Pipe thermostat

[azzy100]

Hi
I have a frost stat fitted at the moment,but with the weather conditions currently in force,it is keeping my heating on 24/7.This i don't want.
Can any one tell me please what i can do to stop my heating comming on and also prevdent my pipes from freezing?

Thanks

 

[stem]

The answer is in the title of your thread. Fit a pipe thermostat on the return pipe after the last radiator, but before the boiler and wire it in series with your frost thermostat, The setting will depend on where the thermostat is located, but it needs to be about 10 higher than the ambient temperature of the place it's located.

When the frost thermostat switches on the boiler, hot water is circulated around the radiators and pipe system, but before it gets too hot, when the warm water gets back to the pipe thermostat, it turns off the boiler. After a while when the temperature drops in the pipe, it will start up again and the process is repeated.

Make sure the pipe thermostat is sufficiently far from the boiler to prevent residual heat from the boiler reaching it by conduction and keeping it switched off.

Many cylinder thermostats can be used as pipe thermostats, they simply clamp on to the pipe using a spring.

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• stem
• 21 Dec 2010
• 3

As an alternative, if your pipe layout will allow it, you could re-position the existing frost thermostat immediately above a section of pipe with a small piece of insulation the length of the thermostat removed. That way, heat rising from the pipe will turn the frost thermostat off when the pipe gets warm. I have seen this in operation and it works, but if the frost thermostat fails, by removing a piece of insulation albeit small, you are increasing the chance of a frozen pipe.

 

[azzy100]

Thank you very much for your reply.
Could you please let me know,what sort of cost are associated with having a return pipe thermostat?

My boiler and the frost stat are located in my garage.
If i was to do it my self,how do i locate the last radiator?
Are these simple to fir?

Many thanks

 

[brig001]

Not really answering your question, but we had a similar problem with our boiler in our integral garage. I insulated the up and over garage door with some polystyrene stuff from Wickes, and added a draught strip to the bottom of the door. The garage has not dropped below 3 degrees C since - and hardly ever below 4. Just a thought - might be easier, and save more if your garage is integral and cooling the house anyway.
HTH, Brian.

 

[stem]

The pipe thermostat will cost about £20 and then you need a length of cable back to the frost thermostat.

To find the return pipe to the boiler, identify the two pipes from the boiler which are hot when the system is running. Then when the system is cold, start up the boiler and the 'return' is the last of the two to heat up. The pipe thermostat needs to be on this pipe, but not directly above the boiler, and far enough from the boiler that the section of pipe cools naturally when the boiler goes off.

I'll knock up a sketch & wiring diagram for you if I get time.

 

[mikely]

Example of pipe thermostat here: http://www.uk-plumbing.com/honeywell-l641b-low-limit-pipe-thermostat-p-1486.html
The wiring diagram titled ‘Low limit (frost protection)’ in the data sheet available from the web page shows how to connect the pipe stat.

 

[stem]

Sketches as promised. These are typical only as I don't know the actual layout of your plumbing, or the actual thermostats you will use. But they should give you an idea.

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• stem
• 22 Dec 2010
• 1

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• stem
• 22 Dec 2010
• 3

Suppose I should have guessed there would be a diagram on the web. Thanks Mikely

 

[TonyOB]

Hi folks

I'm new on here and would welcome some assistance.

I am in need of a central heating pipe thermostat that will operate at or around 4 to 6 degrees C. I have trawled the web but don't seem to be able to find a supplier and/or a (reasonable) price. Can anyone help?

Yours in anticipation.

TonyOB

 

[stem]

I doubt you will find one that goes as low as that.

2 degrees is too low to offer normal frost protection. Because mechanical pipe thermostats are usually inaccurate to a few degrees, the usual starting point is 10 degrees to make sure that the temperature at the far extremities oe exposed parts of the pipe system are still above freezing.

If you did have a pipe thermostat set at 2 degrees that was located in an area where the ambient air temperature was say 5 degrees that may probably prevent it switching on even if the pipe was approaching 0. At the same time other parts of the pipe system could be dangerously lower.

For future reference, it's best if you start a new thread with a new question, and you would probably get more replies too.

 

[TonyOB]

Hi

Thanks for the prompt reply and the comment regarding starting a new thread.

Your comment seems quite reasonable. Whilst I noted the reference to a lower limit of 10 dgrees, what bit of information I was able to glean from the 'net didn't make sense initially but you have provided a simple enough answer.

Thanks

Tony

 

[Norcon]

Danfoss kp75. Setting range 0 ° - 35 ° .
Or a KP71 setting range -5 ° - 20 °.