SMT750I high idle power consumption

[tormento_apc]

This was originally posted on APC forums on 1/14/2011

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Hi community, first post 😉

I have just bought a SMT750I to replace a SUA1000I that was a bit oversized and old.

I have been enchanted from the "green" word I read in a brochure but the previous model, as far as idle consumption is concerned, was greener indeed.

Test conditions:
-UPS attached to main power
-no load attached
-OFF position
-battery charged and 20 mins wait before test to make it stabilize
-wattmeter between plug and power cord

SUA1000I: ~50W
SMT750I: ~60W

I barely tolerated the idle power consumption of the SUA1000I but, hey, it was some years old when the word "green" was only for dollars and leaves.

Now, the SMT750I bad surprise, almost pi$$ed me off.

Why on hell should a turned-off-battery-charged-nothing-to-do UPS consume so much? Its more than 10% of the power it can output at full load! Even off it continuously produce a humming sound. Not as loud as when inverting power but noticeable.

If any APC technician is reading, please, provide me some sort of explanation and, please, a firmware to correct this bad behaviour.

Oh and, please, do not write green anymore on your products.

[BillP]

This reply was originally posted by Llewellyn on APC forums on 12/5/2013

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Just a quick question. When you say Idle power consume, do you mean the unit is still running and that you just don't have any load connected or is it actually power down/off and just connected to mains (brain still on)? If the the unit is still on try turning it off; it will still be charging the batteries if it is off but plugged into mains. If the unit is off already though it would be a good idea to check the internal cabling from the socket to the board as there could be a bad connection. Even check the input cable it self it might be fault as the IEC plugs can develop bad connections over time. So test the cable you are using according to your country standards...continuity, insulation, and cable resistance test.

[tormento_apc]

This was originally posted on APC forums on 1/14/2011

---

Hi community, first post 😉

I have just bought a SMT750I to replace a SUA1000I that was a bit oversized and old.

I have been enchanted from the "green" word I read in a brochure but the previous model, as far as idle consumption is concerned, was greener indeed.

Test conditions:
-UPS attached to main power
-no load attached
-OFF position
-battery charged and 20 mins wait before test to make it stabilize
-wattmeter between plug and power cord

SUA1000I: ~50W
SMT750I: ~60W

I barely tolerated the idle power consumption of the SUA1000I but, hey, it was some years old when the word "green" was only for dollars and leaves.

Now, the SMT750I bad surprise, almost pi$$ed me off.

Why on hell should a turned-off-battery-charged-nothing-to-do UPS consume so much? Its more than 10% of the power it can output at full load! Even off it continuously produce a humming sound. Not as loud as when inverting power but noticeable.

If any APC technician is reading, please, provide me some sort of explanation and, please, a firmware to correct this bad behaviour.

Oh and, please, do not write green anymore on your products.

[marin849_apc]

This was originally posted on APC forums on 7/28/2011

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Did you measure the idle power consumption after several (24) hours to be sure that the batteries weren't charging?

SMT750I should consume 90 BTU/hr according to spec. which is equal to 26,4 Watts.
SUA1000I should consume 100 BTU/hr which is equal to 29,3 Watts.

For reference, my SUA2200RMI2U is rated as 300 BTU/hr = 88 Watts, but I always measure 36-40W (active power) idle with the batteries fully charged and with management card AP9617 installed.

Given that my unit consumes significantly less than 300 BTU/hr I find it strange if SMT750i and SUA1000I should consume twice their rating!
Does your measurements take into account the power factor?

[Olin_apc]

This was originally posted on APC forums on 7/28/2011

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Why would you look at power consumed un-loaded? That's like one person in a bus complaining about fuel consumtion! Just like the bus it needs to be loaded for efficiency to increase.

To be green with no load, stop inverter, turn off the supply, very green 😉

[marin849_apc]

This was originally posted on APC forums on 7/28/2011

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The "idle power" is somewhat constant over the load range and can be said to be the power consumption of the UPS itself or the UPS overhead. Therefore the idle power is interesting to know.

Depending on the application it is not always desirable to have a constant full or near full load on the UPS. For example if
1. The desired backup-time should be more than something like 3-6 minutes (which becomes 2 minutes at the end of the battery service life!)
2. If the UPS must be able to power additional equipment that is not always on (like an administration terminal)
3. If more frequent battery transfers are expected (a fully loaded UPS that often has to switch to battery operation kills the batteries much faster).

If the idle power for SMT750I is in fact 60W (as suggested by the thread starter, but not by the official spec.) it is quite bad. I have a small server, a router/firewall, a switch and a VoIP-gateway which together consumes about 100W. That would be > 40 minutes of backup time with the SMT750I which is just perfect since all three statements above are valid for me. The efficiency would then be just 63% or an additional waste of 60% which is unacceptable. 60W 24/7 would also be 10% of my total power consumption!!!

[marin849_apc]

This was originally posted on APC forums on 7/28/2011

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According to http://www.apc.com/products/efficiency_loss_chart.cfm?base_sku=SMT750I&chartSize=large the power consumption of SMT750I itself must be 8 W or 12 VA which is 1/3 of the rated BTU/hr of 90.

A similar exercise for SMT750RMI2U gives 9,7W or 14 VA. This unit has a rating of only 46 BTU/hr (14W).

SMT2200RMI2U has a loss of 12W / 15 VA and a rating of 215 BTU/hr (63W).

The SMT750RMI2U is the only unit where the BTU/hr rating and the efficiency chart match. WHY? Are the numbers on the APC-website just made up? 🙂 I don't think so...

(I assumed 100% load in the efficiency chart to be either 500W or 750VA for the 750VA unit, and 1980W/2200VA for the 2200VA unit. The efficiency data is measured with a resistive load according to APC so I guess that the calculate W is the correct one and that 100% in the chart means 500W resistive load).

[Olin_apc]

This was originally posted on APC forums on 7/28/2011

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Somewhat consistent indeed.

1. Then the battery is poorly sized, not the UPS

2. Majority of UPS applications I deal with are 24/7 but if load were to be removed why not shut down the unit? Battery discharge will be minimal over short duration and have smal if any,l adverse effect on overall life.

3. I don't see the relevance of this point? But I agree standby specific batteries will be damaged by a high number of discharges.

Can we see input waveforms for the unit?

[marin849_apc]

This was originally posted on APC forums on 7/28/2011

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I don't own any SMT750I, I was just responding to the threadstarters claim that this unit has excessive idle power draw/overhead (which I doubt).
I'm still wondering about the lack of consistency between rated btu/hr and the efficiency chart for several Smart-UPSes.

[Olin_apc]

This was originally posted on APC forums on 7/28/2011

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I am doubting the results too. Impossible to tell remotely, can't be sure it is offline, not loaded or reliable test equipment is being used.

[marin849_apc]

This was originally posted on APC forums on 8/14/2011

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Now I have a SUA1000I.
Its idle power is 19.5 W with an AP9617 installed (without it 16.6 W). However the apparent power is 63 VA. Probably the thread starter used a crappy power meter that didn't measure the power factor correctly.

[tormento_apc]

This was originally posted on APC forums on 1/14/2011

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Fan? I noticed no fan... It is an electric noise coming from the unit even when off. However, any firmware upgrade is accepted 😉 Can you address me to a specific version or file name?

I leaved the unit attached all night long. I have used both a H+H SU201 unit (soho) and a professional ampere measure clamp.

I observed the unit for the whole morning ~4h.

P.S: I think it is almost useless to increase efficency for 1-3% and get such a high idle consumption..

[Occamsrazor · Accepted solution]

Did you resolve this issue in some way? I'm looking at getting either an SMT750i or SMT3000ic and comparing idle power consumptions. One thing I've noticed is that if you look at the datasheets on the SE site, rather than the APC, site, it lists the idle consumption separately from BTU under "number of tare power" e.g.

SMT750i - https://www.se.com/ww/en/product/download-pdf/SMT750I

Number of tare power 15 W

Heat dissipation 90 Btu/H

or SMT3000i - https://www.se.com/ww/en/product/download-pdf/SMT3000I

Number of tare power 55 W

Heat dissipation 375 Btu

Though your real-world figures seem dramatically higher than that. Did you have a chance to retest?