Teledyne Laars EG-175 EG


Old 10-10-04, 01:51 AM
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Teledyne Laars EG-175 EG


I am try to restore a spa system on a house I purchased. The systems hadn't been run in approx. 15yrs. After a half a day of work the two pumps (one was frozen) and the blower are all functioning excellently.

The heater was the last thing I came to. It is a Teledyne model EG-175 Energy Efficient EX. The electrical system for the heater has me baffled. Power comes in one box and passes through a series of two Ranco range/dif temperature sensors, three different electrical devices that I have never seen before (they are clear and plug in with approx. 6-8 prongs in the bottom with springs and coils inside and a voltage and hertz ratings on the outside...what are they?!) and last but not least some kind of timer that adjusts from 1-300 seconds. Like I said earlier I am completely baffled. If this system sounds familiar to anybody I'd be glad to email you pictures if you would make it any easier explaing it to me.

Back to my current dilemma... My dad had the brilliant idea of just overriding this mess and connecting the heater directly to a 120v supply. The heater instantly fired up but then about a second later there were a couple sparks and then nothing. After inspecting what happened it was discovered two wires connected to the pressure sensor (? this is white with a large copper wire/tube? coming out the back) had arced across.

These wires were seperated but now the heater is just plain dead... Also the pilot will not light any more, it just dies out quickly.

Does anybody have any idea what happened? How would that affect the pilot? Maybe it fried the thermocouple.? There's no such thing as a fuse on these units is there?

Any help would be GREATLY appreciated. If pictures would help I will be happy to take some.


Best Regards,
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Old 10-11-04, 07:14 PM
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The "three electrical devices" sound like relays. They are often used as a switch to handle high current loads. A small current can activate a heavy switch for a lot of current or a different flavor of electricity. The electricty that goes to a switch in the bathing area can be low voltage DC for safety and can turn on a high voltage AC motor or blower. Basically an electro magnet pulls a metal bar down to close a set of contacts.

NEVER put power to a heater without water flowing through it. They can burn out very quickly (in which case go shopping). Heaters also have several over/high temperature switches. If the heater or the spa water overheats they kill power to the heater. Some reset automatically when they cool and some are like fuses. When they go they go, but they are cheap to replace. Some of these temperature sensors work like old fashioned thermometers. The copper tube is probably for temperature. There's probably a big "bulb" on one end of the copper wire/tubing and a switch on the other end.

Pictures or a drawing/sketch would help.
Old 10-11-04, 08:17 PM
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Thanks Dane

You may be right about those "devices" being relays. I will take pictures when I get back up there. Hopefully I can get them by the end of this week. Please email me so I can reply with pictures when I get them . The part about the relays being used for low voltage doesn't make sense to me.

The system is run by three air switches. One of the air switches works the filter pump as well as the heater. Power comes from the air switch to a box where it is split. The split feeds the pump motor and then the rest of the stuff in those boxes before it heads out to the heater.

The thing that shorted after the heater was hooked up just two connecters (obviously being fed power) that were too close. The pump was cycling at the time and the heater only fired up for about a second before something blew.

For this reason I don't think it had anything to do with overheating. I'm pretty sure it was the electrical short and it sure seems like there should be a fuse somewhere but I'm not sure...

This brings me to a question about overheating. Is there a "flow" sensor inside the heater or does it just sense whether or not the pump is running (via electrical, not water flow)?

Also, do you have any idea what those Ranco temperature sensors do?

I will get those pictures to you ASAP.

Thanks again for your help!

Best Regards,

Last edited by Shadeladie; 05-24-11 at 03:16 PM.
Old 10-12-04, 04:54 AM
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Generally there is no flow switch, but they are wired so the heater only comes on when a pump is forcing water through it. I've usually seen three temp sensors on spas. There is usually a thermocouple or temp sensor in the chamber with the heater. This sensor works to turn the heater off before it burns up if the pump is not working. There is a "normal" sensor that tells the temp of the water to keep the spa at the desired temp. And finally there is a master safety temp sensor that kills power to the entire spa if the water gets to an unsafe level (usually about 120 f).

The relays can control several circuits with one input. They may be used as a safety. A master relay may be held in/on by a door interlock switch on the access panel for the spa, so when you open the access door power is killed to everything. A relay can be used to power a circulate pump and activate the heater. If the circulate pump is not on then the heater cannot come on.
Old 10-12-04, 01:36 PM
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Just a suggestion

I purchased a used Laars Heater this Spring and I found the manual available on the web. I can't remember the exact website name (probably but find it through google and they may have the manual available as a pdf file that you can print out. I also needed to call their service and parts center and they were very willing to share information. There are a couple of centers and the one in California was the most informative.
Old 10-14-04, 11:49 PM
Join Date: Apr 2002
Location: USA
Posts: 201
I hate to tell you, but it sounds like you did some major damage to the heater.

I also should warn you, be careful taking advise from people the like to help others,. but haven't a clue on what their talking about.

This heater has a transformer in it and operates on 24v. IF, you applied 120v to it (from the short between the white wire and the capilary tube from the thermostat it sounds that way), you probably fried all the electronics, including the gas valve, in the heater.

Also, these GAS heater CAN be wired to constant power as they will be controled by thier pressure switch. Unless some odd external dwitch has been added, the heater has a thermostat and 2 hi limit switchs built into it. All they will do is shut off the heater if it over heats (assumming they are all working correctly).

You can probably find a manual at the manufacturers website;
Old 12-27-04, 09:39 PM
Join Date: Dec 2004
Location: So. Calif.
Posts: 540
Hi Carter, read the post and yes you have a mess, see if you can follow me,

first off the heater is at least 15 to 20 yrs old, it is a millivolt powered heater, this means the thermocoupling [ pilot ] makes electricity from the small flame thats hitting it, now heres the remarkable part in my eyes, were only talking about 1/2 of one volt d.c. current now this voltage runs from to the gas valve neg. and the positive goes up to the pressure switch, [ if the pump is off no water, no pressure no fire] from the psi switch up to the on / off switch if it has one from there to the thermistat, from the thermistat up the side of the heater with the inlet / outlet pipes ti 2 hi limit switches the upper one is rated at 135 the lower one [ has a red dot on it ] 150 from there thr positive wire returns to the gas valve, where when all the switches are closed the heater will fire, with an ohm meter disconnect any auxilary wires connected to thease wires and connect one end to wire going to psi switch from gas valve [ disconnect from gas valve also] and follow through each switch, turn the thermistat up and at the end of the wire that goes back to the gas valve you should have continunity.
now for the bad new, like i said this heater opperates on 1/2 volt d.c.current. when your father connected it to 120v a/c current he more than likely fried something !

as for the Ranco it should say Ramco, this is an outfit in California that made automated spa controls, they were bought out years ago but you can still get parts, sounds like you have a manual spa-temp at or near the spa and this controls the temp of the heater they may use the relays to turn on a pump ? someone needs to look at your set up and evaluate if it can be fixed and if its worth the money.


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