Insta-hots causing light flicker??

[jahilliard]

I am being asked to evaluate and offer a solution to an existing problem at a residence. The house currently has 4-60A insta-hot water heaters that operate independently of each other. When certain lights are on in certain rooms while the insta-hots (1 or 2 or all) are being used there is a slight flicker in the lights only while the insta-hot(s) are in use. I'm looking for any possible solutions to resolve the issue and possibly any cause to this problem other than the obvious of there being a significant amount of resisitive load applied to the system of the house. Thanks

 

[gar]

110112-2350 EST

Solution probably not. You have anywhere from 0 to about 240 A load. I assume these are 240 V heating elements. I also assume the pole transformer is fairly large, and large wires from the transformer to the house. Otherwise the flicker would be more noticeable.

If you could get insta-hots with phase shift control rather than on-off then the effect would probably be minimized.

If it is appropriate to replace incandescent bulbs with GE dimmable CFLs, then the noticeable flicker might be reduced. Notice I did say dimmable CFL.

.

 

[dbuckley]

Yeah, a 60A step change in load is going to be hard to gloss over in a home setup.

If this is a money-no-object house, then you could have all the lighting circuits on a voltage stabilizer...

 

[mikeames]

Yeah, a 60A step change in load is going to be hard to gloss over in a home setup.

If this is a money-no-object house, then you could have all the lighting circuits on a voltage stabilizer...

Money no object.... then its easy..... get an 600 or 800 amp service.....

 

[Electric-Light]

My laser printer drives most lights nuts. This Osram-Sylvania ballast seems to be very well regulated and it doesn't show any signs of flicker despite very rapid fluctuation in line voltage caused by laser printer on the same circuit.

 

[kwired]

Money no object.... then its easy..... get an 600 or 800 amp service.....

You still have to get POCO to install large enough transformer and large enough conductors to wherever it is that they supply the materials, otherwise you will not necessarily gain much if anything. Often the majority of voltage drop has already happened at the service equipment, what is ahead of the service equipment is where the changes are necessary.

 

[G._S._Ohm]

Possibly I have 200 A service.

A 20 A, 240 V load drops the nominal 240 V measured at my load center by 400 mV, so I'd expect this setup to occasionally drop your whole house voltage by 5 V or so, line to line. This would be a 7% shift in incand. lamp brightness.

Substantially more drop than this may indicate a bad connection at or upstream of the load center.

 

[kwired]

Possibly I have 200 A service.

A 20 A, 240 V load drops the nominal 240 V measured at my load center by 400 mV, so I'd expect this setup to occasionally drop your whole house voltage by 5 V or so, line to line. This would be a 7% shift in incand. lamp brightness.

Substantially more drop than this may indicate a bad connection at or upstream of the load center.

Or the length of service conductors is too long or size of transformer is too small or both. I have seen many 200 amp services supplied by a 10 or 15 KVA transformer plus they served more than one customer at times also. POCO will not upgrade the transformer if no one complains - and even then sometimes they are reluctant to do so.

 

[G._S._Ohm]

The pole 'frmr is right outside my house so I may do better than people down the block.
The tolerance on the 120 is supposed to be +/- 5% in my area and +/- 10% in others but I think the Poco can pretty much do whatever they want as to power quality.