Relay instead of contactor.......

[bigspark17]

hi i need a relay instead of a contactor for a large room with two electric ufh mats, relay will be quieter than a noisey contactor, need 16amp 2or 4pole 230v,
Where do youguys/gals buy yours?

 

[SparkyChick]

Something like that, I'd probably start with RS (rswww.com).

 

[mickfred]

Rs ,farnell or ebay

 

[sam400]

This could be a can of worms but I’d say you need a contactor not a relay!

 

[Bobster]

Get a solid state contactor. They're silent.

 

[PJElectricalSW]

Finder do silent (ish) contractors rated at 25A. We run them on our heating systems after customers complained the Tele ones were buzzing and clunked.

Edit. Damn auto spell tat, silent contractors are hard to find, I meant contactor.

 

[Spoon]

As @sam400 says, you might be hard pushed to get a relay, that doesn't have pins for connections.

Here is a contactor from RS
Here is a relay from CPC.

 

[freddo]

These are nice, 240V coil 2 pole relay heavy 30A mains rated contacts. They still click a bit though.

Solid state is silent, but if they fail they generally fail stuck on.

 

[Deuce]

Resistive loads and contactor vs relay debates... I find speaking to many sparks and automation engineers, that the sparks lean towards contactors, yet the automation engineers seem happy for relatively low loads to use relays.

I suspect this is because modern relays are very capable and in the field prove remarkably reliable. They probably do give up before contactors but the benefits of size, quietness and low cost probably more than compensate. And of course, a contactor is just another type (category perhaps) of relay. They were developed when contact materials were less advanced and understood and it was a simple solution to simply have a larger, stronger contact area and breaking spring than in an equivalent standard relay of the time. But who's to say if some modern relays can't out perform a 20 year old contactor design now?

We use relays to control special FX work for live TV we sometimes put two NO relays in parallel, so that should one fail we still get an energised circuit on cue. We back that up with a kill switch in case we need to de-energise the circuit in the event that a relay sticks. We do this for obvious reasons, we have to know that when we hit the go switch, things will happen. But the truth is, over literally thousands of activations not one relay has failed yet. We smashed one to pieces once to see what was happening inside and you could see some darkening around the contacts, but it was very slight.

I should add that we do use flyback diode's, so the relay is fairly well protected during it's duty cycle.

Just offering the above as input based on what we have experienced. Perhaps one solution would be to split the cold tails from the UFH into 2 circuits, and place each on a suitable rated relay - then switch both those relays using a third, itself switched from the stat? Or switched directly from the stat if more convenient. This would also avoid a complete heating failure if one relay did give up. I feel that it's not necessary to use a large, noisy contractor when you're actually switching multiple UFH circuits (as in laid circuits of heat mats) at once anyway, why not just split the load into separate relays and enjoy a quiet life with built in redundancy?

 

[LeeH]

SSRs require a method of disconnection upstream....such as a contactor.

DC contactors for reasons unknown to me are much quieter. They seem to pull in softer. Well, the Schneider ones do anyhow.

 

[Lucien Nunes]

DC contactors have always been quieter and better mechanically - they just pull in and stay in. An AC contactor effectively pulls in and lets go every half-cycle of the mains, i.e. 100 times per second. There is a tendency to chatter as the contacts close and vibration all the time the coil is energised. To minimise the effect and prevent the magnetic force falling to zero each time, part of the pole face of the laminated steel core has a copper shading ring that shifts the phase of the magnetic flux in that part, so that some part of the core is always attracting the armature.

Or you could do what some organ blower makers did with their starters. So that there was no audible clunk in the middle of the sermon when the organist started the blower for the next hymn, the whole starter was suspended on springs inside a hush box lined with rockwool. They often used rectified coil supplies too.

 

[freddo]

Or you could do what some organ blower makers did with their starters. So that there was no audible clunk in the middle of the sermon when the organist started the blower for the next hymn, the whole starter was suspended on springs inside a hush box lined with rockwool.

That would be one of these: