really old flash unit crapped out

[Sbrem]

Hey everybody, we have a very old Hopkins Flash that has given up the ghost so to speak. I'm rying to troubleshoot it, before I have to spend some money. The solenoid seems fine, power is going in, the fan doesn't work, so I think that's fried, but easy enough to replace. It's single phase, so only 2 of the 3 wires out of the heating element are connected to power. I can't quite remember how to 1. measure the resistance (any 2 of the 3 wires?) or 2. what to set my meter on (ohms of course), but the lowest setting since heating element have very low resistance? I seem to remember from long ago that they should be somewhere between 10 - 18 ohms or so? Thanks in advance.

Steve

[ebscreen]

Simple stuff first always. Heating elements tend to have the wire connections corrode over time, something about joining copper wire to nichrome
just doesn't play out long term. Disconnect power and pull on connections to panel/look for crusty wiring.

You mention power going into relay, is it also coming out? Physical relay contacts like to build crud over time.

If you have pic of nameplate or specs (voltage/amps) we can determine what ohm range you should be looking for, but generally
speaking if the panel has burnt out you're probably looking at a new flash.

[Sbrem]

When I get out the weeds I'll dig in deeper and check the points on the solenoid/terminal, but, the legend plate says 2400 watts, 11 amps, 220v single phase.

Update: the formula I found said voltage (220) squared divided by watts (2400) and my calculator says 20 ohms.

Steve

[Sbrem]

OK, I got it apart, the solenoid unit is fine, volts going out are the same as the voltage coming in. So, there are 3 wires coming out of the heat panel, 1 is capped with a wire nut and electrical tape. When I check the resistance between the 2 other wires, nothing. But if I check one of those with the capped off one, I get 11.5 ohms. If I remember correctly, from testing panels in one of old Advance dryers that we used to have, any 2 leads of the 3 should give a reading. Based on this, I think the heating element has a disconnection inside, as mentioned by EB earlier. I'll see if Intek has something we could use. We're also check our local Craigslist, but nothing there at the time.

Steve

[Northland]

OK, I got it apart, the solenoid unit is fine, volts going out are the same as the voltage coming in. So, there are 3 wires coming out of the heat panel, 1 is capped with a wire nut and electrical tape. When I check the resistance between the 2 other wires, nothing. But if I check one of those with the capped off one, I get 11.5 ohms. If I remember correctly, from testing panels in one of old Advance dryers that we used to have, any 2 leads of the 3 should give a reading. Based on this, I think the heating element has a disconnection inside, as mentioned by EB earlier. I'll see if Intek has something we could use. We're also check our local Craigslist, but nothing there at the time.

Steve


I'll take a stab at answering this:

Many electrical devices (motors,heaters,etc) are "dual voltage". Meaning they can be used on two different voltages (each voltage would require a different wiring configuration). In this case the two voltages are probably 120 -or- 240 volts.
FYI, voltage ratings are nominal values, so 110/220 -or- 115/230 -or- 120/240 all mean basically the same thing.

In the case of a flash cure unit, you would have two separate heater elements that can be connected end to end (series) when used on the higher voltage -OR- side by side (parallel) to be used on the lower voltage. The wire that you described as "capped off" is the center point of the two elements. When used on 240 volts the the voltage would be applied to the ends. The current would flow thru the first element to the center point and then from the center point thru the second element. Half the voltage (120 volts) would be dropped across each element. When used on 120 volts, the two end wires would be connected together and voltage would be applied to the center point and the two ends. You would still have 120 volts dropped across each element.

If you need to think of it in plumbing terms, think of two separate pipes.
In the case of a full supply pressure (voltage) you can connect the pipes end to end and get "X" amount of flow.
In the case of a half supply pressure (voltage) you would need to connect the two pipes side by side to get the same "X" flow.

That capped off wire should read the same resistance to either end wire. Since you can only read resistance in only one direction, only one of the two elements is functional. You probably have a wire/element that has burnt open (either inside or outside of the heater element).
As it stands now, if you connected 120 volts to the two wires that read the 11.5 ohms of resistance, the flash would operate at half it's normal wattage output (1200 watts).
If both heater elements were functioning, (and you applied 240 volts across them) you'd have 1200 watts x 2 = 2400 watts.

Sorry.... not sure if that's an adequate explanation. But, you essentially have a flash unit that would do half of what it should be capable of doing.

[Sbrem]

Actually, it's pretty clear to me, once I read it over. After my test I figured the wire had come off the element or something similar. I was thinking of replacing the heater, but the replacement would have to have an opening in the top for the fan to blow though. So, we'll just have to get another flash, as I should spend my time a better way. Thanks though, I did learn something from that.

Steve