Generic thermostats and variable speed air handlers

[happyfirst]

I'm being quoted for our home addition a 1.5 ton 15.5 seer single stage heat pump - variable speed air handler Rheem prestige system with a generic programmable thermostat.

Questions:
1) Is it really a variable speed air handler or just variable at startup?
2) How do generic thermostats control which speed the handler runs at or does the handler just decide this on it's own? Or do I need a special rheem thermostat? I know my current carrier infinity has a special thermostat that makes it all work right.
3) Do I need a special rheem thermostat to make use of the humidity control feature or can I use any generic thermostat with humidity control?

[sktn77a]

Which heat pump and airhandler and which thermostat?

[happyfirst]

Quote doesn't say. Based on Rheem's website, I'm guessing an RPQL-JEZ heat pump, an RHPL air handler, and some generic honeywell programmable thermostat. I also have a trane quote with similar specs, that is, variable speed air handler with generic thermostat.

I'm curious if I really am getting variable speed.

I was told a long time ago that if I was to hook up a generic thermostat to my carrier infinty, I'd loose the variable speed part and other things. I really want to make sure I have the variable speed part. I love how our infinity (5 ton) is on but most times is running slow and you don't hear any air at all and it's real quiet.

[gary_g]

Quote doesn't say. Based on Rheem's website, I'm guessing an RPQL-JEZ heat pump, an RHPL air handler, and some generic honeywell programmable thermostat. I also have a trane quote with similar specs, that is, variable speed air handler with generic thermostat.

I'm curious if I really am getting variable speed.

I was told a long time ago that if I was to hook up a generic thermostat to my carrier infinty, I'd loose the variable speed part and other things. I really want to make sure I have the variable speed part. I love how our infinity (5 ton) is on but most times is running slow and you don't hear any air at all and it's real quiet.

The quote needs to list the exact model numbers of all equipment to be purchased.

Generally speaking, it is the dip switch settings in the air handler that control the blower speed settings.

A good thermostat, like the VisionPro IAQ, can also tweek the blower speed.

I believe the Infinity needs its own special controller to take full advantage of its features.

Take care.

[drumbeater]

Variable speed is only useful with 2 speed equipment and dehumidification. That unit is a single speed unit and a generic tstat generally will not control humidity. Make sure they are not just quoting you a "multi-speed" unit instead of an actual variable speed.

[skippedover]

Variable speed is only useful with 2 speed equipment and dehumidification. That's not a valid statement in most applications. A variable speed motor will ramp up/down for a multi-stage application for sure and yes it does need the proper controls to do that. But on a single stage piece of equipment the dip switches on the unit should be set to give the proper airflow. The VS motor will softly ramp up at start and down at set-point and many have a delayed ramp up on start to provide better humidty control.
That unit is a single speed unit and a generic tstat generally will not control humidity. Again, you missed the mark. If a single speed unit won't control humidity, how in the devil did we manage to get air conditioning (cooling) to the level of acceptance of today? A properly sized system will dehumidfy nicely, with or without variable speed. A multi-stage system will provide better dehumidification but a single stage sustem properly sized does a good job.
Make sure they are not just quoting you a "multi-speed" unit instead of an actual variable speed.

A variable speed blower installed in a system with a reasonable static pressure can save a significant amount of electricity. In fact, that's probably a better reason to get an ECM motor than any, for the electrical savings. The comfort is just a big plus.

[beenthere]

The Rheem won't operate anything like your Infinity.
The stat won't control the blower. Other then if it has the ability to slow it when the humidity is high. Other then that, no control over the blower.

[drumbeater]

How does a slow start help control humidity?

Air conditioners dehumidify, thats what they do. 2 speed units do a better job with a vs motor. And a generic tstat does not have specific humidity control.

Rheem makes a nice version of the infinity. Your dealer should be able to show it to you.

[gary_g]

Air conditioners dehumidify, thats what they do.

Air conditioners lower the temperature.

De-humidification is sort of an added "bonus".

Take care.

[drumbeater]

Latent cooling is produced during dehumidification. That's about 40% of the total cooling produced by a system. The other 60% is Sensible cooling which is basically just temperature change. It's not just an added bonus, it's one of the basic functions of air conditioning. Here in the south anyways.

John

[BaldLoonie]

How does a slow start help control humidity?



Take something like Trane's Comfort R. It starts the blower at 50% for the first minute I believe, then 80% for the next 7.5 minutes. Gets the evap cold faster. That means faster to full latent capacity. Other brands have similar setups.

Today's units can take upwards of 10 minutes before the coil is fully cold and they are at their highest latent ratio. The old low SEER (under 10) systems could do it in 5. So any way of getting the coil cold faster really helps.

[beenthere]

Latent cooling is produced during dehumidification. That's about 40% of the total cooling produced by a system. The other 60% is Sensible cooling which is basically just temperature change. It's not just an added bonus, it's one of the basic functions of air conditioning. Here in the south anyways.

John

You'll find very few high velocity systems ever touch 40% latent ability(average shr is .65 for them).

2 stage units sometimes have a problem doing 75% latent ability in first stage(shr's of .80 in first stage is common on many 2 stage in first stage).

A slow ramp up gets the coil colder faster, and keeps it colder for longer.