HVAC Experts out there?

[lgreen]

I just did some renovations to my upstairs.

I have a windy stairway (open) going into from downstairs to upstairs ending in a hallway, the hallway is open to the downstairs.

There are 3 doors in the hallway going to 3 rooms, one of which is a bedroom suite so its quite large.

A new HVAC system was put in to cool the upstairs, there are vents in all the rooms and 1 return in the bedroom suite.

The hallway that is open to the downstairs has a bunch of stuff- a 2nd return, a thermostat and a heating/ cooling vent.

I am wonding "WTF!!!" If I close all the doors to cool the rooms to isolate the upstairs from the downstairs, the thermostat will never know to turn off the AC or heat right? I don't see the tiny vent doing anything or the return doing anything either.

The contractors tell me that this is a good setup because the return is in the hall near the thermostat; I am thinking they are BSing me, if I turn on the AC 1 notch the rooms get super cold cause the cold air does not make it to the thermostat!

So anyone know anything about HVAC and have any comment?

[ra7]

There can be any number of things happening here.

If you do indeed have a vent for supply and one for return in the hallway, where your thermostat is located, it should be working fine. The problem may well be that the ducts to your bedroom are improperly sized and may be delivering too much air.

It will also depend on what loads you have in your hallway. If you have a window from where direct sunlight is hitting the thermostat, it will obviously work harder to keep the temp down.

[lgreen]

Yes both of those vents are in the hallway and there is no window/ sun there either.

How does the hallway get cold? Its exposed to 1000+ square feet of hot air from the downstairs?

[kuroguy]

Well, you've obviously been screwed by your mechanical contractor. First, the thermostat does want to be located near the return. The real question is whether the return is properly located. Locating a thermostat in an interior corridor when the air conditioner serves perimeter spaces is usually a bad idea. The cooling loads in all of the spaces served by that particular air conditioning unit must track the same. This is rarely the case, and will never be the case when mixing perimiter spaces with interior spaces (such as your bedrooms and your interior corridor. As a result, If you were to be able to get one bedroom to maintain a proper setpoint you would likely find that none of the other spaces track with that one comfortable room. That said, I have found that you can minimize those temperature variations across an air conditioning zone by properly locating the thermostat.

You might get better results if you move the thermostat into one of the bedrooms. Of course, which room is the $64,000 question. The room with the thermostat should maintain a comfortable temperature all the time, but others may want access to the thermostat at inconvenient times (maybe while the bedroom occupant is sleeping, or more inconvenient, having sex). Choose the t-stat location wisely. it can cure your problem, but comes with its own set of problems.

[scott wurcer]

You could install one or more thermostats and balancing dampers to create as many zones as you need. Last time I looked Smarthome.com had all the stuff for DIY multi-zone HVAC.

[Enzo]

And if this is a recent installation, and it is not performing up to your needs, certainly contact the contractor and express that. he should at least have the opportunity to either show you how his system can be balanced, or make corrections to the system so that it can be, or explain to you what options you have. If no satisfactory result can be obtained, that is what the courts are for.

[lgreen]

This is just put in and work is ongoing. The GC insists that the location is good because it is near the return but I fail to see how that makes any sense at all. The sub that did the work has not replied yet.

There are 2 small interior bedrooms and 1 large interior bedroom. I would think that the best location would be the larger bedroom.

[kuroguy]

First off, all of your bedrooms are adjacent to an exterior wall. Pretty much every building code requires it (I say pretty much because although in my career I've never read a code that didn't require a direct exit to the outside, I suppose there might be some code in use in some backwards town that doesn't have that requirement).

the thermostat controls the air conditioner. It only knows that it is too hot or too cold where the sensor is located. If there is a room that is consistently hotter in the summer and colder in the winter, I'd say put it in that room.