ReplyAlso, he only hooked up the 10kW which is operating now, and left the 3rd strip disconnected
Regular Guest
Quick questions: I have a 3 ton Carrier HP and the tech has installed 15 kw of heat strips. We had a 60 amp circuit hookup and he has said that we need an 80 amp and that 15kW is neccessary for this unit to perform properly. the question are:
1) I have read that 10kw is plenty for the size unit and home (1800sq ft ranch), Is this true?
2) Tech said that the strips cannot be staged from 5 to 10 to 15 in sequence, but only 10kw first and then 15 if needed. Is this correct?
3) What needs to be explained here so I can understand this better?
Thanks alot
Regular Guest
Also, he only hooked up the 10kW which is operating now, and left the 3rd strip disconnected
Global Moderator
Only a load calc would tell, but you probably will be OK with 10kw plus the heat pump in VA.
Most of the time, mfrs. have the first 10kw as 1st stage, then then next 10kw (or in case of 15, 5kw) as 2nd stage. The heat kit could be rewired so each 5kw bank can be staged individually but probably not worth the controls or the effort.
Global Moderator
Because the third strip would put you over your 60 amp breaker.Originally Posted by stonemanjr
Last edited by VTP99; 02-26-2011 at 03:22 PM. Reason: Reread post and had it right the first time
God Speed, Jim. We'll miss you - 2-26-23
10KW is probably pretty close to what you need. Give or take 2KW.
Professional Member*
Certain models of the carrier heatstrips can be staged to run 5-10-15. There is a model that runs 3-6-9. Without a load calc, do not know what you really need, but as stated before "typically" in VA 10kw is fine.
I wish I had a $1.00 for every response I deleted.....
"Decidedly Superior in a twisted pathetic way".....
Professional Member*
15 kw usually have a 30 and 60 A circuit to them. If you were in emergency ht on a cold day, you may notice the difference.
some systems disable the extra strip above a preset outdoor temp. It would take a 3three stage tstat or a time delay switch to run the 3rd strip as another stage of heat.
Had a gynecologist that wanted to be able to disable the strips manually, so we put toggle switches on the tstat and modified the control wiring.
Col 3:23
questions asked, answers received, ignorance abated
Professional Member*
Did it really matter he was a "lady Parts doctor"?....lol im still cracking up..
but you guy are all right, you can do anything with proper control wireing, with this "global warming" may be worth upping the amps and getting that full 15kw if needed but thats up to homeowner. just make sure they are on a staged T-Stat so they dont all come on at the same time.
Jason J Saylor
Johnson Controls
"You will encounter many distractions and many temptations to put your goals aside: The security of a job, a wife who wants kids, Whatever. But if you hang in there, always following your vision, I have no doubt you will succeed.”
Professional Member
Yes you need the full 15 kw, You can double check with load calc.
Professional Member
10kw would be borderline, hard to say w/o a load calc. I wouldn't worry about having 3 stages, just do 10kw first and 5 on second. You will need 20A per 10 kw of heat plus your blower (figure 10A). Also you need to have large enough wiring to handle the load, not just a large enough breaker. You would need at least #10 copper for the extra 5kw.
Professional Member*
Who knows what you need without being there. 10 is probably fine. If it's cold outside or as cold as it gets there and it's keeping up, you're probably fine. You can stage anything the way you want it. If the unit isn't equipped to run it this way, you might have to pay extra $$$. What size heat strips did your old air handler have? If you had a 10, then I wouldn't sweat it much. My biggest worry is he's planning on putting an 80 amp breaker to run all this. Is the wire feeding the air handler big enough to handle this extra load? If not, you might have an issue with that, such as a fire.
I like DIY'ers. They pay better to fix.
Regular Guest
Thanks. So can a 10kw heat strip unit be staged with 5+5? or must you have a 15kw unit in order to do staging? It was explained to me that the only the 15kw unit allows a setup for staging the strips??? ALso, where does the setup done? in the thermostat or at the air handler where the board is? And is there an easy way where I can check if they are coming on in stages?
thanks again
also, Someone earlier in this said that using a 10kw unit that comes on full with no staging would be fine. Did I understand that correctly?
Professional Member
Gigitty-gigitty!
God Speed, Jim. We'll miss you - 2-26-23
10KW coming on not staged is fine. During defrost you'll prefer 10KW over 5KW.
Professional Member
You can stage 5 and 5 but you would need to add an extra heat sequencer or contactor (depending what brand of a/h you have) and have a 2 stage thermostat. Personally, I don't like staging anything under 20kw.
Professional Member*
Don't like staging anything under 20KW?>? why would you not, with the technology of the new t-stats and the right sequencing you could have it set up so you dont have 20KW of heat blasting all at once! and watching the Meter spin around like crazy. If you have a heat pump you dont need 20KW just for defrost.
Jason J Saylor
Johnson Controls
"You will encounter many distractions and many temptations to put your goals aside: The security of a job, a wife who wants kids, Whatever. But if you hang in there, always following your vision, I have no doubt you will succeed.”
Global Moderator
True. Why not add strips in steps as needed to assist the pump. Only use what you need.
Professional Member*
By my math you need 41.66A per 10kw of heat @ 240VAC.... 10,000 divided by 240 is 41.66.
Professional Member*
My mothers 3 ton infinity heats her 2300 sf townhouse to below 8f. I know this because the crew didn't know how to set up the controller, didn't tell me, and she called saying "the house is staying 70, but the air coming out of the registers seems kinda cold".
If what you have turns out not to be enough where you are its likely something is pretty wrong with your house. An energy audit should tell you what's wrong with your house. Adding more heat is not always the right answer. Slow the losses.
Professional Member
A 10kw jeat strip usually draws between 19 and 22 amps. A 20 amp breaker for each 10kw of heat plus the 10 for the fan will cover it. If you worked on them you would know this. It is common knowledge.
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