Help--New Lenno System + Arzel Zoning Problems

[jramunni]

Originally posted by machese
My contractor hasn't contacted me today. Can you please be a little more specific on how Arzel handles what you mentioned; i.e., preventing one zone alone from calling the second stage and how to prevent the bypass damper from causing short cycling. Is this done with jumpers on the panel???

thanks!

LJM

We refer to this technique as "CrissCross" wiring.
We send the 2nd stage thermostat signal(Y2)from one zone to the 2nd stg input terminal (Y2)of another zone. This prevents high stage operation until both zones are calling. If two stage thermostats are not being used then jumpers can be wired between zones to initiate high stage when two zones call symotaniously. Y1 from zone-2 to Y2 of zone-1 or any combination that makes sense. Typically I like to group zones by size (two smaller zones) or by load (two 2nd fl zones).
The bypass damper must be adjusted to only the minimum bypass cfm required to eliminate noisy air delivery. Once you have the staging crisscrossed there is a good chance you will not require bypassing. Be sure the bypass is adjusted for maximum air delivery to the small zone.

jr

[jramunni]

Originally posted by crt
I am not sure that the Arzel System controller can cycle first and second stage compressor operation or gas valve operation with the discharge air sensor. It sounds to me that the compressor is coming on in high speed and needs to be low speed. The bypass damper should be before any supply pipes on the system discharge and connect to the return as close as possible to the unit and before any return grille connections. It sounds like it is correct. The system certainly should not be cycling as fast as you are claiming which is why I believe the staging is not happening. If the bypass is their Arzel's "Modulating Bypass" I think you are asking for trouble. Any bypass that modulates is to slow for a variable speed motor. I truly think you have an inexperienced dealer working on something he does not totally understand.

****The Airboss panel can cycle the 2nd stge output based on LAT (Leaving Air Temp). It can initiate 2nd stg operation but will cycle it on and off once engaged. The 2nd stg trip is 5deg from 1st stg LAT setpoint.

******(The Bypass should not(when possible)be connected to the return close to the equipment. A bypass should connect to the return as far as possible from the equipment but before any reductions in RA duct size.) If properly sized and adjusted this becomes less critical.******

*****The Arzel Modulating bypass was developed specificaly for variable speed blowers and works extremely well in maintaining a very steady rpm at elevated statics. Being that the Modupass can open the bypass damper as quick as or quicker than the zone dampers can close, the change in blower cfm is virtualy constant.

jr

[Edited by jramunni on 08-08-2005 at 03:54 PM]

[machese]

Hi All--

for anybody following this thread, I want to provide an update.

first of all--thanks Joe R. from arzel for your advice and for working directly with the HVAC tech on this.

The situation here is better (although it is only 80 degrees out, so I am not yet taking victory laps). here is what was done:

1) The Lennox furnace wasn't configured properly for 2-stage operation. A jumper needed to be cut--the original installers missed this.

2) The arzel panel wasn't properly configured for working with 2-stage stats. There is a switch that controls this on the board that needed to be set.

3) The temperature probe that connects to the arzel panel (to prevent LAT problems) was located too close to the cooling coil (right on top of it), so it was tripping the arzel board and contributing to the short cycling problem.

4) Based on Joe's recommendations, the tech "cross-wired" the panel so that stage two will never be called when only the two smaller zones (the upstairs zones) call for it. this helps the high velocity problem at the registers, since stage two will never run exclusivly upstairs.

5) for testing, I manually shut the bypass damper on the system with a piece of wire on the arm (not sure if I need the bypass damper anymore, and keeping it off simplifies debugging). if air pressure is too excessive still at the registers, I will reactivate & adjust it.

6) one of the arzel dampers installed by the HVAC company was the wrong size, which caused it to become stuck in a closed position. new one ordered.

7) circuit breaker too small for the 5 ton unit, caused the condenser's breaker to trip. this will be fixed.

8) additional sealant will be put on the furnace "joints" to decrease the air obviously leaking from the system.

Doing these things seems to have improved the situation...

Morals of the story--

1) the best thing, as a homeowner, is to get sufficiently educated in the technology. today, if I didn't ask the right questions and test each change, I am convinced that the tech wouldn't have made all the changes above--and he was a very bright tech. as a homeowner, you get to observe the system very closely and your inputs should be closely considered.

2) make sure that all parties are talking with each other!!!

3) don't be afraid to ask questions and watch the work that is going on--not to hover over anybody's shoulders (nobody likes that), but at least to understand the work and get status updates.

Again--thanks all for helping me get educated on this!!! Your consideration and quality of answers is very impressive!

LJM

[geno54]

The age of easy in and out is going by the wayside. The efficiencies are ever increasing and the complexities are too. Variable speed multi stage furnaces or air handlers hooked up to two speed CU's with multi speed condr fans. Then comes zoneing systems to tie into all of this. ( I forsee variable speed everything in the future)

Each one of us has to read not only the install manuals but the service manuals too (if available ) to fully understand all the dipswitch settings, jumpers and jumper cut combinations that are possible. It takes a few installations to get this down pat.

Correct me if I am wrong , but here is the scenario.

The salesman sold the job with great inspiration
The installers put it in with little clue as to what this new contraption is. The service tech comes along and has to figure out what the heck everyone did. This is called the learning curve of high efficiency installations.

[alinnova]

Originally posted by geno54
Correct me if I am wrong , but here is the scenario.

The salesman sold the job with great inspiration
The installers put it in with little clue as to what this new contraption is. The service tech comes along and has to figure out what the heck everyone did. This is called the learning curve of high efficiency installations.

I'm a homeowner, non-pro. That is part of it. But where's the boss in this picture? He lets the installers go out of the shop without the training and without the specific instructions on how this complex job is different from the simple ones that the installers usually do fine by rote.

On my new system two years ago, the contractor/owner did the Manual J on my house and planned the job. In his regular morning meeting with his crews, he handed over the installation manual for the Trane XV80 furnace and highlighted in yellow all the settings that he wanted to match the optional humidistat, the two stage XL19i condensing unit, and the two stage thermostat. The installer paid attention to the details. He knew the Trane two stage thermostat (Honeywell really) inside out. But for the Aprilaire humidifier, he mis-wired, and a service guy had to fix it. In the meantime, the owner learned something about the Aprilaire 700 after I talked with him.

By the way, those highlighted instructions in the furnace manual are the same ones that I've seen repeated here in HVAC-Talk several times.
Al

[machese]

that is the situation exactly. the salesman was quite good--ex lucent engineer, second career. did the manual J, etc. The installers were OK when it came to running thermostat wire and putting the gearin place, but had no understanding of vs equipment (e.g., they grabbed single stat stats rather than dual stage and tried to convince me that dual stage stats weren't necessary--strike one). the first service tech they sent out (on a saturday) had zero experience, it seemed, with the equipement. so I called the general manager, and finally they sent over a good tech--but even this tech needed to be walked through the steps from arzel. so, it is complicate stuff, and you can only hope that the experiences learned are promulgated throughout the firm.

all through this, my fiancee maintained that "maybe the system is supposed to work this way." sadly, there may be lots of customers who feel that the HVAC companies know best, and settle for less than optimal systems.

I am still concerned that my condenser / coil are oversized (5 tons), but we will see on a warmer day...

LJM