Speaking from Florida...

I wish there was the cooling equivalent of heat strips. Then we could design for 'design' days and have a backup for the few days beyond design limits. We design for 93-94 here, and we had two days last summer hotter than that - yes, just two days in the upper 90s.

Perhaps I am not understanding but are you saying then that an ideal system would use aux heating around 32 hours per year (4 nights times 8 hours per night) in a heating dominated climate? I am just wondering because this thread seems pointed at my situation but in my situation with a "right sized" unit the aux strips would be on for 303 hours in an average year (according to bin analysis)

Right sized unit has 92-98% of heating load satisfied without aux strip in heating dominated climate.
Lots of job and climate specific factors. 4 ton for you in my mind is too big. If duct work is large enough and 4 ton guy charges less and is good at his job then fine.
Eliminating aux. in heating dominating client however is not good advice....the thrust of this thread.
j

ah i see. Now we have opted to not install the aux heater even though according to our bin analysis it will come on on the coldest nights, we plan to supplement with our fireplace if needed so in my mind we didn't require the aux heater as if we use the wood if it can't keep up (which will be almost never) it will be fine, is this a correct way of thinking?

"A optimal system will probably have your heat strips come on 1-4 days a year on the coldest nights."
This is the comment I'm adddressing specifically.
You are still planning on auxiliary heat, you simply intend to use wood. My clients prefer the automatic kind.
This is not about newdeal in Niagra Falls.

 If your wood burner (fireplace or stove) is not sealed you will LOOSE more energy than you gain. What are the plans if something happens to the compressor? Aux electric strips are inexpensive, have them installed, you can always disable them until you really need them.

Bergy

The heat strip should NEVER be eliminated, EVER!  All systems should have a heating strip, weather you under size, right size or over size the system.  If you don't want to to come on, disable it, but should always be present in the system. What happens when your Geothermal system stops working in 10 or 15 years on one cold night when it's 10 below outside?  Turn on the Aux / Emergency heat strip of course.  Sure it's expanse to operate, but it sure beats no heat at all.  Better to have it and not need it, than need it and not have it.  And heating strips are cheap, they add very little cost to the overall cost of the system. 

    

TG,

Beware sweeping generalities in a world wide forum - we don't install heat strips on geo systems here in Jax, FL. We do get hard freezes every winter but never of a duration so as to produce freezing temps within any building bigger than an outhouse.

That said, I'm of two minds about strips in northern areas. The only negatives (other than the false economics of oversizing the geo, an issue beaten to death elsewhere) to having them and never ever using them is the cost of the strips, the associated heavy duty AC wiring, and an increase in blower power year round from the added restriction since the strips are mounted in and span across the blower discharge throat at the position of highest air velocity.

While we expect geo systems to be reliable, there are several points of failure (compressor, loop pumps, blower, plumbing, controls, 24 Vac power) that could result in frozen pipes and heavy damage. Strips offer cheap, though not bulletproof insurance, since they still depend upon the system blower to distribute heat.

Other ways to insure against freezing an unoccupied house include deploying several oil filled electric radiators at well-chosen perimeter points. These are fairly safe, cheap, offer redundancy, no moving parts, and operate completely independently of the geo system and its blower. However, they are inconvenient and owner must remember to deploy them.

If I was contractor on a northern install and the homeowner specifically directed me not to install strips, I'd work up a contract rider for owner signature. It would describe the increased risk of a catastrophic freezup absent strips and point out the need for backup heat especially in an unoccupied home during winter.

Finally, I don't know codes up north. It may be that some require strips in certain circumstances. That would trump owner preference.

Side question here: Planning to get a Climatemaster 27 (3 ton unit, 3 150-foot vertical wells) sold under the Bryant brand name with their fancy pants thermostat (I read the manual and saw it does all kinds of things but not sure if it can disable the heat strips itself.) How do you disable the heat strips or change when they will turn on? I'd like for them to work when necessary but if the wife bumps up the thermostat 3-5 degrees F or we program it to turn down at night can I get the unit to SLOWLY work back up to temp and rely on the strips for just the really cold Pennsylvania spells? Thanks. dk

Manual S if the method of matching the unit to the site conditions. A tonnage rating is nominal. Actual output depends on specific model and a number of site specific factors, most important of which is probably entering water temp.

dk, that issue has been beaten to death - do some searches here.

dkubarek, I'm a homeowner (not an expert) that has explored this. Since my fingers aren't sore yet, and I'm originally from PA, here goes. You can:

1) Choose a thermostat that has an outdoor temperature sensor AND an auxiliary heat lockout feature. That way, you can set the lockout temperature and not have the auxiliary heat go on unless the outdoor temperature is lower than the lockout setting. Make sure the thermostat you get has the lockout temperature settings you are interested in before you buy it. Ours goes from 5 to 65 (I believe 65 is correct) degrees F in 5 degree increments.

2) You might be able to turn off the breakers to your strip heat. Beware - if there is a system malfunction, emergency heat will not operate and frozen pipes are not fun from what I've been told. :-) With some systems, emergency heat will be automatically enabled in the event of a system lockout (malfunction), but if you turn off the breakers the emergency heat will not operate. Also be warned, many systems are wired so that the blower fan is on the same circuit breaker as the emergency heat strip, so turning off the breaker if your system is wired this way, or if something else important is on the breaker, would be bad.

3) You might be able to deselect auxiliary heat on the thermostat. Beware of the same bad consequences as #2 above. You may need the installer setup code to do this.

Option 1 is the best option in my non-expert opinion. If it is extremely cold outside, you may not want to setback the thermostat since it can take the system too long to recover, or possibly not be able to recover, without auxiliary heat.

Slight modification to #2 - if your system is set up like mine, and you have more than one circuit breaker for the auxiliary heat, you may be able to turn off one of the circuit breakers (if nothing else is on the circuit that you turn off). For example - our 15kW aux strip has a 60 amp breaker that provides power to 10kW of the aux/emergency heat and the blower and a 30 amp breaker that provides power to the remaining 5kW of the aux/emergency heat. We can safely turn off the 30 amp breaker since nothing else is on that circuit. This will buy some time for the geothermal unit to hopefully recover without 'full' auxiliary heat going on. Granted, if the full 15kW is needed and only 10kW is available, it may start to get colder in here. Also, heat strip stages may be controlled by the thermostat or by the equipment. Make sure turning off a breaker is ok with your installer.

If you go away, re-enable everything you disabled or you may be in for an unpleasant surprise when you return home.

P.S. If you want a fancy thermostat, check out the Honeywell Prestige HD with indoor remote sensor/control, and wireless outdoor thermostat. Way cool man! We have one HD and one SD. Get the HD.

Geome, thanks a bunch. I plan on a fancy thermostat so I'll check it out. I saw some references to adding a switch on the "red" wire on the thermostat to disable the call for it. Does that seems like a good Option 4? I think option 1 seems to be the safest and easiest to fix when you're going away, like you said. Agreed on frozen pipes. Saving a few bucks not worth replumbing a house.

Point taken, but the bulk of the country do not have such mild winters. But your right, I over generalized.

Stat with an outdoor temp sensor is a good idea. Correctly positioning the outdoor sensor away from sun and structure influences is important. Low voltage wiring may have to be run to the sensor, or, if it is wireless, make sure the thermostat adequately warns of low battery in the sensor.

dkubarek, you're welcome. I've read about people using a switch for disabling 2nd stage on the thermostat. I imagine it could also be done with auxiliary heat too, but check with the experts to make sure this is ok and that you use the correct thermostat wire. With our thermostat I can disable, thus accomplishing, the same thing using the settings in less than 40 seconds (just timed it). The Prestige is all menu driven and touch screen, so it's easy to do for someone that has spent some time getting familiar with the menus/settings. (Other thermostats may be easy to change too, but this is the only thermostat that I am familiar with.) The plus side is that there are no extra wires or switches. The down side is that it may be a little more difficult for someone in the house to re-enable it unless you leave detailed instructions. Flipping a switch is faster and easier. I would put a label on the switch with the purpose, disabled, and enabled if you go that route.

P.S. engineer - good idea on the battery indicator.  I believe the batteries that came with the outdoor sensor are long life lithium.  I will check it out and try to see if there is an indicator on the thermostat.  I'll just pull the batteries and see what the thermostat does.

Previously, I learned that the most accurate location (for us) for the wireless outdoor sensor is in a tree relatively close to our house. Also, one wireless outdoor sensor will work with 2 Prestige thermostats. (Since both thermostat packages came with a wireless outdoor sensor, I'm keeping the second one as a spare. You don't have to buy it that way, but it seemed to make sense.) Some online companies offer good pricing on thermostats, but make sure your installer will allow you to purchase it this way. If our installer didn't offer a good price, I would have had him install the cheapest thermostat he had that would work with the system, and buy and install the better one myself later on. Make sure the installer wires the system side to take your future thermostat purchase into consideration. Not sure if doing this would affect the installer's warranty though.  I would ask.

I learned a few things about our Prestige outdoor wireless sensor today:

1) It's probably best to clean it out at least every 6 months or so. It wasn't very dirty, but had to evict 3 small spiders and 2 bugs.

2) Best to open it on the floor in case you need to let go of it suddenly due to bugs inside - that way it doesn't have far to fall. No, I didn't drop it but I am serious about this tip just in case!

3) It takes 2 AA Lithium batteries.

4) When I removed the batteries, the thermostat display showed a big warning (about 30% of the screen). It said that there were multiple alerts. The first alert said that the outdoor sensor encountered an error and must be replaced. The second alert said to replace the batteries on the sensor with 2 new AA lithium batteries. The indoor wireless remote control/sensor just stopped displaying the outdoor temperature.

5) It took 5-10 minutes after the batteries were removed to get the alert. I suppose this could be due to residual power in the sensor (kept transmitting for a little while after the batteries were removed.) Or it could also be caused by the sensor only transmitting periodically (maybe once every few minutes?). Maybe a combination of the two. After replacing the batteries, the alerts immediately disappeared on the thermostat. I suppose if the batteries were removed (or dead) for too long a period, the sensor may need to be re-setup with the thermostat. This is easy to to.

6) I didn't see a way of clearing the alert message (this is good). I suppose a person could disable the outdoor sensor at the thermostat (and the auxiliary lockout), but this would do away with the benefits of using the auxiliary heat lockout feature.

Sorry Joe for getting side tracked on your original thought.

Thanks all for the help. System comes with the Carrier Infinity thermostat but I'll ditch that and go with the HD. It's got adaptive intelligent recovery which seems handy with geo and the display is really cool.

Yea, sorry for the hijack, joe. Thanks again.