Overkill for mdf oven?

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Overkill for mdf oven?

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ECV3	ECV3 posted 10 Years Ago HOT Topic Details
Group: Forum Members Posts: 30, Visits: 106	I am about to build an mdf oven, the size will be L1220mm, W610mm, H635mm. I was going to use a 2KW fan heater as i'm aiming for Max Dwell temps of 80 to 85c, but after reading one of Morepower's posts ( Hi Morepower hope you dont mind) and seeing his AMAZING work i understand that a 3KW needs to be on full most of the time to make 85C (not shore how big his oven is) so it looks like my 2kw's out of the window. Can anyone give me advise on will this do or is it OVERKILL for a mdf oven of my size?? 5kw single phase External size H300 W520 D200 Attachments $_3 (1).JPG (920 views, 37.00 KB) $_3 (2).JPG (919 views, 65.00 KB)
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ECV3	ECV3 posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 30, Visits: 106	ChrisR (23/02/2015) It all depends on how much insulation and heat loss you have through the walls, I have 2 ovens, both use a 3kW cooker element with fan (centrifugal type) and PID controllers, one oven is 8ft x 4ft x 4ft external dims and the other is 7ft x 2ft x3ft, I've not got the smaller one up and running yet as I'm in the process of building it but the other one (the larger) will hold 80deg +/-0.5deg all day if you want and the element only runs for 30odd seconds every few minutes even when it's really cold in the workshop! That's with 50mm celotex to ALL faces (top/btm/sides/ends), all edges/corners sealed/packed & taped and the door made with a really good fit. If you intend to run 5kW (as I'm sure you are already aware), the current exceeds the normal UK ring main & socket rating so you need to run a dedicated spur off the consumer unit suitable for the application (it's draw by the time you include the heater elements, fans, relays, PID controllers etc will probably be getting close to 30A @ 230v) with suitable isolation, earthing, etc, best to get an electrician involved as they will calc the draw and install the correct spur, isolator and give you a part p cert for building regulations Hi Chris The box will be pretty much as you describe, 25mm mdf then 50mm celotex/kingspan on the outside ect. Electronics wise i have had powder coat oven builder make a plug and play system if you like or in other words every thing i need electronic wise (ramp/soak, thermocouple, elements and fans, ect ect) all boxed wired and tested so all i have to do is mount the heater/fan unit and thermocouple to my box. If i can use my 2kw fan heater and not the 5kw unit it will save me the expense of the electrician costs for the spur and labour ect. On your oven how and where have you mounted your fan/heater unit ??. I have seen on pics of peoples ovens on this forum that some people have put the entire fan/heater totally inside the box and some people have cut a hole then mounted the fan/heater outside the box mounted flush and sealed ?. Thanks for your advise! Attachments $_3.JPG (701 views, 38.00 KB) Edited 10 Years Ago by ECV3
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ChrisR	ChrisR posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 363, Visits: 3K	I haven't got any photos of it but the fan motor is outside with the spindle going through the side/end, through the insulation into an ally heater box, then using a centrifugal fan rather than you have in your photos. The element position is similar to yours on one and adjacent on the other due to space restraints. I run a tube (ally) into the centre space of the fan to suck air into from an area of the oven, it then gets blown over / out into another part of the oven. I also have 2 speeds on the fan but I only ever use the slower one. Ideally the controller you have should be able to control the temperature ramp rate and have one or two dwell periods, that way you can heat up to say 40deg to get the resin to flow and after say a B stage cure it can be taken up to 80 or whatever you want to use (check the resin datasheets for the ramp and dwell info). Depending on what I am making I tend to either ramp to 80deg at 0.5deg/min or I ramp to 40 @ 1deg/min dwell for an hour then ramp to 80 @ 1deg/min and hold for 8
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