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Thread: THPRE

  1. #183
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    Quote Originally Posted by garyed View Post
    You're absolutely right but even if we add another .3 or .4 for the coil to his measurements we only get about .7 which is still under the .8 mentioned in the manual. I would expect a very high static in a mobile home setup so the fact that his may not be that bad makes me wonder if the motor is set up correctly. I had a job where an oversized VS AH was installed & the duct system was designed for a 1.5 ton. The place sounded like a wind tunnel it was so noisey coming out of the registers. You thought they were gong to blow off the wall. It was an older model unit & there was no setting lower than 1050 cfm not even at continuous fan. Even two days with the distributor tech support rep & the manufacturer support rep we couldn't find a way to slow it down. I can't remember the tsp but it was so high we were laughing about it. I have no idea of the actual CFM it was moving but I guarantee it was a lot closer to 1050 than 600 even at ridiculously high static. If the OP's ductwork is too small & the motor is set up right it should be blowing his curtains off the walls. If the ductwork is blocked up somehow then his static pressure would go through the roof. Oh, we ended up changing the AH.
    I don't think his air handler is rated to be able to deliver set CFM at statics above .3". Since its rated CFM is at .3", and it only uses a 3/4HP motor.
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  2. #184
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    Dec 2005
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    Quote Originally Posted by THPRE View Post
    Toocool and hvacvegas - you both need to read the earlier posts and then your replies will be more pertinent. hvacvegas - do some homework on the various govt. programs and you will be able to better serve your customers.
    I'm not reading through 15 pages.

    The last test setup I did was a program involving our energy provider.
    I wasn't to satisfied.

    Honestly, the issues you have aren't something requiring extreme testing equipment, or some special government test.
    Just the normal tools on a service truck.

    To prove my point about the inaccuracy of government tests:

    AHRI recently bumped all high efficiency boilers down to 90% (from 95%), because there was a flaw in the DOE's testing criteria, and required all high efficiency boilers to be retested at their new standard.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  3. #185
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    Jun 2004
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    I hope this is not to far off topic. I was at a class today and "Check Me" came up. The instructor said that because of complaints to the state a spot check of all the installs where a check me was performed, 85% failed the spot check. The implications are that most people as falsifying the data. So I would be suspect of the any "Check Me" reports.
    As far as the varying pressures, could it be possible that the airflow is varying because the fan speed is varying?
    My experience with mobile homes is that the duct work is almost always too small for heat pumps. My guess would be air flow. Either fan malfunction or undersized duct. Most likely undersized duct.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  4. #186
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    Quote Originally Posted by beenthere View Post
    I don't think his air handler is rated to be able to deliver set CFM at statics above .3". Since its rated CFM is at .3", and it only uses a 3/4HP motor.
    I see what you mean & you're probably right but I don't believe that they're saying it won't work properly above .3 static, just qualifying the rating at that static pressure. Why they rate it at only one static pressure & no others is beyond me. At least Trane gives you a chart that shows CFM at different static pressures. Even if it loses a little CFM above .3 it is probably not much until it gets much higher. Goodman's PSC motor for their 5 ton units are 3/4 hp. rated for up to .7 & deliver over 2000 CFM at .4 static. I have a hard time believing a PSC motor of the same horse will deliver more air under the same static pressure. That sort one of the main purposes of a VS motor, to deliver constant airflow over a wide range of static pressure.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  5. #187
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    Quote Originally Posted by garyed View Post
    I see what you mean & you're probably right but I don't believe that they're saying it won't work properly above .3 static, just qualifying the rating at that static pressure. Why they rate it at only one static pressure & no others is beyond me. At least Trane gives you a chart that shows CFM at different static pressures. Even if it loses a little CFM above .3 it is probably not much until it gets much higher. Goodman's PSC motor for their 5 ton units are 3/4 hp. rated for up to .7 & deliver over 2000 CFM at .4 static. I have a hard time believing a PSC motor of the same horse will deliver more air under the same static pressure. That sort one of the main purposes of a VS motor, to deliver constant airflow over a wide range of static pressure.
    Just study the data.....Yes the cfm is pretty close, but take a look at the watt requirements for a Variable speed to push the air at the high statics... close to the same cfm but the wattage goes up by 50%!

    That gooman blower section has 0 tech specs on airflow....the coil might and an experiment could be run on the pressure drop across it.
    Give a man a fish, he will eat for a day. Teach a man to fish, he will eat for a lifetime.

    Give a man a capacitor, doesn't know what to do. Teach a man to install it, now he knows everything.

  6. #188
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    Quote Originally Posted by garyed View Post
    I see what you mean & you're probably right but I don't believe that they're saying it won't work properly above .3 static, just qualifying the rating at that static pressure. Why they rate it at only one static pressure & no others is beyond me. At least Trane gives you a chart that shows CFM at different static pressures. Even if it loses a little CFM above .3 it is probably not much until it gets much higher. Goodman's PSC motor for their 5 ton units are 3/4 hp. rated for up to .7 & deliver over 2000 CFM at .4 static. I have a hard time believing a PSC motor of the same horse will deliver more air under the same static pressure. That sort one of the main purposes of a VS motor, to deliver constant airflow over a wide range of static pressure.
    There wattage probably goes up fairly quick after .3", so they used .3" to get there SEER rating.

    Might only drop off 2% per .1" above .3", or it could be a non linear drop off, and lose 15% air flow at .6"ESP. How much it drops off is directly related to what RPM they need to move that rated CFM at .3", the higher RPM they need at .3", the more it drops off with even a small increase in ESP.

    Nordyne also rates their blowers at a low ESP, and they drop off pretty quick as the static increases.
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  7. #189
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    Quote Originally Posted by beshvac View Post
    Just study the data.....Yes the cfm is pretty close, but take a look at the watt requirements for a Variable speed to push the air at the high statics... close to the same cfm but the wattage goes up by 50%!

    That gooman blower section has 0 tech specs on airflow....the coil might and an experiment could be run on the pressure drop across it.
    The OPs coil has a dry coil .18" PD at 1600 CFM, and a wet coil .275 PD at 1600 CFM.

    Pretty sure that blower is rated to move its X CFM at .3" not including the coil PD. So the return static readings that were taken are pretty useless. Most modular blowers don't include the coil, since they don't know what coil will be matched to it.
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  8. #190
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    Quote Originally Posted by beshvac View Post
    Just study the data.....Yes the cfm is pretty close, but take a look at the watt requirements for a Variable speed to push the air at the high statics... close to the same cfm but the wattage goes up by 50%!

    That gooman blower section has 0 tech specs on airflow....the coil might and an experiment could be run on the pressure drop across it.
    I completely agree with you.
    But to diagnose the OP's problem we need to know how much air he's moving across the coil & his static readings don't tell us that.
    Knowing all the dip switch settings would be very useful. If he's set up for 2000 cfm then we would expect very high static & if set for 1000 cfm very low static.
    Gary
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    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  9. #191
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    Quote Originally Posted by beenthere View Post
    The OPs coil has a dry coil .18" PD at 1600 CFM, and a wet coil .275 PD at 1600 CFM.

    Pretty sure that blower is rated to move its X CFM at .3" not including the coil PD. So the return static readings that were taken are pretty useless. Most modular blowers don't include the coil, since they don't know what coil will be matched to it.
    Quote Originally Posted by garyed View Post
    I completely agree with you.
    But to diagnose the OP's problem we need to know how much air he's moving across the coil & his static readings don't tell us that.
    Knowing all the dip switch settings would be very useful. If he's set up for 2000 cfm then we would expect very high static & if set for 1000 cfm very low static.
    If you could measure the static drop across the coil only, with the unit running with filters in and doors on, why can't you then use the pressure drop data for the coil to get an estimate of what the cfm is?

    Does this blower section have electric heat to do a measurement?
    Give a man a fish, he will eat for a day. Teach a man to fish, he will eat for a lifetime.

    Give a man a capacitor, doesn't know what to do. Teach a man to install it, now he knows everything.

  10. #192
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    Quote Originally Posted by beshvac View Post
    If you could measure the static drop across the coil only, with the unit running with filters in and doors on, why can't you then use the pressure drop data for the coil to get an estimate of what the cfm is?
    You can. Just need to know what your doing, so as not to do more harm then good. And end up with a leak in the coil.
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  11. #193
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    As long as coil is spotless.

  12. #194
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    Well two months later an update on my problem heatpump. Goodman had a troubleshooter on the phone and we remeasured the static pressures under her guiedence with a new instrument and a different person --- the pressures were exactly the same as previously stated! So air flow was off the table. After changing the refergerant charge and repeated testing the trouble shooter gave up and refered the problem to the engineering dept. Their solution was to test the A coil for any blockages and then finally replace the "compensator" !!! This is what my first expert suggested and it was the most obvious thing to me. We did this yesterday and it has cured the problem. The high side in heat mode is down and the low side is no longer "searching" -- just nice steady pressures well within the expeced range. So we hope the problem is solved! Thanks to all of you that gave thoughtfull replies and to all those who just insulted me -- maybe you can learn something, but probably not.
    Thanks,THPRE

  13. #195
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    the heat pump refrigerant charge compensator

    I did not read all the posts so don't know if the heat pump refrigerant charge compensator was adequately explained.

    Here is a diagram & explanation: The Heat Pump Compensator

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