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Hi, May I seek some advice regarding BS 7430 requirement on resistance to earth. I see in Annex A regarding legislation (the Electricity Supply Regulations), it states resistance to earth has to < 1 ohm. I think it's referring to TN-S system. But how about TT system? And how about the HV (or...

@catserveng, Thanks a lot for the information provided, much appreciated your help. Just also wondering if there is a separate section called "Piping system basic information" available, as it is being referred in the "Diesel fuel and Diesel fuel systems" section. Many thanks P

Thanks TugboatEng. I understand the general principle to size any pipes or ducts for fluid or air. But I'm wondering if there is any chart or table that is available for diesel fuel and generator exhaust hot gas so that I can use to check the fuel pipe size and the chimney size, same as that we...

Hi, Could anyone please advise me any formula or chart / table for sizing of fuel pipe and the exhaust chimney of a diesel generator? The chimney needs to run vertically to tens of meters above the generator location within a building. Thanks PMCH

Hi Che, The installation is based on IEC, a LV system, there is low power factor penalty imposed by utility company. Thanks.

HI, May I know if there is any rule of thumb to reserve the breaker provision for future capacitor bank and active harmonic filter in an electrical system - i.e. sizing the breaker for the future cap bank and AHF. The reason is that at the moment of design, we don't have any information about...

@nuuvox000 the humidity range I described must be maintained. I'm just wondering if the chilled water coil can already do the job without a dehumidifier. Though the load is basically near to 100% of sensible load, we may still have a bit of latent load due to infiltration, or if there are...

@nuuvox000 Basically I'd like to understand how to determine the pressure drop of the air path if a flooding system is used, e.g. a pressurized raised floor system with the AHU just immediately connected to it with air outlets at various locations. I see such kind of raised floor design...

@MintJulep Thanks for your response. May I understand a bit more on the theory behind?

Hi, May I have some advices on air flooding system. Assume I have to design an air flooding system, e.g. a pressurized raised floor, how to estimate the air pressure drop of this flooding system in order to size the external static pressure of the AHU ? Thanks.

Hi, I've a case where it requires an indoor air conditioned environment be maintained at 16 to 25 degC and 20% to 50% RH, for tape storage equipment. Assume the load basically is sensible load (tape storage equipment only). If just using a normal chilled water system, e.g. 7 degC supply and 12...

It's transfer on failure

The two sources ultimately coming from the same utility feeder, so suppose won't have major difference between their phase angles if they are in the same phase, e.g. L1, right? However, if the inputs are from L1 and L2, then the difference might not be expected to be minor right? Given we don't...

@waross Transfer time is just few milliseconds with synchronous inputs.

@waross It's a single phase 30A 220V STS supplying critical load IT load, that's why a reliable transfer is a must.

Hi, Would like to seek some advices on STS. The design consultant designs with the source 1 and source 2 input to a single phase STS in different phases (e.g. S1 on L1 and S2 on L2, S1 and S2 originate from different power transformer). Assume this is incorrect / bad practice as normally S1 and...

Hi, Is different brand of breakers not suggested to be mix-used in power distribution to avoid discrimination issues? Thank you.

Thanks all for the valuable advices!

@ thermionic1 We have 2 cases: 1. single genset not connecting to grid any time. 2. multiple parallel gensets, also not connecting to grid any time. Thanks

Hi, May I seek some advices about the reverse kVar protection: is diesel genset normally equipped with reverse kVar protection?