smoke alarm to cut out circuit

[chloebear]

Hi all,
I have a bit of a strange requirement for a client of mine - they have a pump room for their pool circulation equipment and the main pump is on all the time. this pump has a 'built in' thermo-cutout and in the event of a fault with the pump causing overheating it 'should' automatically cut-out and cease to work (in theory) however, my client has already had one of these pumps burst into flames and is now a little concerned that the new pump's cut-out will not function as it should.
I have been asked to fit somekind of smoke/heat alarm in the pump room that will, when it senses heat or smoke, sound the alarm to all other interlinked smokes and also cut the power to the circuit that the pump is on.

any good ideas?????????

 

[Sintra]

How about having an interface put onto the system. Is this a proper FA system with panel etc.?

 

[davesparks]

Use a relay base with an aico alarm and a contactor

 

[chloebear]

so on activation the relay activates the contactor, that bit I understand, but how does the contactor disconnect the circuit that the pump is on??

 

[davesparks]

On activation the relay drops the contactor out so that it operates in a fail safe arrangement

 

[UKMeterman]

You might also want to consider proving an external overload protection for this motor, have a chat with the supplier and see if Thermal Overload Relays | Farnell element14 could help.

 

[ruston]

You might also want to consider proving an external overload protection for this motor, have a chat with the supplier and see if Thermal Overload Relays | Farnell element14 could help.

I'm surprised it hasn't got adequate thermal overload protection to be honest.

 

[UKMeterman]

Some back up won't harm. I do know of one major uk extract fan manufacturer where I had one with a stuck bearing, the abs case had turned brown but no thermal trip. They said they had a batch where the thermal trips don't work. I would also suggest RCD protection, to protect against tracking / motor insulation faults, check the exsisting earth leakage. Is the pump house heated, if not all your kit has to meet pollution degree 3. You may want a shunt trip from the RCD to some monitored contacts.

 

[tazz]

Is this commercial or a private dwelling??

 

[chloebear]

Is this commercial or a private dwelling??

it is a domestic dwelling with pump-house attached to the house. the pump circuit is already on an RCBO.

 

[Des 56]

Use a relay base with an aico alarm and a contactor

The Aico relay bases are excellent products,I use them when I install positive ventilation fans,along with a contactor they would be perfect for his job

 

[tazz]

As above will do the job, but keep the pumps system intact for warranty purposes.

 

[chloebear]

Thanks for all the help with this, however I seem to be having a problem with the wiring up of the circuit with the relay on the smoke alarm & contactor.
could anyone run through the circuit for me??

 

[a1guvner]

Where have you got to so far and what are you stuck on, think of it as a simple switch

 

[chloebear]

has anybody got a diagram of the circuit - brain has gone into fade mode

 

[a1guvner]

If you had your control circuit going into the (c) of your relay base then take n/c to your n/o contactor on a1 then obviously introduce n to a2 then connect your load through the contactor

 

[chloebear]

where the relay from the smoke alarm connects to activate the contactor

 

[chloebear]

so - live into relay (C) - n/c from relay to (A1) of contactor - neutral on (A2) of contactor

so when the smoke alarm is in normal (not alarming) the relay will hold the contactor closed so that the load will be operating through the contactor & when the smoke alarm activates the relay will operate the contactor & cut off the circuit???????????

 

[a1guvner]

so - live into relay (C) - n/c from relay to (A1) of contactor - neutral on (A2) of contactor

so when the smoke alarm is in normal (not alarming) the relay will hold the contactor closed so that the load will be operating through the contactor & when the smoke alarm activates the relay will operate the contactor & cut off the circuit???????????

You got it,
bear in mind where your control circuit is coming from in relation to the power for the smokes

 

[chloebear]

I was going to take the control power from the same circuit as the smoke detector - it is a different circuit to the one supplying the load, unless that is a problem

 

[a1guvner]

From my limited view so far you should be fine

 

[davesparks]

Have you designed this to stay off until it is reset by a deliberate action, or will it switch on again when the smoke alarm deactivates.
It would be a bit daft if when the smoke clears the contactor drops back in again and the machine starts smoking again!

 

[UKMeterman]

Ok,
To be clear you need to be building a power control panel that is completely seperate from the pump controls. The only link between the two is the power to the pumps / pump controls.

To quote EN 61508 you need to be designing a system that is de-engergise to trip. You need a feed from the alarm system that is live when the alarm is NOT sounding. The normaly open contacts, that are held closed by the feed from the alarm system shall be in series with the main contactor coil. You need separate push button to cause the contactor to pull in when the alarm has been cleared. The relay mentioned above is to be wired as per the stop button or guard interlocks as shown on Safety - Protective Measures and Complementary Equipment

It would be useful if you could also have some status indicators on your unit. A typical DOL motor control box with a box with relay to one side may work in this application.

 

[ruston]

Have you designed this to stay off until it is reset by a deliberate action, or will it switch on again when the smoke alarm deactivates.
It would be a bit daft if when the smoke clears the contactor drops back in again and the machine starts smoking again!

And some form of consumer alarm, they are going to love it if it cuts the pump out on a false alarm and they jump into a freezing pool.

PS. they may not hear alarm from plant room.