Hard to say. You do know that a ton is 12k btu so technically a 5 ton is a tiny bit undersized. Obviously 2 systems has some flexibility and is generally considered ideal in a 2 story house.

That being said, you have to go back to the man J and look at design temp. It is probably based on 5 deg - something which happens 5 times a year at worst. So really, you are requiring back up for those 5 times a year - maybe not a big deal. Let's say that on those 5 nights, you are that cold for 10 hrs - for the year you are at 100kbtus below need - that costs $3-4 for electric resistance.

Now - if the man J is off by 10% - you might be looking at a very different situation. You have to imagine how hard it is to predict heating needs for a larger 1870s house that is getting retrofitted with insulation.

I am inclined to think the #1 and #2 are using typical scare tactics to justify an oversized system. If it were me, I'd go with experience and watch my backup usage. If it were unacceptably high, then I'd use some of the money I saved to improve the insulation even more (if that was possible). I suppose, the other option is to improve the insulation even more than you are doing now (I don't know if you are doing windows and could spend some extra money now and do triple pane for example). If you aren't doing windows, then insulated window treatments might make you comfortable within 5 tons. A bit pricy but cheaper than 2 systems.

Thanks, I appreciate the reply. I agree with you that window treatments and extra insulation would be cheaper in the end than two systems. We just don't want to do this and a) overdo and overpay for a system that is too big or b) end up with a system that is inadequate because it is less expensive.

Only one company gave us design conditions (cooling: 75 inside, 55% humidity, 95 outside; heating: 70 inside, -5 outside). The others probably used something similar?

For the dual heat pump quotes, are they planning to install the GT heat pump unit on the second floor? If so, think twice about that.

I have a GT system with 2 heat pump units in the basement and 1 on the second floor - new home. After they installed the system, the vibration noise from the second floor unit was unbelievable. The scroll compressors aren't loud when you are stading in front of the heat pumpand they are on, but the vibration noise through the floor is remarkable and annoying - unacceptable to us. I had to go through some heroics to add vibration dampening springs to lower the vibrration noise. It is tolerable now but not ideal. I also do not like having a methanol-water antifreeze solution running in the supply and return tubes through the walls of the house up to the second floor. The thought of having a loop pipe break or leak is unsettling to me. If I could do it over again, i would have put all of my heat pump units in the basement and ran ducts from the basement to the second floor. Hind site...

Also - how are the dual heat pump guys planning to design the loop system? Will it be a single shared loop between the two heat pump units with one loop pump or will each unit GT heat pump unit have its own independent loop and pump? If it is a shared loop - does the quote include a backup pump?

If they propose a shared loop (which is what I have) make sure that they install a loop pump controller (can be done with simple relays) or a loop pump center so that when there is no demand for GT, the loop pump shuts off. That will save you in electricity. I also have a backup pump and like that feature too. The backup pump is normally off but if (when) the pump fails, I can switch over very easily and keep my loop system running.

If they are independent loops, then each will have its own loop pump and control so no worries there.

If it were me - I would go with the guys who have been going GT for decades (#3) and have installed many systems. That was the same criteria that I used and am glad I did. The design of the system is key to getting what you expect and if/when it breaks you want s pro who can trouble shoot it quickly and fix it.

Also - ask the 3 vendors what type of monitoring or guages are they planning to add to the system so the you will be able to check and see how the system is running. I would be very interested to hear back what each of them say. I had to add guages after the fact so that I have the ability - without calling them in - to periodically check up on my system.

What brand of heat pump are each of the vendors proposing?

Thank you for the detailed reply!

1) They are proposing to put one in the basement, and the other in the attic. I didn't think about noise levels or the anti-freeze running through the walls. Someone else mentioned the possibility of the water pan (?) leaking and coming throught the bedroom ceilings as well.

2)I don't know if it is a shared loop or not--if we go with one of the 2 system companies I will be sure to ask.

3)I will also ask about monitoring/gauges.

4) Estimate A is offering a 3 ton and 4 ton Climate Master. Estimate B will install a 3 ton and 4 ton Carrier. Estimate C offers 1 5 ton WaterFurnace.

Looks like all good equipment.

For the single 5 ton system, how is that going to be installed? If they put the unit in the basement, what will be on 2nd floor? Will they run ducts?

I know several people who have had issues with the heat pump vibrration noise. If they design for it (if it is in the bid), they can provide vibration dampening isolation to limit the noise. I suspended my unit about 6 inches off the floor with 4 split threaded rods - each rod has a viration isolation spring on it. I cut the noise down significantly. You can still hear the unit but wife says it is now OK for her (that was the true acceptance test)
. If the vendors tell you they are going to put a rubber mat down under the heat pump - that will not take out the vibration noise and will actually amplify it and make it louder.

I actually had a leak in my geaothermal loop pipe in the second floor. It was a tenee tiny leak that was probably there when it was installed - but it took me a long time to find it. I repaired it but I had to cut drywall out from a bedroom ceiling. It was a pain. After I was done, I thought about how bad it really could have been. Imagine if the pipe broke and my loop pump was on - pushing 300 gallons of methanol-water into my house into the second floor. Now that would be ugly.

I recently added a pressure sensor switch to my system that allows me to montitor the loop pressure and if it drops below a settable amount, the loop will pump shut off. I was that concerned about the ugly scenario that I had to add this sensor switch in.

BTW - my system needed methanol for the anti-freeze because I had an issue with the initial mixture (i think it was glycol and water) - long story as to why. Methanol might not be the best anti freeze to use for your application. I would ask them what they plan to use.

The other little trick I learned is about air bubbles. I would ask your vendors about this. The loop system has to have all air purged to run properly - which they will do when they install it (using a purge cart). Over time air biubbles can/will creep into the system and when it does, you will hear it gurgling when the loop pump is running as the air bubbles passes through the pump. I had this happen seveal times in the last few years and I had to pay the HVAC guys to come out and purge the system. Purging is very easy but can take a few hours to get every last little air bubble out. That means you pay them an hourly rate to sit there and watch anti freeze cycle through the purge cart. I was so mad about this I built my own purge cart and now do it myself. But there is a better way...

I recently installed an air vent on my system. This little valuve device "burps" out air bubbles automatically as the loop pump is running. So as my loop pump runs it is self purging. As the air bubbles burp out of the vent, the loop pressure will drop a little. I check my guages and add in a little water in (they call this juicing the system) to put the pressure back up. When I mean a little water - I am talking about less than 1/2 cup.

Ask your vendors what they are going to do to ensure that air bubbles stay out of your system. They now make a loop pump center that has an air vent with auto water fill built right into the system. Or you can make one like I did by adding the air vent to the highest point in the loop. The vent costs 40 dollars.

I discovered that my system was designed really well BUT the monitoring and air issue were not addressed because the HVAC company wants to sell service agreements where they will come out twice per year and tune up the system. I was not interested in that becuase I am a geek and like to tinker. I want them to come to my house and fix it if it's broke, but other than that I would rather not see them. It took me a while but I am there now.

Goodluck!

Sniffdog, the company with the 5 ton unit will run ducts through a first floor and second floor closet (one closet right on top of another, luckily, so no zig zags) up to the attic and then I presume come into the bedroom ceilings from there.

You've given me a lot to think about, thanks!

You have not mentioned whether the proposed systems will be liquid-to-air or liquid-to-water or triple function.

If liquid-to-air, has zoning been proposed? How about a 'split' system (i.e.: geo in the basement, air-handler in the attic)?

Have you even considered an all hydronic system? How is your home presently heated? If hydronic, what type of radiators and at what water temperature?

You have provided no details of the proposed ground heat exchanger, energy rates and fuel availability (i.e. N.G.) in your area.

SR

Our home currently has an oil furnace with hot water baseboard heat on the first floor, and electric baseboard heat on the 2nd floor. The oil furnace also heats our hot water, current temp 120 degrees. Oil is presently $3.29/gal, and our electric rate is about 8.9 cents. Natural gas is not available in our area. We really want to be off the oil completely.

I'm afraid I do not know anything about liquid to air/water/triple function, but I can tell you what systems have been offered:

1) They recommend a 4 ton Carrier Geothermal System Model 50YDV for the downstairs and a 3 ton split system for the upstairs, including programmable thermostats, 15 KW heater for downstairs, 10 KW for upstairs, hot water generator, fiberglass ducting, 80 gallon tanked electric water heater. Vertical closed loop, I believe he said 3 wells?

2) They recommend a 4 ton 2 stage ClimateMaster TTV049 with 20KW backup heat for the 1st floor, and a 3 ton 2 stage ClimateMaster TTS038 with 15KW backup heat for the second floor. He uses metal ducting and would include a 50 gallon preheat tank as well as connecting our already installed hydronic floor heat in the kitchen. Vertical closed loop, 2 wells 400' each.

3) They recommend a 5 ton WaterFurnace NDV064T dual capacity w/410A refrigerant, ECM blower motor, desuperheater, Aux Heat EAL20, electrostatic air filter, insulated duct board and flex duct, 50 gallon water heater for preheat tank. Vertical loop, heat fused polyethylene pipe joints, total pipe 1500 feet plus header. Also an 80 gallon water heater and up to 4 zones possible. I believe they also said 3 wells?

This is all the info I could get off of the three estimates. I am still learning about this so I apologize if this is not the information you were asking about. :-)

if you can avoid putting any of the GT equipment upstairs, I would go for that option. I wish I had done that - even with giving up some square footage on the main level and second floor for ducts. It is just not worth the risk. if you want a hot water tank up there, put a tanless hot water generator in (gas or electric).

I would ask vendor 3 what steps he takes to insulate and seal the ducts. For the long run upstairs, the ducts should be as insulated as you can get. They should also be selaed and pressure tested. My HVAC guys were fanatics about sealing, pressure testing, a fixing leaks after pressure tests. They did not use duct tape - instaed they used a duct sealant caulk which is like a grey goop. The goop seals better and will last longer than the tape. I think that sealing and pressure testing ducts for GT systems is very important since the heat coming out of the system is not as high as a gas heater - so you want to keep it as warm as possible as it travels upstairs and cools down along the way. I would pay for extra insulation outside of the ducts - it is reelatively cheap to add once they have the walls open.

You might also want to consider a propane second stage heating option instaed of the electric backup heat. I realize that that would require you getting a propane tank and the additional expense of putting that in. But in my experience the electric auxilliary heaters aren't very good. I actually have the electric breakers turned off so that my backup electric heaters cannot come on. These are basically gigantic toasters and they gobble up electricity. Plus when the power goes out that toaster backup won't do you any good.

In my opinion if you go with GT you must have a backup heat option that is not electric (power grid) based. If you loose power, you will loose your GT heat. The nice thing about oil or gas is that a small backup generator is all that is needed to power the electronics and fans to keep those systems running.

A 5 or 7 ton GT system would need a very large generator to run those. Here are some ideas:

a) if you have a very good wood burning fireplace insert (rated as a heater), you can use this with free standing fans (powered off a small backup generator) to move warm air around the house. This is what I use.

b) You could add a second stage propane heater to your GT system. However, the wiring would have to be set up so that if there was a power outage - your backup generator could provide power to the heat pump fans, heat pump contoller, and thermostats so that this portion of the GT heat would still function. My GT heat pumps would not allow for this type of wiring - all electrical components were powered off the main 30 amp or 50amp power provided to the heat pumps. You would have to ask your vendors on what is possible with the equipment they propose.

I understand that cost is an issue and I do not know what your power company relaibility is. In my area (no. VA) the relaibility has gottent better. But when we loose power (usually due to ice storms), it can be out for 1-2 days and that is just unaccepatble to us.

When I ordered my GT system I had no idea what I was getting into. Now that I have lived with it for 3 years (and love it), I have learned how to survive with it when things don't go as planned (usually when you need the heat or AC the most). Loosing heat in the dead of winter is by far the worst case scenario for me. I can live without AC for a day or 2.