Geothermal with a Hot Water Boiler

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  #1  
Old 06-27-12, 06:33 AM
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Geothermal with a Hot Water Boiler

Is anyone running, or have setup a Geothermal system with their hot water boiler?

I was told that this geothermal system can be tied into a boiler system nicely. Still can't wrap my head around it as my ground water is 45'F in the summer.

If all of what I have heard about this type of heat is true, I'm probably going to make the big jump in the next 1-2 years.

My goal this year is the cut the heating bill down to 45% of what it was last year (~$1000 a month worth of oil). This was totally brutal, and did add some financial strain as we werenít expecting it to be that bad (previous owner was full of crap when they said average was $600 a month).
To reach this extreme goal, Iíve been insulating the new windows and doors the previous owner had installed, but failed to insulate around them. There was 1/8Ē to ľĒ gaps around all these new windows with only some nailed in trim keeping the weather out. The boiler has not seen any maintenance in at least 4 years (no filter change, cleaning, anything). Iím going to be bringing in the local boiler guy to completely strip, clean and replace anything that can or should be replaced. The boiler is a late 90ís oil burning unit.
Iíll be adding hour counters to both circulation pumps so I can see which floors are demanding more heat. I installed two 5-day programmable thermostats late in the winter, so the hour counters and the scheduling should help tune our heating habits and or identify floors that should have their insulation reviewed/addressed first.

The next year after that, Iíd like to target shaving 25% off the previous bill per month. I think by that point, Iíll need to start looking at something drastic which is where the geothermal thoughts are coming in.

Any thoughts on this?
 
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Old 06-27-12, 06:56 AM
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I guess I should put some numbers in to clarify the previous post.
From the end of December to the end of March, we averaged a tank of oil every 6 weeks. Current rate on oil is locked in at $1.14 per letter.

So based on that info;
This past winter cost us ~$1000 a month for oil.
This winter's target is ~$450 a month (based on $1.14 per letter for oil)
Within 2 years, Iím hoping (dreaming) of ~$338 average per month (based on $1.14 per letter).
 
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Old 06-27-12, 08:09 PM
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We have done a ton of geo with boiler back up.
It works soooo well with in floor heating.

I heat my cottage, garage and hot tub off a 4 ton water to water with no back up heat for about 800 a season.
My geosource is a lake loop using about 600 feet of 3/4" PE piping.

There are many things that geo is great for, but there are so many bad, cut throat installers out there that really take all the good away.

You need to make a good plan, and understand geo and heat pumps well to do a good eff. installation
 
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Old 06-28-12, 07:42 AM
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Thanks TOHeating.
I have a co-worker that has a lake loop with an electric backup, and she loves it.
The numbers I am seeing from the few people I know that have these systems are crazy. The ROI screams it's a must do upgrade.
If I can easily tie it into my existing boiler system (pipe work), I would only really have the outside work to do and the few pieces of tie-in gear. Cooling would be another issue, but right now cooling doesn't cost me anything (open the windows).
 
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Old 06-28-12, 08:08 AM
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TOHeating,
How many square foot are you heating and are you using it year round?
 
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Old 06-28-12, 04:13 PM
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I would say about 1600 sq feet in total with the gargage, main building and loft.

I can use it all year, but it would only heat the hot tub.
Mostly that is done with solar, but there are times it needs some boost
 
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Old 06-29-12, 05:15 AM
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Thanks for the info.
I'm going to seriously look into this and if it'll work out as good as everyone says it does, I'll be looking to put something in next summer when we build the new garage.

This will however add an interesting challenge with the garage build as I'm probably going to look into tieing into it for the garage, which will add another ~1152sqft onto the heating space.
I'm currently heating (directly) ~2860sqft and indirectly heating (heated with bleed off heat from the loop boil), ~1145sqft basement.
 
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Old 07-03-12, 11:21 AM
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Heat los calculations.... Do them.
Don't let anyone tell you otherwise.
They are so damn'd important especially with Geo.

I would offer my help to you should you need it.
 
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Old 07-03-12, 01:56 PM
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What are the maximum water temps you can achieve with a geo unit without using backup? About 120F or can you go higher?
 
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Old 07-04-12, 04:30 AM
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The first google hit I found with numbers indicated that 120'F is about max. After a few more links, I started seeing a couple different numbers, but all within about 10'F of the 120'F mark.
Here is an interesting read which does play with some numbers. DIRECT-USE TEMPERATURE REQUIREMENTS:A FEW RULES OF THUMB

My boiler is set (if running properly) at 160-180'F. Unfortunately I do not know what my return temp (cold side of the boiler) was last year, but I suspect it was below 120'F.
If I was to stay with the same boiler (will be way oversized as a boosting system), I would only have to fire the boiler to bring the water up the few extra degrees.
I'm going to look pretty heavily into this shortly. It sounds like the direction I may be considering to bring my overall heating costs down.
 
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Old 07-04-12, 04:37 AM
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I have run to 130 F before.
You lose efficiency very fast up there.
That being said , the next generation HP's are said to be able to go much hotter. In the area of 180.

Believe it when I see it though.
 
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Old 07-04-12, 04:43 AM
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I was going to say, the energy required to obtain the higher temps would go up a fair bit as the temp goes up.
 
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Old 07-04-12, 04:50 AM
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We typically design to about 70-75 percent capacity.
Much over that, starts to become cost in efficient. What I mean by that, it the return on investment start to decline quickly. The cost of the extra borefield, usually in the 3-4000 $$$ per ton, does not justify the few days per year that you need the extra heat output.
Now, if your the borefield contractor, then things are a bit different as the cost per ton is lower. The equiptment cost per ton does not nearly go up as fast.

You need to fully understand how geo works and what makes a "happy" geo system.
For instance, you would not top up "the extra few degrees", you would instead use the boiler to charge the buffer tank and you would shut down the heat pump.
There are times you can mix the two, but rarely does it work to any great efficiency.
If you want to keep the oil boiler, you could. You could also get a instant hot water heater and heat exchanger and handle the last 25% heat load that way.
Then your DHW heating costs get reduced as well.
It all depends on the amount of money you want to put into the system. Generally though it does pay back in the end.
 
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Old 07-04-12, 04:57 AM
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Thanks for the info.
I am not attached to the boiler, so if it has to go, not a big deal. I would however like to stay with the hotwater rads as the cost of running HVAC ducting through my house would be very costly.
 
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Old 07-04-12, 05:00 AM
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Stay with rads for sure...
Way more efficient that scorch air.

But, what about cooling ?
 
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Old 07-04-12, 05:27 AM
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Cooling will be something I'll have to run HVAC for. The heating is the critical aspect of this, with the cooling being a nice bonus.
We currently don't have any A/C in this house (had central air in the previous house), but with the numbers I posted in the second post, my main focus is heating.
 
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Old 07-04-12, 08:30 AM
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Mike, I know cooling is O/T here, but take a look at 'mini-split' AC systems. I don't have experience with them, but have been looking at those myself recently. I'd love to get rid of the window units!
 
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Old 07-04-12, 09:13 AM
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There are also those high velocity systems. The ducts are small enough to fish into 2x4 walls minimizing the demo work.
 
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Old 07-04-12, 09:24 AM
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I am going to be looking into the cooling aspect as I know it'll be cheaper do do both at the same time then one here, and the other retrofitted down the road.
With the large air space between the false ceilings on the main floor and the second floor, I should be able to run the ducts through there with ease (have about 2ft space between the false ceilings and the original ceilings).

In the end, I'm looking at the fesibility of going geothermal with what I already have in the house. The cooling will be an extra bonus for hopefully not too much extra cost.
 
  #20  
Old 07-05-12, 07:33 AM
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My point being,

Look at equiptment that can utilize chilled water.
You water to water heat pump can be reversed, and instead of heating water it will cool water.
Chilled water is VERY good at cooling, and at ZONED cooling.
 
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