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Post Info TOPIC: Suburban Therostat DIY Repair - cheap
bruceg


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Suburban Therostat DIY Repair - cheap
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The mains power 55°C set-point thermostat in my Suburban water heater, model SW6DEA, failed 'closed'.  This caused it to heat up to trip the safety thermostat at 77°C.  So I got either cold water or dangerously hot water direct to the kitchen sink in my caravan.

New thermostat required, so I looked at prices online - $110 from Caravans Plus, $50 - $80 direct from the US.  What ???  >$100 for a bi-metallic switch ?  Ridiculous.  I needed to look into this to see where the gold plating is.  So I unplugged the heater, took off the gas burner assembly and the thermostat cover and guess what; 2 bog standard, 1/2", 301 style thermostats, joined by a piece of fuse wire, riveted to a small piece of stainless steel.  Total cost to the manufacturer <$5.

Hmmm, surely I could source an equivalent thermostat for just a few dollars, rivet it into place and solder the cut-off terminal to it.  And I could increase the holding temperature to 60°C in line with current health and safety recommendations for hot water storage; bonus!

I could see that the fuse (fusible link) was fine and I knew that the 77°C manual-reset switch was Ok, so I drilled out the rivets on the 55°C thermostat and removed it ... except it wouldn't come away, it had welded itself to the stainless steel when it failed.  A sharp rap with a hammer and chisel broke it away.  I then cut through the terminal that the fuse wire was welded to, as close to the failed thermostat as possible, then twisted the wire to have the flat of the cut off terminal facing down.

So to the internet.  '60 celsius NC temperature switch' got lots of hits, mostly from China with a delivery time of some months.  When I scrolled down past these I found 'Australian Stock for Quick Delivery' with 2 x KSD301 thermostats for $8 with delivery under 1 week.  Sold!

When they arrived 3 days later I filed the excess melted metal off the bracket, riveted the thermostat in place, and soldered the cut off terminal on top of the new terminal.  It then took less than 10 minutes to fit the plate, cover and burner assembly back onto the water heater, plug it in and start it heating.  30 minutes later 60°C was available.  60 minutes on and the 77°C safety hadn't tripped.  Yah !

thermostat ID.jpg DIY repair.png

After re-reading the advisory on storage hot water temperature (link below) I'm going to do the gas thermostat asap, the extra safety with 60°C over 55°C is just too important to me.

Overall this was a fast job, cheap, a bonus upgrade and easy.  The only difficulty with this DIY fix is the soldering.  The terminals are coated with a corrosion resisting metal (Cadnium I suspect) so they must be abraided with sand paper, chemically cleaned then soldered at a highish temperature with an agressive flux.  Normal resin cored 70/30 solder will work, just, but higher temperature is essential.  Pre-tin both parts before attempting the joint.

SW6DEA Part numbers - 232317 for 240V/10A 120V/15A mains complete unit, 232319 for 12V gas controller unit

60°C auto resetting thermostat - KSD301

80°C manual resetting thermostat - MP-05EN-80DEG-NC  (77°C = 140°F is almost impossible to find in Australia !)

Does anyone know of a designation/grade/size/rating for the fusible links ?

 

Hot water storage advisory - https://www.elgas.com.au/blog/360-legionnaires-disease-from-your-hot-water-tank/

bye.



-- Edited by bruceg on Friday 11th of February 2022 01:22:53 PM

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Gus1949


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Think I would have spent the $100 and be done with it.

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Peter_n_Margaret


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And if someone tries to follow your advice here and dies as a result, you will be liable, fully licenced gas fitter, or not.
Cheers,
Peter

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OKA196, 4x4 'C' Class, DIY, self contained motorhome. 960W of solar, 400Ah of AGMs, 310L water, 280L fuel. https://www.oka4wd.com/forum/members-vehicles-public/569-oka196-xt-motorhome
 

 
Mike Harding


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Nice write-up Bruce, thank you :)

Be a little cautious of the KSD type thermo switches and ensure you buy a quality brand with electrical and mechanical approvals, in my experience the Chinese ones are usually crap and will fail within a relatively short time.

---

Peter:

I hereby advise people to jump off high cliffs, ideally ones at least 50m high, I further advise them this is a fun thing to do and no harm will come to them.

I don't believe I'll be liable for anything if anyone is stupid enough to follow that piece of advice.



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"I beseech you in the bowels of Christ think it possible you may be mistaken"

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KJB


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bruceg wrote:

The mains power 55°C set-point thermostat in my Suburban water heater, model SW6DEA, failed 'closed'.  This caused it to heat up to trip the safety thermostat at 77°C.  So I got either cold water or dangerously hot water direct to the kitchen sink in my caravan.

New thermostat required, so I looked at prices online - $110 from Caravans Plus, $50 - $80 direct from the US.  What ???  >$100 for a bi-metallic switch ?  Ridiculous.  I needed to look into this to see where the gold plating is.  So I unplugged the heater, took off the gas burner assembly and the thermostat cover and guess what; 2 bog standard, 1/2", 301 style thermostats, joined by a piece of fuse wire, riveted to a small piece of stainless steel.  Total cost to the manufacturer <$5.

Hmmm, surely I could source an equivalent thermostat for just a few dollars, rivet it into place and solder the cut-off terminal to it.  And I could increase the holding temperature to 60°C in line with current health and safety recommendations for hot water storage; bonus!

I could see that the fuse (fusible link) was fine and I knew that the 77°C manual-reset switch was Ok, so I drilled out the rivets on the 55°C thermostat and removed it ... except it wouldn't come away, it had welded itself to the stainless steel when it failed.  A sharp rap with a hammer and chisel broke it away.  I then cut through the terminal that the fuse wire was welded to, as close to the failed thermostat as possible, then twisted the wire to have the flat of the cut off terminal facing down.

So to the internet.  '60 celsius NC temperature switch' got lots of hits, mostly from China with a delivery time of some months.  When I scrolled down past these I found 'Australian Stock for Quick Delivery' with 2 x KSD301 thermostats for $8 with delivery under 1 week.  Sold!

When they arrived 3 days later I filed the excess melted metal off the bracket, riveted the thermostat in place, and soldered the cut off terminal on top of the new terminal.  It then took less than 10 minutes to fit the plate, cover and burner assembly back onto the water heater, plug it in and start it heating.  30 minutes later 60°C was available.  60 minutes on and the 77°C safety hadn't tripped.  Yah !

thermostat ID.jpg DIY repair.png

After re-reading the advisory on storage hot water temperature (link below) I'm going to do the gas thermostat asap, the extra safety with 60°C over 55°C is just too important to me.

Overall this was a fast job, cheap, a bonus upgrade and easy.  The only difficulty with this DIY fix is the soldering.  The terminals are coated with a corrosion resisting metal (Cadnium I suspect) so they must be abraided with sand paper, chemically cleaned then soldered at a highish temperature with an agressive flux.  Normal resin cored 70/30 solder will work, just, but higher temperature is essential.  Pre-tin both parts before attempting the joint.

SW6DEA Part numbers - 232317 for 240V/10A 120V/15A mains complete unit, 232319 for 12V gas controller unit

60°C auto resetting thermostat - KSD301

80°C manual resetting thermostat - MP-05EN-80DEG-NC  (77°C = 140°F is almost impossible to find in Australia !)

Does anyone know of a designation/grade/size/rating for the fusible links ?

 

Hot water storage advisory - https://www.elgas.com.au/blog/360-legionnaires-disease-from-your-hot-water-tank/

bye.



-- Edited by bruceg on Friday 11th of February 2022 01:22:53 PM

 I enjoyed your story....nice fix.  (this is the sort of activity that built Australia - initiative, invention, action, - productivity  etc....)  we have  enjoyed the benefits of that period and now people just want to be entertained, protected  and supported (the money to keep this up runs out pretty quick - then it is back to hard times for the future generations....)    KB



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KB
patrol03


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Great job Bruce. A couple of years ago I had the same problem and carried out the same repair. I used a thermal circuit breaker/switch from jaycar. Price $5.75.

The only difference I can see with the unit we have (SW6DEA) is that the base plate was aluminium and not stainless steel. I used the 70 deg unit and soldered the fusible link back in place.

Our unit is 10yo now so I expect it will be the tank that rusts out next.

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