Two Switched fused spurs for oil boiler and Hive thermostat.

[8bit]

Hi there,

I have just moved into a place with an old oil boiler which was using a Sangamo timer to turn on/off the circulation pump but weirdly not the boiler so you had to manually turn the boiler on and off.
I picked up a cheap hive which i now have up and running and doing the job pretty well. I'm not sure however that I have done the power supply correctly.
The oil boiler says it requires fusing with a 5a fuse but the hive says a 3a fuse so i am switching the boiler via a relay and feeding the hive with a 3a fused switched spur and the boiler with a 5a fused switched spur....Now these two switches have replaced an old single switch metal MEM fuse box which comes off a 6a MCB about a 50cm from the main house fuse board.
Am i able to have two fused switches side by side off one cable straight from the MCB?

Thanks

 

[EFLImpudence]

The oil boiler says it requires fusing with a 5a fuse but the hive says a 3a fuse so i am switching the boiler via a relay and feeding the hive with a 3a fused switched spur and the boiler with a 5a fused switched spur...

Just use one 5A fuse for both items. It will not matter.

There should only be one switch that controls the whole heating system.


Fuses etc. are to protect the cables; not the appliances.

 

[Harry Bloomfield]

Am i able to have two fused switches side by side off one cable straight from the MCB?

Yes, but it would be better, with a single master switch, which isolated the entire boiler system and so marked.

 

[Taylortwocities]

Yes, but it would be better, with a single master switch, which isolated the entire boiler system and so marked.

“Better”? It’s essential. One switch to isolate the whole heating system. That’s the rule. Plumbers are at risk. And we don’t want to lose any of them.…

 

[Harry Bloomfield]

“Better”? It’s essential. One switch to isolate the whole heating system. That’s the rule. Plumbers are at risk. And we don’t want to lose any of them.…

The two switches are co-located, according to the OP, and fed from the adjacent MCB. That would satisfy the need.

 

[8bit]

Yes the mcb is right above and feeds both. Surely any competent person would switch this before any work commences or isn't this considered a master switch?
Would there not be any liability if i fed the hive receiver with a 5a fuse when it clearly says 3a, in this instance is it not protecting the receiver?

 

[EFLImpudence]

Would there not be any liability if i fed the hive receiver with a 5a fuse when it clearly says 3a, in this instance is it not protecting the receiver?

No.

 

[8bit]

Ok, tbh one makes my life easier and i'll still switch the boiler via a relay so no real chance of more than 3a being drawn through the hive receiver.

 

[ericmark]

Well I thought you had been to my house when I started to read. It had one boiler, two pumps, with a plug/socket, and two FCU's.

In fact two diffrent distribution units. Now all from on FCU.

The idea is isolate one device isolates whole circuit. Well since definition of a circuit is all from the same protective device can't be otherwise.

The question is two fold, one does an oil boiler really need a 5 amp fuse, and is Hive really limited to 3 amp, if so simply don't use Hive.

However most oil boilers use the same components and my whole house at moment is using 850 watt, and with boiler off around 350 watt so in real terms it is using around 2 amp with two pumps, so 3 amp should be ample.

Even if a 5 amp fuse is used, 2 amp over Hive rating is unlikely to be a problem.

 

[Harry Bloomfield]

However most oil boilers use the same components and my whole house at moment is using 850 watt, and with boiler off around 350 watt so in real terms it is using around 2 amp with two pumps, so 3 amp should be ample.

Even if a 5 amp fuse is used, 2 amp over Hive rating is unlikely to be a problem.

Starting current???

 

[Taylortwocities]

Starting current???

I have installed several heating systems with multiple pumps and valves. None had a problem with a 3amp protective fuse.

 

[EFLImpudence]

The idea is isolate one device isolates whole circuit. Well since definition of a circuit is all from the same protective device can't be otherwise.

I would say one device (switch) should isolate the whole system.

What happens when the parts of system contain several fuses?


Also:

What about this instruction that no one ever minds ignoring?

 

[8bit]

For your own safety you SHOULD ...but legally not required right?

Where as it also says you MUST install it with a 3a fuse and you're saying a 5a will be fine?

 

[8bit]

By the way i'm not arguing that there shouldn't be a single switch to isolate the system but as i have the MCB just above the system which is clearly marked i was wondering if this was acceptable but it sounds like it isnt.

 

[EFLImpudence]

What bout this common one?

There are no 16A fuses for them.