Hot water too hot, changed element and thermostat

[Tony H]

hot water tank water too hot, i have replaced the thermostat and element but still the same issue. Th element is housed in a 4" section of pipe fed from the base of the tank to to top of the tank.
Any help appreciated.
Any advice welcome, Tony H

 

[Basher]

I think what you have is a "Willis" heater.
There are pages of discussion about it on this forum:

Willis Water Heating System

In another thread .... The Irish it seems have cracked it with the Willis system, where it heats from top of cylinder down, so you get hot water fast, and time on controls how much heated, so in that case yes controlled time would help never used a Willis system I am Welsh we have not worked it...

www.diynot.com

One of the comments I saw in that thread is about them overheating if the pipes are not sized correctly.
It seems a scheme popular in Ireland, but rarely anywhere else!

Could you just turn the thermostat set temperature down?

 

[John.g]

Your best bet is to install a pipestat on the heater outlet pipe and wire that in series with its own stat.
I advised that to someone who had increased all the pipework to 22MM and it seems to be working pretty well.

 

[John.g]

Meant to post this trend last year Tony, but better late than never.
Not mine, but this is used with solar pv to divert the output to a 3kw element on a vented 120L HW cylinder,
a pipestst is used to switch the element on/off and the immersion stat(s) are used in a supervisory role as the control stat ( a few tried) just couldnt/wouldnt give consistent switching, it would seem that these external immersions will only run at very high outlet temps even though I've never seen any complaints from the thousands of users.

The green line is the Ipower (export) switching in/out as the pipestat cuts in/out, the power is the scaleX10 (watts) Blue is the temperature at the cylinder bottom.
Yellow is the temperature at the cylinder middle.
Red is the temperature taken on the 22mm pipe from the immersion top.

Would also suggest installing a 2kw element if available as you can see that the outlet temperature falls by over 10C as the power output approaches 2kw or lower.