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Author Topic: SNRM Variations  (Read 628 times)

vic0239

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SNRM Variations
« on: October 12, 2017, 07:37:43 AM »

Iíve started to see some regular variations in my SNRM. Something is affecting DS for about an hour overnight causing DSLstats to send me alarming emails that my SNRM has dropped to very low values, but recovers after about 1 hour. This has happened during the last 8 nights, but only to this extent on one of my lines, there is a tiny dip in the other lineís SNRM at the same time.

As itís happening overnight it isnít causing any issues for me, but I am curious as to what might be causing this. Iím in a rural village with no heavy plant as far as I now, although there is a sewage pump at the end of my drive, but itís been there for years.

There are also swings on the US SNRM, but during the day and pretty much mirrored on both lines which seemed to start around the time the FTTC capability was increased in the cabinet.

Any thoughts on this?
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burakkucat

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Re: SNRM Variations
« Reply #1 on: October 12, 2017, 05:41:04 PM »

Looking at the example SNRM plot that you have attached, the cause does not appear, at a first glance, to be some electrical or electronic item being switched on for some "nightly task".

Purely guessing . . . However it might be connected to the operation of the sewage pumping equipment. If the mains contactor has worn contacts, there might be localised arcing occurring whilst the pump is in use. Hence you could have a local "1900s style spark transmitter" situated at the end of your driveway.  :-\
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vic0239

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Re: SNRM Variations
« Reply #2 on: October 13, 2017, 07:31:12 AM »

Thanks for you input b*cat. Same again last night so I think it may be worthwhile contacting the water company so see if such a timed event occurs.
« Last Edit: October 13, 2017, 07:35:32 AM by vic0239 »
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JGO

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Re: SNRM Variations
« Reply #3 on: October 13, 2017, 08:15:19 AM »

Why not check if the drop in S/N coincides with radiated noise on a portable radio near the suspect pump ? It could strengthen your case for contacting the water company.
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vic0239

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Re: SNRM Variations
« Reply #4 on: October 13, 2017, 08:41:48 AM »

Indeed, I did consider a nocturnal reconnoiter, but would necessitate setting the alarm, not a popular move!  :-\  The water Co. are pretty good at responding to such queries, so hopefully I'll get some good feedback from them. Thanks.

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vic0239

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Re: SNRM Variations
« Reply #5 on: October 13, 2017, 05:35:10 PM »

Looks like I can discount the pump.
Quote
The Wastewater Team Leader has advised that the pumps come on periodically throughout the day and night, but they do not come on at specifically timed times. The operation of them is determined by weather and rainwater levels, so that during times of heavy rain they will operate more frequently.
I'll just keep an eye on it meantime. I am just concerned it becomes a daytime phenomenon.
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kitz

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Re: SNRM Variations
« Reply #6 on: October 13, 2017, 10:06:08 PM »

Hard to tell from the graph, but does it occur at bang on 1am?

Is the neighbour close or attached?   Many years ago a house we bought had economy 7 storage heaters which used to start storing at 1am.  Our neighbours used to take advantage by setting timers for things like washing machine over-night too. 
I don't know how much it is used these days, but someone else I know bought a new flat  (well about 10yr old) that also had electric heaters which also stored overnight.  We never got to the bottom of it, but we were pretty sure that his SNRM spikes were caused by a neighbouring flat as it happened even if his was turned off completely.  Just a suggestion now that the weather has started getting colder again.


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ETA

Just checked..  yes its still in use, although times can vary depending on supplier:
The seven off-peak hours might be 11pm to 6am, 12 midnight to 7am, 1am to 8am or even 1.30am until 8.30am
The hours usually change when the clocks go back or forward Ė so your Economy 7 times could be 1.30am to 8.30am during British Summer Time and 12.30am to 7.30am in the winter during Greenwich Mean Time.


 
« Last Edit: October 13, 2017, 10:10:37 PM by kitz »
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vic0239

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Re: SNRM Variations
« Reply #7 on: October 14, 2017, 08:01:11 AM »

Thanks for that.

Pretty much at ~1:02am, but for some reason nothing last night - flat SNRM.

The neighbours are not too close and all detached. The houses were built about 20 years ago and all had oil fired heating originally, my immediate neighbours still get oil deliveries, but any of the others could well have changed fuel. We have friends who, like you say, have an similar tariff to economy 7 and make similar use of the cheaper times so this is plausible.

Either the water board have flicked a switch (unlikely) or the nocturnal activity responsible doesnít occur on a Friday night!
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