Ski Builders Forum

My electronics knowledge is fairly poor, but want to see if I'm right here.

I'm using 240V supply with 2x 2000W heat blankets. 2000W/240V = 8.3A each, right?

This means on a standard household 10A plug, I'll need two leads to my mains power to run it?

There are also 2x Auber PID controllers and the SSR, whose power usage are negligible, so I haven't bothered to count them. Running them off the same power as one of the blankets should be fine, I think.

If I use a single 10A plug, will it overheat the line/blow a fuse in the house trying to draw too much power, or will it simply heat up slower?

If your going to use two plugs, be sure to keep the circuts seperated, using two plugs to get power to your unit then just tying them together isnt smart. if one plug fails or gets weak, all the current will try to flow though the other plug.

Id reccomend just using one large plug rated for atleast 1.5x what you plan on using it for.

We have our power come into a small single outlet box with an electric stove/dryer style recpitcal on it and wired up the appropriate plug into some heavy gauge insulated wire that goes into our control box with our PID and ssr's etc. Ours is rated for 50amps, and i belive we are only using 20 peak. Large margin of safty and it only cost around 30 to do properly.

-Jacob

Alex13 wrote:My electronics knowledge is fairly poor, but want to see if I'm right here.

I'm using 240V supply with 2x 2000W heat blankets. 2000W/240V = 8.3A each, right?

This means on a standard household 10A plug, I'll need two leads to my mains power to run it?

There are also 2x Auber PID controllers and the SSR, whose power usage are negligible, so I haven't bothered to count them. Running them off the same power as one of the blankets should be fine, I think.

If I use a single 10A plug, will it overheat the line/blow a fuse in the house trying to draw too much power, or will it simply heat up slower?

I don't think a 220/240v 10A circuit exists. Are you confusing 120 and 220?

I'm in Australia. I could be wrong, but I'm fairly sure our normal mains plugs are 10A 240V.

I need to run both heaters from the one SSR, is there a way to do this and still keep the circuits separated?

-edit- I was trying to avoid modifying the house to accept the heaters, but I may need to put in a 20A wall plug. This would give me ~4800W max which is a FOS of around 20%.

Alex13 wrote:I'm in Australia. I could be wrong, but I'm fairly sure our normal mains plugs are 10A 240V.

ahhh. In the US normal home plugs are 120v single phase 15A.

Alex13 wrote:I need to run both heaters from the one SSR, is there a way to do this and still keep the circuits separated?

Using 1 PID or 1 SSR? Using 1 PID sin;t ideal, becasue each blanket will perform differently in your press, and may need to be controlled differently. You could wire the single PID to control 2 SSRs, and each SSR would be fed by its own branch.

Not sure how you are looking at things, but odds are if you see 2 outlets in 1 room they are on the same breaker. So if you only have 10A available, and you plug 2 9A devices in, you might trip the breaker....

I'm doing it the same way Head Monkey is doing it. Two PID's, one ramp/soak to control both blankets with the thermocouple on the bottom blanket, one PID monitoring the temp of the top blanket through a separate PID.

If I notice consistent temp differences between the two I'll replace the second PID with another ramp/soak controller and second SSR to control the top blanket separately.

I've checked the mains wiring going in to the switch in the shed, it's 12awg which is rated to 20A. It's on a 16A breaker, but I'll replace that with a 20A breaker.

My theory is as long as I wire up the plug from the controller side with 20A wiring, and don't use the second outlet, I should only need the one plug.

The power is 10A 240V here.
Increasing the breaker to 20A will work by the sound of it but is not the safest thing to do. You're right I think that you can draw 20A from a household circuit and the major concern is the wire melting if you pull too many amps. Ideally you would have 20A power and then you could draw all the power through one plug.
The plugs themselves here are rated at 10A so trying to draw 16A through one plug technically may cause melting (whether it actually would I don't know).
One other solution is running an extension cord from somewhere else in the house for supply to one of the blankets. Generally your house has more than one PowerPoint circuit and each circuit is rated to 10A. So if you plug the separate 10A plugs into different circuits then you should be able to pull 8.3A from each of them.

One problem I forsee is how you are going to run a double power supply through one ssr. I reckon a good and cheap solution might be to get a second ssr and run two sets of wires from your pid output. One set to each ssr and then a separate power supply through each ssr to the blanket. I reckon this might be the safest

I think headmonkey can draw the 16A from one circuit. Therefore he just runs the live wire of this circuit through the ssr then splits the power To each blanket after the ssr. Therefore each blanket is on a parallel circuit and can draw it's full amperage.
For your setup you would need to run the live wire from each power supply to the input side of the ssr. I don't know if doing this allows the blankets to draw 8A from each supply or whether the total available is still only 10A.
I think the two Ssrs with common pid is the way to go. The only doubling up then is the small volt/amp dc pulse to the ssr and each blanket is isolated.

I've checked the mains wiring going in to the switch in the shed, it's 12awg which is rated to 20A. It's on a 16A breaker, but I'll replace that with a 20A breaker.

That's essentially what head monkey has done. It should work. You are just making the choice to draw 16A through a socket that "officially" should only supply 10 and through a plug rated to 10A also. That's the risk I guess.


My theory is as long as I wire up the plug from the controller side with 20A wiring, and don't use the second outlet, I should only need the one plug.[/quote]

2*2000W! Sounds more like melting the skis!...
Just kidding.
Take it easy with the fusing. You don't want a wire fire!

No workshop - no skis!

I spoke to an electrician about putting in a 20A power point in the shed. He said I'd be better off using a 10A or a 15A power point to save money, as the only difference in the points themselves is a larger earth so you can't plug a 15/20A chord into a 10A socket. As long as the wires going to them are safe to supply 20A then it's fine.

I figure theres a factor of safety already put in to the rating system of the wires themselves, so it should be right.

I think you're right.
I've seen a mate cut the 15A plug off a welder and put a 10A one on and it worked fine.

Hahaha. Sounds like a lot of work, we just used the angle grinder to grind the earth down so the 15A plug fit in a 10A socket :P

I'm planning on running two blankets as well but through a 220V socket. I've seen that a few people have run one SSR (two PIDs) with two blankets. Do you guys only have one thermocouple with that set up?

My initial thought had been to run a thermocouple top and bottom and two PIDs, that way if there is a difference in temp. between top and bottom only one blanket would need to switch on to correct the error. I believe this set up would require two SSRs but I'm unsure. Does that setup make any sense or should I just stick with one TC, PID, and SSR and have both blankets turn on if temp is low on the side of the board the TC is on? Any insight would be appreciated.

I'm planning on running two blankets as well but through a 220V socket. I've seen that a few people have run one SSR (two PIDs) with two blankets. Do you guys only have one thermocouple with that set up?

My initial thought had been to run a thermocouple top and bottom and two PIDs, that way if there is a difference in temp. between top and bottom only one blanket would need to switch on to correct the error. I believe this set up would require two SSRs but I'm unsure. Does that setup make any sense or should I just stick with one TC, PID, and SSR and have both blankets turn on if temp is low on the side of the board the TC is on? Any insight would be appreciated.

If you are using two actual PIDs then you get independent control of each blanket which is ideal. You will need 2 SSRs to do this and also to make it worthwhile need a thermocouple monitoring each blanket. This will be the most expensive, but will give best results.
What others have done is not to have 2 PIDs, but to have a PID and a temperature display eg. head monkey (Nb. you can actually use a PID for its temperature display function alone). They have a TC monitoring each blanket, but only one is used to regulate the control of heat. With this setup both blankets are fed the same amount of electricity through one SSR. You get a read out of temperature for both thermocouples that shows if there is a big discrepancy between top and bottom heat.