Earth energy and radiant floors

John Ruhnke

Mark,

I had a jet pump in my house. It had two pipes. I replaced the jet pump with a submersable well pump instead. I rented a ditch digger from the electrician to bury the wire in the ground. I estimate that the new well pump will cost half as much to operate. I then had one pipe left over. I installed a heat exchanger into my radiant floors secondary loop for upstairs. I then cut a tee into the cold water main and ran the well water through the other side of the heat exchanger and into a soliniod valve. The solinoid valve dumps the water back down the well through the abandonded jet pump pipe. The water comes in at 56 degrees and precools the floors in the summer. I estimate that it could handle 30% of the cooling load. I have a regular A.C. system too. Bob Gagnon did something simular to this but dumps into his lawn sprinkler system. He claims it handles 30% of his cooling load.

It didn't cost much to do, it was simple.

John Ruhnke
JR@ComfortableHeat.com

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Ken Caverly

Earth energy and radiant floors

I am reading a publication on earth energy systems. It says that a heat pump can only heat water to 120F. It states "you must make sure your radiant floor heating system is designed to operate within the temperature capabilities of your EES.

It claims that at water temps of 120F that the ground source heat pump will produce 2.5 units of heat for every unit of electricity used to operate it.

Then it adds that if the required water temp is reduced to 105F it will produce 3.1 units of heat for every unit of electricity consummed. In other words , it will be about 25% more efficient.

My questions. #1. Is this as good of a system as they claim. My electricity rates run around 7 cent a Kwh.

#2. What temp are most home systems designed for. Are they designing for lower temps to accomadate for ground source or possibly solar conversion as these systems improve or oil prices continue to rise.

zac_2

what I use

#1: yes, the efficiency really is that good. even better if you use deep well water as opposed to a closed horizontal earth loop because of the higher ground source temperature.
we converted our system at our plumbing and heating shop from an electric boiler to geothermal with vertical closed loops and our utility bills dropped by about half.

#2: when i design a typical radiant floor system i usually use 120 F as my supply water design teperature regardless if its geo or not, you don't want your floor temp to be above 90 F for comfort/health reasons.

while ground source heat pumps can reach teperatures up to 135 F their efficiency drops off drammatically past 120 F.

[Deleted User]

It depends...

Three are two variables on GSHP systems. One is the availability of energy (source), and the other is the demand (load). A heat pump, as the name implies, is nothing more than a heat transfer device. It moves heat from point A to point B. THe less of a "hill" it has to move it up, the higher its' efficiency. So if you have a shallow hot spring, your co efficients of performance (COP) may be high if your final temperature is low. If you availability is low temp (32 or below) and your demand temps high (120 degrees F) then the COP is low.

What usually stumps people is how you can take 40 degree F ground temperatures and turn them into 120 degree F water temps. The secret is in compounding, or compressed btu's.

Each pass of the ground loop may only be dropping 5 degrees F, but it is flowing at an extremely high rate,say 20 GPM. So, 20 GPM at a 5 degree F difference, will generate about 10,000 btuH. This 10,000 btu's would raise the temperature of a 20 gallon tank 60 degrees F. So, if the water started out at room temperature, say 70 degrees F, then it would end up at 130 degrees F. That is the effect of compressed btu's. Low grade (low temp) to medium grade (med. temp).

What's great about it is that the "source" of energy is FREE. You're only paying transportation cost to get it from the ground into your home. The higher the ground or source temps, and the lower the final needed load temp, the more efficient the transportaion system, the lower your cost of operation.

Personally, I think every large surface radiant panel system, regardless of whether it is floor, wall or ceiling, should be designed around the lowest water temperature possible, like 120 degrees F. This will cost more from the stand point of tubing, but it is worth it in the long run due to inherent increases in efficiency from gas fired modulating condensing appliances. It's a one time up charge that will show a quick return on the investment.

GSHP is not for everyone. The cost to construct a VBH well field is not cheap. Occasionally, a person with a back hoe and lots of land may be able to get a geo loop field for relatively cheap, but that in and of itself is a rareity.

Bottom line, besides solar thermal, it is the most efficient method of heating today, with efficiencies approaching 150 to 350% depending upon the direction of energy flow.

It has proven itself to be THE most efficient method of cooling, but unfortunately, not everyone has 300 days/year of cooling load.

ME

Kevin O. Pulver

ME, I've been wondering...

Even of you were doing baseboard, in terms of efficiency, wouldn't it make sense longterm to use more baseboard at lower temp than less baseboard at higher temp? Kevin

GMcD

Geo-exchange systems

As with any heating and cooling system, the first step is to minimize the loads in the house. The lower the heat losses and heat gains, the smaller the heat pump needs to be, and the lower the heating water temperature needs to be, and the higher the cooling water temperature needs to be. Combine a 60F "chilled water temperature" with a 90F heating water temperature and the Coefficient of Performances (COP's) of most water to water geo-exchange heat pumps will be in the 4.0 plus range, now that's efficiency. Geo and radiant are a well matched system, since you can use your radiant system for cooling as well as heating, provided you have proper ventilation with humidity control in humid summer climates.

The geo system has to be matched to the heating and cooling system it serves in the house. It would be extremely difficult to take an existing house and simply replace the existing heating/cooling plant with a geo system and hope that it works. You gotta have the house heat losses and heat gains matched to a geo system performance envelope if there is any hope of a good match.

[Deleted User]

Mix-n match

Hi Geoff, Good to see your words here. Recently, we've taken a new approach in our efforts to promote GEO. We design the GEO around only the AC loads, which around these parts are the lesser of th etwo loads. We then augment it with modcon boilers. This results in a HIGHLY efficient, relatively low cost system. It uses the geo to base load the heating side, and provides THE highest cooling efficiency of anything on the market. It also allows th econsumer to make decisions about what % of the heating load is carried by the more expensive alternative.

It has resulted in a LOT more interest than GEO alone due to cost of installation.

I'm still waiting for the golden opportunity to do GEO radiant cooling...I'm thinking it will happen commercially before residentially.

ME

Ken Caverly

Cooling concerns ?

I do have 20 acres so having the open space for the buried loops is not a problem.

I originally assumed that radiant cooling was a given if you had the piping already there. From these replies it sounds like even you experienced tradespeople haven't played with it much.

The fellow who first got me interested in radiant said it was easy. He hooks his loop system up to his domestic water and runs the tap very slowly, sending water thru certain loops in areas he wishes to cool. he has an outlet at the return end and he runs a hose from there to his garden. He doesn't appear to have a problem with condensation, perhaps from a combination a picking loops located in open areas and running the water very slowly. He says only a little cooling can make a huge difference.

I would assume after reading about radiant that there is an objection to running all this oxygen thru the pipes, but I thought these "chillers" I hear about had solved this.

Is the condensation the biggest problem with this cooling and could isolating the cooling loops to open areas resolve this. (or design the loop system to accommadate some loops in open areas.)

Thank you for the responses to date. they have been very helpful. I am going to go and add a brick to the wall.

Weezbo

Are you already in contact with a professional contractor

in your area,visited any of their installs or been to any of their rough ins? Besides reading a book some actual "cop "ping a Visual" would probably give you a much better picture in your minds eye as to some of the other minor technicalities involved...*~/:)

Really, unless you are into pioneering a system and are willing to live with the consequences hear say would be something somethingelse

my apologies for "cop ping " your mind on this.

Geoff has a book he wrote , i would suspect there are some additional reading suggested printed somewhere in that book

as to water temps,yesterday the floor emmitters were being maintained with 65 degrees . there is alot more to the performance of a system than the highest water temps available.....

V Chill

this is 2 cents from the peanut gallery .

GMcD

Radiant cooling

The "myth" of condensation comes from two assumptions:

One: you need really cool water for an effective amount of radiant cooling (nope).

Two: most houses and buildings are designed so crappily that there is too much infiltration of humid outdoor air in summer, and the house doesn't have any kind of de-humidification system so humidity indoors = humidity outdoors. (We can design better than that nowadays)

The key is to "design properly" and take into account the whole building as a system. There are many examples of functioning radiant cooling systems in humid climates that work just fine without any danger of condensation, both residential, as well as commercial/institutional. Here are some weblinks for further reading:

www.ourcoolhouse.com
www.healthyheating.com

And then do a Google search on "radiant cooling design" and read through some more fun stuff there. The key is to keep cooling loads as low as possible so you DON"T need very cool water temperatures for the radiant cooling. De-humidification can be dealt with by your ventilation system (HRV with a small splt coil/DX condensing unit in humid climates), and act as a source of second stage cooling via the air system depending on your system.

Adding a small air cooled chiller or geo-exchange heat pump system is the main source of the cooling for a radiant system, and if all of the piping is PEX, there is no "oxygen" issue to deal with.

GMcD

Thanks Mark

In spite of my usual cynicism about "large air conditioning manufacturers" design propaganda, one of them has come put with a rather nice website and set of links. Their Design Manual is actually quite good and touches in enough detail on the basics to be a useful tool. At this link:
http://www.mcquaybiz.com/McQuay/DesignSolutions/GeothermalPage5

Your "design for the AC and supplement the heating" is a standard design approach for up here in the cold climates, but further design and investigation could probably allow you to use the system for a "skewed" heating vs cooling load profile, if other factors are considered. I'm always looking at the "best efficiency" fit for these systems. There are local examples of geo-exchange systems serving radiant heating/cooling systems where I am, and more residential projects down in California that I am familiar with. Not black magic, just follow the laws of physics and all will be well.

Ron Schroeder

Question Geo Thermo Cooling

Have any of you heard of using 200'of 24" sewer ie pvc pipe burried below frost line and blowing into house ductiing to be used as AC. I was told years ago that it would be a great system as only cost once installed would be the blower, also in winter used as iniftration air supply as your only pulling in 40 degree air rather than zero or below. The things you learn while working in the sewer trenches.

GMcD

Yes- ground coupled air system

Yes, that type of approach has been used but has to be carefully designed to allow cleaning, and to optimize the heat exchange from the ground through the pipe to the air passing through the pipe. There is an example on a large scale used at the Earth Rangers Centre near Kitchener, Ontario, and I've used this system on a small scale for smaller systems. There are no hard and fast "rules of thumb" to design these systems, because of the variables- pipe size, material, depth of bury, soil conductivity, ambient air temperature vs soil temperature at depth, etc. "Air" as an energy transport and heat exchange medium is not very efficient. Much bigger bang for the buck to use hydronic systems for geo-exchange.

JackFre

\"Earth tube\" cooling

Sure it can be done, and has been. The problem is the humidity of the entering air and it can be quite a breeding ground for critters and bacteria/mold.

J Matthers_2

That is what

I basicly have. I matched my geo unit to my cooling needs and suppliment the heating needs via mod/cond Knight. I have been playing with the controls a bit. Currently I look for a drop in my buffer tank to below 105* for the boiler to kick in via a Flatplate heat exchange. the geo kicks on when the buffer gets to 110* and off at 120*. When the load is to great for the geo and tank temp falls to 105* the backup kicks in. I would be interested in other control concepts.

i played with radiant cooling a bit as well. I have Warmboard through out and Unico for cooling. The Unico keeps the RH to about 45 to 50%. By running my pumps to the floor loops as well as to the air handler coils it cools the house nicely. I have not done it extensivly for fear of condensation under my flooring eaven at the low humitity. The less the air handler runs, the less humitity control I have.

Wayco Wayne_2

Do you

keep the Geo running when the boiler kicks on, or do you turn it off like a dual fuel air system? Very interested. WW

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Ron Schroeder

Thanks

mike parnell

earth energy,radiant cooling

ive got radiant in three floors of the house,still under const, talking about radiant cooling, if i just let the circulators run,without the boiler would the two basement zones,mix with and cool the upper level floors??? the two zone total approx 1500' of pex in the slabs witch in the summer months,are rather cool. if it mixes with the rest of the system it might just do a little bit of cooling who knows.any ideas??? can it work??? thanks ....mike

viccipe

condensate prevention with humidstat control

Henry_6

Geothermal Heat/Cool


I have had great results from geothermal heating and cooling systems in large residential applications.As noted by others, the key is to minimize large temperature swings and utilize weather responsive controls with a radiant floor design temperature of 120F. My area of the world, (Boston) has a very high level of humidity, as well as 50 F temperature swings, so we have not applied the geo systems with radiant panel cooling. The systems that we have used are designed for entering water/Propylene Glycol temperatures below freezing. This provides latent heat addition during the winter months and allows the sizing to be closer to the heat loss of the building. The other factor is combustion air. The less required the better, but so many people pay no attention to the fact that they are using conditioned air for combustion. When air is properly separated from the outdoor environment, as suggested by Mr. Geoff McDonell, it becomes very easy to maintain temperature and relative humidity in the inside structure. Infiltration is always the enemy of a comfortable home. The cold climate geo system uses a brazed plate heat exchanger with a very low pressure drop and the ability to use a small circulator(1/3-1/2 hp) to circulate the water/glycol mix into a deep well (250-750').This can be designed as a water to air system or water to water with the ability to produce chilled water for multiple air handlers. The heat recovered during the cooling season can make DHW for free. The Scandinavians are way ahead of us. After 20 years of designing, specifying, and installing multi-function geothermal systems, I am convinced that this is the best method of making a home comfortable and affordable.I wish that we could get an American manufacturer to produce these systems with domestic hot water demand capabilities.

Bob Gagnon plumbing and heating

30 % John?

My radiant cooling provides 100% of my cooling. The cooling season in New England isn't that long, but it gets humid, and 2 years ago when it was 100 degrees outside, my house was 70 degrees inside. it is too cold for some people. The key is using a fan coil unit, also using well water, to remove humidity, move the air around, and to provide enough cooling. It is much more comfortable that standard air conditioning, equal to radiant heat comfort. You cool off fast when you are walking on a cool floor. Bob Gagnon

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