ComfortBridge and Variable speed Heat Pump AVZC20

[wiznillyp]

Hello all, long time lurker, new member. I previously worked on the commercial side designing controllers for a large HVAC company for about a decade.

Equipment:

• Amana AVC20 Variable Speed Heat Pump
• Goodman GMVC96 - Two stage heat, variable speed fan furnace
• Honeywell HZ432 Zone controller with 4 zones
• 15-20x Honeywell dampers
• 3x Honeywell TH8320 wireless Redlink t-stats
• 1x Honeywell TH8321 hardwired stat
• Misc Redlink comm gear.

Setup:

• All of the stats connect to the zone controller and only and single of each W (heating), Y (cooling), and G (fan) signals are sent to the furnace.
• The furnace is connected to the heat pump via a 2-wire (ComfortNET, it seems) interface.
• In heating mode, the furnace is configured to ramp up slowly to 100% (over 60 min) before eventually kicking on the gas stage(s) (60 additional min). This is done via ComfortBridge, if I am not mistaken.

I bought a variable speed unit because I want a constant temperature and humidity in my home. I expect the system to run at a constant operating point throughout the day as/when needed.
Instead, when there is a heat/cool call in any of the zones, the system ramps from a starting point and shuts off immediately when the calls are removed. It has never remained on when a call is removed, it cycles like 40 times a day. Aside from the ramping during prolonged calls, it behaves like a single stage unit.
As expected, the behavior is the same whether one or all four zones are calling.

Unfortunately, my contractor does not understand the system.

Questions:
1. How should this system behave with ComfortBridge? Should it integrate the calls over time and pick a percentage to run full time? Is there a way to get my desired operation with ComfortBridge /this system.
2. The zone controller has three W (heat) outputs and two Y (cool) outputs and the furnace has two Y and two W inputs. Would connecting two of these help with the modulation of the unit? For example, if the furnace sees one call for cool it will start at 30%, but if it sees two, it will start at 60% or whatever?
3. What is the best setup I can have with this hardware? Is there a piece to upgrade that will improve this?

[beenthere]

With no call for cooling or heating from any thermostat, it will shut off.

Comfortbridge/Comfortnet won't do anything special, since your controlling the units with a 24 volt legacy zone panel.

What size/BTU is the furnace and A/C?

Are either of the units over sized for the home?

What size are the zones, even with a modulating system, its possible to have zones too small.

What CPH are the thermostats set to?

AFAIK. It only drops to about 60% of high capacity. So if your zones are smaller than 60% of high capacity, you won't have long run times, when only one zone is calling.

[wiznillyp]

Thanks for your reply!

The furnace is 60k BTU and the AC is 3T.

3T is the suggested size for my home from the contractor, but this unit has an enabled boost mode of another 5% (I believe) capacity.

The zones are roughly equal in size. Two of the zones cover bedrooms with stats in them that may have a closed door.

Assuming CPH is "calls-per-hour", at the time of writing the original post it was 5! Based on some research I did since writing the OP, I have lowered that number to 1.

When you say it only drops to 60% of high capacity, do you mean what ComfortBridge commands in capacity? If so, I think that is incorrect as I have seen it commanding 25% this morning through the CoolCloud app.

[beenthere]

The inverter will run at 25%, but true capacity will be higher. Has to do with the coils being sized for 3 tons. So your still gonna be 30 plus % of high capacity.

I may be off on how low at 60%, but I was going by what was in a manual for them by BTU.

CPH is cycles per hour. The time from on, to off, and back on again is 1 cycle. But setting it to 1 should help a lot.

How large are the bedrooms in each bedroom zone.

[wiznillyp]

Thanks a lot for your reply.

The inverter will run at 25%, but true capacity will be higher. Has to do with the coils being sized for 3 tons. So your still gonna be 30 plus % of high capacity.

I may be off on how low at 60%, but I was going by what was in a manual for them by BTU.

Ok, I see what you mean by true capacity. There is non-linear (or at least offset) behavior due to the size of the coil.

CPH is cycles per hour. The time from on, to off, and back on again is 1 cycle. But setting it to 1 should help a lot.

I changed these values in the stats. So I believe that is what you meant.

How large are the bedrooms in each bedroom zone.

One of the zones contains 3 adjacent bedrooms at maybe 150-200 sq ft per room. The human occupied one has the stat in it, door is closed at night only.
Another zone contains about 800 sq ft with the 500 sq ft master bedroom containing a stat. This door is normally opened at night.

[beenthere]

Those zone sizes sound okay.

If the CPH being set to 1 doesn't help. Then without using a communicating zoning system that controls capacity, it won't get any better.

[Bazooka Joe]

“Unfortunately, my contractor does not understand the system.”

Did he at least set up your system correctly, the indoor coil comes with a Flowrater piston ( if he installed a AHRI matched system ) as it show on that site the Contractor needs to remove the piston and install the OEM TXV, which is mounted external to the coil, and can be easily seen.

[wiznillyp]

Did he at least set up your system correctly, the indoor coil comes with a Flowrater piston ( if he installed a AHRI matched system ) as it show on that site the Contractor needs to remove the piston and install the OEM TXV, which is mounted external to the coil, and can be easily seen.

There is an external Danfoss TXV mounted where the non-insulated refrigerant line enters the unit, this sounds different than what you are saying.

Most of what you are saying is foreign to me. I will ask them. Honestly, I think at this point, I am going to get a third party contractor involved (probably on from this site) to audit the system and get back to me.

[Bazooka Joe]

There is an external Danfoss TXV mounted where the non-insulated refrigerant line enters the unit, this sounds different than what you are saying.

Most of what you are saying is foreign to me. I will ask them. Honestly, I think at this point, I am going to get a third party contractor involved (probably on from this site) to audit the system and get back to me.

That sounds correct, a TXV metering device external of the coil box.