Jump to content

2LW 74 Deg thermostat


Featured Posts

A few other suggestions Chris as I had a similar issue initially with my Lister.


If your thermostat doesn't have a wobble valve to aid bleeding ensure a 2mm bleed hole is drilled near the edge.


If the housing is horizontal ensure the thermostat is positioned with this hole at the top.


If the bleed hole is any bigger than 2mm it will leak coolant to main circuit prematurely, probably causing over-cooling, so bin it and start with another.


Consider as I have done successfully below, using a "T" port valve to allow bypass of calorifier circuit. This allows quick warm up with plenty of hot water after valve is set to feed thermostat bypass through to calorifier. In fact I see top rail temperature drop by as much as 10°C after switching over before it rises again. Forgetting to move valve from quick warm up position shouldn't be an issue other than not getting any hot water, since thermostat will just open sooner, bringing main larger bore cooling circuit (skin tank) into play.




Connections to the right are to/from the calorifier. Top left is feed from thermostat bypass. Valve is shown in quick warm up position which provides the secondary advantage of killing any thermosiphon effect when engine not running and you have a calorfier immersion heater on.


You could automate the quick warm up switch over but this leaves you in control and is simple and inexpensive.

Link to comment
Share on other sites

Thermostat now replaced with new 74C unit. The existing thermostat was already a 74C so I was not expecting a significant change. Both appear to be the same make, marked "Waxstat", however there is a noticeable difference in length from the main flange face to the bypass valve disc (about 2mm), not sure this made much difference and I did not have the time to measure the length at various temperatures to determine when the bypass port would open/shut. I will measure this properly next time. The new stat gives warmer running, about 77C on the outlet. I think I'll run like this before making any significant plumbing changes.




Edited to remove typos.

Edited by jonesthenuke
Link to comment
Share on other sites

:D cauliflower is sometimes used as a nickname for calorifer on here.


For bypassing the calorifer a 15mm TMV would do as it's only dealing with the flow through the calorifier coil, not everything.


The hot inlet of the TMV would tee into the feed to the calorifier coil, the cold inlet of TMV would be connected to the calorifer coil outlet, and the outlet of the TMV would connect to the return to the engine.


That way the TMV would draw from the hot side, bypassing the calorifer coil until the temperature of the water from the engine reaches the TMV setpoint, say 65°C. When that happens it'd start to draw from the cold side so allowing flow thru the calorifer.


Most TMVs only go up to about 45°C so it needs choosing one that goes up to 65°C, they are often used on solar thermal systems, and sometimes go on Ebay for about £15-25. Eg of one:




cheers, Pete.


Link to comment
Share on other sites



I has been thinking of a big bore version (28mm) to act as temperature control on the skin tank as the return temperature is so low.





Just checked, I have an unused TMV bought for a solar heating project, its a 22mm Caleffi with 85C rating. Time to break out the plumbing gear ........

Edited by jonesthenuke
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.