Building RIMS - electrical question

This might not be the best place for this question, but I'm at a loss of where to go with this. I just put together my temperature regulation unit for the HLT on the RIMS system I'm building. I ran into a snag when testing it. If someone knows a better forum for electrical questions such as this, please help a poor soul out

I put together a PID temp controller and solid state relay to control a 115v water heater element. The PID can run off 110v, so I'm tying it into the same circuit (as the manual suggests).

The initial tests were going just fine - for about 5 minutes - and then my 15amp breaker would pop. After about 5 repeats, I move the unit to a unoccupied 20amp circut and things were going smoothly. Until about 20 minutes in I heard something pop. I'm beginning to suspect that it was the SSR, since it no longer seems to want to carry a load and all other connections are kosher. It'll gen ~110V, but won't carry a load. Happens all the time too - even when there isn't a signal on the DC side.

So, I think I didn't follow the diagram that came with the PID correctly. Maybe somehow I was overloading something with incorrect wiring.

Here's the diagram that came with the PID:



And here's basically what I did. The boxes above the AC line are junction connector blocks:



Did I misunderstand something from the product diagram, or did I just get a bad SSR?

How many watts are you pulling? If you are pulling more than 2000 W on a 110 VAC circuit, it's too much.

The other observation I can make is that your SSR needs a heat sink. I was having problems with mine and I installed a CPU heat sink and integral cooling fan onto the back of it and it seemed to fix the "cutting out" problem I was having.

tnlandsailor help me get mine put together with no problems. Can you give us the wattage of the element you used, and the which pid controler, and scr you are you are using. The more info we have the better we can help you.

PID is a TET-7100, manual is here

The SSR is 8-32v DC on signal side, 32-320V AC 40A on load side - and it did seem to get warm - although I didn't check it when I heard the pop. I'm thinking it just blew out as it isn't wanting to do its job anymore. Oh, and now it doesn't get warm at all.

The element is 120v, 3000W. I have a 240v 4500W if that might be a better replacement for this application.

You say more that 2000W on 120V is too much... makes me curious why someone would even manufacture a 3000W element for 120V...

Thanks for the help.

I don't see why a 2kW element would be a problem if using a 20A-25A circuit. A 3kW would require at least 30A. But then again, I know very little about wiring electric. I would definitely have it on its own circuit, for example if you have a circuit installed for a tablesaw or somesuch.

BeeGee said:

I don't see why a 2kW element would be a problem if using a 20A-25A circuit. A 3kW would require at least 30A. But then again, I know very little about wiring electric. I would definitely have it on its own circuit, for example if you have a circuit installed for a tablesaw or somesuch.

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In my garage, the main outlet (with GFI) is 15A, and the breaker popped (not the GFI) a couple times before I realized I should stop using it.

Then I noticed that the deep freezer was using a 20A breaker. I unplugged the freezer. I used a powerstrip with a 15A breaker on it in between that and my setup. Once again, after about 2-3 minutes, the breaker would trip. That's when I took the powerstrip out of the loop and just plugged direct into the 20A. About 10 minutes later, and no breaker tripping, I think I lost the SSR.

The SSR is rated for 40A - so I would think that the breaker would have popped first - if indeed the amperage were a problem with the SSR. I'll be replacing the SSR, so maybe I should get one with a larger amperage rating?

I'm thinking I might want to replace my main garage breaker with something a little more than 15A. Now that you mention it, that is the circuit I use for the table saw and my metalworking lathe/mill. It pops about every other time I turn on the table saw (granted it is a 50s era Craftsman). About every 3 times with my 12" compound miter saw (brand new). And my house is just a little over a year old... builiders these days... taking shortcuts wherever they can...

I'm still wondering if my translation of the schematic was bad and causing a short/overload somewhere that it shouldn't be...

You probably want a 20A for your tools, and just run one at a time. If your house was wired like mine (a Centex home) then the GFCI in the garage is on the same circuit as the outdoor GFCI's.

BeeGee said:

You probably want a 20A for your tools, and just run one at a time. If your house was wired like mine (a Centex home) then the GFCI in the garage is on the same circuit as the outdoor GFCI's.

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Yep - that's the deal for me too. Found that one out when the contractors building next door blew the circuit while attempting the discreetly "borrow" power from my house...

akula169 said:

Yep - that's the deal for me too. Found that one out when the contractors building next door blew the circuit while attempting the discreetly "borrow" power from my house...

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At least they were discreet! My wife, who works at home, walked out one day to see the crew building the house next door running their wetsaw on our power AND water! Since she's Mexican she was able to give them a proper earfull.

My system is made with a 1440 watt element it pulls 13 amps (Measured with a amp clamp) so if you have 3000 it is going to pull at least double. You also described that it took a bit to trip the breaker. A dead short will trip a breaker instanly, verus a over amp will trip it 20 sec to a few mins based on how many amps over the breaker rating you are. Take a close look at the scr to look for physical damage, if you see none then you should be ok with it. Usally a scr will show physical damage if you hurt it.

hope this helps

I wrote a short article about heat exchanger (HX) design on my website. In it, I discuss the viability of heating HLT water with electricty. Basically, the practical limit on 115VAC is about 2000 Watts. This is equivalent to 6830 BTU/hr, or, less than what you get on an average stove. Unless you are heating a gallon or less, 2000 Watts is pretty puny. If you are using your HLT, you will be trying to heat quite a bit more water than that. That's why most brewers who use the HLT for their HX's use propane instead of electricity. The alternative is a small, stand alone heat exchanger in the 1 gallon range powered by that same 2000 Watts. Read more here:

http://sdcollins.home.mindspring.com/HERMSDesignSpecs.html

jjsscram said:

My system is made with a 1440 watt element it pulls 13 amps (Measured with a amp clamp) so if you have 3000 it is going to pull at least double. You also described that it took a bit to trip the breaker. A dead short will trip a breaker instanly, verus a over amp will trip it 20 sec to a few mins based on how many amps over the breaker rating you are. Take a close look at the scr to look for physical damage, if you see none then you should be ok with it. Usally a scr will show physical damage if you hurt it.

hope this helps

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If by 'scr' you mean my solid state relay, I see no physical damage. But, it is not operating as it would be expected to right now.

After discussing the situation at length with the guy at my local electronics supply distro, he seems to think that the SSR was faulty. Being rated at 40W, it just doesn't make sense that with my setup it would burn out in normal operation if there wasn't something wrong with the component.

The other problem is that I don't want to drop another $35 to gamble with burning out another SSR.

tnlandsailor said:

I wrote a short article about heat exchanger (HX) design on my website. In it, I discuss the viability of heating HLT water with electricty. Basically, the practical limit on 115VAC is about 2000 Watts.

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Great article, btw.

So, leads me back to an earlier question: if anything over 2kW is impractical on 115VAC, why do I have a 3kW 125VAC heater element? I'm probably looking at a 30Amp load at the moment. Or is the 125VAC rating the answer to my question?

I guess Ohm might have the answer too: 3000W / 120V = 25A

My original intention was to avoid getting another 220VAC circuit installed in the garage. Knowing that it might take forever and a day to get 10+ gallons of water heated to a strike temp on 110VAC, I was thinking about getting it up to temp on propane and moving over to AC to control the temp throughout the mash.

Is it looking like I should just bite the bullet and get a 220 circuit installed? I also have two other heating elements (240VAC 4500W) that I could use. At that point I might as well just move off the propane over to full electric...

Im confused on your SSR ratings Akula... the power side is rated at 40W ?? Seeing how it didn't just burn up, I would think that this is the power dissipation of the SSR when at max rated load. Is there a current rating on the power side as well? This componenet should have some rating similar to your load. It should either state a load current or a power rating at least equal to your heater element.If this is indeed the max power carrying capacity then its a gone'r and is probably shorted. I have seen many modes of failure of components such as this. Sometimes these will short and not burn up but with the current your heating element is drawing and the size of this SSR (if this is in fact the max load capacity) I would be suprised that it did not 'leak the magic smoke out'.

Clarify the ratings on the SSR and I could be of more help. The wiring according to your schematic is correct.

Please put all the spec from side of the ssr. I also looked at the manual for the controler, It show it also has a relay contact. It may be possable to use that contact to run a coil of a second relay size for your applcation. It is possable to run a 30a curcuit on a plug but not a standard 15 or 20 amp. Most hot water heater that would use a element of that size or problem going to be hard wired.

I am an extract brewer considering all-grain. I see you guys are talking about heating elements, do you brew indoors? I have the perfect basement (mini science lab) for brewing but no ventilation which is why I brew outdoors and then carry the brew kettle downstairs (which sucks). Can I safely brew indoors? electric?

DyerNeedOfBeer said:

Im confused on your SSR ratings Akula... the power side is rated at 40W ??

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Ok, so maybe I wasn't exactly clear on the nomenclature - the LOAD side is rated 32-330VAC, 40Amps. The signal side (if that is power) is 3-32 VDC - there is no amperage rating on that side...

ok, if its rated at that amperage, it should do but as TNlandsailor suggested, perhaps a heat sink on the component would have saved it. If you are spending that much on an SSR, perhaps you should take the advice of jjsscram and use a relay driven by the output of the PID controller. This would be a much cheaper avenue and you can certainly tell if they are working or not. No guessing as is the case with the SSR (unless you have the test equipment to check the SSR).

http://www.radioshack.com/product/index.jsp?productId=2062477&cp=2032058.2032230.2032277&parentPage=family

this is 30a load rating with a 12v dc coil

akula169 said:

So, leads me back to an earlier question: if anything over 2kW is impractical on 115VAC, why do I have a 3kW 125VAC heater element?

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To answer this question - perhaps this element was not meant for regular household usage?

When I said anything over 2 kW was impractical, what I meant was that it would take special wiring or a special circuit to handle the current load. One of my specs for the HERMIT was that it needed to be portable. That meant a standard 20 A circuit that is in most garages or outdoor circuits. By limiting myself to 2 kW, I designed the rest of the system around that.

As I mentioned previously and in the article, you're going to need at least 5 digit wattage to even come close to heating 8 - 12 gallons of water with electricity quick enough so that a HERMS type set-up will work like you want it to. That is my completely biased opinion, I'm sure someone out there has a system like you describe who swears by it, but I'm just saying you stand a much greater chance of success if you keep the basic principles I outlined in the article in mind when you design.

Propane kicks ass - huge outputs are possible with minimal equipment, but it's hard to control automatically. I've seen systems with electronically controlled gas valves, but that was more than I wanted to deal with. Electricity is easy to control, but outputs are puny compared to propane. That means if you want to take advantage of electricity, you will need a small, efficient, heat exchanger. Personally, I think this is the easiest, cheapest, and simplest way to go (again, totally biased). I'm not an electrical guy. My advice here is on overall design. Even if you get your 3 kW element to work, I think you are going to be disappointed in the performance of your system