Tepid hot water - what to check...

[gregcope]

A far better solution is remove this valve and install a blender/ mixer valve on the domestic hot outlet. More hot water will be available, only clean potable water flow through the valve, obviously less restrictions on primary circuit (pipes from an too engine).
Downside is the preasure relief blow off will probably open more frequently

As PVB linked too above

will the water not get really, really hot
And cause an issue?

 

[gregcope]

As LadyInBed has said, that's a thermostatic valve for a domestic radiator, and it's absolutely no good for your purpose. You need to replace it with a proper thermostatic mixing valve, such as this one - Thermostatic Mixing Valve for Hotpot Calorifiers (15mm)

Is that from the hot feed to mix in colder water to increase the apparent hot water volume?

ie not replace in place, but put in another feed and replace the existing thing with a simple pipe.

 

[VicS]

Is that from the hot feed to mix in colder water to increase the apparent hot water volume?

ie not replace in place, but put in another feed and replace the existing thing with a simple pipe.

I think you have got the idea.
Do away with the existing thermostatic valve, connecting the engine coolant flow and return pipes directly to the calorifier coil.

That will make the water in the calorifier unacceptably hot Therefore install a thermostatic mixer valve between the calorifier cold water inlet and hot water outlet to blend hot and cold water to produce a water supply to the taps which is an acceptable temperature. It will, as you realise also increase, the total volume of hot water available.

Ideally you want to set a temperature which is hot enough to sanitise a shower head, if you have a shower, but not too hot to be a scalding risk . I forget the relevant temperature range but you can enjoy finding out if pvb does not tell us.

 

[wingcommander]

will the water not get really, really hot
And cause an issue?

Potable stored water is best heated to above 60 ° C to prevent nasties breeding, yes a direct feed from engine will increase temperatures well beyond this hence the need for a blending valve. Hot water will expand , so if you have a non return valve on the cold feed in ( maybe integral with the domestic water pump) then an expansion vessel fitted would help prevent the 3 bar red prv from opening.

 

[wingcommander]

yes that looks like the one!



The little copper pin moves around 4mm up/down.

yes that looks like the one!



The little copper pin moves around 4mm up/down.

Try running engine with the thermostatic head disconnected, if it worked before you may just have a faulty sensor head ie it is possible that its pushing the pin in even when turned too max temp. You can sometimes verify this by putting your finger in the valve base and rotating the temp control, you should feel the plunger moving up and down, the bit that acts upon the pin .

 

[pvb]

Is that from the hot feed to mix in colder water to increase the apparent hot water volume?

ie not replace in place, but put in another feed and replace the existing thing with a simple pipe.

Yes, a thermostatic mixing valve blends cold water with the hot water to maintain a set temperature. There's a good diagram of the installation method in this Surecal document - https://www.surejust.co.uk/images/uploaded/documents/Surecal Horizontal Calorifier Connection Instructions.pdf

 

[vyv_cox]

will the water not get really, really hot
And cause an issue?

There is no thermostatic mixing valve on my calorifier. The engine is indirectly cooled. Over the years we have made all-day motoring trips in the Aegean Sea due to flat calms. We have never had any issues with excessively hot domestic water, nor have taken any special measures when using it after trips.

 

[RichardS]

There is no thermostatic mixing valve on my calorifier. The engine is indirectly cooled. Over the years we have made all-day motoring trips in the Aegean Sea due to flat calms. We have never had any issues with excessively hot domestic water, nor have taken any special measures when using it after trips.

I also do not have any thermostatic valves on my system. However all the taps and the showers are the mixer type so the hot and cold water are simply mixed at the outlet.

Richard

 

[pvb]

A point worth remembering is that most calorifiers have immersion heaters. Even if your engine doesn't produce very hot water, the immersion heater certainly will. I've got my thermostatic mixer valve set so that the hottest water I can get in the shower is still bearable.