Two Speed AC Systems

don_185

Two stage equipment is not so much about saving as it is
comfort.

I would think any unit that does not run would be cheaper then one that runs all day no matter at what speed its in.

The effects.Customer complaints that its too hot.You being
call out because it must be something wrong with the ac.
They get mad at you because you hand them a service invoice for just tellin them that the energy system has them out.

You received another call with the same complaint,maybe two
more times before they get enough schooling from you on some other guy product.

Thats when most of them realize that they do not want to be
inconvience by the product any longer or, they no longer want to follow the program the enery guy setup to save them money and they have it disconnected.

allan_7

Two Speed AC

In our area (Southern NJ) the local utility offers a radio frequency controller that will cycle off the outdoor unit when they need to manage/shed the load- a load management device.

I was wondering what effect this device will have on two speed systems if the client opts to have it installed.

Personally, I do not care for them.

That being said, so they cycle off the outdoor unit, leaving on the indoor unit. The temperature continues to rise activating the second stage of the thermostat Y2,

When they return the unit to operation, the system will be trying to go right into second stage cool (since Y2 is now hot), how does this control strategy help conserve energy??

Seems like it would defeat the whole purpose of two stage systems since I thought it would be preferable to use the first stage as long as possible as long as the comfort conditions were maintained.

What do you think?

Paul Fredricks_6

Yeah Don, I think you have it right. Ideally, they will leave it hooked up to help out the electric company during times of peak demand, help save energy, help save the earth, etc.

Push comes to shove, the not in my backyard mentality kicks in. "I need my A/C, let everyone else save the earth. Besides, I don't use it that much."

I don't think it matters if it's one stage or two stage.

mtfallsmikey

A great advertising opportunity!

Get a local newspaper to do an interview with you, explain the effects of this, blah blah blah...Priceless!

allan_7

Please..

re-read the last paragraph.

Yes, I understand the premise of better comfort, but I think energy savings is part of the equation.

Please remember that in first stage, your suction pressure will normally be higher and therefore your latent heat removal capability will be less.

don_185

Hi Alan

Sure the suction pressure would be higher giving you a warmer coil but, for how long.Check your capacity on two stage equipment, not that much difference.So to me its a wash.Even more so in a dry climate.

I've seen many of ac that come out of setback and the coil temp reach dew point rather quickly.
If latent heat removal was that big of a concern and I know it is in some places then...dehumidifiders along with a ac system would be the better choice.

I'm not sure where you're trying to go with energy saving
issue.

Are you saying when it comes to energy saving that its better to have equipment run on low speed all day verse one that drop the load fairly quickly and then shuts off?

Thanks for posting and welcome to the wall!

Techman

Two Speed

Here on Long Island, our utility co. has a two stage controller ,it is a Carrier/Honeywell device.It's about saveing the entire power grid during certain hours, after that it's a differant story!

Constantin

Hmmm... not sure I agree.

Most two stage systems use a copeland scroll or similar device that operates at 66% of capacity on stage 1, 33% at stage 2. On my condenser, the 2-speed fan has a similar load profile. As a result, there shouldn't be a world of difference between a stage 1 or stage 2 profile on the grid. Rather, it's that a condenser is on at all (i.e. 70% vs. 0%).

IIRC, the load shedding devices basically disable the condenser until the grid has spare capacity. At that point, (and this is very important) the various condenser units are selectively enabled so that the grid is not hit with a wave of condensers coming on at the same time. For example, many devices will feature a random time delay from the time that the "all clear" signal is sent until they re-enable the condenser.

For me, the real question is whether a house can be built well enough where a condenser not being on for a few hours does not mean the end of the world. For example, in AZ, the local utility built a few high mass homes that are only cooled at night and which freewheel through the day. Similarly, if there is a question between grid stability and a few hours of warmer indoor conditions, I'll take the warmer indoor conditions.