now for something completely different, two stage cond. fan compatible w ICM325 head pres. control?

archibald tuttle

I'm just working out my staging control for a pair of Amana two stage ASXC160601 condensors. According to the nice theory of ops discussion in the installation manual ( https://www.theacoutlet.com/documents/Installation-Guide-Amana-ASX16.pdf ) page 18 these are not variable speed motors but utilize a solenoid to allow some hot gas bypass internal to the compressor thus reducing to 67% capacity (and these are similar to the GSX goodman units)

I'm assuming that the solid state control supplied on the unit just figures out what starting should look regardless of whether both stages are calling. I don't know if that means it starts with the gas bypass open in order to make for less starting load and then closes those gas ports if both stages are calling or if its designed to start at full load anyway.

And I'm assuming that is simply the Y1 is the first stage and Y2 the second and it figures it out on its own from there.. So I wasn't so worried about that aspect although i'm theorectially interested. I am more concerned about how to control the condensor fan for head pressure. I got a Goodman tech who told me the compressor was ECM unit afor staging and it started soft and ramped up which is decidedly not what the documentation says and similarly there are discussions of ECM variable condensor fans but this does not have one. I tried to point out the distinct two-stage rather than variable nature of this unit but was not making much progress so i gave up and i'm back to the wall.

With this two speed ball bearing fan motor i don't know if the onboard control is brainy enough to start it on high and drop back or . . .? And then I had already been planning to install an ICM325 head pressure control because i need a fairly consistent evaporating temp to avoid freezing the chiller. This is confounded by ambient as well as highly variable building load. Now moving to four stage from the previous two-stage setup might just soak this all up on its own and i should just stop worrying, but it seems like from the diagram you grab the capacitor side to regualte through the ICM325 so it would be unaffected by the fact that there are two separate power leads I would imagine tapping the coil at two different places. So I'm guessing the ICM would then vary speed in what would then become high and low 'ranges'. That would be theoretically ideal but i'm wondering if i'm tempting fate 'turning down' a fan that is already running at lesser speed or perhaps should set it a little more aggressively (e.g. choose a sleeve bearing setting which i think dos not allow as much turn down before simply turning off). Much has been made of how many people have had excellent experience with these ICM head pressure controls and condensor fan motors have not appeared to manifest shortened life. But has anyone installed an ICM325 on a two stage fan like this and if so recommended settings/experience?

thanks for taking in the latest version of War and Peace in the HVAC world.

brian

ratio

Disable the two speeds & just let the ICM control the fan speed. The ICM controller will slow the fan down to keep pressures up, regardless of why the pressure is down.

ChrisJ

I think I've already done this to my unit but don't have time to check model etc.

I think mine is an ASXC16036. 16 SEER 3 ton.

If it's the same I can explain how the PCB interacts etc. Goodman's support was useless and it was strange they had no idea how this worked and said it couldn't be done yet the board is clearly setup to do it


It came with a 2 speed fan motor controlled by 2 relays on the PCB and the wiring diagram is wrong.

One relay does on/off and the second relay switches between high and low. There's a quick disconnect near the relays to get power after the on/off relay but before the high low one.

I swapped the 2 speed motor out for a 70C ambient ball bearing motor but if you want to just leave the OEM motor wire in only the high speed. The low speed isn't needed.

This is only for the 16 SEER units. the ASX18 18 SEER have some kind of ECM motor, but I don't know the details on it other than I think it only does high and low as well.

ChrisJ

Here's the thread I had created when doing this.
You'll find a crude schematic I drew up showing the actual wiring of the fan.

https://forum.heatinghelp.com/discussion/162536/head-pressure-controller-2-speed-fan#latest

ChrisJ

@archibald tuttle What happened with this?

archibald tuttle

I'm going to start it next week so I'll let you know. Icm recommended just tee both stage 1 and 2 fan calls to the high speed winding and then let the control run off the condenser temp sensor regulating off high speed.