variable speed air handler operation

[bdx]

I recently upgraded my air handler to a variable speed York (4ton). It was installed this week and the tech did an outstanding job installing and hanging the unit.. a work of art and the unit runs great

The unit I had was undersized and the duct work was incorrectly sized as well.

I was hoping someone could tell me the operational differences I can expect with a variable speed unit.

So far it runs on a high speed only. It will slow down when the fan is put in the on position and room reaches temperature and the compressor kicks off. Thx BDX

[beenthere]

If the outdoor unit is a single stage, and you didn't get a humidistat installed, it will run on high speed any time the stat calls for cooling.

If you have the humidistat installed, any time the humidity is above set point, and the a/c is running, the blower will only go to 83% till the humidity is down, or the stat is satisfied.

[bdx]

Thanks for the reply.

Unfortunately, I was not home when this was installed, I will call the person tomorrow, but how can I check to see if I have a humistat and if not installed, where would it go into the return air line? thx BDX

[beenthere]

It can be installed in the return duct, or on the wall beside your t stat.

If your installer put in in, he should have told you, and gone over its operation. So good chance he didn't.

[johnl45]

Most VS units have a ramping profile controlled by dip switches.

[beenthere]

The profile is some what limited on york.

Standard slow ramp, and a delay set to the metering device.

But not very noticable by the H.O.

Most just notice a better air volume.

[bdx]

Thx again, I will check it out.BDX

[newhomeboston]

beenthere,
so if you only have a single stage compressor and a regular stat, there is no way for a VS air handler to vary its speed or ramp up slowly, etc? I have a Trane VS with a plain jane stat and a single stage compressor...trying to get contractor to get it to work with varying speeds but he hasn't stopped by yet since he has to ask his Trane dealer how to set it correctly. Did I get screwed in this case buying a VS but not getting any benefits of it?

[beenthere]

I don't know all of the abilities of the trane VS blower.

But you should be able to add a humidistat, to slow the blower down, to remove more humidity.

The VS blower varies its own speed to the conditions of your duct work, air filter, and grilles, to deliver the cfm that the board is set to. This is the best thing about them. The fact that some manufactures have even more things programed into the modual is an even bigger plus.


Trane may have a better speed program then York.
But I can't tell you for sure, maybe one of the Trane dealers will catch this post and respond.


I have a few York units that I "tricked out" to give added blow cfm control, but I don't know how well they would work on a Trane.

[dash]

Originally posted by newhomeboston
beenthere,
so if you only have a single stage compressor and a regular stat, there is no way for a VS air handler to vary its speed or ramp up slowly, etc? I have a Trane VS with a plain jane stat and a single stage compressor...trying to get contractor to get it to work with varying speeds but he hasn't stopped by yet since he has to ask his Trane dealer how to set it correctly. Did I get screwed in this case buying a VS but not getting any benefits of it?

VS is worth the money,but you can get more benefits with "comfort-R",and a humidistat added to it,this will cost more then you paid .

[j-bill]

the variblespeed blower does not correct for undersized or oversized ductwork.too small ducts will cause water & noise problems,even in a programmed enhanced operation the motor will seem to be on a high speed run,when only its fighting the static pressure caused by too small ducts. standard PSC motors will slow down in response to static problems verses a variblespeed that will maintain proper rpm's by adding more power to the motor as needed.VS motors purpose, are high efficiency on a properly sized system & ductwork,with added enhanced humidity control.we see too much mis-app of these high end products down in the tampabay area installed by no-permit hacks,their customers end up calling me up to diagnose & give the bad news that the ducts too small or a rare hack too large ducts ,or oversized capacity to make up for poor ducting.then hear "cryin eddie" from them about the cost to fix & why they would get fined because of no permit if they called the city to report any code violations,next they would blame the manufacture ,who will sell the products to anybody with green & a licence,unfortunately.