Powered Damper system for HVAC

[beelzerob]

Thanks for the input guys!

Ok, so the ocelot controls the secu16 which has a relay which controls a relay through which the current goes to operate the damper. Does that sound about right?


The damper will go in the HVAC output (vent) main duct that handles all 2nd floor outputs. None of the returns will be dampered, on any floor.


I'm not too concerned about using CQC for this, though a "hard wired" solution inside the ocelot is not a bad idea. But either way, this isn't really a critical function for the house. If the damper gets "stuck" closed, then it can still vent to the entire downstairs...which is what we're trying to get it to do anyway! If it gets stuck open, then we're in our current situation, which isn't so bad really.

Is there any particular arguement for getting the 3 wire then? Is it more reliable because it doesn't use spring action to operate? Does it work more reliably against the airflow? etc?

Any insight about the power for the damper then?

 

[beelzerob]

Man, is this a LOT harder than I thought???

I just got the return call from the HVAC guy. They had quoted me $2300 originally for the "2 zone system" which involved 4 dampers. (1 to cut off the 2nd floor output, and 3 to cut off the 1st floor output). I felt that was really too high, so I asked him to re-quote it for JUST the 1 damper to close off the 2nd floor. In fact, I also told him not to worry about a thermostat or even power/control, that I would handle all that. So ALL it was for was to install a single power damper into the duct.

He called me back and it's now down to $1300. What am I missing here?? Is it really harder than cutting a section out of the duct, putting in the damper, and then taping with that metal tape?

He did mention that installing even that single damper would also require installing a bypass damper. And that the original quote for the 4 power dampers also included 4 bypass dampers. So...what the hell is a bypass damper for?? I looked at them...aren't they essentially a manual damper? Is there whole purpose to allow you to manually bypass the power damper?

I can see then how that would add to the cost, as they'd have to add ducting just to go around the power damper. But unless it's illegal to do so, I just don't see why I'd need a bypass damper in this case. If it's a code thing...well then I'll worry about it when we go to sell (never).

 

[Neurorad]

Get a couple/few more quotes, compare notes.

If it's so easy to install a damper, then why don't you do it?

HVAC guys have a monopoly on HVAC. Info is protected well. Just like home security.

 

[beelzerob]

If it's so easy to install a damper, then why don't you do it?

Well, what scares me is the idea that this is one of those things that seem so easy to do, but in reality there's little tiny details that if you omit, you house will burst into flame from the very pits of hell....

Otherwise, I'd just go for it and see what happens.

My first thought at this point is to take apart the duct where the round meets the square, and seal that off, which seals off the 2nd floor, and then see if that actually makes any difference.

 

[sic0048]

Well I am just starting to look into stuff like this. But I think you really do need more than just the single damper.

First, I would install a bypass damper like one of these. It will automatically open if the pressure in the system build up too much. Otherwise it stays closed so you don't waste any heat. You mentioned having a basement and I assume the easist thing to do is to simply vent this bypass damper into the basement. Then you don't have to worry about "overheating" the unit by continually recycling hotter and hotter air through the unit. You would install this bypass damper in the main supply duct as close to the HVAC unit as possible; certainly before it split off to the different areas of the house.

Then I would also recommend that you install a normal damper on both the supply AND return for the upstairs. However, I guess not having one on the return isn't the end of the world. The return is going to suck air from the path of least resistance, so if there is no air being pumped into the upstairs, then there probably won't be much air being sucked into the upstairs return. But being able to close off the upstairs return would allow for the most efficient system IMHO.

I think you would also want to get normally open damper controls for the upstairs ducts. Then you could use a simply relay to close the upstairs supply and return if it got too hot upstairs and you wanted to shut the heat off. The bypass damper shouldn't need to be hooked up to the relay because it uses a built in barometric relief settings which will automatically open it up if there is too much pressure in the system. If something goes wrong with the control system (it goes off line, etc), then the two upstairs dampers open up and the HVAC system works as initially designed.

I think this is a relatively easy job and one that could be done DIY if you felt comfortable doing the work. By adding a thermometer or thermostat upstairs, I'm sure you could create some CQC rules to automatically control the damper. For example, if the upstairs temp was more than 2 degrees hotter than downstairs, and the heating system is on, then close the upstairs dampers by energizing the relay.


PS - actually looking at those bypass dampers, not only do you need square ones in your situation, I think you want to find one that has an automatic barometric relief setting but is also normally closed. That way if the control system goes down, you are not pumping heated air into the basement. The rest of the system would fail in such a manner as to mimic the original HVAC system, so you would want the bypass damper to also mimic the original system. Since there was no bypass damper on the original unit, you would want this to fail in a closed position.

 

[beelzerob]

Well, so I can understand the full scope of the equipment I'll be needing...let's say a normally open powered damper (2 wire), a bypass damper, and then....? I'll be using a secu16 for control, so that has relays, but I need to use those relays to power other relays, which feed the actual power to the damper, right? And the other question is..what is that power? Where do I get suitable 24v power for a damper? Is that just a "24 v power supply" I would google for, or is there a standard place HA people get their power supplies from?

Still a shame I can't use my rain8net....it sits sadly in a box, as it has for years.

 

[sic0048]

Well I know the HVAC system probably has a transformer for 24v power. I know mine does as I just installed my TR-16 thermostat yesterday. I used the 24v power right from the HVAC unit. But you would want to check the amount of draw that the dampers use and see if the system can handle it. If not, surely one of the zone control manufactures makes a 24v power supply for this exact situation.

 

[icellama21]

Keep in mind that this is usually 24V AC, not DC! Almost all HVAC applications are not rectified, makes it easier to just attach a transformer to the line. Can't really imagine why they haven't gone to DC yet.

 

[beelzerob]

Looks like smarthome sells some dampers WITH power supplies, or they also link to this, which would seem to do the job.

I think I'm going to do some more research into seeing if the rain8net is up to the task without killing anyone or anything. Then I'd have control and power all in one device.

 

[sic0048]

Looks like smarthome sells some dampers WITH power supplies, or they also link to this, which would seem to do the job.

I think I'm going to do some more research into seeing if the rain8net is up to the task without killing anyone or anything. Then I'd have control and power all in one device.

Since I have no experience with either the rain8net or dampers, take this with a grain of salt. But just looking at the thing, I'd have to say that the rain8net should work fine. Afterall, it is simply turning on 24vac power to the proper sprinkler zone when asked to. So you'd think you could send 24vac to the correct damper when asked to. It also looks like the power supply is rated high enough to power two "zones" at the same time, so you could power two different dampers (like the upstairs supply and return damper) and the same time.

Of course you would need to use CQC to turn on the zone and then turn it off. The automatic timer function of the rain8net has no real application in this setting. But it's simple enough to write the logic with CQC based on the temp upstairs vs downstairs and if the HVAC system is currently on.

 

[WilliamMcCormick]

Since I have no experience with either the rain8net or dampers, take this with a grain of salt.

But just looking at the thing, I'd have to say that the rain8net should work fine. Afterall, it is simply turning on 24vac power to the proper sprinkler zone when asked to. So you'd think you could send 24vac to the correct damper when asked to. It also looks like the power supply is rated high enough to power two "zones" at the same time, so you could power two different dampers (like the upstairs supply and return damper) and the same time.

Of course you would need to use CQC to turn on the zone and then turn it off. The automatic timer function of the rain8net has no real application in this setting. But it's simple enough to write the logic with CQC based on the temp upstairs vs downstairs and if the HVAC system is currently on.

I have installed the damper control systems, and to be honest even a 6 zone control system is under 300 bucks to buy. You do not have to use all the zones, but it is nice to have a couple extra incase down the road you want your bathroom or other room to stay at one temperature.
 
What most people do not buy is the barometric damper, that damper allows air, to recirculate from the supply plenum back to the return, if static pressure rises above a certain pressure.
 
I just did an existing three ton system, and installed a 14 inch bypass damper into the system. It requires some large flex, a large "T", some plastic "P" or zip ties, and a large take off, that you cut into the supply plenum. Then you basically just cut the flex to the registers or diffusers you wish to regulate, add on the power damper, it is just a short piece of round duct that has a damper inside of it. Then you put the flex back on the damper. They also make square dampers as well. I used four round dampers. One fourteen inch round power damper, and three six inch power dampers. The fourteen inch damper feed a 14 inch round duct, that had round take off's cut into that feed the same large room.
 
Each damper is controlled by its own thermostat. All thermostats in the house go to the damper control panel. As do all the damper wires. Three wires are needed for the PO power open and PC power close dampers. Common, PO and PC.  
 
In a normal state the control panel opens all dampers, as soon as there is a call, it closes all the dampers that are not calling and turns on the air handler. You can turn on the fan, and send air to just the damper that is calling for the fan. You can even turn on the Air Conditioning on one thermostat and the heat on the others. Every fifteen minutes of inactivity from a heating cycle, will give the thermostat  calling for AC a chance to run the compressor. To buy the stuff you need, to do something like that you are looking at about $1300.00
 
But you get outrageously hot air, outrageously cold dry air, because of the bio-metric damper recirculating the air within the unit. The air handler is  protected by a heat sensor monitored by the control panel, that limits the temperature in the supply duct, either to hot or to cold. If you are supplying one six inch duct, with 3 tons of AC, you are going to have to shut the compressor down, if there is some strange occurrence that keeps that thermostat calling for air-conditioning.
 
If done right they are amazing. if done wrong they are horrible.
 
I have fooled with back feeding thermostats and it can cause problems, sometimes when you back feed a fan terminal on a thermostat it will turn on the Y1 and run the compressor. So I tend to avoid crazy wiring schemes. Unless I have a lot of time to fool around.
 
You actually need three NO (Normally open), NC (Normally Closed) relays just to isolate, each damper, from each thermostat, and air handler, it is not at all worth it, to try to do it yourself. If you only need two zones the controller is about $100 bucks. And leaves you with an extra zone capability.
 
The bio-metric damper, that works on gravity, very easy to setup, very simple, is about half the price of the same size power damper. Dampers are about $100 bucks no matter what size they are.
 
               Sincerely,                           
            
 
                          William McCormick

 

[WilliamMcCormick]

I used a EWC Controls, BMPlus-5000 control panel. A very nice little unit.
 
 
                   Sincerely,                             
 
 
                            William McCormick
 
 

 

[WilliamMcCormick]

There is a lot of duct work that is often needed. Especially where you have multiple hits in one room. You have to create manifold and use one large zone damper and then branch out from there to multiple hits in the same room. You also need a barometric damper to allow the system to bypass back into the return. It pays to get the right sized damper.
 

Definitely worth it.


Sincerely,

William McCormick