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  1. #14
    Join Date
    Jan 2004
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    Lancaster PA
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    Quote Originally Posted by stonemanjr View Post
    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?
    10KW coming on not staged is fine. During defrost you'll prefer 10KW over 5KW.
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  2. #15
    Join Date
    Jul 2010
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    SE Texas
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    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.

  3. #16
    Join Date
    Apr 2005
    Posts
    412
    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
    Pinellas County Schools
    HVAC Tech
    Pinellas County Florida

    "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.
    Larry Flynt quote

  4. #17
    Join Date
    Jan 2010
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    5,812
    Quote Originally Posted by saylor240 View Post
    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.
    True. Why not add strips in steps as needed to assist the pump. Only use what you need.

  5. #18
    Join Date
    Jun 2010
    Location
    Western Nebraska
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    246
    Quote Originally Posted by ThirdCoastAC View Post
    <snip>You will need 20A per 10 kw of heat plus your blower (figure 10A).<snip>
    By my math you need 41.66A per 10kw of heat @ 240VAC.... 10,000 divided by 240 is 41.66.

  6. #19
    Join Date
    Jul 2008
    Location
    Rochester NY
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    4,632
    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.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  7. #20
    Join Date
    Jul 2010
    Location
    SE Texas
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    Quote Originally Posted by westval View Post
    By my math you need 41.66A per 10kw of heat @ 240VAC.... 10,000 divided by 240 is 41.66.
    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.

  8. #21
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    Jul 2010
    Location
    SE Texas
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    Quote Originally Posted by VTP99 View Post
    True. Why not add strips in steps as needed to assist the pump. Only use what you need.
    You can do whatever you want. Most heat strip packages come with one sequencer or contactor for each 10 kw of heat. A 15 kw package would have two sequencers and you can stage them if you would like. The problem we run into is people complaining the air coming out of the vents isn't warm enough so we just wire Y1 and Y2 together in the air handler. Now I'm referring more to strip heat only systems and not so much heat pumps. Even though it is code most existing heat pump systems around here don't have enough power to the A/H to get enough heat strips to stage. The technology is definitely there but the customer usually doesn't want to pay extra when what they had before worked just fine.

  9. #22
    Join Date
    Apr 2005
    Posts
    412
    Quote Originally Posted by ThirdCoastAC View Post
    You can do whatever you want. Most heat strip packages come with one sequencer or contactor for each 10 kw of heat. A 15 kw package would have two sequencers and you can stage them if you would like. The problem we run into is people complaining the air coming out of the vents isn't warm enough so we just wire Y1 and Y2 together in the air handler. Now I'm referring more to strip heat only systems and not so much heat pumps. Even though it is code most existing heat pump systems around here don't have enough power to the A/H to get enough heat strips to stage. The technology is definitely there but the customer usually doesn't want to pay extra when what they had before worked just fine.
    ....you mean W1 &W2?...... ok i can see your point some what on a straight electric heat that you would want instant heat out of register....but we are talking about heat pumps.... no?....
    Jason J Saylor
    Pinellas County Schools
    HVAC Tech
    Pinellas County Florida

    "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.
    Larry Flynt quote

  10. #23
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by ThirdCoastAC View Post
    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.
    A 5KW rated single phase heater draws between 18 and 22 amps depending on supply voltage at that location.

    I work on them.

    240 volt 5KW=20.83 amps
    240 volt 10KW=41.67 amps
    240 volt 15KW=62.5 amps

    Of course, very few places have exactly 240 volts. And the heaters resistance will change slightly with the temp of the heater as it varies with air flow. So the amp draw will change also.
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  11. #24
    Join Date
    Jan 2011
    Location
    Lynchburg, VA
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    72
    Exactly. You can't get around the physics of it. If your 10 kW strip is only pulling 20A, it is only giving you 5kW of heat unless it is being run at 480v.

    The strips are normally 5kW each and more are added to get to whatever total you need.

    Lower voltage will give lower amps and you take a double hit on power. As an extreme, say you connected these elements to 120v. You cut the voltage in half, the current is also cut in half, this means that the power (Power = V X I) is cut to 25% of initial value (10kW of elements would produce 2.5kW of heat).

  12. #25
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    Jun 2010
    Location
    Western Nebraska
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    Quote Originally Posted by ThirdCoastAC View Post
    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.
    Sorry man. You are wrong. Ohm's law is correct.

    Your memory is close for a 5 kw strip which is what most are. There is typically 4 each 5kw strips in a 20kw package. 2 of these strips are typically energized at a time. More than likely what you are measuring is the amp draw per element, which once again is typically 5kw, not the draw for both elements. It'll come to you over time. You just gotta learn to listen to the old guys. We were in your shoes at one time too!

  13. #26
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    Dec 2002
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    in a house, Appomattox, Va.
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    3,192
    lady parts doctor was doing the change due to complaints in the exam rooms. he didn't have any complaints for the heat
    Col 3:23


    questions asked, answers received, ignorance abated

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