Commercial radiant job, need design help for air change/ AC!

Kca_3

I have a great project that I'm "Design Build" for. I'm installing Radiant for approximately 8000sqft. 8 offices and a reception area.
The issue and challenge comes in when the requirements for air change & AC come in. The Radiant is broken down into 10 zones. The (3) roof tops the tinner is putting in will controll 3 or 4 of my zones. When a radiant zone is calling for a 68deg comfort level,lets say, and the roof top is blowing AC, what happens to the office that's asking for a 75deg comfort level. The heating system is fighting the AC. Right?
As well, the fresh air 400+-cfm needs to be heated. Coils?

How do I advise the tinner to zone the AC? How do we reheat the fresh air?

Radiant doesn't go into commercial like this and this may be the reason. We've put it in shops and wharehouses but offices?

Thanks for your help

:-) Ken

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Weezbo

the office building having any radiant cooling ?

theres a heck of a lot more to office buildings and various floor layouts and window types and arrangements and lighting and control stradgey that aguy needs to collect a bit more accurate information...consider room sensors that pull back to the boiler room...plastic bubble lock outs on t stats

Kca_3

Without getting to detailed


Lockouts on stats? You mean allow only one temp setting on the Radiant? I suppose that would help but it doesn't allow for individuality.

I'm stumped right now..

Reheat coils that come on and heat the AC if another zone is calling for AC?

:-) Ken

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Weezbo

take a look at rb's site. Healthy Heating .com

maybe theres a good idea or thwee *~/:) he's lots of info on intergration...

S Ebels

Anymore.......

After having done some and worked on others, we install these types of systems with a building management system, not regular t-stats. This allows you to get into a host of if/then scenarios. For instance, the heating and cooling system can now talk to each other and you can program it according to how you or the occupants want the system to act.

We are in the process of doing this in an office (14,000 sq ft) occupied by 60 women in the 40-60 year old range. (read between the lines on that) There are currently 7 zones of baseboard and 9 airhandlers with HW andAC coils in each. A total of 16 thermostats. One stat is calling for heat and the one 20 ft away is running the AC when its 5* outside. It's currently a disaster.

Get in touch with your local Honeywell rep and talk with them about a building managment system that you can integrate all the functions into one control point. They work well and you can set up the system so it can be monitored off site through Al Gore's own internet.

I'll give you a couple examples of what this type of system can do. For cooling during shoulder seasons and colder weather, we are installing motorized dampers connected to ducts terminating outside. Along with this there will be sensors on the H/W coil and supply plenum that will look at coil temp and leaving air temp. This provides lots of nice fresh air into the building as well as avoiding running the A/C condensers when it's below 50 with all the problems that happen with that. All of these actions can be predicated on what if scenarios that you program into the master computer.

On the H/W baseboard, the standard Z/V's are getting the axe in favor of modulating valves which will gradually open and close much like a TRV. We are also setting up the BB as stage one of the heating system before allowing the AHU's to come on. Options are practically unlimited.

For your app, I would think a two stage scenario would be a good thing. Use your floor as the base or first stage and cycle your AHU's to provide additional heating when/if needed. There's too much flywheel in a radiant slab to provide comfort during rapidly changing weather and/or loads.

Me_8

Fresh air

There are many ways to zone the rooftops if the airflow needs could be dealt with. It might even be possible to have as many zones as the radiant. Have you considered a hrv or air to air heat exchanger setup for the fresh air ? Just my opinion but in most cases the ventilation should be a seperate system especially with smaller buildings most people just drop a rooftop with an economizer and set the minimum position for enough fresh air that works with real big stuff but not smaller ones.

freon12

zoning

motorized dampers on supply and return duct,2stage heat cool tstats,400 cfm on 8000 sq isnt much with a fresh air recovery unit(renwair,aprilaire,etc),only issue would be cfm on roof tops,either have to go with discharge bypass or constant circulation and a return in main area.

jerry scharf_3

oops

double post

jerry scharf_3

I'm with Steve on this

Lose the tstats and move to a unified building management system that knows about both the heating and cooling. It should do your job in terms of having the A/C and haet work cooperatively.

As for zoning, I will make the leap that the zones you constructed are based on building layout, glass, etc. If not, go back and make it that way. If so, then it would be logical to zone the A/C in the same way. If you have three rooftop units and 10 zones, you decide which zone is easiest to duct to which unit, then you use motorized dampers to control the flow to each zone. The rooftop units should be variable air volume (VAV) so you can handle the changes in airflow from the dampers.

Not to be mean, but it sounds like you are in over your head a bit. Maybe time to call for design help.

I have never installed them, but it sure looks like the Caleffi iRadiant system could be a really nice small commercial building control system. You might want to check that out.

hope that helps,
jerry

Weezbo

some interesting reading...

Greening The Triple Botom Line....... with High Preforming Buildings Part ll...do a google search on the Greening The Triple Bottom Line...

Kca_3

I guess

The problem is that I don't supply the AC or RTU's. I'm just installing the Radiant. So.. the controls and AC / RTU have to fit into this budget that was pre existing.

Interesting though.. Thats the second time now in 2 days that I've heard of Caleffi manufacturer. The Owner asked of the zone valves and I was unaware of the brand. They make control systems too?

I'm in over my head because I'm attempting to make something work that may not. The 5lbs into a 3lbs bag ya know..


:-) Ken

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Weezbo

well, ... that being said you have a golden opportunity *~/:)

if the owners like the caleffi zone valves .....the controls,room sensors, lowloss headers,an the abilities of computer side goodies ...means you bust out the books real fast and read the pdfs on their site....then if you like controls man You Are In! zone the place like you Mean it!

Brent_2

tsat

Another contractor is going to have 3 RTU's so that means he will have 3 tstats. You should have 3 of your zones controlled by his heat/cool tstat. Your other 6 or 7 zones should have a heat only tstat.
The office should run constant fan in the winter (and summer) time and this will bring the in the minimal outside air. 400 cfm is next to nothing so I would not worry about that.
You could have a zone calling for heat while the AC is on if they set the cool setpt a little low or the heat a little high but don't get too worried about it. Are you going to turn the heating system off above 65° outside temp? If you do those concerns would be minimized.

brent

CDM2

Ventilation Air/ Zoning

What type of RTU's are being used here? A thought on ventilation- have they considered Demand Control Ventilation (DCV)? This control strategy will keep the RTU sizing down, with the use of space CO2 sensors, only the appropriate amount of ventilation air will be introduced when needed. As people load increases, CO2 levels increase, economizers open to reduce CO2 levels, then will go back to minimum position.

I agree with using a DDC zoning system to control all your RTU zones, and your radiant zones. Depending on control system selected, you can program virtually any type of input and outputs from your sensors. They won't care if they are controling forced air or hydronic. talk to your local commercial TM supplying the RTU's.

DM

joel_19

erv

commercial realestate is the biggest energy pig we have ERV should be law. why just pump in outside air? Imean think about it if we are going to do that why bother putting in insulation and good windows? Get an ERV and abetter controll system.

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Wayco Wayne

Here in the DC area

Most new office buildings have a warm up cycle in the morning, and then run A/C the rest of the day. Due to internal gains, heat is able to perpetuate itself once the temps are up to comfort levels. Ventilation is easy then. I don't see how a radiant floor would make much sense in a commercial office setting, where the temps are up and down and ventilation is required by code. CO2 sensors are the best way to go for ventilation, but check and make sure the local code inspectors allow them. I like the fresh air heat exchangers but boy are they pricey on a commercial level. WW

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Weezbo

re iteration...intergration *~/:) terse and propitious Dean

jerry scharf_3

Ken,

> The problem is that I don't supply the AC or

> RTU's. I'm just installing the Radiant. So..

> the controls and AC / RTU have to fit into this

> budget that was pre existing.

>

> Interesting

> though.. Thats the second time now in 2 days

> that I've heard of Caleffi manufacturer. The

> Owner asked of the zone valves and I was unaware

> of the brand. They make control systems too?

> I'm in over my head because I'm attempting to

> make something work that may not. The 5lbs into

> a 3lbs bag ya know..

>

> :-) Ken

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 341&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

jerry scharf_3

Ken,

First,

Good on you for trying to make something work when it's not clearly your job.

I would look around and put together a framework of something that would do the job well. Then I would write up a memo to the owner explaining the problem you forsee, and a possible solution for it. Explain that because it's dealing with the whole building as a system, you can't just go and do it. Since the owner has already shown some interest in this, he/she may really appreciate you looking out for his long term interest.

Either way, it's out of your scope and your control (sorry for the pun) so you have to get budget and cooperation "from above."

It may also be something that can be done in such a way that it doesn't have to be done to commission the system, but the systems are designed to allow this to be added without major rework.

Caleffi is an Italian brand of hydronic components. They have some really slick ideas.

Let me know how I can help. If you want to talk by phone, drop me an email.

jerry

Kca_3

I'd like to

talk to you about controls


E-mail me.. I would you but don't have it other than this medium

:-) Ken

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