Zoning Rheem Classic 90 plus modulating gas furnance

John Mills_5

Zonex, aka California Economizer, has the Digitrac 4+2 board times up to high after so many minutes. But they will throttle the furnace back to 1st stage if they detect the supply air getting too warm. Most panels shut the furnace down altogether causing a lot of inefficient cycles. This panel will let the thing run constantly on low if that's all that is needed. Most common is on/off on/off under light load. We have this panel in our office. Since my room is in the warehouse, it needs heat much of the winter while the 2 bigger zones don't. The 2 stage furnace runs on low steadily if just my zone is calling.

The Honeywell TZ4 is a nice panel. Can be wired with % of zones calling so only would fire high if both zones are asking for heat at the same time.

With a 2 stage stat or zone panel, first stage is a very low 40%. If 2nd stage calls, the furnace ramps up to 65% for 5 minutes then 100%. If 2nd stage drops out, it goes back to 40% fire.

jjkt

Zoning Rheem Classic 90 plus modulating gas furnance

Building a large house that will consist of radiant heat in the basement/garage, and forced air heat on the first and second floor levels. The heating subcontractor has given 2 options for furnaces --either the Rheem Classic 90 Plus Modulating or the Trane XV90 variable speed. There will be a furnace for each floor level, and it is being designed for 2 zones on each floor. The literature for the Rheem Classic 90 Plus Modulating furnance indicates that Rheem does not provide or support zoning with the modulating furnance. The heating subcontractor indicated that if he uses the Rheem furnances, he would not use modulating thermostats, but two stage thermostats instead due to the zoning. This seems to me that it defeats the purpose of using the modulating furnance. Just wondered if anyone has used the Rheem Classic 90 Plus Modulating furnance in a zoned situation or felt that the Trane XV90 variable speed would be a better way to go.Thanks

John Mills_5

Zoning the mod

If you don't want to use the modulating capability, then it is simple. Without the special Mod stat, the board functions as a 3 stage furnace. Get a GOOD zone panel that knows what to do with a multi stage furnace (most don't) and wire it using W1 and W2 just as you would the Trane. Instead of Trane's 60% and 100% firing, the Mod will give you 40%, 65% and 100%. Great furnace, more reliable than the XV90 in our experience.

jjkt

Any recommendations on a "Good" zone panel?I believe the subcontractor was considering using either the Aprilaire or a Honeywell system.
Thanks

Jeff Lawrence_24

I like

Honeywell.

Good sales team, excellent support if you need it. IMHO, their boards are a lot better than the other companies stuff.

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D lux_2

I think

the main consern with zoning is the blower with icm motor it will deliver the set air cfm weather the dampers are open or closed . so much for saveing $ on power for that blower . I have ck. amp draw on 2.5 ton air setting at .8 amp not too bad.Might want to call rheem but I dont think zoning is a good thing

S Ebels

Thinking outside your contractors box here

If you have a radiant floor in the basement, and therefore require a hydronic heat source, why not use a boiler and hydronic airhandlers instead of the furnaces. There are some really nice variable speed AHU's out on the market that would provide you with good comfort and A/C capacity also. Why maintain what sounds like 3 burners when you can do it with one and have DHW from it besides?

Many of these AHU's are designed to work with <160* water temp and would allow you to use a condensing and modulating boiler for maximum efficiency. This would eliminate the problem with your zoning issues to a great extent also. If your contractor is unfamiliar with this type of setup, send him here. If he says it won't work or it's "no good", find another contractor that knows about this type of system because if he did know he'd probably do this instead of the proposed setup.

Of course this is just my humble opinion and I haven't laid eyes on your particular job. Suffice to say we have done this many times and it offers a lot more flexibilty than a furnace setup. Many contractors, especially furnace/tin-knocker types, have no experience or knowledge of a hydro-air system and don't suggest it for those reasons.

BTW: please tell me none of the mechanical equipment is going in the attic!!??

jjkt

Thinking outside your contractors box here

I'm not familiar with the hydronic air handlers and not sure if the heating sub contractor is either. Can you provide any literature/web site for these type of systems? One of the forced air furnances was to be located in an insulated room in the attic area.

harvey

rheem

I agree with Mr. Mills about the Rheem Mod. furnace. We like the Aprilaire zone system but have not used the ca. Econo system. Mr. Ebels also has a good idea that we have also used. We sizr hot water coils for 140*

D lux_2

talked to rheem service guy at supply house

thought was not to zone , use sencer in all the rooms and use mod t stat . if you zone it will mess with heat rise and blower supply .

hr

On the plus side of having furnaces

is the redundancy. With air handlers if the boiler goes down you lose all heat and DHW. I like having an ace in the hole

I'd bet high efficiency modulating furnaces would be as efficient, or more so than an air handler and boiler package. You always lose some efficiency with energy exchange. Burner to hot air would be more efficient than burner to hot water than hot water to hot air. Not only the actual heat exchange but the cost of running a circ and related pressure drop and insulation of the piping to and from. Small wet rotor circs only run about 25-30% electrically efficient.

I work along side of an HVAC contractor that installs all top line Carrier furnaces with zoning. I must say this dyed in wool wethead sees some pretty good performance and comfort from a properly designed and installed system like that

Although hydro air does away with additional gas lines and flue piping to all the furnace locations. Pros and cons both ways.

hot rod

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Empire_2

Just a thought

There are alot of different zonning systems out there. I like the April Aire, Calif. Econo, and the Arzel system. Arzel uses numatic to control damper position and the lines are color coded and so easy to run. The price is nice to. Check out the web sight (www.arzelzoning.com)Most control panels come with a LAT on the board instead of seperate ordering.