YORK TRIATHLON NATURAL GAS ENGINE DRIVEN CONDENSING UNIT

[jnsrose]

Man it has been a least 20 years ago. Just reading this thread brought back a lot of memories. Did bring it up at a York training class once and the guy basically told me that they were an experiment that failed. Basic problem was, like I said above, you have to be able to diagnose engine problems before you can service the unit. I did forget to mention above that in addition to the natural gas line, the heat piping you also had refrigerant piping plus electrical. That's a lot to have to run to a condenser.

[54regcab]

Electrical should have been able to work on a standard 120V line, dedicated circuit of course. Gas line could be a PITA depending on location. We have the gas meter, power meter, and breaker box all within 5' of the condenser, others not so lucky.

Becoming a small engine repairman in addition to HVAC is where the problem lies. However, NG powered small engines have become more reliable with the advances in electronic controls. They are common in backup generators and don't give much trouble. If somebody tries to do another one, it would be smart for them to market to the commercial side. Something the size of a car engine could be used to run the chiller.

[syndicated]

The service life on CNG powered engines is much longer than gas powered engines due to the fuel being pure. I've pulled apart car engines that ran on LPG and CNG, after 200,000km they still look new internally.
To further that lifespan, running at one fixed speed with the proper oil and maintenance one could expect it to be the longest lasting part of the system.

[54regcab]

I dunno about running fixed speed, I would think variable speed would increase overall efficiency instead of cycling on/off.

[syndicated]

I dunno about running fixed speed, I would think variable speed would increase overall efficiency instead of cycling on/off.

Agreed, but therein lies the fundamental difference between internal combustion engines and electric motors. Gas engines need to operate at a minimum rpm to make any useful power, and must fire in fast enough intervals so it doesn't shake itself to pieces think of a lawn mower about to stall.
To get a variable pumping capacity wouldn't an unloader to the job easier?

[mark beiser]

I think it could be interesting again if they were able to use one of the newer magnetic coupling technologies to drive the compressor. It would do away with the inherent problem with using an open drive.

It would still leave the issue of HVAC/R techs having to learn small engine diagnostics and repair.
I'm thinking they could do better with an engine manufacturer other than B&S too...

[54regcab]

Agreed, but therein lies the fundamental difference between internal combustion engines and electric motors. Gas engines need to operate at a minimum rpm to make any useful power, and must fire in fast enough intervals so it doesn't shake itself to pieces think of a lawn mower about to stall.
To get a variable pumping capacity wouldn't an unloader to the job easier?

Idle speed is enough to prevent the motor shaking like crazy. At idle the engine horsepower will be minimal. Electric motors don't operate efficiently at less than about 40%, I think the gas engine has the advantage in part load capacity. Underloaders would be more complicated to implement that just varying the throttle position of an engine. Why produce the power then unload it?

[supertek65]

B&S sucks!
Put in a kohler and they are good units!

But if you get free gas?

Get a gas air conditioner!

[mark beiser]

Idle speed is enough to prevent the motor shaking like crazy. At idle the engine horsepower will be minimal. Electric motors don't operate efficiently at less than about 40%, I think the gas engine has the advantage in part load capacity. Underloaders would be more complicated to implement that just varying the throttle position of an engine. Why produce the power then unload it?

An engine designed to operate at one speed can be optimized for long term reliability, emissions reduction, and fuel consumption, better than one that has to operate at a range of speeds.
If the engine and compressor were magnetically coupled, unloading could be accomplished via allowing the magnetic coupling to slip at part load.
The engine RPM wouldn't change when at part load, but the work being done, thus the fuel consumption, would be lower.
You would want the system to be variable cooling/heating capacity to reduce/eliminate start/stop cycles, which ultimately are what send an engine to its grave.

[ICanHas]

Idle speed is enough to prevent the motor shaking like crazy. At idle the engine horsepower will be minimal. Electric motors don't operate efficiently at less than about 40%, I think the gas engine has the advantage in part load capacity. Underloaders would be more complicated to implement that just varying the throttle position of an engine. Why produce the power then unload it?

What type of motors are you referring to and its inefficient below 40% of what?
You'd want to modulate the system in such a way that it provides the best COP over a long averaging time (BTU-hr fuel heat content to BTU-hr cooling work)

An engine designed to operate at one speed can be optimized for long term reliability, emissions reduction, and fuel consumption, better than one that has to operate at a range of speeds.

Traditionally, AC portable generators had to run at 900, 1800 or 3600 RPM as rotor speed dictated frequency.

The Honda EU series inverter ones don't. The voltage and frequency are regulated by inverter and the actual generator is a high frequency three phase alternator much like the ones we have in our cars. It actually achieves better fuel economy by lowering the engine speed when the load is low.

If the engine and compressor were magnetically coupled, unloading could be accomplished via allowing the magnetic coupling to slip at part load.

No, it would be very inefficient. The slip has to be dissipated as heat. This is why multi-tapped PSCs are incredibly inefficient. You can only vary the speed of AC motors two ways.
1.) Changing the input frequency with a VFD.
2.) Changing the torque by using taps and varying the degree of magnetic slip.

Use a watt-meter and compare the power use of those portable fans. The input power at lower settings are disproportionately high, because much of the shaft power reduction is done through magnetic slippage.

To get good efficiency at multiple speeds on an AC motor without a VFD you'd have to use a mechanical transmission much like a drill press.

The engine RPM wouldn't change when at part load, but the work being done, thus the fuel consumption, would be lower.
You would want the system to be variable cooling/heating capacity to reduce/eliminate start/stop cycles, which ultimately are what send an engine to its grave.

I don't know how Yanmar does it, but the programming of PCM tune is one of the most important part of efficiency.

An unloader type compressor like Emerson digital coupled with a large flywheel would present itself as a variable torque load on the engine. The modulation speed needs to be fast enough for the flywheel weight so it would impress a fluctuating load on the engine.

The throttle and compressor modulation should then be controlled in coordition with the PCM mapping to follow optimal efficiency curve just like how the vehicle PCM coordinates air, transmission, fuel and ignition. Gas engines suffer from more pumping loss at low throttle opening.

[54regcab]

As you stated running a typical A/C motor at below 40% of it's rated output won't reduce input power very much.

[ICanHas]

Air handler fan is a different setup. The output is varied by increasing the slippage at motor. If it used a single speed motor and load was changed by changing the load on the motor by mechanical means the efficiency drop won't be as dramatic. So, variable geometry fan blades or a solenoid shifting transmission box.

Technically feasible but too expensive. Instead, they went with BLDC(ECM) which is the same technology as the fans in your computer and compressor motor in ductless splits. The guts of even the X13 is technically capable of operating like true VFD, but instead they're designed to work with legacy setup so instead they use taps and assign program to each tap.

As for the compressor, there are two ways... the scroll unloader like the one from Emerson Climate control or using BLDC and inverter motor drive to change the rotor speed.