Pipestats

Zapata123

Hi Cardew,
Sorry for the delay to your “ normal operation”, IT trouble!

The output of the pipestat goes to a terminal block pin xyz, to signal demand for boiler and pump. But other signals go to the same pin, such as roomstat demand.
So the roomstat could be signalling no demand, (hot enough), but depending on its setting the pipestat could be signalling demand, so it is affecting normal operation.

Apart from pipestat failure, this is why they can have tamper-proof covers on pipestats I guess

Regards

Londoner_1

Zapata123 wrote: »

Hi Cardew,
Sorry for the delay to your “ normal operation”, IT trouble!

The output of the pipestat goes to a terminal block pin xyz, to signal demand for boiler and pump. But other signals go to the same pin, such as roomstat demand.
So the roomstat could be signalling no demand, (hot enough), but depending on its setting the pipestat could be signalling demand, so it is affecting normal operation.

Apart from pipestat failure, this is why they can have tamper-proof covers on pipestats I guess

Regards

Hi,

I have a old combi WB 240rsf outside in the outbuilding, attached to it is a pipestat and a room frost stat. Pipe state was set to 40c whilst room stat set to 5c.

It was like this when we first moved in.

I did not know how it worked until one cold night i noticed heating was on. Then I researched it and found its there to protect the boiler and pipes, and it would come on for 15 mins until a set temp was reached. I realised during a very cold snap, heating would come on often all night when we are in bed.

I tweaked it, set room frost stat to 1c and pipestat to 15c, it has stayed like this since then and worked through all major cold snaps since 2005.

Gas bills were ok, not really high as i initially feared but will need to replace the boiler as its over 22 years old.

Cardew

Zapata123 wrote: »

Hi Cardew,
Sorry for the delay to your “ normal operation”, IT trouble!

The output of the pipestat goes to a terminal block pin xyz, to signal demand for boiler and pump. But other signals go to the same pin, such as roomstat demand.
So the roomstat could be signalling no demand, (hot enough), but depending on its setting the pipestat could be signalling demand, so it is affecting normal operation.

Apart from pipestat failure, this is why they can have tamper-proof covers on pipestats I guess

Regards

I still don't understand your point..


Your system will always operate normally using the time switch and room stat.


The whole purpose of the froststat/pipestat is to switch on the boiler if the temperatures where they are situated gets too low. That will happen if the 'roomstat is signalling no demand, (hot enough),' or if the roomstat is demanding heat.

How is that affecting normal operation?

Normal operation is for the boiler to operate from the roomstat/timer OR froststat/pipestat.If the froststat/pipestat is controlling the boiler, it doesn't prevent the roomstat from operating.

matelodave

Generally the room stat does not signal that it's satisfied, it just signals a call for heat so the frost stat is in parallel with the room stat and will just override the room stat if the temperature drops too low.

However as it is testing the water temperature rather than the room or ambient temperature it should only kick on for a couple of minutes until the water temp is up to 15 degrees, not the whole house. The normal flow temperature of the boiler when heating is around 60-70 degrees.

It wont inhibit the operation of the room stat which will switch the boiler on and off according to demand.

ianto11

I agree...as Dave says....

And I do feel you're overthinking it.. I have a system with separate CH and HW, if either of the motorised zone valves fail I'm wasting energy....your's however is designed to protect your property, so I'm assuming the stats are adjustable ?
Make the setpoint something you.re comfortable with, and the rest is in the lap of the gods.....:)

If the pipestat fails you'll have a toasty house, and you'll go !!!!!!, and notice ?

regards

AndyPK

Ian. Motorised valves have a switch in them. Only when the valve opens fully, is the boiler and pump commanded on.

ianto11

AndyPK wrote: »

Ian. Motorised valves have a switch in them. Only when the valve opens fully, is the boiler and pump commanded on.

Thanks Andy, I understand the operation of them, but I have had the CH one replaced as it was passing in the closed position.
But as you rightly say, it only heated the radiators when the DHW motorised valve was open

Cardew

matelodave wrote: »

However as it is testing the water temperature rather than the room or ambient temperature it should only kick on for a couple of minutes until the water temp is up to 15 degrees, not the whole house. The normal flow temperature of the boiler when heating is around 60-70 degrees.

It wont inhibit the operation of the room stat which will switch the boiler on and off according to demand.

As the OP states in their first post, the pipestat and froststat are in series.



So as the boiler and froststat are in the garage it is possible, particularly if the OP lives in Siberia;), that the froststat will be the dominant cause of the boiler firing - in theory 24/7.

matelodave

If they are in series then both of them have to call for heat so the one with the lowest set point will be the dominant stat. ie if one is set to 15 and the other to 5 then the heating will only come on when the temperature drops below 5.

The 15 degree one will have been calling for heat when the temp dropped below 15 unless the 15 degree stat is configured in the N/C mode in which case it will override the 5 degree stat and turn the heating off when the temperature is above 15.

ianto11

The drawings on the Worcester Bosch site show the froststat as NO and the pipestat as NC, so < 5deg the froststat completes the circuit, > 15deg return temp, the pipestat opens the circuit