Marquee heating dilemma

[louise73]

Hoping for some friendly advice please. We are supplying a marquee for a customer on Christmas day and of course due to the weather they have asked for heaters. Its a small marquee so the normal indirect diesel heaters not feasible in this case. We have a range of 2-3kw heaters and the marquee is very small, only 9m x 3m. However the last couple of times we supplied these heaters there seemed to be issues with fuses blowing etc. Now I have a limited knowledge of electrics, but I thought my sums were correct in that 1 heater 3kw could sufficiently be powered by a 13amp plug so as long as all heaters used were in separate plugs then that would be ok?

is it wise to use RCD's in the socket? I have heard that these can be very sensitive and may cause problems?

Any advice to put my mind to rest that would be great. Thanks

 

[mattmoo1974]

Hire one of those gas fired jobbys they kick out plenty of heat...
Propane Forced Air Heater 131703 BTU Max
something like that..

 

[Cyberprog]

Yes, if you're using them outside then you should be RCD protecting everything - how are you powering the marquee? Generator or House Power?

 

[NMc]

Depending how many heaters you are using you could overload the ring. Any marquee that size is going to take some heating

All equipment used outside needs RCD protection

 

[Cyberprog]

Hire one of those gas fired jobbys they kick out plenty of heat...
Propane Forced Air Heater 131703 BTU Max
something like that..

You're not supposed to use those with people in the areas, as they're directly fired - i.e. the exhaust gases go out into the room. You'll give people a headache and risk carbon monoxide poisoning.

 

[mattmoo1974]

Iv used them for years for stuff like that and never had a headache..
And a marquee isnt the most airtight of things
If you want a cheap way of heating a marquee without rewiring your house, Hire that and a RCD skt..

 

[Engineer54]

Hoping for some friendly advice please. We are supplying a marquee for a customer on Christmas day and of course due to the weather they have asked for heaters. Its a small marquee so the normal indirect diesel heaters not feasible in this case. We have a range of 2-3kw heaters and the marquee is very small, only 9m x 3m. However the last couple of times we supplied these heaters there seemed to be issues with fuses blowing etc. Now I have a limited knowledge of electrics, but I thought my sums were correct in that 1 heater 3kw could sufficiently be powered by a 13amp plug so as long as all heaters used were in separate plugs then that would be ok?

is it wise to use RCD's in the socket? I have heard that these can be very sensitive and may cause problems?

Any advice to put my mind to rest that would be great. Thanks

If using a portable Generator to supply those heaters, make absolutly sure that the generator is equipped with a AVR (automatic voltage regulation) unit!! And if it has a grounding/earthing point USE it!! Those fuses were probably blowing/failing because of the lack of electrical stability on the output of the Generator(s) being used at that function...

 

[Rockingit]

Hi Louise, as someone who's spent his life doing event electrics:

1) I'm guessing that you're coming off from house power for the usual reasons of noise and hassle and budget
2) How much else is running in there - chandeliers, any catering (inside marquee OR house?)
3) Band / stage?

You're right in that 1 x 3kW fan heater = 1 x 13A plug, but you also have to know that there are only so many times that you can plug 3kW into the house circuit before it will trip through overload. It may pay dividends to suggest to your customer that they get a registered sparks in for an hour to ascertain what can be plugged in to where. Also, as others have said, anything that is being used outdoors (and I would include inside a marquee in that) needs to be protected by an RCD. If you're running from the house then the sockets may already be protected (again - refer to a sparks to look), if not then you need to use some rcd plugtop adaptors (as for lawnmowers). BUT - be aware that damp air overnight can cause these to trip out when turned on first thing in the morning which is why if at all possible I'd suggest leaving them on, but in some zero heat state.

Hope this helps, and if you're anywhere near Somerset and get stuck, pm me.

 

[HandySparks]

However the last couple of times we supplied these heaters there seemed to be issues with fuses blowing etc. Now I have a limited knowledge of electrics, but I thought my sums were correct in that 1 heater 3kw could sufficiently be powered by a 13amp plug so as long as all heaters used were in separate plugs then that would be ok?

is it wise to use RCD's in the socket? I have heard that these can be very sensitive and may cause problems?

You're right that a 3kW heater will take about 13A, and so is OK on a normal 13A plug. If you're supplying the 3kW heaters from a typical house then, yes, only use one heater per socket outlet. In addition, don't plug in more than two of these into any single 30A or 32A socket circuit (13A x 3 =39A =overload). Try to get your supply from a circuit that isn't already heavily loaded with other appliances.

If the circuit you're taking the supply from is already protected by a 30mA RCD at the fuse box/consumer unit then you don't need additional plug-in ones, but using them won't cause a problem. If not already protected, then you MUST use them.

If you say where in the country you are, you may be able to get some direct help from someone on here who's local to you.

Edit: Beaten to it by Rockingit!

 

[louise73]

Hi, many thanks for the quick responses from everyone, all very helpful stuff. Just on the RCD's the heaters will be plugged inside the house, we will be running extensions into the marquee, so no damp problems etc. How will I know that the circuit is already protected by RCD?
In the marquee itself there is only 300w coming from the chandelier so no other worries about the power, just the heaters.
If I am reading correct I am guessing I should space the plugging in of these heaters around, ie if there is a double socket, don't necessarily plug both heaters into the two sockets there? Is that right? Its the circuits I really don't understand, ie reply from handysparks on the not plugging in more than two into a 30a socket circuit? I'm a bit lost there....would you need to know how the house was wired up to understand that?
the more you learn the more you realise you don't know!

 

[Richard]

No. You could well have two rooms worth of sockets on the same circuit. If its a 32A ring then you should only be plugging in 2 heaters to each socket circuit.

If your using extention leads make sure you unreel the whole lot as they will melt in no time!!

 

[nick611]

check the fuseboard a modern one will have an rcd [saftey trip fitted] . if the wiring is fairly modern there will be at least an upstairs and downstairs power circuit and hopefully a kitchen power circuit, avoid this one because it will be the most heavily used allready. the house owner will probally have some idea of their cicuits

 

[Rockingit]

Louise - the issue of damp isn't about where the sockets and connections are, it's about the way the actual heaters work. When you turn them on in the morning, they will be physically sucking damp air in one and out the other. Moisture can and does settle on the heating elements inside them, effectively causing enough of a 'short' to trip a sensitive RCD until such time as the damp dries out.

To the sparks - I've seen on more than one occasion a very large professional marquee literally dry out when watching an RCM across the incomers; over-ride the actual trip and watch the numbers slowly fall from sometimes even amps worth of leakage down to 'normal' figures after about an hour - just caused solely by damp air overnight.

 

[HandySparks]

How will I know that the circuit is already protected by RCD?

Generally, any device with a "Test" button will be, or will contain, an RCD. So, if you find a socket with test and reset buttons, it will have an integral RCD. Similarly, if the circuit breaker protecting the relevant house socket circuit has a test button, it will have the additional function of an RCD. If there is a main switch with a test button controlling the whole installation or the relevant part of it, that again will be an RCD. If in doubt, use an additional plug-in one anyway.

If I am reading correct I am guessing I should space the plugging in of these heaters around, ie if there is a double socket, don't necessarily plug both heaters into the two sockets there? Is that right? Its the circuits I really don't understand, ie reply from handysparks on the not plugging in more than two into a 30a socket circuit?

You can plug two heaters into the two outlets of a double socket, but don't plug a third into an adjacent socket unless it's on another circuit.

I'm a bit lost there....would you need to know how the house was wired up to understand that?

To a limited extent, yes you do need to know how the house is wired up. As nick611 says, if the consumer unit is marked up properly with a good description of what each circuit breaker controls, then you might well be able to, for example, plug a couple of heaters into "Garden Sockets" a couple into "Conservatory Power" and a couple more into "Garage Power", if it's a large house with lots of different circuits. Obviously, if there's only "Sockets Upstairs" and "Sockets Downstairs", your choices are a bit more limited.

the more you learn the more you realise you don't know!

So getting in a qualified electrician for an hour or so to advise may be well worth while. (I'm in NE Hampshire, where are you?)

 

[HandySparks]

So getting in a qualified electrician for an hour or so to advise may be well worth while.

Particularly if he will show you what he's looking for in the wiring of the property and explaining why you should (or should not) be taking power from particular locations.