Ground Source Heat Pumps and Other Information
In my house, I will use one 4.0 ton Ground Source Heat Pump. I originally planned on using two units, one for the main floor and one for the upstairs. I shied away from using a unit upstairs in order to avoid problems such as mold. During the summer, your system will remove water from the air and will need to drain the water. If the tube from the unit to your drain becomes clogged, you will have water in your attic or a crawl space. I just didn’t like the thought of having to be diligent over this issue, so I decided to buy one unit and damper the ventilation system. Some folks have a couple of systems in their attic and they work just fine.
This is where everything comes together.
Did you engineer your Loops correctly?
Is your ventilation system OK?
Do you have enough pumping capacity?
Is your electrical system ready?
Did you right size your wonderful GSHP?
The GSHP is the heart of the system and the most expensive component. Take your time in getting this right.
Sizing the GSHP correctly is really important. If you buy too large of a system, you will shorten the life of it by short cycling the unit. It turns on for a few minutes and then turns off. It can also cause humidity issues by not allowing enough air to circulate through the system during a run.. This is called Short Cycling.
Short Cycling… Let’s describe Short Cycling this way. Let’s say you have cozy 1,000 square foot house with a 20 TON unit. (A 20 TON unit would typically cool a small office building.) That unit will go on for a few seconds and the go right back off. It will not be able to filter through all of the air in the house to “condition” it. It’ll just cool it down after sending a quick winter blast through the house. It’ll do this many times an hour and eventually burn itself out. GSHP are designed to run longer with few on/off cycles.
The only benefit you can derive from an oversized system is the amount of time it will take to deal with a spike in needs. For instance, if you have teenagers constantly running in and out or you have a big party, then the system can easily meet those demands… However, over sizing defeats the purpose of being well engineered. You want to maximize your ability to efficiently heat/cool your house.
How do you right size your GSHP? Easy… When you are ready to buy one, ask the vendors what they think. Be prepared to answer a LOT of questions about your house. You should see a matching pattern of answers and this will give you comfort that you are on the right track. From there, you can start drilling down into details. I liked working with the folks that gave me good solid answers even if I didn’t want to hear bad news. If you already have a house, you are already in the ball park of what your needs will be.
When I purchased my GSHP, I got really lucky and found a dealer that had a GSHP sitting in the showroom unsold… for 18 months. He was willing to make a deal and I was willing to take on a slightly older system at a really nice price. If you get creative, you can find a great deal. I did decide to oversize the unit; however, right now it appears that I made the right decision.
One of the first things that I looked at when I was looking for a unit was the COP and SEER values. I felt that the higher the better for these values. (I’ll let you look up COP and SEER.) The next issue that I considered was cost. The higher the COP and SEER, the more expensive the unit. Everything in me wanted the very best unit (I considered going over budget as well); however there comes a point in time when owning a high end unit was not cost effective for me.
Along with the COP and SEER, various government and utility rebates require these values to be at a certain level. You don’t want to go super “cheap” and then be denied rebates because your unit is too inefficient.
Look at it this way. You are looking for a car. Car “A” costs $25K and gets 25mpg. Car “B” costs $26K and gets 40mpg and is very similar to “A”. Purchasing “B” is straightforward. Now let’s say that car “B” actually costs $40K. Now the comparison between the cars gets much more interesting. You can buy a LOT of gas for the $15K difference in the price of the cars. However, knowing you get great gas mileage is something that I personally like very much and I might be willing to pay for it. It’s a calculated cost versus an emotional stake.
It is the same with GSHP and their overall “savings” that they can provide. For me, I can easily calculate the Car “scenario”, with a Geo, I had no clue as to how much energy this would really use based on our “usage”. If you go with a high end unit, is the cost between unit “A” and unit “B” going to save you that much in electricity in order to pay for the cost difference any time soon? Or do you just like the idea of saving more?
Get creative with your purchase. The first unit I got serious about, was USED. The gentleman sold it because his Open Loop System (he was using a well) dried up in the summer. It caused me to open an account on eBay and actually bid on it. I lost that bid by the way.
After watching the installers hook up my system, I felt that I could have probably did it myself… although my unit is pretty complex with series of internal switches that I knew nothing about. If you decide to install one yourself, see if you can jump in on a manufacturers installation class or get the manual and read it carefully.
When you are purchasing a new unit, you HAVE to worry about a warranty. The best kind of warranty to have is a manufacturers warranty. As long as the manufacturer is still in business, your system is covered. If you buy an “after market” warranty, you have to get concerned about the reputation of the company that is backing it. I understand that these companies can and do go out of business leaving warranty holders with a worthless contract agreement. I have very little experience in this area and I’m sure that some of you have horror stories.
The next question to start looking at is the compressor within the unit itself. Sometimes, a dealer will talk openly about some of the issues that various units have. I suspect that many units have “shared” components in them. I keep hearing that a Copeland Scroll Compressor is the way to go. You can do the search on that. This site just has some great stuff in it… http://www.hvacrinfo.com/
A desuperheater is a great feature to have. A desuperheater uses the “waste” energy (heat) from the compressor and pipes it into your hot water heater. It saves the hot water heater from having to warm all of the water up. Besides COP and SEER values that government and utilities need for rebates, a desuperheater “may” be required as well. If you are going for the tax incentives or rebates, look at the fine print. If a desuperheater is required for those incentives, make sure the unit has that option AND make sure you hot water heater has the capacity to handle the output. Sometimes, a 50 gallon hot water heater is the minimal size required to handle a desuperheater.
When you are looking at a GSHP unit, do you think the unit can handle the cold weather?
If not, can the unit handle an auxiliary heating element to handle the really cold days? What are your neighbors doing and what are the vendors saying?
What are the vendor recommendations for cycling the unit? What is too long? What is too short?
Is your unit dual stage system? These are more expensive options; but, a dual stage system will run a different speeds and keep same COP. A two speed system will drop the COP rating to run at the higher speed.
Do your Loops cover the anticipated GPM requirements of the GSHP?
Does your system have high efficiency ECM blower motors? GSHP’s like electricity and these things munch on the juice.
Does your unit need an external Flow Regulating Valve? Some of the older models required a certain GPM flow into the system. A regulating value helps nail this.
Where does the warranty come from? Manufacturer or 3rd Party? What kind of market share does your system have? (Good luck finding that number.)
When purchasing your GSHP unit, another group of folks to talk to are the Loop and better yet the Pump vendors. These folks have no vested interest in the GSHP units; however, they hear the stories of who is good and who is not.
Again, MANY of the features I mentioned are great features; but, they can significantly drive up the price of the system.
Antifreeze in a Closed Loop System
Typically, you only “need” antifreeze if your pipes are in danger of freezing in a Closed Loop system. If you need to use antifreeze, I think there are really only two rules you have to follow.
1) Is it legal for you to use a particular fluid?
2) Do your pipe, pump (Flow Center), and GSHP support the fluid that you will use?
There are other totally environmentally friendly antifreeze solutions; however, they have to pass the both of the checks previously stated. A concern that I have for more friendly solutions is friction at colder temperatures. These frictions will definitely increase pumping costs… sometimes excessively.