# New System HP. High Pressure cut-off in heat mode?



## TimberlineMD (Jan 15, 2008)

I just installed a new 410a Heat Pump package unit. The cooling side works fine (135 low, 375 high). The heat side starts, but the high pressure switch kicks in when reaching 550 lbs pressure. Ambeint is 92 degrees outside. Is this a restricted TXV problem or could it be that the engineers did not anticipate a call for heat with 92 degree ambeint?


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## beenthere (Mar 5, 2009)

Too hot to run it in heat mode.


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## flashheatingand (May 3, 2008)

I wouldn't be so sure that Homey is out of the woods. 92 degrees going across the "cooling coil" shouldn't be too high, unless it's 92 inside the house. Still, that shouldn't be too high either. At least he has a package unit, so mismatched coil is not the issue here.

The first thing that comes to mind is air flow.


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## firedave19 (Aug 5, 2011)

Not too hot for heat airflow problem


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## beenthere (Mar 5, 2009)

flashheatingand said:


> I wouldn't be so sure that Homey is out of the woods. 92 degrees going across the "cooling coil" shouldn't be too high, unless it's 92 inside the house. Still, that shouldn't be too high either. At least he has a package unit, so mismatched coil is not the issue here.
> 
> The first thing that comes to mind is air flow.



No manufacturer recommends running the heat pump when its that hot outside. Some don't even post operating data for temps above 65. Many newer Carriers stops at 60. Carrier even had to put fan cyclers on some of their units to be used at temps above 60. Or the units tripped on high pressure.


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## firedave19 (Aug 5, 2011)

Wrong again been there as usual


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## flashheatingand (May 3, 2008)

B.T. is a sharp m.f. and, I have picked up quite a bit of useful tidbits from many of his posts. 

Having said that, I don't see why it would be ill advised to run a h/p in heat mode with an ambient temp of 92 degrees. If that were the case, one shouldn't run an air conditioner if the indoor temp is 90+ either (at least that is the way I'm seeing it). Which is something I never heard of.

I could understand how they don't want to bring up the indoor temp to 90+, and the literature is there for legal purposes, but mechanically speaking, why not?


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## firedave19 (Aug 5, 2011)

Yep Ur right no reason not too and been there is usually wrong


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## beenthere (Mar 5, 2009)

flashheatingand said:


> B.T. is a sharp m.f. and, I have picked up quite a bit of useful tidbits from many of his posts.
> 
> Having said that, I don't see why it would be ill advised to run a h/p in heat mode with an ambient temp of 92 degrees. If that were the case, one shouldn't run an air conditioner if the indoor temp is 90+ either (at least that is the way I'm seeing it). Which is something I never heard of.
> 
> I could understand how they don't want to bring up the indoor temp to 90+, and the literature is there for legal purposes, but mechanically speaking, why not?


An A/C or heat pump moves 400 CFM per ton give or take a few through the inside coil. The condenser moves 700 CFM per ton plus. Some 2 and 3 ton units move 1000 CFM per ton.

So in heat mode, there isn't enough air moving through the indoor coil to keep the head pressure down when its that hot outside.

If you look at his readings in cooling mode, there is no indication of low air flow at the indoor unit.


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## TimberlineMD (Jan 15, 2008)

BT's answer mirrors the manufactures techs. TOO HOT! High head pressure normal at 92 degree ambient. Thanks!:thumbup:


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## beenthere (Mar 5, 2009)

TimberlineMD said:


> BT's answer mirrors the manufactures techs. TOO HOT! High head pressure normal at 92 degree ambient. Thanks!:thumbup:



Your welcome.This is what we're here for.


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