Hi-Lo stats

[Nordio]

Hello everyone,
My Woodwarm stove shows how to install Hi-Lo stats but the 4 pipe layout shows the LO stat on the return from the gravity circuit.

How will this prevent cold glugs of water returning from the CH system and entering the stove?

The 2 pipe layout shows the stat clearly on the return from the CH system and sensing the return flow directly.
Is the four pipe layout flawed?
Many Thanks. 🙂

 

[oldplumber]

the hi stat ensures the boiler/hw cyl water is hot enough before turning on the ch pump and when the lo stat operates it is to turn off the ch pump to stop the ch water cooling the hw cyl. if you read the instructions it is explained in detail and eassy to understand (i did read them and after a little thought fully comprehended the set up)

"A high temperature Pipe Thermostat.
​

​

This is clamped on to the main 28mm gravity flow water pipe and switches the pump on when the boilers/pipe​

temperature rises. It should be set at between 85

oC and 95oC and thus ensures that the copper Cylinder hot water

does not boil but is dissipated safely around the radiator circuit.
2 ​

​

A low temperature Pipe Thermostat.

​

​

This is clamped on to the main 28mm return pipe and should be set at between 45​

​

oC and 55oC and thus switches

the pump off when the temperature of the water returning from the system/hot water copper Cylinder to the
boilers begins to fall. It ensures that ​

​

cold water does not circulate through the stove boilers and the circuit as

this would:-​

a. Allow the heating circuit to rob the heat from the hot water copper Cylinder"


Not trying to be sarcastic here, but the manufacturers write their instructions for us to follow, they dont seem to get it wrong very often otherwise they would go out of business very quickly
​

 

[Nordio]

Thanks for the reply but have a look at page 21............
http://www.woodwarmstoves.co.uk/_assets/manuals/new instructions with photo 060508.pdf

The Lo stat is positioned on the gravity return!

Are you suggesting the gravity flow through the cylinder will cool the return quick enough through "thermosyphoning" to shut off the pump and avoid the cold water entering the boiler?

 

[oldplumber]

I dont have time to go and look now but as before follow what the manufacturer says unless you know better and are happy to invalidate your warranty and proobably any household insurance for knowingly contravening mfiS. Or if you really want to know, ring the manufacturers for their response, it might be short

 

[Nordio]

I've contacted Woodwarm and a number of other manufacturers who advocate this arrangement and also HETAS and the Solid Fuel Association in the hope of finding an answer.
Its seems to be an industry standard.
It's not so much the four pipe arrangement that I consider flawed but rather the "control" aspect.

Also from the MI's (relating to cold water below the recommended mimimum entering the boiler and the problems it can cause).............​

a. Allow the heating circuit to rob the heat from the hot water copper Cylinder
b. Cause acid condensation to form on the boilers inside the stove and them to fail early
c. Create a cold flue/chimney and the associated condensation/tar problems​

With the control system the manufacturers are advocating then I believe cold water will enter the boiler when using the four pipe layout as described.
The boiler in my stove could fail early due to an inferior control system advocated by the manufacturers!
Thanks again.​