OK, after that I
ran some new numbers......

est. UA ~=344 (sticker indicates more like 400+, by the original heater + temp ratings).

say 70 F - 17 F = 53 deg

53 * 344 ~= 18,232 BTU. Just over my equipment's rated capacity at
that temperature.......and if this industry is like most others I've
seen, "don't believe the rating"..??

Well, now I wish I'd have dug a little deeper before taking this
plunge. (Didn't notice the 17F rating before either.) Why go to all
the effort and expense to have something that only helps for maybe half
the winter? Sigh.

Would still be very grateful for any *informed* opinions on my two issues though! (vs. my own amateur opinions)

I'm not so sure I 100% follow your reasoning and questions but will respond in simple terms that apply to what I pieced togeather from what you wrote. A. If the unit is 22 years old,you are lucky it still works at all,much less be energy effecient. Few heat pumps built in the 90s were capiable of much heating when temperature dropped below 25F. B. If " it cuts out with an over-limit error whenever the electric backup heat runs along with the heat pump" means furnace/airhandler high limit switch is activating,that's easy to remedy. You are either getting air too hot by running too many heat strips,or fan isn't flowing enough air,or evap coils are dirty,or blower wheel is dirty,or blower wheel is loose on motor shaft,or duct work is inadiquate in size,or one or more ducts have collapsed,or high limit switch is defective,or,,,,,,,,,,,,,,,,,,well hopefully you get the point. I won't go farther until I'm sure we are talking about the same things.

You shouldn't try to get the heat pump to run without the strip heat, the strip heat is there when the heat pump goes into defrost mode.

There is a right way and a wrong way. Right way everything works as designed. Wrong way and you're most often left playing around.

Over limit error? where did you get this information? It sounds to me like something that is probably well over your pay grade and that it is shutting the equipment down trying to protect the equipment.

Everything being equal: Don't believe the rating, when you don't know what you are doing. If the equipment is going off on faults how do you expect it to perform?

Magic 8 balls says: you're in the deep end of the pool and you may want to keep a look out for fish that bite.

NOTE: system capacity issues do not wind up in fault code hell. The unit will just run and run and never cycle off, signifying the load is too great to over come.

" may want to keep a look out for fish that bite."

Is there a limit to info emerging from the ball? When fish warnings emerge,does it say whether they are Bluegill that might nip at you,Barracuda that can remove entire small body protrusions or sharks that consume victims whole? BTW Austin,did I ever tell you that I learned to swim while skinny dipping turtle infested waters using only one hand?

Thanks much for the replies. I am starting to understand things better.

klem: Sorry for the ambiguity. The original electric furnace (heaters + blower) are ~22 years old; the heat pump is new.

Over limit - I meant to say "high pressure lockout" - from the blinky lights on the outdoor unit. Now that you say that, I recall he did turn the blower speed down - then again, this furnace never had a heat pump on it before. What temps should it be going at? I think the strips are all wired together, only 1 stage; would it be helpful to make 2 stages, one mostly for defrost and the other for regular aux?

How hot _should_ the aux heat air be for defrost?

Pay grade - you're probably right :-). Theoretically getting a real pro is easier, but I don't have a lot of cash for that......... Plus I'm just so curious! It's chronic, really; maybe even terminal. But I may just end up calling someone.
Fish......I think those metaphors swam off with you guys :-).

Also.....it's worse than I thought, I double-checked my numbers and I had put the wrong model into the AHRI info page. I only have ~10KBTU at 17F. That explains it. But somehow I ended up with a 3-ton capable inside unit and only a 1-1/2 ton outdoor (from a friend, before I had really studied much of this stuff), so maybe I could upgrade the outdoor one someday....

Oy, I didn't need a new hobby. Guess I just don't have the capacity I'd hoped for, but it should still help during the shoulder seasons.

Thanks again for any help you can give.

"How hot _should_ the aux heat air be for defrost?"

Auxiliary heat does not perform the defrosting. The system switches to cooling mode for defrost so the outdoor coil gets warm. Auxiliary heat serves to reheat the cold air that would normally be blowing in the house in cooling mode. Capacity of the heat strip needs to be sufficient to counter the cooling capacity of the system.

Is there a limit to info emerging from the ball? No, because it's all in the questions and how you ask them. The ball may put you off, so you have to be persistent.... As far as skinning dipping with turtles and swimming with one hand, I'm sure there was a good reason for those parameters...

High pressure lockout is more likely to be caused by improper installation of the heat pump... while it could be a number of things, because it's new - recently installed and the line of questioning are what they are the ball is pretty much dead set on this answer.

It's probably not a good idea to move your wallet to your front pocket, you don't want that fish to miss and take the family jewels too. (PS, I am just telling you what the ball said...)

You haven't mentioned what you have for a thermostat. It seems that much of what you are asking depends upon what the thermostat is capable of. You should be able to lock out the backup heat above a certain temperature, and lock out the heat pump below a certain temperature.

You could disconnect the strip heat if you don't want it. The heat pump will still go off on fault. No heat problem is not going to get resolved adding insult to injury, John Doe.

There is no substitute for doing it right.

Did you install a matching coil in the air handler when you replaced the outdoor condenser unit? Sounds like the indoor coil is getting too hot when the backup heat kicks in and causing problems downstream at the condenser.

I gather you installed this yourself, or with a DIY friend, and you may need an experienced, qualified HVAC service to get it up and running properly

A 3-ton blower with a 1.5 ton condenser. What size evap coil was put in the 3-ton blower? One for 3-tons or one for 1.5 tons? How was the blower set (how many CFM)?

OK......thanks folks for the help for and asking more questions that helped me. Turns out the indoor coil is actually a 2-ton, inside a case(?) for a 3-ton.

Things have been working better the last month, not giving me over-pressure...

CFM.....the "low" setting on my blower. I believe it was on medium previously, with the 50kBTU electric heat. Sorry, no idea on exact CFM. I do notice that there's almost no flow to the other side of the house (double-wide) any more.

This is in a ~7,000 HDD climate, by the way. Might "want" to use the A/C for only a couple of weeks in the summer, so this is definitely a heating-dominant set up.

Do you think it makes sense for me to pay an actual pro to set this thing up with stages, so as to be able to still use the heat pump below the 25-30 degree balance point? I.e. my simple mind says, it's still more efficient than the strip heat, down to maybe 15, but won't do enough....so why not add a bit of electric for comfort, while using what I can of the efficient hp heat? (But presumably only part of the strip heat to avoid the over-pressure problem.)

You never answered the question about the thermostat. You need a thermostat that supports multiple stages and an outdoor temperature sensor in order to set a balance point. If you don't have this then the pro you hire will have to install a new thermostat and sensor before anything can be set up.

jone,it's possible to bring in a strip"to help the pump"but you are in over your head and no amount of self help forum will completly change that. The process is faily simple IF YOU KNOW WHAT YOU ARE DOING. The function require's the correct t-stat,an extra outdoor temperature sensor,2 or 3 dpdt relays,a few incidentals and a working knowledge of electric control circuits. Aside to properly installed, balanced equipment,it will be very important to establish the temperature that trigger's the change. That last part is something the average technician is not capiable of doing,it's not something they need to know. From what you have said,it sound's like your buddy has more training or skill than you. If that's the case you are handicapping the project by filtering this information then telling him how it's done. Soooo,I suggest you find someone that is willing to do this that know's how. No contractor in his right mind would touch it at this point.

Sorry, I was just taking it for granted that my tstat supports multiple stages. Yes, it does. I have been using a Honeywell but having some trouble with it, and bought a Radio Thermostat CT80. It seemed to have all the features and settings........but now I'm realizing it doesn't support an outdoor temp sensor! :-( Maybe back to the drawing board again......

Thanks for the help, folks. My question is not so much, Can it be done (multiple stages), but, Does it gain me anything to do so?

I took a look at the Radio Thermostat CT80 installation manual. This thermostat claims it can control up to three stages (2-stage heat pump plus auxiliary heat). So to answer to your question yes multiple stages can be controlled. But the big question is how does it control multiple stages, and can the controlling mechanism be changed to better suit the user's needs.

Not sure if I am reading it correctly? Did you say he set it up so the heat pump shuts off when the emergency strip heat is on? I have done tons of research as I am replacing my system. In the "old" days people didn't think a heat pump could produce heat below 20-30 degrees. The modern heat pumps can produce heat in very cold temps. They won't be able to heat your house completely if it is below zero however it will still provide some heat and help out. With a new system I don't think you should ever shut your heat pump off unless it is physically not working for some reason.

I know when I first moved into my current house a tech told me to shut my heat pump off because temps were close to 15 below zero. When I got up the next morning it was only 59 degrees in my house with the stat set at 65 degrees. (my strip heat is undersized). I turned the heat pump back on and it was back up to temp in a couple hours. It will produce some BTU's at those temps.

I can't answer the question since the manual does not describe how the staging works.

Don't run the emergency heater at the same time. Its emergency for a reason. Hear pumps rely on ambient. Surrounding in combination with the water supply to work. It's to much heat at once..refrigerant is trying to flip ambient + electric heat all at once. Good luck!

www.heating-repair-chicago.com

Also was wondering why you would install a heat pump in cold climate? They are designed for warm climate applications. Not a great primary source of heat up north at all.

www.heating-repair-chicago.com

Heating Repair Chicago said, among other things: "It's to much heat at once..refrigerant is trying
to flip ambient + electric heat all at once."

Uhhh ... flip what??

"Emergency heat" strips are intended to be run simultaneous with the heat pump/compressor when functioning as auxiliary heat to supplement the heat pump's output.

"Hear pumps rely on ambient. Surrounding in combination with the water supply to work."

What water supply? Can you explain this?

"Don't run the emergency heater at the same time. Its emergency for a reason. Hear pumps rely on ambient. Surrounding in combination with the water supply to work. It's to much heat at once..refrigerant is trying to flip ambient + electric heat all at once."

Hmmm............ not sure about this comment or the subsequent one???

Emergency heat uses the same resistance coils as the auxiliary heat. OP, you are correct, HP should be more efficient than electric resistance down to ~10 degrees but the aux heat may come on to supplement the heatpump, hence your friend should NOT have relayed it out of the system when the heatpump is working.

This system should work fine as is. Something in the installation/setup is wrong. Get someone in who knows what they are doing to figure it out.

If you wired up the thermostat, I can see problems developing.

Once I repaired the heat pump myself. And heating repair denver was not successful. I have spent a lot of time and energy. And in the end I had to look for a specialist. Enjoyed the service of these guys https://www.summitheatingco.com. Trust the professionals.

What is the duct static and temp rise at the coil? If it hapens when the heaters come on it is a sizing issue, duct static issue, or could be a wiring issue, or all three.