A/C question for the pro's on here...

[scurvy]

Originally Posted By: XS650
AKA: If more is better, then too much is just right.
Too much is always better than not enough.

In this specific case if a 1.5 ton unit isn't able to keep the house cool, a 2 ton or even 2.5 ton unit should be installed... which sounds like exactly what happened. This 'oversized is bad' idea is silly unless the compressor is GROSSLY oversized for the system.

Originally Posted By: StevieC
House dropped from 80C to 72c (where they had it) in about an hour.

Wow, they like it hot! Thought you'd have to run the heat full blast to get a house up to 80C!

ITYM °F

 

[StevieC]

We do have summer in Canada.

It was 80C without the air on...

 

[Gary Allan]

The last rhetoric I heard on the topic was that you size a system to run at a max 75% duty cycle for the peak demand based on the climate history.

Too big, as Bill stated, runs too short a cycle and shoots way past the setpoint temp.

This isn't necessarily a bad thing if one wanted a temp level without dehumidifying the environment. Something like a commercial aquarium live storage area would be one such situation where you don't want maximum drying of the air as your principle comfort producing attribute.

 

[SteveSRT8]

A modern thermostat is easily adjusted to compensate for an oversized system. Some of the fancy electronic ones have a multitude of settings to allow complete customization of the cooling curve.

And many systems have variable displacement/speed compressors and air handlers which will dial the cooling down to a very low amount as the setpoint is approached.

This can mitigate the 'oversized' problem.

 

[StevieC]

He has a Carrier Weather Maker furnace that can vary the fan speed settings and the compressor we noticed is a 2 stage and will spin the evaporator fan outside at 2 different speeds depending on the load of cooling. It starts out slow and then speeds up if needed.

Neat setup.

It uses their Puron 410A as operates a 70% higher pressure. It has warnings on the side of it and a sticker the service man placed on the side of the furnace letting other service tech's know not to put any other gas in it and that it's a higher pressure system than normal. It also says it has POE oil in the compressor and to only use POE if recharging.

They also put the filter dryer inside the house (Emerson brand) on the return line and it has 2 quick disconnects so it can be changed out without draining the system of refrigerant.

The service tech told them to change the dryer every 3 years to keep the system running in tip-top condition and the new dryer units come charged with positive pressure R410A Puron and when you screw it into the quick connects on the line it will puncture the seal and thus not letting any air into the system while changing the filter.

I was impressed by this and told Adam and his parents to change the filter yearly instead of every 3 years because it was so easy and only $50 from Carrier.

Steve

 

[javacontour]

Originally Posted By: StevieC
We do have summer in Canada.

It was 80C without the air on...


Yeah, but 80C

That's what folks are on you about. I didn't think humans could survive very long at 80C

 

[StevieC]

DUH!

I see the error now... 80F...

 

[javacontour]

In case you are wondering, I don't think we'd live too long at 80 Kelvin either.

 

[440Magnum]

Originally Posted By: StevieC
Originally Posted By: 440Magnum

I assume you checked out the start cap and potential relay (if present) and tried a hard-start kit if it didn't already have the above?


Yes we checked these... No good. Then the thermal overload kicks in and cuts the power and then it tries again with no go.

They said the compressor was noisy for the last couple of weeks leading up to this but thought it was just because it was hot outside. Amazing how the truth comes out after you find the problem.

No kidding! But in this case with a hermetically sealed compressor there was nothing to be done once the noise started anyway. I asked about the start cap because a compressor that would otherwise have decades left in it can be toasted that way. Even worse, they sometimes fail because the thermal protector itself burns out kicking in and out all the time, with nothing physically wrong with the motor or compressor.

Have you seen that Australian guy's youtube vids of cutting open hermetic compressors and looking at failure modes. Very cool- especially the pair of twin Bristols where one of them grenaded the bottom end, and the other ran for months (years?) longer until the motor windings could't take it anymore. Lemme see... here we go:

http://www.youtube.com/watch?v=hW4gsH3dOK0

 

[XS650]

Originally Posted By: 440Magnum


Have you seen that Australian guy's youtube vids of cutting open hermetic compressors and looking at failure modes. Very cool- especially the pair of twin Bristols where one of them grenaded the bottom end, and the other ran for months (years?) longer until the motor windings could't take it anymore. Lemme see... here we go:

http://www.youtube.com/watch?v=hW4gsH3dOK0



Great video

 

[StevieC]

Thanks for the video...

 

[ItsuMitsubishi]

Hey Stevie are you a refrigeration tech perchance?

 

[ItsuMitsubishi]

Originally Posted By: 440Magnum

Have you seen that Australian guy's youtube vids of cutting open hermetic compressors and looking at failure modes. Very cool- especially the pair of twin Bristols where one of them grenaded the bottom end, and the other ran for months (years?) longer until the motor windings could't take it anymore. Lemme see... here we go:

http://www.youtube.com/watch?v=hW4gsH3dOK0





Ah yeah, that's the guy that tried to make an air compressor out of an old AC compressor. Turns out it couldnt start up again with pressure on the high side (just like the refrigeration system it came from)

 

[StevieC]

Originally Posted By: ItsuMitsubishi
Hey Stevie are you a refrigeration tech perchance?
No sir...

 

[ItsuMitsubishi]

Originally Posted By: StevieC
Originally Posted By: ItsuMitsubishi
Hey Stevie are you a refrigeration tech perchance?
No sir...


Haha, alright. I thought I read you say somewhere "I'm just gonna head on up there with some R410a" or something. 'I just keep a tank handy, you never know when you'll need some' , combined with spending a lot of time on the road for business, just thought I'd ask

 

[StevieC]

Oh that is because my dad has his A/C license from mechanic days and can purchase the gas so that is how I can get my hands on it.

 

[lewdwig]

Originally Posted By: StevieC
When I buy a house for Adam & I, I told him I didn't care if I spent $10K but I was going to put in the biggest/best A/C & furnace I could find because it will last longer and use less energy


Check out possibly installing a geothermal system...I don't think it would be too cold in SW Ontario. I'm on the east side of Lake Michigan (ten miles east of the lake) and I've had mine for 14 years next month. In that time I had to have a loop circulation pump replaced and the high refrigerant pressure switch replaced. It has saved me money, but I don't have natural gas where I'm at.