Need advice. Two reputable dealers have conflicting advice.
The problem: 35 y/o ranch house with a 12x20 addition to the master bedroom for a long larger bedroom and bath. Currently has three registers,the two that go to the end of the bedroom and the bath are served by two insulated flex ducts that go through the unheated crawl space of the addition. The third duct remains in its original position. They tapped these flex ducts off the ducts that were at the outside wall prior to the addition. The ducts [about 23 ft long from the supply trunk] don't seem to have very forceful airflow and the addition portion of the room is never as cool or as warm as the rest of the house. The temp differential can be 4-6 degrees on really cold or warm days. The addition has three sides to the weather. I know most people are not fans of air boosters but I have been using a single small surface mount register booster that really changes the temperature of the addition potion of the master br up to that of the rest of the house.Only bad things are that it is noisy and the bathroom doesn't change its temp. Rest of house is very comfortable. Have a 400 sq ft north facing sun room that currently is served by a 21 yr old 80% 71k btu Carrier furnace and a 2 ton a/c unit. Has 3 large skylights and windows all around. Rest of house has a 119k btu 80% Carrier furnace and a 4 or 5 ton lennox a/c[label unreadable for size of unit]. The entire house is about 3000 square ft including the sun room.
One contractor says that he would leave the sun room on a separate furnace since it would give us the best control. Even though he sells ECW zoning he said we would be better of with increasing the supply to the addition in the master bedroom by running an additional 8" supply directly from the plenum giving us an additional register at he end of the bedroom and the end of the master bathroom. This would give a total of 5 registers [2 new 3 old and weak] for the 500 sq foot master. I thought this would work. He would use a 105k btu 90% rheem mod variable speed and a 3.5 ton 12 seer rheem for the main house and a 2 stage 50,000 btu 80% rheem and a 1.5 ton 12 seer rheem a/c for the sun room. He thinks the variable speed will solve 90% of the problem. He didn't do a manual J but the rheem mod will tend to compensate for that.
The other contractor who also seems to know what he is talking about thinks we should replace both furnaces and air conditioners with one a/c and furnace and zone [honeywell] the sun room 400 sq ft on one zone, the 500 sq foot master on one zone and the 2100 sq ft rest of the house on one zone. He is willing to do a manual J if he gets the job to finalize the size of the units. He initially proposes an american standard 90% 2 stage 112 btu variable speed and a 4 ton American std 12 seer a/c. He thinks that if we don't zone we will have the same problem when we are done since we have 3 sides to the weather and we will cool in the winter and heat in the summer faster than the rest of the house. Says that the zoning will solve our problem by allowing the furnace or air to turn on when the master needs it without waiting for the whole house to chnage temp. He will however run an new 8" supply from the plenum and run 3 registers off the new supply which will give us one additional register for a total of 4 registers [3 of the new 8" supply and one decent old register] in the master. Wants to use a bypass humidfier which will serve as a mini bypass damper. He seems very certain that this will work. I am concerned about trying to put 4 tons of cooling into the sun room or master bdrm. He says honeywell has a temp sensor in the plenum that will shut compressor or burners if certain temp are exceeded but the blower will run on to warm or cool the HX. Doesn't this sound like short cycling. Unless your zones have about the same load it would seem like this would always happen. Thinks we probably won't need a true bypass damper. Is it hard on the compressor or the gas valve and ignition to keep going on and off frequently. Can you get consistent temperatures with zoning as with a dedicated furnace. Unfortunately our basement has finished ceilings so access to the ducts is ltd.
They both sound reasonable and are the owners and have good brands with 10 yr parts and labor. We have no experience in zoning and it seems that people don't have as much experience with variable speed blowers and zoning. The one furnace system and zoning wll be significantly less expensive initially but seems more complex and trouble prone. The other choice is more expensive but I like the Rheem mod based on what I have read here. That will be an expensive mistake if we need to zone in the future if the second contractor is correct. The second contractor will do what first proposes but we will be responsible if it doest work. I apologize for the long question but this is a complicated expensive decision for someone who doesn't have the experience or knowledge. Any comments are appreciated.
first they should do manual j right off the bat so you know exactly what you need as far as size. not after the fact. zoneing works well in most cases and if done right.
i would recomend getting more info from both on just what they plane to do and how.
flex is very restrictive and can cause problems down the road. the bedroom area should have a main trunk line ran sized for the amount of cfms and then flex or pipe ran off of that. trunk duct is less restrictive and will deliver the correct amount of air flo.
next look into carrier infinity
look into lenox harmony damper control with a two speed condenser. this will ramp the blower up and down to match the cfms with the zones that are calling at the same time changes the compressor speed from high to low as needed
will also change a two speed furnace from hih to low when needed. the lenox is a true two speed compressor
if it is a 4ton unit high pseed is 4 ton low speed is a little over 2 ton. it only come with the new ozone safe refrigerant 410a and is i think 13 seer.
i am not to up on carrier but know they are good units also
both also give you cfm ramp capability with out a bypass
1.Manual J,S,and D ,if you want to get it right and save money.
2.Zoning if you want the best control of temperatures.
3.Carrier Infinity zoning for the best zoning available.IMHO
1 and 2 are facts,3 is close but still an opinion.
Thanks for your replies tinknocker and dash.
Does honeywell trol a temp have any ability to ramp up the cfm on the ECM motor for dehumidification or cooling? Honeywell is what one of systems that was quoted for me. Seems that it relies on a temp sensor in the plenum to prevent overheating or freezing when one zone is calling. I see that carrier infinity and lenox harmony give more sophisticated control but can you use those systems on other makers [trane,a/s or rheem] equipment? I would prefer to use the other makers because of better warranties and records for reliability.
I agree that a two stage compressor would be ideal for zoning but that is only available from what I have seen in the very end high seer equip. I won't get much payback here in the Chiacago area.
You want it to ramp down for dehumidification,and as far as I know Trol atemp,can't do it,you could add a dehum control separately the will do it
Infinity and Harmony will only work with the mfrs. equipment.
Warranties are available on any brand ,to match what ever warranty you see in another brand.Longer warranties doesn't mean the product is better,just the warranty.
Carrier Puron systems are very dependable as is the Infinity ,with or without zoning.
Zoning systems and design is a complex issue.In my own home,we installed Infinity ,to replace a Carrier Comfort Zone II,no other changes ,and our Kw consumtion has dropped 6 to 10% per month .The Infinity has control of the GE 2.5 ECM motor,and the motor is only found in Infinity,as far as I know.
[Edited by dash on 04-13-2005 at 10:01 AM]
Thanks much. What I meant about ramping up was that I thought the infinity and the lennox controls would start the ECM out at a lower cfm to dehumidify and later would ramp up to normal speed.
The dehumidifier control that you mentioned, who makes it and does it effect the ECM output? I need to be able to
ask my contractor if he can do it.
There are numerous brands,most variable speed fans have "dehum" terminals,the they can connect to the slow th ECM motor,when the the humidity is above the set point.
If they aren't familar with setting this up,they can get info. from their distributor or the mfg..
as much as i hate to say this after doing some research and checking with my carrier supplyier it would seem carrier infinity is a better product only because it has a much higher seer rating dam
if you plam to do zoning then i recomend useing what is designed for the equipment you are using and not aftermarket or add on controlers. you will find in the long run they dont work as well. also the warrenties are not the same as the manufactors warrenti
with harmony you can get up to 10 years parts and labor
not sure about carrier but i assume it is the same
honeywell and ecw add on i would think is 1 or maybe 2 years. this is a major undertaking and you are on the right track buy wanting it right. get some more prices from recomended contractors from manufacors. davelenox.com can give some names in your earea and carrier has some to
just so you know lenox harmony does not have humidity control as of yet. only damper control
Manual J should be used 'TO SIZE' the equipment FIRST.
It shouldn't be an afterthought.
I'd get more estimates if I were you.
I haven't dealt with Carrier's Infinity yet. (I feel left out.)
But I have fixed some trol-a-temp systems and have installed Carriers Comfort Zone I and II systems.
Not sure of all the Trol-a-temp line, but from what I've seen, its just full open / full closed to control a zone.
The ones I"ve seen use manual thermostats in each zone.
If a zone wants cool, it turns the unit on... opens the damper full open... then when the zone satisfies, it shuts the unit down.
Carrier's zone system modulates the airflow to each zone.
It adjusts the zone dampers sorta like a gas pedal.
It calculates and delivers air flow to each zone so that all zones are at the required temp when the unit shuts off.
It also uses Digital Stats. I like the backlit display at night myself... sorta like indiglo.
[Edited by wormy on 04-13-2005 at 08:03 PM]
Thanks to all for the information. I really find your information very helpful. I must say that I wish some of you had companies in the chicago suburbs. I have had 8 companies with decent ratings out over the last two years trying to find someone who does HVAC the way you guys recommend. Only one person did a manual J prior to submitting a bid. Unfortunately my neighbor had a bad experience with that company and strongly discouraged their use. The other two companies would do a Manual J only if they got the job. The most common thing was to look at the old equipment. Two companies said I would not need a modulating damper with zoning and a variable speed fan. In fact they said that I would not need a damper at all. Two companies gave their bids by phone with nothing in writing. One company came out and never submitted a bid. It is quite hard to evaluate the contractors when so many say different things than what I have read here.