Does Rheem Comfort Control System2 = more efficient?

[awestaa]

Hi There, First post after digging around here and thanks in advance for all the information I have found so far. So my question is basically about my recently installed 4 Ton Rheem system below:

RASL-048JEC - A/C
RGPE-07NBRQR Heater/Air Handler
RCFN-HM4824CC Coil

Here is what I learned from asking the customer service rep at Rheem. With a Rheem 501 thermostat, the communicating system will control the fan speed per the stage this is engaged and the 'differential' in temperature. My assumption is that with all the 'communicating' going on, that the unit will operate in the most efficient (in terms of electricity used) manner controlling the airflow and the compressors as it relates to the temperature setting. I care about this since I live in Phoenix where we use the A/C a lot of the year, as you can imagine…so eking out any extra efficiency is a good thing in terms of our electric bill.

So one question would be is my assumption true about this being an efficient system for the reasons I cited above? I am sure there many factors that enter into efficiency, but I am looking to see if there was any benefit to buying a system with the CCS2 communications.

OR is the 'CCS2' system designed mainly to keep the temperature from fluctuating very much and minimize fan 'noise'? i.e. to maximize 'comfort'. Not a bad goal either...

Or both (hopefully)?

Ok, now for the second question which I have seen answered in a variety of ways here after digging through a lot of conversations, but I want to ask it directly in the context that I care about:

Assuming that there are some efficiency benefits per above, does using another brand 2 stage thermostat (in this case a Honeywell 6000 series 6320U1000) eliminate those benefits of the CCS2 system? And while I am interested in the overall answer including things like fan speed/noise, my question is specifically focused on efficiency.

Of course, what happened was that my installer told me in advance that there would be 'no difference' using the Rheem thermostat, that they 'could' install it, but that it would be $200 more, plus 'they had more failures with the Rheem' than with the Honeywell. What I have noticed since the install is that the unit comes on with a ramp up of the motor, but once at speed, there is no change in the speed. My understanding is that this would be different with the Rheem 501. Anyone know if that is true?

Also, without understanding why, I noticed that the air coming out is not as cool as at first as my other A/C was. After speaking with the Rheem customer service guy, I think I understand that is because it comes on with the first stage and then the second stage will kick in, based on a setting in the unit for time elapsed. That makes sense to me, but I 'think' he was also telling me that with the Rheem 501, the second stage will kick in based on what the thermostat says and detects, and not based on a setting in the unit itself (as it apparently is now using the Honeywell) Any truth here?

I am sure I can get them to come out here and install the Rheem 501, but it is kind of annoying that it would appear I did not have all the facts before they installed it, and that I have to search so hard simply to get all the facts.

Any comments from you guys? Much appreciated in advance…

Andy

[BaldLoonie]

If you get the 2 stage furnace, you'd want a 2 stage thermostat. Forget the built in timer, that's nuts. Most situations, after a furnace runs a while, you need less heat not more. So why time to HIGH just when you need LESS heat? The 6320, IF properly wired, can also stage the high fire based on need, not time. But that's it.

The 501 communicates with the A/C and the furnace so you have lots more control. Also it can give the tech a good picture of what has been going on with the system in the event of an intermittent issue or if something has gone wrong, there are many error codes it can report. For what you are spending for the nice equipment, the extra for the 501 is minimal and worth it.

For cooling, you should have 2 speeds, low cool and high cool. There may be a 20-25% reduction when the thermostat, whichever you have, drops from high to low. The variable speed blower monitors duct conditions and varies speed slightly to adjust for dirtying filter or closed registers to maintain preset amount of air. The 501 doesn't change that but gives you dehumidify capability that the Focus Pro can't do. If you deal with humidity at all, that's a great feature.

[awestaa]

Hey Thanks.

If you get the 2 stage furnace, you'd want a 2 stage thermostat. Forget the built in timer, that's nuts. Most situations, after a furnace runs a while, you need less heat not more. So why time to HIGH just when you need LESS heat? The 6320, IF properly wired, can also stage the high fire based on need, not time. But that's it.

Yeah, that makes sense, they did give me a 2 stage thermostat. Maybe I misunderstood what the customer service rep was saying about timing in the unit. Anyway, I think I turned on the heat maybe 20 days total last year and that was only for a short period at night to warm up the house when it got cold, and it basically stayed warm, so I assume the heater will work decently no matter what.

The 501 communicates with the A/C and the furnace so you have lots more control. Also it can give the tech a good picture of what has been going on with the system in the event of an intermittent issue or if something has gone wrong, there are many error codes it can report. For what you are spending for the nice equipment, the extra for the 501 is minimal and worth it.

Well this was the one thing the salesperson told me explicitly - that the 501 shows the diagnostics remotely, but he said that was the only 'real' difference. I am getting them to replace the Honeywell with the 501, but I still want to understand exactly if I can, what it does in terms of changing or controlling the behavior of the system, besides the benefit of the remote diagnostics. And if there is any difference as I suspect, would it also be reflected in energy consumption, especially during the summer with such high A/C usage and high heat here in the desert?

It was kind of odd really, if they had said something like "You need this communicating thermostat to get the full benefit of the the system, but if you want to save $200 we could give you this one and it will mean X, Y, and Z", I would have have just said "of course, give me the communicating 501 thermostat". But instead, while researching the system myself, I found out about the 501 on the Rheem site, and when given the estimate I saw the Honeywell on there and that is when I literally asked about the 501. He never would have even brought it up to me. Anyway, then he called his internal 'guru' back at the office and came back and told me "Well, yeah, we can do it if you really want it, But it will $200 more and we have had reliability problems with the 501, but the Honeywell is a great unit". So what was I supposed to do? heh... It would be nice if I could depend on the recommendations of the 'experts' and not have me telling them what I should have...seems like it anyway...I would expect good advice for 'what I am spending' as you mentioned . I find it baffling too...

For cooling, you should have 2 speeds, low cool and high cool. There may be a 20-25% reduction when the thermostat, whichever you have, drops from high to low. The variable speed blower monitors duct conditions and varies speed slightly to adjust for dirtying filter or closed registers to maintain preset amount of air. The 501 doesn't change that but gives you dehumidify capability that the Focus Pro can't do. If you deal with humidity at all, that's a great feature.

Again, thanks for the comment. But let me make sure I understand. Are you saying that there would be a 20-25% reduction in speed from the blower when it drops from high to low? Or does the blower speed only change for the duct conditions you mentioned? (other than startup and shutdown of course when it ramps smoothly). So far I have detected no change in blower speed even when it changes stages and the air it blows is cooler. In terms of humidity, we have very little here in Phoenix. Is that dehumidify capability something that would provide benefit here somehow do you think?

[crmont]

The communicating system's main purpose is to simplify the initial setup for the installer. As you have already mentioned, your fan speed may not be reflecting the stage of the compressor. This may be due to an improper initial setup. Such mistakes are lessened when using the communicating system.

The enhanced humidity control provided by the communicating system may not be so important for your particular climate. However a discharge air sensor can be added and it's temperature reading displayed at the thermostat.

There is a multiple speed, user selectable "fan only" function that is gained with the communicating system, but is overridden by a call for heat or cool.

Then of course the diagnostics are also displayed on the communicating stat. The diagnostic codes are also displayed on the control board of the furnace and condenser units.

There is a gain in functionality, not necessarily efficiency. IMHO the cost difference that you are being offered is a bargain.

[awestaa]

Thanks for the notes...

The enhanced humidity control provided by the communicating system may not be so important for your particular climate.

In terms of the humidity control, the quote from the manual says: "On Demand Dehumidification improves the comfort level in your home by reducing the humidity level. This is accomplished by slowing down the system fan speed and lengthening the run time. The humidity setting may not be reached before the call for cool has been satisfied as the system priority is to maintain the temperature in the home"

I guess there is no way to know in advance, just turn it on at 50% maybe and see if it ever kicks in and the fan slows down. Is that what you would suggest? And per my original question, if it does kick in I am guessing that longer 'run times' with a slower fan speed does not necessarily mean better or worse efficiency. Do you think that is correct and that the differences are so small as to not be a factor? That this is purely and literally a 'comfort' setting?

However a discharge air sensor can be added and it's temperature reading displayed at the thermostat.

In terms of the discharge sensor, how would this help me and should I ask for this do you think? In the 501 manual it says there are readings for Return Air Sens, Supply Air Sens (is this one the discharge sensor?), and Outdr Temp Sens. All of them are apparently 'optional field installed". Can you think of any reason I should ask for any of them to be installed in particular and what would knowing those temps do for running the system? Are the readings purely informational?

There is a gain in functionality, not necessarily efficiency. IMHO the cost difference that you are being offered is a bargain.

Agreed. I am not complaining at all about the cost of it, merely that I was literally 'sold' a different thermostat and the topic of the communicating one never would have even been brought up if I had not asked. Then it turned out that there was misinformation being given to me when I asked questions about it.

I had no idea there was such sophistication in home A/C systems and variables to factor in to any equation....crazy stuff! There is a lot to know to be an informed consumer...painful at times. Am I out of my mind digging in this far and asking these things? gad...being a software engineer I can't help myself I guess, I always just want to know what is going on and how things work. I am a stickler for getting to the facts I guess.

Seriously, i appreciate the help and information.

[crmont]

In a humid climate, reduced humidity is an energy saver because comfort can be achieved at a higher temperature setpoint. In a dry climate, comfort is achieved at a temperature setpoint only as humidity usually isn't a factor.

The discharge sensor is a simple diagnostic tool that a inquisitive home owner can find useful, and can help a technician with repair and installation issues.

If nothing else, the communicating stat will iron out the lack of a low speed fan when the 1st stage of cooling is calling.