Radio interference when pump switches off

[Andagain1001]

Hi
I've recently noticed that when the pump which pumps water to the boiler from my thermal store switches off I get 1-2 seconds of interference on the radio.
Can anyone tell me if this is anything to worry about or just one of those things. It doesn't actually bother me in terms of annoyance, just wondering if it could mean there is a problem with the pump.

Thanks v much

 

[Agile]

It will mean that the contacts of whatever is switching the pump are arcing.

They will probably fail sometime so its better replaced soon.

The pump is fine!

Tony

 

[Andagain1001]

Thank you for the reply.
The pump is linked to the thermostat on the thermal store, via a box on the wall.
Could you tell me if the arcing contacts will be in the thermostat itself or in the box on the wall?
Many thanks

 

[glasgowgas]

what radio station are you listening to?

i had same problem when daughter was listening to Galaxy.......

permanently fixed to 96.3 Rock Radio now................

so much better

 

[Agile]

I dont know how yours is connected and it could be either.

It needs very careful observation or possibly a test with a scope.

Tony

 

[kevplumb]

question tony

shouldnt there be a cap across the switch terminals ( supressor ) same as some of the baxi gas valves

just a thought btw not trying to have a pop

 

[Agile]

Its not just a capacitor in the Baxi unit. Its 0.1 uF capacitor and 100 ohm resistor in series.

Virtually no other boilers have them because if the stat is in good condition they switch quickly.

However, they are probably more likely to be fitted to prolong the life of the stat as the unit adsorbs the inductive spike when the stat opens.

Unfortunately I dont know how the OPs is configured and it could be either the stat or the relay arcing.

Tony

 

[Andagain1001]

Thanks for the replies,
the latest is that the the pump is no longer switching off once the thermal store is up to temperature...could this mean that the stat/relay has failed or more worryingly a problem with the boiler itself? If I turn the stat temperature down manually the pump does switch off.
Any thoughts greatly appreciated.

 

[Agile]

It does sound as if the stat has failed! That is what I predicted on the 5th October!

They usually make a click as they switch! Do you remember it doing that before?

Tony

 

[Andagain1001]

Thank you, the electrician is coming next week to have a look.
I'm confused because the stat does switch, with the clicking sound, just at a lower temp than before. I guess this could mean that the boiler isn't heating the water to as high a temp as before, something I don't want to think about!
If the stat has failed or is failing, will it still be able to switch but at a lower temp?
Many thanks

 

[Agile]

There are two aspects to a simple thermostat.

There is the mechanical action which is designed to "snap" quickly once it nhas reached the transition temperature. This is both closing and opening so that the rapid close or break causes the least arcing ( mostly a problem when opening.

Then there are the contacts which may or may not have a high resistance if they become burned or are arcing ( often as a result of a failing "snap" action ).

A well designed switch has contacts designed to "wipe" sideways slighty to mechanically clean the contacts every time thye sritch.

The stat also has a built in hysteresis. This is a small difference between the opening and closing temperatures, often about 2-5° on a boiler thermostat, less on a room stat, often about 1° C on a mechanical stat and 1/2 or 1° on an electronic stat, sometimes selectable.

On an older simple boiler the hysteresis is used to create the anti cycling delay.

Tony

 

[Andagain1001]

Hi Tony
Thanks again for the reply.
By 'hysteresis' do you mean the differential?
The stat on the thermal store has a differential of 6 degrees.
Before the problem began the stat would click and turn the pump off at 75 degrees and turn the pump on again at 69 degrees.
Now the pump just stays running unless I manually adjust the store stat and the stat reads from 64 to 70 approx.
What I cannot tell is if the water temp coming from the boiler has actually lowered (i.e. the boiler has a fault) or the stat has a fault and is clicking open and closed at an incorrect temp.

Hope that makes sense.
Many thanks

 

[Agile]

I think that hysteresis is the correct word for a mechnical stat but differential could possibly be used for an electronic stat.

A system may be explicitly designed to exhibit hysteresis, especially in control theory. For example, consider a thermostat that controls a furnace. The furnace is either off or on, with nothing in between. The thermostat is a system; the input is the temperature, and the output is the furnace state. If one wishes to maintain a temperature of 20 °C, then one might set the thermostat to turn the furnace on when the temperature drops below 18 °C, and turn it off when the temperature exceeds 22 °C. This thermostat has hysteresis. If the temperature is 21 °C, then it is not possible to predict whether the furnace is on or off without knowing the history of the temperature.

Tony

 

[Andagain1001]

Hi again
Well the electrician came and tested the pumps and the store thermostat and connections and could find nothing wrong.
He also said that there wouldn't be arcing becuase the current is too low.
I have no idea if this is true or not.
Plumber is next to come and have a look.

A couple of other questions that I am wondering about...
I have an Ideal Classic HE12 boiler which heats the thermal store. Does anyone know if there is a pump over run built into this boiler or not?
If not is it necessary to have one?
The reason I ask is because when the thermal store stat is satisfied it switches the boiler off straight away and sometimes I get what sounds like a ratchet type noise from inside the boiler...
As far as I know there are no valves on my system so could it be a valve in the boiler? Or momentary boiling of water as it stops right next to a still red hot heat exchanger?

Any ideas greatly appreciated.
Thanks

 

[kevplumb]

Does anyone know if there is a pump over run built into this boiler or not?

nothing in the mi's

if it's built in you usually have to wire the pump from the boiler