SEER question for the legendary Seer

[chrisprickett]

Sir George (or anybody else who knows what they're talking about)[]

I have a warranty inspection next week. The owner is suspicious because he paid for two upgraded 14 SEER units. The units SAY they are 13.5. the HVAC guy (according to the owner) said they add a "coil" to the units bringing them up to 14. He described the "coil" as something small enough to fit in your hand.

It sounds like it might be BS, whatcha think?[:-bigeyes]

[Norm]

Take the model and serial number down and call the local distributor for the particular manufacturer. They will tell you what the SEER is. There are instances where the units are labeled 12 SEER and a variable speed air handler is introduced into the system which raises the SEER. I have never heard of a coil which fits into your hand used to accomplish this. Besides, adding a component violates the UL or other testing laboratories approval unless the system was tested with the particular component.

NORM SAGE

[Terence McCann]

Would that be a hand held evaporator or condenser coil?[]

Never heard of a coil that fits in you hand raising the SEER of a unit.

Variable speed air handler/VAV systems are on commercial systems that I've seen and then they have all sorts of controls such as defrost stats on the evaporator, hot gas bypass, anti-recycle timer due to lower air movement across the evaporator which can cause ice buildup. Has anyone ever seen a VAV residential system?

If the condenser fan is VAV it is intended for low ambient conditions - allowing the system to run below 50 degrees. Carrier use to call this a motor master, Liebert called it Lee-Temp and I'm sure others have their own acronym.

Norm brings up a good point about the UL listing as well.

[chrisprickett]

A lttle more info: The units are York, that's all the builder uses out here. All info I have comes from the homeowner, via a phone conversation. Having not seen the "coil" myself, he could be talking about a wire, clip, chip, or anything else. I've never heard of a "13.5" SEER unit, I've only seen them with even numbers.

Checking the serial numbers is a good idea. Any more info is appreciated!

[a46geo]

Chris,

I can't add anything to what has already been said. If you can get the numbers off both the condensing unit and the A-coil, York can tell you what you need to know.

George

[Norm]

Terry & Chris, Et. Al.

Variable air handlers are common here in S. Florida in residential installations. In certain circumstances they do increase the SEER of the system. In the case of the York systems Model #s' beginning with the letters HDH range from 12.0 to 13.50 SEER with a variable speed air handler. I recently wrote an article titled : "SEER SO WHAT", which was published in the Gulfstream ASHI Digest and the newsletter of the Florida Association of Building Inspectors which I would be glad to send to anyone interested. Better yet, I will send it to Mike "O" and he can use it as a resource. For immediate reference go to the following link http://www.energystar.gov/ia/products/p ... d_list.pdf you can access 15 pages containing the model numbers and SEER of 455 models produced by 28 manufacturers.

NORM SAGE

[Terence McCann]

Hello Norm:

As I was thinking about the VAV systems some of the higher end homes - 600k & up might have a zoned system which could be thought of as a VAV (of sorts). They also have VVT systems but again those are mostly commercial applications.

For cookie cutter residential applications up here we always see constant volume.

I'm curious as to why they would choose VAV in your neck of the woods? What is the advantage?

What do they do for evap controls etc? Do they zone or is the main AHU VAV? What controls the speed of the fan - are they controlling to static pressure?

The best known up here was the Carrier Modu-Line system in which the used perimeter heat on an indoor/outdoor reset and supplied 55 degree air to the modu-line VAV boxes. Worked great. Heat the skin and cool the interior but again this was commercial grade. During the late 80's they stated to make a shift to fan powered mixing boxes with either electric heat or h/w coils in the box. They used a frequency drive on the main AHU.

Sorry for the barrage of questions but it has really peaked my interest.

Thanks!

[Norm]

Terry,

As I am informed by the folks at York, Rheem, and Trane when you are dealing with a split system air-cooled central AC installation the following applies. The electronics measures the resistance in ohms at the evaporator coil. When the coil moisture level raises the resistance raises. This triggers the blower motor fan to increase in speed. If there is an integral humidistat installed in the system when the relative humidity in the conditioned space rises above the manually adjusted setting it will trigger the blower motor to reduce it's speed allowing the air to remain on the coil longer in order to extract more moisture. Please bear in mind I prefaced this post by saying "I am informed by......" that's different than "I know or I understand". I hope this helps.

NORM SAGE

[Terence McCann]

Thanks Norm!

Never heard of that before. [:-boggled]

I will have to research further. Sounds like it's a device for controlling RH%, interesting!

[a46geo]

Originally posted by Norm

Terry,

The electronics measures the resistance in ohms at the evaporator coil. When the coil moisture level raises the resistance raises. NORM SAGE

Norm,

I'm with you, I don't know. BUT since water is a conductor, wouldn't resistance decrease[:-?help]

[Chad Fabry]

I'm not an A/C guy...we have only about ten days a year that you really need it here.

Wouldn't a thermistor be used to monitor evap temp and blower control be factored off of that? I don't see how decreasing air speed is going to remove more moisture in a closed system. Wouldn't the difference in moisture removal per pass be offset by by more passes per hour w/ increased fan speed?

[Norm]

George,

It sure would seem so. I got most of my information from Nick Liotti with York. 1-800-219-9192 select technical support. If you leave a message Nick is good about returning calls.

NORM

[Terence McCann]

Chad:

The bigger the evap surface area the more moisture removal you could expect. It was vogue to size the evap coil 1/2 ton larger than the size of the condensing unit for better dehumidification - not sure if they still do that though.

Having said that, if you slow down the air across the coil it will lower the dew point and allow more moisture to be removed from the air also, the leaving air temp will be colder. This however, doesn't mean you cool the room any quicker, lack of air flow. If you speed the fan up it will remove less moisture and the leaving air temp will be higher. The big problem with slowing down evaporator fans is ice buildup.

I'll give Nick a call with York to pick his brain a little. I'm curious about control sequence.

Thanks for the # Norm.

[Jim Katen]

Originally posted by chrisprickett

Sir George (or anybody else who knows what they're talking about)[]

I have a warranty inspection next week. The owner is suspicious because he paid for two upgraded 14 SEER units. The units SAY they are 13.5. the HVAC guy (according to the owner) said they add a "coil" to the units bringing them up to 14. He described the "coil" as something small enough to fit in your hand.

It sounds like it might be BS, whatcha think?[:-bigeyes]

Not necessarily. I'm not at all familiar with York equipment; there's little of it around here. However, you can tweek the seer ratings of most AC and heat pump systems in a bunch of different ways.

The first thing that came to mind when you mentioned something small enough to fit in your hand is a thermal expansion valve. It's not a 'coil' but it will boost the seer (if the system didn't have one inside & out already).

Adding a variable speed blower will also boost seers. They're becoming quite common, even up here where humidity isn't much of a concern.

One other thing. I might be wrong about this, but UL lists components of these systems, not the systems themselves. It seems to me that an installer can add all sorts of options to these things without affecting the UL listings. HVAC equipment is probably the most customizable system in the house.

- Jim Katen, Oregon

[Norm]

I believe UL lists whatever was submitted to them for testing. I had a personal experience with this several years ago. At my own home I installed a light source box for fiber-optic lighting in my swimming pool. The unit the cord and plug with which it was tested and listed by UL. I wasn't entirely comfortable with the exposed plug in connection and hardwired the unit using liquidtite conduit. The electrical inspector refused to allow this arrangement since it violated the UL listing. I believe the same would apply in the case of a modified A/C system unless the system had been tested in conjunction with the particular component which is added in the field.

If I'm wrong please correct me. That's what learning is all about.

NORM SAGE

[Jim Katen]

Originally posted by Norm

I believe UL lists whatever was submitted to them for testing. I had a personal experience with this several years ago. At my own home I installed a light source box for fiber-optic lighting in my swimming pool. The unit the cord and plug with which it was tested and listed by UL. I wasn't entirely comfortable with the exposed plug in connection and hardwired the unit using liquidtite conduit. The electrical inspector refused to allow this arrangement since it violated the UL listing. I believe the same would apply in the case of a modified A/C system unless the system had been tested in conjunction with the particular component which is added in the field.

If I'm wrong please correct me. That's what learning is all about.

NORM SAGE

Well, here's how I see it. Your light box is like a Lego. UL lists the Lego and says it'll be safe if it's not altered and if it's installed under a certain set of conditions. You changed the Lego in a way that UL's tests didn't anticipate, so the listing no longer applied. The inspector was correct to smack your butt, even if you had managed to make a safer Lego.

A heating system is more like a collection of Legos. As long as you use each one according to the terms of its listing, and as long as you don't alter them, there are any number of ways that they can be assembled in the field. The manufacturers usually have long lists of which Legos can be used with which other Legos. Some combinations are cheaper, some are more efficient and some are non-sensical, but still allowed.

Of course, it's possible to violate the UL listings in any number of ways, I'm just saying that it's also possible to alter the components in a heat pump or AC system without violating them.

- Jim Katen, Oregon

[Norm]

Jim,

I agree with you. The catch is that so long as the lego which is to be added to the other lego in the field has been tested with the first lego and is listed as such there is nothing wrong. Wow, almost sounds like lawyer language, the party of the first part and the party of the second part and the aforementioned not withstanding etc. I think we are on the same page. The problem we encounter in the field is that we are usually not provided with the listing specifications. That maybe a blessing in disguise since I'm not sure I would want to review and accept or decline the technical information.

NORM

[Terence McCann]

Well…. The wife and I went to the NARI home improvement show at the IX center yesterday and I stopped by the Carrier booth and talked to one of the tech’s about the VAV furnace.

Carrier calls their technology the “Thermidistatâ€

[Jim Katen]

Originally posted by Terence McCann

Well…. The wife and I went to the NARI home improvement show at the IX center yesterday and I stopped by the Carrier booth and talked to one of the tech’s about the VAV furnace.

Carrier calls their technology the “Thermidistatâ€

[Terence McCann]

Gentlemen Jim:

The rotary tuner needs some bumping/jiggling upon occasion and I'm finding it increasing difficult to find a tube testing machine in our local drug store but you can't beat watching Jack Paar on it.

BTW, you sound like you were reciting from the Carrier brochure - soft start etc. [:-thumbu]

OK, I need to ramp-up a little on technology.

[Chad Fabry]

Hi Terry,

In an earlier post I presumed that a thermistor would be used to control blower speed. Thermistors don't sense moisture they react to temperature. If the evap coil were 50 degrees the thermistor would have a specific value of resistance,say 200 ohms. As temp of the coil increases the resistance through the thermistor decreases and the data from that event can be interpolated by the system's operating controls to control blower speed. There may be a direct correlation to moisture content as figured from other input devices like motor load and temp input and output but the thermistor itself doesn't measure humidity, it reacts to temperature.