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Discussion Starter · #1 ·
I have a Trane X14i with I believe a 4TE air handler. This summer a PRO1 T755 thermostat was installed, replacing the old Trane thermostat.

I am a little unhappy about how it is working in winter. We get a heat swing that is greater than what we had with the old thermostat.

The thermostat is set for a heat swing of +/_0.4. I could go as low as 0.2 and I'll try it eventually.

My real question concerns the air flow. When the heat first goes on the air flow is very low. I would like to up it a bit but have no idea what controls it and how to do that.

What controls the speed of the variable speed blower in a heat pump?
 

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The call for heat(heat pump only, or heat pump and aux heat). And how the dip switches are set.
 

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My real question concerns the air flow. When the heat first goes on the air flow is very low. I would like to up it a bit but have no idea what controls it and how to do that.

What controls the speed of the variable speed blower in a heat pump?
This kind of irritates me as well. Different modes of operation operate at different fan speeds, and those fan speeds are factory specified for optimum operation. To a certain extent you can customize the speeds through the on board dip switches (fan speed) but you will never have total control over the fan speed.

I would love the ability to have better control over the fan but if you start screwing around with speed too much then it has to come with the understanding that the machine's seer rating may no longer be accurate, and the manufacture's idea of optimum performance is out the window.

I have been looking for some kind of 'universal' ecm motor controller with a simple rheostat speed control which would allow me to completely customize fan speed to my own liking.... but so far nothing. But I would love to have just a single and constant fan speed across the board in all modes of operation instead of this shifting up and down all the time.
 

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In order to be legal/advertising and get the AHRI approval for SEER and be eligible for utility rebates the manufacturers must set those fan speeds.

Doubt there is any demand for a universal controller. People would screw up the fan speeds and overheat/damage furnaces and freezeup/damage ACs.
 

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I would love the ability to have better control over the fan but if you start screwing around with speed too much then it has to come with the understanding that the machine's seer rating may no longer be accurate, and the manufacture's idea of optimum performance is out the window.
on the goodman furnaces there are dip switches which control ecm ramping profiles.

not sure about their air handlers.
 

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Discussion Starter · #6 ·
I guess I assumed too much when reading the Trane's hype about the unit having variable speed.

When my unit starts up, in heat mode, the air flow is so low that I feel as though the house heat loss is greater than the input until the fan speed goes up. I know that I need insulation, but at my age I decided to live with it.

What tells the fan to speed up? The air handler or the thermostat, and when?

Love the way this forum works. I would consider it a model site.
 

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on the goodman furnaces there are dip switches which control ecm ramping profiles.

not sure about their air handlers.
They have ramping profiles as well. They are kind of nice because the blower kind of eases into existence instead of just blasting on, but there is no way of just setting a single consistent speed. The speed even ramps up during defrost (the element fan speed is different from the stage one condenser fan speed). I did fix that by taking the w1 wire from the condenser and connecting directly to the element relay.... in effect simply bypassing the furnace controller so at least fan speed during defrost is the same and it all goes unnoticed.
 

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What tells the fan to speed up? The air handler or the thermostat, and when?

Love the way this forum works. I would consider it a model site.
The controller on the air handler sets the speed. Although there are some thermostats which will give a choice of whether the thermostat controls the fan or the furnace controller does.
 

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The controller on the air handler sets the speed. Although there are some thermostats which will give a choice of whether the thermostat controls the fan or the furnace controller does.

Only communicating thermostats/controllers take fan control a way from the furnace/air handler board. With the exception of slowing the blower to dehumidify.
 

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Because a communicating tstat uses a digital signal they can do that and all kinds of wonderful tricks.:smile:

Basic 4-6 wire on/off tstat has no brains or abilities.
 
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