combined hot air and radiant

Norm Brulotte

house has hydro air ducts in all rooms on zone ,some rooms have radiand heat in floors ,my question is how do you seperate these rooms to take full advantage of the radiant. If you use registers with manual dampers would the pressure in the duct system increase and make the system noisey. Any suggestions out there.

don_9

anything possible

You can add two stage tstat and the room with infloor
first stage to control infloor,seconds stage to control
zone damper for the force air,If you choose damper system you will have to have a static bypass damper for additional
friction added by closing damper,not to mention extra
relay,transformer,summer and winter switch over, switch.
IT can be done,but it will come at an expense.Set down think about pros and cons and map out a plan.don

Bill NTSG

Hi Norm

Norm is my neighbor [almost, about a mile away] I have both in my house. I use the hydro-air in the early fall and late spring "just to take the chill off" . Until this spring, my living room which I recently remodeled, was underadiated.[not enough radiant panel] So if the outdoor temp dropped below 20°F the room was cool. The t-stat for the hydro air would kick in and make up the difference. If your t-stat is in a room away from the radiant heated rooms and you close the dampers to the radiant heated area you should be ok. If you have velocity noise through the duct you may be able to slow the fan speed in the air handler. Most air handlers allow you to set a slower speed for heat and a higher speed for cooling. If not, a relay and some creative wiring should help. How much of the house is radiant and how much is FWA ? what style of construction? The radiant might handle most of the load in mild weather and may only need the hydro from christmas 'til March ?? You think we will have a winter this year ? Last January I was washing my truck in a tee shirt on a 70° day.

hr

Another simple option

would be a set point control on the radiant rooms. I have done this both with a sansor mounted below the floor, or on the return piping. More of a floor warming system really.

It will take a bit of owner fiddling to get it set, and they may change settings in the spring and fall. It is a simple inexpensive option. The latest tekmar two stage wall stats are also a nice option, lots of programming features for the radiant portion. This control would need enough wires at the wall stat location to be useable.

Depends on how "automatic" the system needs to be

I not a forced air expert, but I don't think you want to start closing down a lot of supply dampers, without some sort of bypass as mentioned. A contractor with duct sizing expertise should look it over first, perhaps.

hot rod

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don_9

my opinion

never close off any supply vent,It throw the whole system out of balance,the trick with any force air system is its ability to push atmosphere air back to the receiver(return)
Closed vents not only produce higher static in the duct system,but it also put stress on the fan motor.The return can only receive the air that is brought to it.By closing door and vents,we produce a negative pressure in the areas where theres only one return for the entire system.If you have a envelope that has lots of leaks,you pull in air from outside which adds additional load to your system.

Bill NTSG

Well

I really don't see how closing a supply in one or two rooms will reduce the return air supply. What goes out must come back. Choking a return would cause trouble, but stopping a few CFM from going out is not going to effect the return. If it doesn't leave the duct work it doesn't have to come back does it ?? I may be wrong .Dirty air filters will cause more harm. I have been in several dozens of homes where home owners do this all the time. [not saying it is right] If too many registers are closed it will cause heating and cooling problems ,I agree. But on the heating side with lower fan speed [lower than cooling speed] and less static pressure I can not see where this will cause any great harm. If the duct is sized correctly there will be enough margin of error.Very few jobs ever get "balanced" at the time of new construction any way. I should know, I am a service tech and get too see some of the worst work ever installed. Not to be disrespectful Don, just a realistic view.

don_9

Bill you are correct

> I really don't see how closing a supply in one or

> two rooms will reduce the return air supply. What

> goes out must come back. Choking a return would

> cause trouble, but stopping a few CFM from going

> out is not going to effect the return. If it

> doesn't leave the duct work it doesn't have to

> come back does it ?? I may be wrong .Dirty air

> filters will cause more harm. I have been in

> several dozens of homes where home owners do this

> all the time. [not saying it is right] If too

> many registers are closed it will cause heating

> and cooling problems ,I agree. But on the heating

> side with lower fan speed [lower than cooling

> speed] and less static pressure I can not see

> where this will cause any great harm. If the duct

> is sized correctly there will be enough margin of

> error.Very few jobs ever get "balanced" at the

> time of new construction any way. I should know,

> I am a service tech and get too see some of the

> worst work ever installed. Not to be

> disrespectful Don, just a realistic view.

don_9

Bill you are correct

I sometime forget we are living in the real world,and so many duct system as you say or the worst ever.I should never
had assume that we would not be talking about a duct system
that wsa totally seal,and properly balance.Oh well that being the case,close off as many has one see fit.and don't
worry about slowing down the fan speed,the higher static it
will bleed off in to the attic or crawl any way.If they never had it they are not going to miss it.Bill you are never disrespectful,and I thank you for your opinion.don

BillW@honeywell

Zoning

It is entirely posssible to zone a forced air system of any kind. First, the ductwork must be correctly sized to handle the load, sealed and otherwise properly designed. Except for huge custom homes, most can be split into 2 or 3 zones to minimize the cost and equipment needed. A zoning system consists of thermostats(sensors), an equipment interface module, a damper inteface module, and zone dampers. A static pressure regulating damper is required to vent excessive static pressure when only one small zone is calling for heat or cooling. This is an automatic device, ussually located in the basement or mechanical room. A special sensor protects the AC coil from freezeup in low demand conditions. Some equipment may have a variable speed fan that responds to loads, too. Acessories like remote telephone access and alarm capability are available. Zoning takes a pro to design and install. Do yourself a favor, and deal with a local hvac pro with zoning experience...click the "find a contractor" button above. You also can vist the www.honeywell.com/your home website and click on the "zoning" icon for more info.