerations.

As I have stated, I am just not really impressed with the technology currently offered up by this bunch. They don't take future service needs in to consideration (6 man hours to replace a friggin circulator due to rediculous access?, no expansion tank or air elimination on their loop fields, no operating ccontrol on their compressor package, only a manual reset high limit and the list goes on and on...)

In order to use GSHP, you FIRST Need to do as MUCH conservation as possible, then convert to a low temp, high efficiency radiant or air delivery system to make it compatable with the low temperatures of avaiability that you will see. I see a bright future potential for GSHP, just not sure we are ready right now. I know I'm not impressed.

ME

Rich L.

Geo with radiant

I've had my system, GSHP with radiant floors both levels, ODR controls, in operation since the fall of '06 and been very impressed with it's operation and efficiencies. I decided to install it in my new home after several discussions with my boss who has had it in his home since '93 (forced air). In that time he's had to replace his thermostat once. That's his only faliure on the system. Since '93 he's only had 2 winters where he's spent more than $200 on heating his house. His house - built in '93, 2x6 walls, energy efficient 2 pane windows, slinky loops buried 5' underground, etc. He has a seperate electric meter for his heating system and was an original study by his electric utility (Linn County REC) so he's kepy very close track of all his expenses since his original installation.

I personaly find it to be a very viable option and am very pleased I went with it.

Jim, see you at the Iowa Heat Pump Conference. It will be my third time there. You won't be disappointed!

Best regards, Rich L

*Edit: Just to clarify, that's $200 per heating season, not per month. RL

realolman

I don't want

to hook it up to BBH. I have been considering changing at least some of my house over to in the floor radiant, even with my present oil boiler. If Geotherm would be compatible with that, I thought it might make even more sense, with the conversion to the geotherm in the future.

realolman

Are you

located in the north?

Rich L.

Location

I'm located in East Central Iowa. Winter design temp is -5*.

Rich L.

Converting to radiant

Realolman, IMHO it makes all kinds of sense to make the conversion. Even before the transition to GEO you would be gaining all the benefits of radiant. One big consideration would be in the conversion process. If you did part of your home at a time you would need to mix down the water temps. Your radiant would most likley require lower temps than the BB. If you have a cast iron boiler return temps of 140* or so would need to be maintained to protect your boiler and your floors may not need that high of temps.

Do you have any experienced people in your area doing this kind of work? Do your homework! This is a great place to start. Check out the online store for books on radiant. Ask lots of questions.

A good GEO info source is: http://www.igshpa.okstate.edu/index.htm

Regards: Rich

Randy Calvi

Geothermal heat pumps

If you are having 6 to 12 starts per hour, you may be short-cycling the compressor. Do you have the recommended 10 gallons of buffer tank per ton of capacity? That flywheel gives the heat pump enough run time to prevent the short cycling and prolong the compressor.


RC

Randy Calvi

Geothermal data

Source is the earth loop side of the heat pump - load is the hydronic side. EWT - Entering Water Temperature. SWPD -Source Water Pressure Drop (each unit should have a curve relating GPM to pressure drop through the coil - very useful for troubleshooting) LWPD - Load Water Pressure Drop. Heat output in BTUH X 1000 ** AT THESE CONDITIONS **.
As the source side goes down or the load side goes up, the BTU's go down, the kW go up and the COP (Coefficient Of Performance) goes down.

Also, don't plan on adjusting your output by increasing the flow rate through the unit unless the manufacturer specifically advises it. You can cause some serious erosion on the water coils if you increase the flow too far.

Hope that helps.

RC

Mark Eatherton

Buffer tanks properly sized...

Most of the homes we have these in have numerous micro zones. They all have different exposures and cycle at different rates. I don't think ANY of the GSHP manufacturers ever thought this would be a possibility. I think they thought every house only came with a single zone. Such is not the case.

I also don't think they ever thought of the concept of doing DHW preheat with reverse indirect /buffer tanks either. But we do (did).

What is your background and experience Mr Calvi?

Welcome to the Wall.

ME

BC_8

very cool

I always enjoy seeing projects like this - thanks for sharing.

[Deleted User]

THank you for sharing...

your TIME and your KNOWLEDGE. They are both greatly appreciated on THE Wall.

Like my ol' Pappy used to say, "If you don't learn something new every day, you were either, A: Not paying attention, or B: Gone fishing. And if you WERE gone fishing and you didn't learn something new, you WEREN'T paying attention... Best fishin' buddy I ever had.

Missin' ya Pa:-)

Your fishin' buddy...