Central AC and Closing Interior Doors

[chachp]

Only one return in my house

My mom’s house was built in 1969 and it had a vent on the floor in every room that supplied the cool air and returns up by the ceiling in every room.  I remember my Dad used to play with the dampers in the basement when seasons changed.  He eventually took a marker and indicated where each should be for Cooling and then for Heating.

I’m not sure if any of those dampers controlled the returns in the rooms.  I just remember he had an HVAC guy there a couple of times to help him work through it all.  We switched those twice a year religiously and it seemed to keep the house comfortable. They had a large ranch (about 3,500 sq. ft) with two units.

Our new house is a 2,500 sq. ft. ranch.  We have only one return towards one end of the house.  We have a zoned system in this house and I still don’t quite understand how it is supposed to work.  My office is on one side of the house and the Master on the other.  When I switch on the thermostat in the Office it reduces the air to the Master.  I had the guy here a couple of weeks ago and he talked a lot about pressure and returns and quite frankly it went over my head.  We agreed he would come back when it’s not so warm upstairs (our unit is in the attic) and investigate.  I guess all the runs have dampers in them and he has to observe how they change as the system calls for different things.

I work from home, so I switch it on during the day and in the afternoon I switch it off.  The house is pretty well insulated, so it stays very comfortable.

We’ll see what he says. Does anyone have experience with a zoned system like this?

 

[drhardee]

Transom windows

Ahh, transom windows. They're very common in older homes in the south, where they provide an important source of air movement from room to room. Our home, built in 1947, has four or five of them, including the hall bathroom.

We keep them open year around; but if we have guests, we'll advise them to close the guest room transom if they're going to be "noisy" in the night...

 

[circlew]

I'm very surprised to see transom's in a house built as late as 1947. Around here you don't usually see them in buildings constructed after the teens. They add a nice touch to your attractive home.

 

[streakers]

Appnut

My heat source is natural gas. And from when I had the HVAC serviced last - the bloke tells me that it's only got two speeds - and I've only noticed it ever run at two speeds...

I could be wrong...?

Aaaaaaaand - those speeds are not adjustable through the Nest either - they're preset through either Heating or Cooling mode... Kind of strange...

If/when I ever have to upgrade it - I will be getting a unit with far more flexibility with fan speed options - if there is such a thing though...

Hope that helps...

Cheers
Steve.

 

[appnut]

Steve, yes it helps.  As I believe I've stated, I do have  variable speed air handler.  I also have a multi-stage compressor for both the AC function as well as the Heat Pump (heat portion--which is actually one-in-the-same).  I remember from all the previous years with central air, the fan motor speed was controlled by dip switches set at the time of installation according to guidelines.  Combo52 is the individual responsible for providing me the information at a wash-in in 2002 resulting in me selecting the system I have currently. 

 

[DADoES]

 
Most interior HVAC blowers have multiple speeds.  Non-variable speed units are hard-wired to a specific speed, usually higher for cooling and lower for heating.  Changing the speed can be done by switching the appropriate wire connection(s) .... the installer selects the correct speeds for the required cu ft/min airflow rate.  My system runs the same speed for both cooling and heating (heat pump).

 

[tolivac]

One guy here at work had the variable speed blower motor--had it replaced with a two speed one when the variable speed motor died.The new variable speed fan motor was going to cost almost $600-the two speed one cost less than $300 from Grainger.The circuitry in the variable speed motor was sealed in epoxy-you couldn't repair it.

 

[DADoES]

 
Variable-speed (ECM) blower motors are very expensive.  My understanding is that they vary the speed to maintain a specific (set) cu ft/min airflow rate for low, med, high, whatever recirculation speed is called, to compensate for variations in ductwork design and 'obstructions' such as filters.  Is that right or am I misunderstanding?

 

[tolivac]

The variable speed fan motors were for energy saving-if the cooling or heating conditions don't require a full airflow the motor would be cut back in speed saving power.In theory this sounds good but really doesn't work out as we see these variable speed motors replaced with fixed speed versions.The cost doesn't pay off for the little energy saving you may get.Thecircuits in those motors fail often-unless they have been improved.And it seems like any other piece of HVAC equipment it fails when its scorching hot outside or blustering cold.Also some HVAC systems have variable speed compressors.Don't know the failure rates on those.Imagine it would be steep in cost!!

 

[DADoES]

 
I had a Lennox 2-speed heat pump system with variable/ECM blower at my previous house.  The blower motor failed (during warranty!) in a way that caused it to run backwards.  This was in the early 2000s.  I was told it would been $600-something (or maybe it was $800-something) if not in warranty.

On the other hand, my current house has a single-speed heat pump with what I assume is a non-ECM/non-variable blower (it runs at the same full speed for both heating and cooling).  Blower motor failed on it at 7 years.  The cost was $664.  Flat-rate, non-itemized invoice so I don't know what was the breakdown for part vs. labor vs. diagnostic, blah-blah-blah.  I told the HVAC servicer in no uncertain terms that the charge was outrageous.

 

[washman]

Which causes me to question why the love affair with these so-called energy efficient HVAC systems when a simple motor replacement often wipes out whatever savings you may have obtained energy wise.  And if you really want to take it in the shorts, try replacing a control board or defroster board.

 

Even more absurd is the fact most if not all of these motors are sourced from China or Mexico. Neither is a haven for expensive labor so what gives?

 

[vacerator]

It's all about the economy of scale

in profit, and investor market dividend.
Cheaper labor, higher profit, higher dividends. So investors are fine with the risk of repair or replacement because they make incremental dividend's on their portfolio, pension plan, or 401k.
Yes, the repairs are expensive, but with a 2 stage variable speed Lenox for example, at least includes a ten year parts warranty. A non heat pump 2 stage variable speed furnace costs at least $3,500.00. No doubt, one repair wipes out any energy savings.
Inducer motors are also frequent repairs.
Fasco was among the worst some time ago. Now I don't know.