I have asked and gotten some answers from a bidder whom I really like. I tried to highlight my Q's but it won't take in this body. So all fonts ar the same size and color. Bear with it but you will be able to read my Q's and the answers. Should I ask or check into anything else. Also, is Is DX better than water? My Q's and A's: Since you put me at 4 ton stating that since I am zoning you could drop from 5 to 4. What happens if I have the same temperature set at both levels with zoning for days on end? Can a 4 ton provide for my needs? I don't want to under or over size. The loop field is designed to cover the heating load. The odds of all three zones calling is slim and if that should happen the zones are prioritized. There is a balance between the heating and cooling loads that we need to size the equipment. If we size to the heating the cooling will be over sized and vice versa if sized to the cooling the heating is under sized. The zoning system throws in another hand full of variable as in the odds of the system being needed all zones at once is very slim. The heating and cooling requirements for each zone vary, for example the basement heating requirements are higher, due to the nature of a basement, than a zone on the main floor. What is the heat load and cooling load? Heating is 74863 cooling is 48611 (sensible) for the entire house What winter and summer design temperatures are you using? Winter is 0 degrees and summer is 94 degrees What are you suggesting for the system-ethylene or propyline and what is the concentration in water? 10% propylene 90% water we can use either it just changes the fluid factor on our btu exchange What is the ARI for heat loss for my home? Will you be able to show me? I have the manual J form What size backup heat stripes do you suggest? 20kw Is this a 2 stage HP? yes Do I have a third stage for the electrical back-up? The electric will be third stage and the heater itself is staged How much KW will the unit take, especially in auxiliary heat mode as I don't want to blow up my generator? Amperage will very, worse case scenario KW will run 3.07 in heating with a full load, the heater will take up to 20 KW if being used I am interested in the LRA (locked rotor amps) and how many amps is in the LRA. 96.0

48611 btuh sensible cooling sounds high for a nominal 4 ton unit. Are you certain that cooling figure isn't for total cooling?

In round numbers a 4 ton unit might make 3 tons (36 kbtuh) sensible and another ton (12000 btuh) for latent. Latent cooling is the unit's capacity to dehumidify the air. If you are in a very dry climate, latent capacity is less of an issue but a 4 ton unit won't output all 4 tons in sensible form only.

Zoning may slightly reduce total system capacity but not likely by a full ton.

20 kw aux heat sounds a bit high, almost as though the designer intends aux to be able to carry the whole heating load all by itself. Nothing really wrong with doing that since aux strips are cheap unless electric service upgrades are needed to provide the extra 20 kw. Sizing a generator to backup all 20 kw plus everything else may be impractical, but it should be a simple matter to split the 20 kw into two 10 kw sections and back only 10kw up via generator. That should get you through a winter power outage without freezing yourselves or your plumbing.

Disclaimer - all of the above is free advice via internet and is not nearly is good as opinions held by competent folks whose boots have darkened your door.

Engineer, You are right about cooling side -it is for total cooling. This is central va mixed climate. about 6-8weeks real cold and the same for real hot 90's. I have a 16KW now that I want to move and hook up. Are you saying to back up a portion of the heat strips (if I put these in?)House main floor 2400sf and walk out basement finished part 1800sq ft partically underground. Remainer unconditioned for storage.

In that case 4 ton may suffice. In many cases it is better for comfort and economy to be right sized or even marginally undersized for cooling. You'll be undersized for heating but the strips will make it up and they won't run that often, just on the coldest days and then only for a few hours.

16 kw genny will be marginal to start a 4 ton heat pump. Locked Rotor Amps may be 6-12 times running amps.

It may still be possible to connect some aux heat (possibly only 5 kw) to the generator if there is a means to delay its start until after the heat pump compressor gets going. Another option would be to forget hooking strips to genny and have a half dozen oil filled portable space heaters stored in the attic against the day when you need aux heat and are on the genny. That option would depend on having adequate receptacle circuits to support the plug in heaters.

Engineer: Thank you again for your responses. I REALLY APPRECIATE it! I will have wood burning tiled stoves for both up and lower levels. That will be my "emergency" and for real cool days. Can you get me smarter on heat strips. Is there a basic number required for each ton. Are they used for auxillary (stage 3.) Sounds like I may not be able to use my generator (16KW) for startup. My contractor gave me this info: Amperage will very, worse case scenario KW will run 3.07 in heating with a full load, the heater will take up to 20 KW if being used the LRA (locked rotor amps) is 96.0. Someone did state that their running load for their 4 ton HP was just under 3Kw plus the fan load (?). I read in one of the back pages here that someone had a guardian 15Kw and it ran a 3 ton plus a water pump plus other house hold needs, But NOT the electic backup. He did have room for a 5KW heat strip heater. Sounds like I may have 3 choices if they can work. 1. connect HP to generator (auto) but somehow do not connect the electric backup at all to the Backup generator (which I can't think of anyway to seperate out of the HP right now). 2. Not automatically connect the heat pump to the generator but have a capability to manually switch to a seperate 5KW strip if I want. Just need to figure out how to seperate the heat strips. 3. have only one 5KW heat strip installed to support manually/automatically. I do like to switch things out like I do now when I need too. Here is some more on the BTU's from my last bidder email received.--- One Q: (My Q) you say my BTU's are 74863 for heating and cooling is 48611 , now these numbers are a mean extreme for the purposes of the loop field. I do not want a loop field to be under sized. (Contractor Answer) Over size loop fields give you better operating temperatures. If I use the normal temps for this area the load changes to 69,872 heating and 47297 cooling (sensible). Keep in mind these are worst case scenarios, the majority of the seasons will not require the btu's that are listed."

Lisa,

Aux heat is controlled by the thermostat. If you get the right thermostat, you can have complete control over when it is turned on. It does act like a third stage.