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Need to source a radiator fan switch at 70 C


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The Ruston manual states the cooling water outlet should be at 71 degrees C and should not exceed a max of 81. The cooling is done using a 12v Bosch car auxiliary pump, which comes on with the ignition. This means the engine takes ages to reach operation temperature. I aim to fit a thermo radiator fan switch into the outlet pipe which will then turn on the pump when the engine reaches temperature, but I've been scouring the net and car ones all seem to be set too high, I know you can get capillary ones that are adjustable, but I can't see how they can be sealed, so ideally I would like a standard threaded type. Anyone know a good source for me?

Regards

Casp' 

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Rather than 'into the pipe' have you considered a simple pipe thermostat which straps onto the pipe - same as used on a domestic hot water tank?  The old design, low cost ones are just a bi-metal strip with an adjusting knob to set the switch over temperature, so not much to go wrong.  As they are usually low power AC if you do go this way, I would use it to switch a 12v relay to power the pump.  The only concern I have with your idea is being confident that the pipe layout will ensure hot water reaches the point in the pipe where the sensor is before the engine overheats.  I would probably also have a second unit to sound a buzzer in case of failure of the pump system to ensure there is no danger of overheating, together with a switch to force the pump relay on - in case you want to run the pump when the temp sensor says there is no need.

  • Greenie 1
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I know this isn't what you really want, http://www.ebay.co.uk/itm/DC-12V-1-Single-Channel-Thermal-Relay-Control-Sensor-Module-Temperature-Switch-/221464199564?hash=item33904b818c:g:99QAAOSwsXFZGuMF  but I used one of these to control a kick space fan heater that I installed, the sensor is on the outside of a section of copper pipe  on the heater matrix.

It does work well enough and the fine tuning to get it on and off at the right temp is easily done, they're only about £6 give one a try, it will pass 10a @ 12v, don't know if this is enough to run your pump.

 

Bazza

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46 minutes ago, casper ghost said:

The Ruston manual states the cooling water outlet should be at 71 degrees C and should not exceed a max of 81. The cooling is done using a 12v Bosch car auxiliary pump, which comes on with the ignition. This means the engine takes ages to reach operation temperature. I aim to fit a thermo radiator fan switch into the outlet pipe which will then turn on the pump when the engine reaches temperature, but I've been scouring the net and car ones all seem to be set too high, I know you can get capillary ones that are adjustable, but I can't see how they can be sealed, so ideally I would like a standard threaded type. Anyone know a good source for me?

Regards

Casp' 

On Ebay look for 12 Volt digital Temp. Controller ,they are for panel mount and can Switch 10 AMPS.

Adjustable and easy to set up,the one I have (all over the Boat) have the Brand name of Willhi

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The outlet hose exits at the highest point so it should get the hottest water. The hose is rubber so I guess I can't put an external one onto it. The outlet connectors are thick cast iron so not sure they will give a fair temp reading either.

 

The ones that just have a probe to gain the temperature; how could I seal those? The digital ones look a bit fancy and cheap, so I wonder how reliable they would be. I like the simple, car type, screw in ones, but I can't find one.

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If you can source a Kenlowe fan thermostat kit, they come with a shaped bit of rubber to allow  the capillary to pass into the hose yet seal properly.

Edited by pearley
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26 minutes ago, casper ghost said:

The outlet hose exits at the highest point so it should get the hottest water. The hose is rubber so I guess I can't put an external one onto it. The outlet connectors are thick cast iron so not sure they will give a fair temp reading either.

 

The ones that just have a probe to gain the temperature; how could I seal those? The digital ones look a bit fancy and cheap, so I wonder how reliable they would be. I like the simple, car type, screw in ones, but I can't find one.

I think a pipe stat will work fine on the rubber pipe, it will need to be set just a little cooler to ensure operation.  If you want fancy probe type (eg http://www.ebay.co.uk/itm/DC-12V-Thermostat-Digital-Temperature-Control-Switch-Temp-Controller-20-90-/141755772403   ) where you can set the hysteresis to reduce pump cycling then to make the probe water proof, drill a blind hole into a brass/stainless bolt with a hole slightly wide than the probe and then with a dollop of epoxy, glue the probe into the bolt.  A thin film of epoxy will not insulate your probe.

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20 minutes ago, Chewbacka said:

I think a pipe stat will work fine on the rubber pipe, it will need to be set just a little cooler to ensure operation.  If you want fancy probe type (eg http://www.ebay.co.uk/itm/DC-12V-Thermostat-Digital-Temperature-Control-Switch-Temp-Controller-20-90-/141755772403   ) where you can set the hysteresis to reduce pump cycling then to make the probe water proof, drill a blind hole into a brass/stainless bolt with a hole slightly wide than the probe and then with a dollop of epoxy, glue the probe into the bolt.  A thin film of epoxy will not insulate your probe.

They are certainly very cheap, if they work well..

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37 minutes ago, casper ghost said:

As it says for MAN or Mercedes, it's used in the truck engines, and BEHR (the makers) may have an agent in the UK that can supply you with the required information.

 

Peter.

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2 hours ago, casper ghost said:

They are certainly very cheap, if they work well..

Chewbaka is on the money.  I've used those and similar for loads of jobs, often with the probe taped to the pipe/housing. Chose your tape well.

The ones I bought have proved reliable with good repeat performance.  At the price get two and pick a second monitoring point.

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The usual way to control temperature is a combination of thermostat and bypass arrangement. The bypass allows coolant to circulate around the engine, moving heat from hot to cooler parts of the engine to ensure the engine heats up evenly. I don't think suddenly introducing cold coolant to hot parts of the engine by switching the pump is the best way to go.

I can't see the pump or cooler in any of your other postings, do you have a bypass plumbed after the pump?

Have you concidered running the pump at a lower speed during warm up? There are electric pumps and controllers available on the motor sports market, perhaps just a controller with your existing pump?

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Isn't what I'm considering doing exactly the same as how car engines are cooled, with a thermostat allowing cold water in at a certain point?

My pump is an inline 12v pump which are used in cars as an auxiliary pump, it just circulates water through the engine and the swim tank, though it can be diverted from swim tank to the hot water tank. I plumbed the cooling system and don't know what you mean by a bypass.

The pump does pump a lot of water, this engine is meant to be cooled through a gravity fed radiator, so my system is currently cooling it too well..

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So you currently have two routes for the coolant, swim tank or hot water tank; both of which will cool the engine. A bypass can be plumbed (tee connection) from the output of the pump to the return hose, effectively a "short circuit" (or third route) that allows the coolant to recirculate around the engine. Vehicle engines would then use a thermostat to divert the hot coolant to the radiator; the main difference with vehicle engines is that most of the "plumbing" is internal to the engine.

In normal use the coolant will take the course of least resistance through the bypass during warm up. A valve (manual or thermostatic) placed in the bypass can be closed to send the coolant to the swim tank or hot water tank when the engine is up to temperature.

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1 minute ago, Eeyore said:

 

In normal use the coolant will take the course of least resistance through the bypass during warm up. A valve (manual or thermostatic) placed in the bypass can be closed to send the coolant to the swim tank or hot water tank when the engine is up to temperature.

Wouldn't that give the same result; cold water being pumped into the engine once it's reached temp. The only difference being that some watet is circulating during warm up.

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3 hours ago, casper ghost said:

Wouldn't that give the same result; cold water being pumped into the engine once it's reached temp. The only difference being that some watet is circulating during warm up.

I knew I shouldn't have said "manual" valve! Just confused things.

I suspect most vintage engine owners would tweak a manual bypass valve to maintain a steady engine temperature, a thermostatic one would do it for you. In effect this blends bypass coolant with coolant returning from the skin tank to maintain engine temperature. 

Thinking of its original radiator, what do you image the temperature of the bottom hose would be? Not cold, thats for sure.

Its all about complicated things like thermal cycling, thermal shock etc about which I do not have detailed knowledge. That said, the vehicle industry has been paying out to have this system fitted to there engines for at least 60 years to improve warm up times and extend engine life.

Edited by Eeyore
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4 hours ago, casper ghost said:

Isn't what I'm considering doing exactly the same as how car engines are cooled, with a thermostat allowing cold water in at a certain point?

Nope. In a car the water circulates only around the engine when it's cold. This allows for a fast warm-up. As the temperature rises the thermostat will begin to open, causing the coolant to now also flow through the radiator.  This enables it to be cooled down. 

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I wonder if I could get an old Landy thermostat and housing and somehow fit it into the cooling pipe, but also have a bypass/ shortcut so there is always some circulation.

It's probably just that my swim tank is too big, but it's all guess-work..

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17 hours ago, casper ghost said:

I wonder if I could get an old Landy thermostat and housing and somehow fit it into the cooling pipe, but also have a bypass/ shortcut so there is always some circulation.

It's probably just that my swim tank is too big, but it's all guess-work..

Spot on! Two tops and the centre part (with the elongated port) from a series 2/3. The standard sleeved bypass valve thermostat has a slightly  higher temperature setting, but probably ok.

Edited by Eeyore
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On 22/06/2017 at 16:23, pearley said:

If you can source a Kenlowe fan thermostat kit, they come with a shaped bit of rubber to allow  the capillary to pass into the hose yet seal properly.

Yes I'd ring Ken Lowe up I found them to be very helpful. their capillary thermostat as supplied for land overs was basically a standard 240v unit off a burco or something like that and as pearly says came with a little rubber insert so you could slip the capillary bulb into the top hose and hold the rubber bit in place with the original hose worm clip. Worked just fine on my old V8 defender no leaks and controlled the ruddy great kenlowe fans without problem

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