yep, I've briefly looked at GC, assorted laser/UV and the lead tape systems but, as always, the cost (20k per system) is in danger of scaring the client away.
The sensors used in personal gas monitors (cost c. £/$100) is really what we want, we just need to find one that will work sans oxygen
Hi folks
I need a H2S sensor that will work in the absence of oxygen.
Our gas is 80% Nitrogen, 20% methane 25 ppm H2S,
Ideally what I want is something with a 1-5V/4-20mA output that covers the range 0-30 ppm.
Everything I've found so far either only works with H2S as a trace in air as they...
Scotty, I did the adiabatic one from the regs and that came up with 700s to raise the temp from 90 to 250, assuming that's linear and ignoring temperature related resistance changes that gives about a 20 degree increase in 90s.
I did try niceic (don't know...try the cable manufacturer) Draka...
Cable is 50mm2, 5m long and carries 280A for 90 seconds
my own workings from first principles and assuming no heat loss from the cable…..…
Resistance of 50mm2 cable = 0.386 ohms/km
Resistance of 5m of 50mm2 = 0.386/200 = 0.00193 ohms
Total energy into cable = I2.R.t = 280 x 280 x 0.00193 x...
Code (or regs over here) says bigger, on a permanent job we'd certainly go bigger, the rest of the panel is 95mm but that's designed to last 20 years when running 24/7.
The temporary job just needs to run the pump for 4 90 seconds runs spread over 12 hours, my thinking is that whilst the...
the standard charts say that 50mm tri-rated can do 200A presumably all day for 20 years
Does anyone have short time ratings? We need to run a 280A pump for a day. Pump is on softstart and runs for 90 secs about once every 4 hours.
Cables would be about 5m long.
Gut feel says it will be ok but...
to expand on IRstuff's post, add a series resistor and you'll be able to detect the full set, fault open, fault closed, normal open and normal closed.
You will need an AI instead of a DI for each circuit which might get expensive depending on numbers and/or PLC used
Differential means it will trip if the current through each pole isn’t the same, they are pretty low tech, each pole has a resistance in it which heats up with current flow and mechanical linkages trip it if either all three poles are passing too much current or one pole is different to the...
those look like standard thermal rather than electronic.
You'll be lucky if one selected for three phase current will turn up enough to cover the equivalent single phase current
it's DHW in residential.
my thoughts were that if the pump goes off then thermal stratification will reduce the amount of stored HW available when demand resumes and once the pump comes back on it will mix everything up thus further reducing the amount of HW available.
might there also be...
bayoubare ......"-- you do not ever recommend test a cable ? Even if the entire switchgear is de-enegized a cable must be moved to be tested. Using your logic that may cause a fault when it is re-energized so it should not be done?"
you are correct, a cable moved/tested whilst de-energised...
Gents
it's bit of an open question but....
We have a Hx, primary fed by boiler with control by diverting valve, secondary is DHW fed into a storage/buffer tank. Controls temp sensor is attached to buffer tank and there is a circulating pump in the Hx/buffer circuit.
at times of low demand is...
I'm leaning towards the 25W short sharp option rather than the 2W 10s one as well.
I did think of a capacitor but the flash tester trips at 5mA so I didn't think I'd be able to charge it up without lot of messing about with series resistors
We have a couple of samples to practice on before...
Thanks…..
No other circuitry, two wires go into the potting compound, each is soldered to a piece of copper mesh, the resistor is soldered between the two bits of mesh.
They want to blow the resistor but keep the connections to the mesh
