They are essentially just big resistors. They won’t mind a bit of PWMing.
Just make sure you are using an SSR and not a mechanical relay. A mechanical relay will not survive switching very often.
I was under the impression that most Australian houses have circuits with 16A breakers, and some also have 20A circuits (for ovens, driers etc). My house has entirely 20A circuits @ 240V.
I am therefore keen to buy a 3200W element. However, it would be great if they were available in a smaller size since I brew small batches using a 32cm diameter pot.
Standard plug outlets in NZ are rated at 10A (230V nominal). I’m in a rental property and can’t do any rewiring so I’m think of using 2x 2500W elements running off 2 separate plugs.
I’m curious as to how you plan to PWM AC? or do you just mean time proportional output with a short (eg ~1 sec) switching cycle?
I opted for 3200 W because in germany the power circuits are 230V * 16A = 3680W. You could also provide a model with 3 phases. German oven connectors have 3 phases á 230V (16A fuse each phase).
By writing this, I’m thinking about the following option: 3-phase electric power circuits can provide 400V by connecting 2 phases (e.g. L1 + L2) instead of connecting phase an neutral connector (L1 + N = 230V). This would result in potential 6400W power (16A fuses) and would allow me to run HLT an BK with one 6000W element each (HLT: L1+L2, BK: L2+L3). Or am I wrong?
I’m no specialist in this. Does anybody here run their system this way? This would be an interesting option.
My feeling on 3 phase connections is that the elements should be single phase, and have 3 phase into the control panel, with each element on a different leg. afaik, 3 phase elements are really just 3 separate elements in one package.
The plan is to have a relatively slow PWM period of 10 seconds. Then the zero transitions at 50Hz do not really matter.
Yes, they are exactly that. Instead of one 3 phase elements, you could also wire 3 single phase elements into a 3 phase configuration. Each element has one end on live and the other on neutral, but you can switch all 3 at once with a 3 phase SSR.
From the response so far, I think buying 2500W, 3200W and 5000W is the best way forward for me. I’ll also get a sample 3 phase element for testing.
Here is a comparison part from a supplier in the UK. I reckon you could undercut him on price? http://brewbuilder.co.uk/3kw-lwd-elements.html
Here in the UK the choices made by brewers are pretty straightforwards. Most brewers I know use 3kw / 3000w elements, usually immersion ones as below:
https://www.bes.co.uk/products/107a.asp
They are the largest rating that are generally considered safe to use on good quality domestic 13amp fittings. Those with larger volumes using more than one element on seperate circuits. Personally I use those elements but have round blue 16amp ‘commando’ style sockets to ensure safety and durability over time.
Other brewers with smaller volumes or concerns over safety/cost of good qality fittings often use the 2400w ‘kettle’ elements.
Thanks,
Dean.
Thanks for the feedback. I can beat that price, but that element seems to include a housing, which we sell separately.
I don’t think I can beat his price for element + enclosure, but it will be in the same ballpark.
I don’t want to stock 2500, 3000, and 5000W.
3000W is 13A on 230V, which is right on the limit. The elements have a +5%/-10% and the power grid also has +/-6% if I am not mistaken.
I would go for 2500W if your circuits are 13A.
I think with 2500W, 3200W and 5000W I’ll have a good offer.
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5500W @ 220v for use on a 30A circuit
You’re right. But, is it possible to connect a heating element with 400V * 16A by using e.g. L1+L2 instead of L1+N (230V * 16A). This would give me more heating power. Any ideas?
I can fully appreciate your reasons for wanting to go for the 2.5kw element, they are common here even if I see most brewers looking for a 3kw instead. The danger I suppose is that in offering 3.2kw some brewers may be drawn to that one judging it to be close enough!
I know you can’t account for stupid decisions but it might be worthwhile including in your product listing a mention that they should not be used on UK 13A fittings etc.
Dean.
The elements are custom, so I could offer a 2800W too probably. What would you consider the perfect element?
Are there any guide lines anywhere for recommended element power for a given batch size? There are plenty of calculators available to calculate how long it will take to change the temperature of a given volume by a given amount but what sort of time should we be aiming for? Also what sort of power is required to maintain a vigorous rolling boil for a given volume?
I’m doing BIAB (single pot) at this stage so same element for mashing and boiling. Aiming for 30L batches (60L pot).
I think the deciding factor is the temperature ramp that you can achieve.
Heat capacity of water is 4.2 kJ per degree per liter.
So for your 30L, with a 2800W element, you would get:
4.2 kilojoule / (liter * kelvin) * 30 liter / 2800W = 45 s / K
I used kelvin here because with Kelvin you can just copy/paste this into google. But apart from the offset, Kelvin is equal to Celsius.
So 45 seconds per degree.
I think for your mash steps you want to aim for max 1 min/degree, so that a 10 degree step takes max 10 minutes to achieve. With a HERMS setup, you’ll be heating your HLT and your mash tun with 1 element, so you are probably heating double the amount of water.
Keeping a rolling boil is no problem, it is getting there that requires power.
In the end it just comes down to: the max your power circuits can handle. You can always run the element at lower power with PWM.
Okay, new plan:
- 2800W@230V foldback element, 280mm + 240mm, Watt density 11.8 W/cm2 (fits 30 cm kettle)
- 3200W@230V foldback element, 330mm + 290mm, Watt density 11 W/cm2 (fits 35 cm kettle)
- 5000W@230V Ripple element, curvy, Watt density 14 W/cm2 (fits 40 cm kettle)
About 3 phase elements:
Even a 10 kW element would keep the current under 16A per phase. Anyone in the market for really big elements?
8500W to keep it under 13A.
Elco I really would like 3phase heaters. I thought about 6kw in HLT and around 4,5kw in Boil Kettle. Maby its overkill in Hlt but being able to raise temp fast just cut off alot of time during a brewday. Can you calculate how much watt a boil kettle needs to keep a good boil with 60 liters? But even tho less is more then enough then i would prefer lots of watt to raise temp and then PWM it to a good boil.
The domestic mains power supply in Australia is 240V AC, 50Hz. Standard 3-pin earthed power outlets are rated at 10Amps and are usually switched. The 3-flat-pin plug is used in all States of Australia (including its external territories), New Zealand, Papua New Guinea and Solomon Islands.
Most Australian switchboards have provision for 15Amps and 32Amps but require heavier wiring to be run to the GPO and a matching face plate with larger earth pin. Just changing the GPO(PowerPoint) in original setups is dangerous if the wiring is not the right gauge.
Regarding the PWM / 10% comment, in practice (e.g. in your preliminary sous-vide experiment) how many times per minute are the SSRs being switched once you’ve reached a temperature goal? And what is the impact to the rest of the service on the same circuit? For example, assuming the pumps are on the same circuit do they suffer from all that switching or do they basically not feel any effect?
I wouldnt drive pumps and brewpi on same circuit as heating elements, ill driwe those on a seperatly 3phase connection. but in theory there should be plenty overhead, and no problem doing so.