It is 18 kW. Two runs of some pretty large wire. Maybe #8.
Perhaps a pair of 40 amp circuits I think.
-----Original Message-----
From: Robert
Sent: Tuesday, December 4, 2018 7:24 PM
To: [email protected]
Subject: Re: [AFMUG] OT Linear Circuit
I am looking at various tankless water heaters, what amp circuit are you
feeding that one with?
On 12/4/18 6:15 PM, [email protected] wrote:
I discovered that the 240 VAC line coupling cap only has about 25% of its
rated value. Most of the voltage was getting dropped by that cap. So
once I get the replacement part, then the whole circuit can get proper
power and we will see what voltages we have at the different places in the
circuit. I think I must have had a bad surge. Lost this water heater and
the digital read out on my main manual lathe is totally goofy now too.
*From:* Chuck Macenski
*Sent:* Tuesday, December 4, 2018 6:59 PM
*To:* [email protected]
*Subject:* Re: [AFMUG] OT Linear Circuit
Did you look at REFf with a scope? Is that an oscillator?
On Tue, Dec 4, 2018 at 3:44 PM <[email protected]> wrote:
They also have a pair of LEDs in parallel with each other but in
series with the op amp power rail to indicate output. Crazy all
over the place.
*From:* Mark Radabaugh
*Sent:* Tuesday, December 4, 2018 2:29 PM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] OT Linear Circuit
Check the V- side of the circuit - is it tied to 0v or is that the
output?
https://www.edn.com/design/analog/4320338/Op-amp-can-source-or-sink-current
version (e) looks a bit like what you have and they are using the
negative rail of the chip as a constant current source.
Mark
On Dec 4, 2018, at 3:51 PM, [email protected] wrote:
Nope. The sensor is a different part of the circuit.
*From:* Mark Radabaugh
*Sent:* Tuesday, December 4, 2018 1:41 PM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] OT Linear Circuit
Seems like one of those resistors is the sensor? To me it looks
like the output is going to try to stay just over 3V but will lag
‘ref out’ up or down if there is any voltage on it. I can’t
recall if op amps can sink current or not.
The wife was annoyed that the contractor blew up the new fan hood
for the kitchen remodel with a dead short on the output. A
Replacement board was 8 weeks out. “Can’t you get out your
special catalog and fix it?”. I suppose - hum.. this circuit
board is built to drive more than one fan. Let’s take this SCR
out and move it over here, solder a new fuse in here… yep - don’t
even need to order parts.
Mark
On Dec 4, 2018, at 2:43 PM, <[email protected]> <[email protected]>
wrote:
I am reverse engineering a temp control circuit on an electric
tankless hot water heater.
Manufacturer says no user replicable parts inside. Oh yeah?
It has this as a reference voltage circuit (below) for a
comparator to compare against a thermistor and pot combo.
LM324
Odd taking a reference voltage from an input. Have never seen
this circuit before. I think I have drawn it correctly.
The op amp will drive the output to minimize the differences
between pins 5&6 so pin 6 should reflect the voltage of the
divider with lower impedance.
Anyone see why this wouldn’t work? I was sure I had traced it
incorrectly, but I think this really is the circuit.
It seems the values of R10 and R11 are not critical. Or are they?
<image[1].png>
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