Low ambient disable for split system

ChrisJ

Sorry if this post is crude I'm on my phone. Does any thermostat support disabling the compressor below a set outdoor temp?

Ironman

Honeywell TH8300 series with an outdoor sensor.

njtommy

Vision pro 8k or higher will do it. Most heat pump t-stats that have out door air temp sensor capabilities will do it no problem. Getting ready for you heat pump?

ratio

Look for a stat labeled as "dual fuel", that should almost assure you a low ambient lockout.

Also, another vote for the Honeywell 8000 series, which can use a wireless or wired outdoor sensor. I'm a little leery of using wireless for that kind of control.

njtommy

For the new vision pro 8000 you can do it from what they call the cloud aka the Internet

ChrisJ

So wait,
My current 8000 series would do it if I connect an outdoor sensor?

It could be set for, say 55F and it would lock it out?

njtommy

Is your current 8000 t-stat heat pump compatible?

ChrisJ

njtommy said:

Is your current 8000 t-stat heat pump compatible?

Yes,
But it looks like I need a TH8320/TH8321 for the lockout option but even then, it only allows up to 40F. I'd want 50-55F.

JUGHNE

Are you getting a heat pump or simple AC. The above references are, I believe, to lock out a heat pump for maybe a dual fuel set up.

My guess it that you want a LACO for your AC to keep it from running when below 55. I have seen simple close on rise button t-stats inside a Carrier unit.....maybe 55-60 degree to close.

ChrisJ

JUGHNE said:

Are you getting a heat pump or simple AC. The above references are, I believe, to lock out a heat pump for maybe a dual fuel set up.

My guess it that you want a LACO for your AC to keep it from running when below 55. I have seen simple close on rise button t-stats inside a Carrier unit.....maybe 55-60 degree to close.

Yes, just as a safety device for cool only.
Do you have a link for what you're using? My dad also wants such a thing on his system.

Harvey Ramer

Install a Nema 3-r mechanical thermostat in the outdoor unit that breaks the wire to the y terminal.

njtommy

You could probably do it with a $20 Klixson if you can track down the right part number.

ChrisJ

This may come across as silly but, why don't the outdoor units come with such protection?

Wouldn't it help on warranty repairs?

JUGHNE

The one I saw was in a 5 ton unit at a church that I service.
It is a simple button hanging on control wires connected with 1/4" push on terms.
Some Carrier/Bryant tech here may know a part number.
It was NEMA 1 device sheltered from the rain.

It is one of those 5 dollar items that you can buy for maybe 20 bucks.

ratio

http://www.icmcontrols.com/Twowire-temporary-dryoutconstruction-thermostat-55F-Cool-Can-also-be-used-as-a-low-ambient-cutoff-switch-for-condensor-fan-motors-Prodview.html

njtommy

Good find @ratio

ChrisJ

Awesome!

http://www.supplyhouse.com/ICM-Controls-SC055-SC055-Dryout-Thermostat-Low-Ambient-Cutoff-Switch-55-F?gclid=CJmd18uwkc8CFU5bhgodixoLuQ


Thanks @ratio

JUGHNE

That is similar to what I saw.

Did you notice the ICM site specs 55 degrees +/- 9*
Supply house site specs +/- 5*

These could save many compressors where many hands are on the T-stat. (Public places....churches etc.)
It is one thing the layman public person can not over ride

ChrisJ

JUGHNE said:

That is similar to what I saw.

Did you notice the ICM site specs 55 degrees +/- 9*
Supply house site specs +/- 5*

These could save many compressors where many hands are on the T-stat. (Public places....churches etc.)
It is one thing the layman public person can not over ride

That's why I want one.
Even with only my hands on the thermostat, accident's happen and with something so easy and cheap to protect it I don't see how you couldn't.

I really don't understand why manufacturers aren't including these in the product.

The downside is the airhandler will still run and the indoor thermostat won't say anything. I guess, unless you looped the indoor t-stat run outside to the sensor somewhere. That would take both the air handler \ furnace and the condensing unit out.

JUGHNE

2 Amps max.

Fan only running will tell you someone is playing with T-stat.
The placebo effect of fan running will "cool" some people off.
That is why Placebo T-stats are popular.

ChrisJ

JUGHNE said:

2 Amps max.

Fan only running will tell you someone is playing with T-stat.
The placebo effect of fan running will "cool" some people off.
That is why Placebo T-stats are popular.

I certainly hope that contactor doesn't exceed 2 amps. If it does I really oversized the system.

ChrisJ

Looks like a delay is recommended when using the ICM SC055 for this as well. Going to order both a 5 minute delay and 55° thermostat.

Here's the delay.

http://www.supplyhouse.com/ICM-Controls-ICM201F-ICM201F-Delay-on-Break-Timer-6-Wire-Leads-5-Minute-Delay

And the thermostat
http://www.supplyhouse.com/ICM-Controls-SC055-SC055-Dryout-Thermostat-Low-Ambient-Cutoff-Switch-55-F?gclid=CJmd18uwkc8CFU5bhgodixoLuQ


Seems like extremely cheap insurance to me.

SWEI

JUGHNE said:

Did you notice the ICM site specs 55 degrees +/- 9*
Supply house site specs +/- 5*

Fahrenheit versus Celsius?

ChrisJ

SWEI said:

JUGHNE said:

Did you notice the ICM site specs 55 degrees +/- 9*
Supply house site specs +/- 5*

Fahrenheit versus Celsius?

I don't know, I'd assume a typo.
I just emailed ICM for clarification as my dad isn't liking the +9 possibility. He's been known to fire the system up when it's in the low 60s and humid out.

SWEI

I'm somewhat unclear whether it represents setpoint tolerance or deadband.

JUGHNE

Both sites said F* I believe.

Many control transformers have a 3 amp fuse in the 24 VAC secondary.......only open with a problem in system. The 2 amp for the contactor should be good.

Most T-stats have a programmable time delay (up to 5 minutes) for compressor, the "cool" flashes while you wait. That has been enough usually.

For cooling below 65 or so ambient, many use the ICM head pressure control for the AC. It varies the cond fan motor speed based on the liquid temp in the unit.

ratio

If there anything fancy (zoning, etc.) going on, or I think there's any chance it'll need to operate when it's cool out, she gets low ambient kit. Head pressure, cch, freezestat, the works.

ChrisJ

ratio said:

If there anything fancy (zoning, etc.) going on, or I think there's any chance it'll need to operate when it's cool out, she gets low ambient kit. Head pressure, cch, freezestat, the works.

I was looking into this for my setup, but Trane / AS claim it's safe down to 55F stock, and down to something like 40F with defrost control, but I could never find out what "defrost control" is or if the TAM7 airhandler comes with it. It's certainly not listed as an accessory.

Is a low ambient kit still beneficial to these units at cooler temps and can the ICM control vary a single speed fan motor? I thought most setups simply cycled the condenser fan on head pressure?


With a low ambient setup I wouldn't be concerned about low temp protection, the unit would be fine at 40-50F should it end up on some how.

ratio

There're pressure switches that will cycle the fan on & off, & a number of devices to vary the speed of the condenser fan. I've used these with good success. ICM also offers a selection. In fact, I almost bought one this morning for a unit that I'm expecting to kit up for a long dehumidification season. Then there's the Big Boy stuff, flooded condensers, head pressure control valves, accumulators, receivers, all sorts of neat stuff, but not perhaps cost effective for residential work.

And I still haven't looked up those manuals yet, but I will.

ChrisJ

ratio said:

There're pressure switches that will cycle the fan on & off, & a number of devices to vary the speed of the condenser fan. I've used these with good success. ICM also offers a selection. In fact, I almost bought one this morning for a unit that I'm expecting to kit up for a long dehumidification season. Then there's the Big Boy stuff, flooded condensers, head pressure control valves, accumulators, receivers, all sorts of neat stuff, but not perhaps cost effective for residential work.

And I still haven't looked up those manuals yet, but I will.

Do you typically do a crank case heater with one of these controls or no?

It looks like all you do is strap a sensor onto the condenser, wire the badboy in and tweak two settings on the ICM controller and you're up and running when it's chilly out.

ratio

You should. If it's going to operate in cold weather, then for sure, but if you think you're just going to go a little further into the swing season then I might not.

JUGHNE

I have seen/installed the ICM variable speed controller on AC units for commercial kitchens, flower shop with reach in self contained compressor which overheated the building on cooler days, and movie theater which requires cooling dependent upon occupancy count.
You probably don't need it if you don't run AC below 55* amb. IMO.