Hi amazing people,
I'm a sw eng with limited electronics knowledge and need your help and advice. During a (18-hours!!) power outage, my basement flooded due to a sump pump not being activated. The pump, when power returned, caused backflow from the kitchen sink. To prevent future floods, I'm cycling the pump (5 seconds on, 10 seconds off) with an esp-32-controlled relay. That's a simple relay (srd-5vdc-sl-c) but I doubt it can last long considering it's now undergoing 2,500+ daily cycles (tipically the pump runs for ~4s every 35s).
I bought a HiLetgo 2pcs SSR-25DA 25A 250V Solid State Relay but it comes without a snubber circuit, unsure if it suits my sump pump, especially for inductive loads. I'm looking for the right SSR to handle this safely and efficiently.
Any suggestions or advice on setup would be greatly appreciated.
Thanks!
ps: the pump is 1 HP
Edit:
The pump has a float switch that ultimately activates it only if there is water. I use an AC current sensor (SCT013) to check whether it's running for more than 5 seconds at a time, in which case I switch the relay off.
Should be good for your project. No snubber needed as they turn off at the zero crossing point of your AC power, so there is NO inductive load at that point.
However, your operating the pump with no water will shorten the life of any rubber seals in the pump. Water is used as a lubricant for those seals.
I would expect that your pump will be destroyed in about an hour, they are not normal designed for that short of duty cycle. With your pump cycling as much as it is, get some professional help, something is wrong. It could be as simple as the high/low settings are not set properly or something more serious. Where does it discharge to?
You may want to think about a check valve on your kitchen sink drain. I would start with that before messing around with changes to how the pump cycles. Next if your basement is prone to flooding during power outages I would start thinking about a backup generator.
I do agree that the relay, especially those cheap off the boat relays is a poor way to go. They can't begin to handle the loads they claim rated for. Contacts fuse together, your pump runs dry, now you need a new pump so yes, a SSR is a good way to go making sure it's a quality SSR. Also as mentioned with zero crossing you shouldn't need a snubber.
I tried to keep the post short and skipped on many details.
The pump does have a float switch that ultimately activates it only if there is water. I use an AC current sensor (SCT013) to check whether it's running for more than 5 seconds at a time, in which case I switch the relay off.
Normally the float switch is enough, but I plugged this system in to prevent flooding my house in case the power goes out and back on at night or when we are not there.
For the long run I am about to install another pump that I plan on running regularly and that will push the water out in the backyard (using the sewage line is illegal (tell the previous owner). However I still want to keep this pump too as a backup, just to create useful redundancy in case the future main pump will fail at some point. On top of that I had the idea of actually using that water. Anyway I need to pump it, so I would rather prefer to use it for my plants instead of dumping it in the sewer!
That said, I am still somewhat confused on my main question, just because of what I read here and there. Any advice on a specific model of SSR, that would be good for my application?
I ordered a FOTEK SSR-40 DA, that has a snubber integrated and still zero-crossing feature, despite a couple of comments saying that the snubber shouldn't be required.
I played this game. As long as you use a zero crossover SSR you do not need a snubber. Zero Crossover? What that means is the SSR will only turn On or Off when the incoming voltage (sine wave) is crossing through zero volts. This is why there is, as mentioned, nothing to snub.
I eventually went to two pumps in our sump just in case a pump should fail. One pump set just above the other maybe by an inch. Next, just about every house on my short street is a violation as they sump into the sanitary sewer system. We are the highest point on the street. Not unusual for those below us to have raw sewage back up into their basements. I found the storm sewer line and use it.
Whatever scheme you use just do not run a pump dry.
They do market pumps with battery backup. I rely on a generator fully automatic transfer and start. Should that fail I have an old 4 KW Coleman Power Mate gasoline powered generator for emergencies on top of emergencies. Hell, I even have a spare pump out in the garage just in case. Call me paranoid.
Just make sure that your SSR is from a reputable supplier and the current rating of the SSR well exceeds the pump current maximum you can expect to see. I run each pump on a dedicated 20 amp service from my circuit breaker panel.
Those FOTEK relays are cheap for a reason.
I seen a teardown on youtube and the 40A model had a TRIAC rated at only 24A and there was no real thermal connecion to the metal backplate.
I understand you have a float switch so running the pump when dry will not happen
Your goal for running the pump 5 sec on and 10 seconds off is an attempt at "slowing" down the discharge to your drains don't back up. Not sure how well this will work out. You might consider tapping in a valve right near the pump, Open the valve only slightly and direct the valve flow back into the sump. This should in effect "slow" down the flow to you plumbing system.
I disagree with @Paul_KD7HB regarding the snubber. AC motors are inductive, meaning the current lags the voltage. A TRIAC will only turn off when:
There is no more current going into the gate (i.e. the on/off signal is off} AND
They current in the Triac drops to essentially zero.
Because the current lags the voltage, when the current is zero, the triac will turn off but the voltage will have by then increased to some amount. The snubber will reduce any issues caused by not turning off at zero voltage.
Thanks for your reply Ron, and... we can only understand each other, as we have a very similar problem!
I totally feel you on the backup pump, especially after having had my basement flooded, with the water reaching the water heater and turning it off, and going for the furnace - had I not done the 5 seconds ON 10 seconds OFF thing for 45 min straight
Do you also live in Santa Clara CA? we might be neighbors LOL
That said, I think now I have the full setup in mind:
cheap standard magnetic relay to control my current sump pump. I hooked up an SCT013 (AC current sensor) to check for how long it runs
I got a new pump, it's more like a water pump rather than a sump pump (it's both, actually). It's 1/3HP, and definitely way more silent than my current one. This new pump will move the water from the basement to my backyard, so it won't be illegal anymore. I only have a small backyard but it has a raised garden. This is near future work, but I'm excited about it: I'll remove whatever soil is in the raised garden right now, and hide a water tank and a pressure water tank in there. Then I'll cover it and turn it back into a raised garden. The idea is to only use this new pump and actually feed the water to my plants rather than dumping it in the sewer. Especially in hot California, I believe this is great. I basically have a well in my basement, and even if (fortunately) during drought times it's dry, now it's been 2 years that it removes water continuously)
However, I don't want to dig another hole in the ground to fit the new pump, and the old one is in a pretty inconvenient location. So I'll just stick a hose in the existing bucket in the floor (where the current pump is), and with a check valve positioned well on top of the pump hopefully it won't turn dry at any point in time.
And now what's the best part as it took me a while to figure this out: since there's no space for another float switch, I thought of using an ultrasonic distance sensor mounted right on top of the "bucket in the floor" (again, where my current pump is), to reveal the water level. I'll then configure it so the new pump will activate right before the current existing pump would.
I will control this one with the SSR I got, which is rated at 40amp, while the pump will only absorb ~6.5 amp at start (and then less)
I got a 4k-ish W generator today as weather forecast showed floods and strong wind. Thankfully just a false alarm this time
I have one more tiny (probably 1/10HP) pump that you know... can't hurt
I got a 3kW inverter for my Prius. Also here I went way over what's needed (plus if I understand correctly the 12v battery of my 2016 Prius can only draw up to ~1400W from the hybrid motor battery, but anyway... I think it's better to over size as these things are rated way higher than they can actually tolerate
I got an UPS that can serve as a maybe 1h or 2h emergency energy fund. I don't have space for a full sized automatic generator, but hey, that's the next project maybe!
Power outages happen mostly in winter, and usually we are home. But what if we aren't?
8. Arduino will ping a service that sends me a notification when it doesn't for more than 5 minutes (because of either a power or internet outage). Still have to work on that but I checked a few days ago and there are free services like this.
So yeah, again, I totally feel you, and you can call me paranoid too as you can see ahahha
Years ago we had a power loss where the power company predicted a 4 or 5 day outage. We went to your local Home Depot and had to purchase a generator that was bigger than we wanted. Put it in the car and drove home. When we got home the power was on. We still have this generator. It came in very handy a few years ago when we had an ice storm in October, it was murder on the trees.
Thought, is there a reasonable 12V sump pump? You can get a car battery (or better and RV battery). Keep the battery on a very low current "charger" (often called a battery keeper). Solves the outage problem, maybe.
This is getting off topic but... When I met my wife she was providing home healthcare for her mother who had brain surgery for an aneurism which did not go well. When she walked into that hospital it was the last time she walked. Following surgery she was a vegetable. Well as time passed I was seeing more and more medical equipment come into the house including a vent machine and oxygen concentrator on top of all the other stuff. Most had battery backup but after 20 min I would be in the driveway yanking batteries off the trucks.
That began with a trip to my local Lowe's and a 4.0 KW (5.0 KW Surge) Coleman Power Mate generator. That was maybe 30 years ago. Eventually mom passed away but the little Coleman was replaced by a much larger whole house auto start and transfer system. That ran fine for about 10 years and when needed most it failed. Thank God I still had the old Power Mate Coleman. The 13 KW Generac was replaced with a new unit. Went with 16 KW and natural gas fired. I hate cold and dark and NE Ohio winters can be very cold and dark.
That old Coleman is still out in the garage just in case.
As long as you use a zero crossover SSR you do not need a snubber. Zero Crossover? What that means is the SSR will only turn On or Off when the incoming voltage (sine wave) is crossing through zero volts. This is why there is, as mentioned, nothing to snub.
