Geothermal Conversion

Tombig_2 · July 2006

A couple of basic points;

Q: First, how can I tell if it was steam or HW? I have two pipes out of each radiator with inter-connections at top and bottom. Each of the radiator's set of pipes (~1-1/4" iron pipe) head straight for the boiler in the basement.

A: By your description it sounds like you have a HW system. Is the system pressurized. If it's been dry for 30 yrs you need to pressure test to make sure all the house piping and rads are tight. If you have leaks and need extensive repipe it might change your whole approach to this thing. If theres no pump or expansion tank at the boiler, check the attic for a fill tank. Call a pro to do this!!

Q: Can anyone point me to a good resource to calculate heat loss/gain for this house and radiator output at a given water temp? I tried a heat loss cal on the web (heatload.com) that gave me 80,000btu total heat loss and 42,000btu heat gain for this home.

A: Get Dan's book E.D.R., or find a pro with a copy and you can determine the output of your radiators at given water temps. Match it to your room by room heatloss and that will give you the needed circulating temps.

Q:I am really interested to know if I could marry up my cast iron radiators (we love them) with a new geothermal horizontal ground coil/loop system?

A: You really need to find a local professional with geothermal experience and knows a bit about dead men piping strategies, especially if your existing system is gravity. You're probably over radiated but I doubt you can heat with 115* at design temps.

Good luck.

Steve Carlson_2 · July 2006

HW Boiler to Geothermal Conversion

I searched through the threads here for a couple of hours and did not run into exactly what I was looking for. I appologize in advance if this is in a FAQ or something. This forum has got some great discussion for people interested in HVAC! Here it goes.

I just relocated to another state (southern MN) and purchased a 1915 two story brick farm house (1250sf foundation size) that has hot water heat with big cast iron radiators in every room. The home needs complete renovation so one of the first things I am starting with is the heating/cooling system. Current oil/wood fired boiler setup has not been run in 30 years. (owners wintered in AZ) My first reaction was to put in a new oil fired boiler, but then started reading about other fuel alternatives like corn, wood, and geothermal. My main questions are around geothermal/geoexchange.

First, how can I tell if it was steam or HW?
I have two pipes out of each radiator with inter-connections at top and bottom. Each of the radiator's set of pipes (~1-1/4" iron pipe) head straight for the boiler in the basement.

I am really interested to know if I could marry up my cast iron radiators (we love them) with a new geothermal horizontal ground coil/loop system?

I know I need to do a heat loss calc for the house and then figure out how much heat the radiators could put out with a certain water temp. Have these type of conversions been done succesfully in the MN climate? How does a system like this cool? Through the radiators? I would appreciate any words of wisdom here.

Can anyone point me to a good resource to calculate heat loss/gain for this house and radiator output at a given water temp? I tried a heat loss cal on the web (heatload.com) that gave me 80,000btu total heat loss and 42,000btu heat gain for this home.

As a guide, if this were an insulated framed home, my gut would tell me to put in a 150,000+btu gas/oil unit to heat this big home. I have no experience with solid brick homes though.

My wife is concerned that geothermal will be cold in the winter and inadequate cooling in the summer. I'm hoping it will work.

Thanks in advance for your advice/comments.
Steve

Leo · July 2006

In my area

In my area of Massachusetts Geothermal is uncommon so I don't know how well it works. What I do know is service isn't readily available. Make sure if you go to this form of heat someone is close by if you need servce. The best system in the world is no good if no one is there to keep it running.

Leo

Unknown · July 2006

can

Can u post some pictures of ur bolier and radaitors? What are u using for fuel now?

JimmyJam · July 2006

A few tidbits for you.

JimmyJam · July 2006

A few tidbits for you.

JimmyJam · July 2006

A few tidbits for you.

We install a fair amount of Geothermal systems but have never done a conversion like you are looking at so I by no means am an expert in this application. However what I do know is that the maximum supply temperatures produced by our water to water heat pumps are between 110-115 degrees, If you have an acual heat loss of approximately 80,000 you would need to have around 2,700 sq. ft. of radiation if I am reading my charts correctly which is probably quite a bit more than you actually have.

If you are doing an extensive remodeling project maybe you should consider panel radiators. Some of the common manufacturers are Dianorm, Buderus, Thermo Tech and Myson and can have good outputs with low water temperatures if designed and installed properly.

If you aren't up to that, condensing gas boiler technology is probably your best alternative to geothermal unless you enjoy splitting wood or filling up the corn bin.

I did an accurate heat loss calculation on almost the exact same home you are describing today and the heat loss came up just short of 65,000 at -18 design temp. We don't normally design at this temp as the Ashrae standard for our area is -12. Homeowner requested lower design criteria so I obliged.

If I can be of any assistance I am located in Faribault and we go as far out as Albert Lea, Austin and Blue Earth.

71 Gibby

Boilerpro_5 · July 2006

I think you are way too big in BTU's

I'm south of you, in northern Illinois with a design temp of about -5F, and the heat load in my 2800 sq ft 2 story 1905 home with 700 sq ft of glass is just under 50,000 btu/hr. Add a little for the basement and you may need about 60,000 boiler output. Sounds like you have about 2500 sq ft. If you insulate well, and with brick you are usually quite airtight, and the thermal mass evens out low temps over 3 days (assuming 12 inch brick walls), I would expect you would not need many more Btu's than I. If you look around at this site, you will find Slantfin's heatloss program, give it a try. 80,000 still sounds high, but it depends on alot of factors. In most homes if you upgrade insulation, windows, etc. you cut the heat load by 40 to 50%. In most higher end homes rads were designed to run at rather low temps(160F average) it seems, so instead of 150Btu/edr its probably about 130 and then half that and you only need about 70 btu/edr, giving you a supply temp on design day of about 115F average.

Boilerpro

joel_19 · July 2006

????

I quess my question would be why convert to Geo at all?? the cost of electricity is sky high and where i am it comes from dirty coal plants for the most part so there is probably no enviormental improvement either.

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Steve Carlson_2 · July 2006

Geothermal Conversion

I'm located just outside of New Ulm.

So is cooling acomplished via hydronic cooling, or do you install a second heat pump setup for forced air geoexchange cooling. I want to cool the second floor (bedrooms) for sure. Can you pipe cool water to an exchanger in the attic or second floor and blow air across it? I've never seen one of these systems.

Is there a rule of thumb to use for installation costs?

-=Steve=-

Steve Carlson_2 · July 2006

SlantFin

I downloaded the SlantFin program and will try it out soon. Thanks for the tip.

How do you cool your home in the summer?

-=Steve=-

Steve Carlson_2 · July 2006

Savings

My understanding is it saves 50% or more on electricity costs in a year. It probably requires more electricity to heat than forced air, but way less electricity than standard ACs in the summer. Install costs I believe are high, so many people defer to the cheaper upfront costs of other systems.

-=Steve=-

Steamhead (in transit) · July 2006

Steve, before you do anything

you need to do a heat loss (for heating season)/heat gain (for cooling season) calculation. There are several good programs available, or your contractor can do it for you. The nice thing about doing this on a computer is that you can easily see how many BTUs you can save with new windows, upgraded insulation and other improvements. You can also easily calc the loss or gain at different temperatures. Try to get your BTU losses and gains as low as you can.

If a contractor says these loss/gain calcs are not needed, find a different contractor.

Once you know the heat loss, you can figure how hot your water needs to be to heat the house. This assumes you do have a hot-water system. If you have to let the air out of radiators with a small valve operated by a key, it's hot water. You may find that the needed water temp is low enough that geothermal can run the system in all but the coldest weather. A boiler can supply the remainder.

A/C is best handled by a fan-coil unit that can (unlike standing radiators) dispose of condensate from the air's humidity. Mini-duct systems like Space-Pak or Unico work well in retrofit applications if designed properly.

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Steve Carlson_2 · July 2006

SlantFin help!

I just completed entering heat loss data into the SlantFin Heat Loss Explorer 2 and its telling me I have a heat loss of 159,000btu/hr Even when I choose triple glazed windows it only brings it down to 133,000btu/hr. Why is this tool so different than what others were estimating based apon the rough info I provided? (2,800sf 12" think brick home)

-=Steve=-

Boilerpro_5 · July 2006

HMMMM

Couldn't really tell you without seeing the place. It's quite a trip to Southern Minnesota, however!
Right now , I'm sitting next to a little 6,000 btu/hr window unit. Cools the whole house pretty well until we start getting into the 90's on multiple days. Looking at conventional ductwork (put in the drops to the first floor already), a hi velocity system, or maybe ductless split system units in each room. A few other things need doing first, however, in this old house.

Boilerpro

JimmyJam · July 2006

With a Geothermal system cooling is provided by a hydronic fan coil unit that draws cool water out of a "buffer" tank and through forced air provides the cooling.

There really isn't any "rule of thumb" pricing as each system has it's own "characteristics" such as size of heat pump required, "loop field" or "pump and dump", system piping requirements, system clean up, ability for home to accept air ducting, whether your current power supply is adequate to accept the new load and on and on.

Depending on your electric service provider, alot of times in the outstate area the electric Coop's normally have a "dual fuel" program with a reduced energy rate of approximately .04 cent per kw rate which is equivalent to approximately .95 cent per gallon L.P., during the peak load times they would shut down your heat pump system and you would need a backup heating source such as a gas boiler or gas fireplace.

71 Gibby

Geothermal Conversion

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