Build a low cost semi-automatic generator transfer switch.

[Naam]

i wish Crossy was my neighbour and liked Portwine

[Crossy]

I like port Naam, sadly I'm not you neighbour

Anyway, the bump reminded me that I was going to update when my pukka generator controller arrived.

I bought one of these http://www.ebay.co.uk/itm/New-Generator-Controller-GTR-17-Auto-Start-Stop-Function-/221390800443?pt=LH_DefaultDomain_0&hash=item338beb863b

As well as the controller you will need:-

• 3 off 12V car relays with change-over contacts
• A 12V 1.2Ah sealed lead acid battery
• A 12V 1A switching power supply (or a linear PSU) needs to be adjustable to about 14V.
• A 1N400x 1A rectifier diode
• A box to put it all in

Assorted crimps, wire connector blocks etc.

The manual for the controller is here http://www.monicon.com.tw/03products/PDF/GTR%201X/SG17V08E.pdf

This is the circuit

I also bought one of these http://www.ebay.co.uk/itm/Digital-AC-100-300V-50A-Blue-LCD-Amp-Volt-Ammeter-voltage-Panel-Meter-gauges-/231046353676?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item35cb6f930c

To monitor the genset output during operation.

Some photos of the completed unit including the settings of the DIP switches on the controller.

As shown in the diagram it works with the modified genset shown earlier in this thread.

[Crossy]

The transfer switch has also seen an update with one of these http://www.ebay.co.uk/itm/Adjustable-Over-Under-Voltage-Protective-Relay-/221381033800?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item338b567f48

I was finding that just using the timer relay meant that if the mains was on, but at a really low voltage the timer didn't drop out so the genset didn't start. This device makes the on / off limits predictable.

I also replaced the timer with a regular relay (same pin out) mainly because I 'borrowed' the timer for something else.

This is the current arrangement

The leftmost breaker is our 50A incomer which goes via the Amp/Volt meter to feed the three breakers in the middle. First 40A feeds the aircon and water heaters (not genset backed up), the 16A in the middle feeds the transfer switch (doesn't need to be 16A, 5A would be more than adequate, I'll get around to changing it one day), the final 40A breaker goes to the big 80A relay which is the generator transfer. The lamp is across the genset output to show it's running (if I need to look I've gone deaf).

[getout]

Great posts on building an ATS/Genset. I am trying to logically understand the processes and I'm having some trouble. My simple understanding of the process is this:

ATS handles the fail over (switching) between the supply of mains power or geni power available to the load by way of a big relay or expensive contactors.

The genset handles starting and stopping the generator engine in conjunction with the ATS by way of closing the circuit to the starter motor to start and by earthing out the magneto once the engine is running to stop it.

Q1. Can you please explain (again..) where the communication between the ATS and the Genset comes from and how it functions? I can see the "Control J?" wires in you "Simple Circuit" diagram of the ATS, I'm guessing that this is what communicates with the Genset to start the generators engine but I'm not sure.

Cheers

[Crossy]

Getout, you've pretty much got it.

The diagram shows the ATS in the 'mains off, waiting for genset' position, in this state J? pins 1 and 3 are connected via the timer contacts.

At the genset connecting the ATS terminals will start the engine, so with J? 1 and 3 connected to the ATS terminals in this condition the genset will start.

When the mains returns, the timer times out and J? 1 and 3 are no longer connected together, thus the ATS terminals are also not connected and the engine stops.

[getout]

Thanks for your promt reply! So there is no signal as such being sent to the Genset? Is K2 a relay that, when there is no power energizing its coil (mains failed) closes a circuit that is wired between the generator's battery and starter motor??....

If the relay closed this circuit between the starter motor and the battery wouldn't the starter motor just keep running? Doesn't that circuit need to be closed until the engine fires and then opened again? Ah....is that done whne the geni produces power back to the ATS?............

If so then when mains comes back on does the K2 relay switch the connection the third Control wire.........to earth out the magneto to stop it?

Also in your example of using the GTR 17 Genset you give it its own power source and battery in its construction. Why does it need a psu and battery, couldn't it get any power it needs from the battery located with the generator?

Thanks again for your time I really appreciate it.

[yankee99]

BTW been using that eBay relay for several months with no issues.

[getout]

Hi Yankee99,

Does the relay that you have used in place of an ATS have only on common input as I have seen on most relays? How does this do the job of switching the input from one source to another?

[yankee99]

I didnt exactly go on the budget the op did. I used this relay with a 12v coil from a chinese vendor http://www.ebay.co.uk/itm/350684868742?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I used a deep sea electronics controller from aliexpress or ebay cant remember.

[Crossy]

The relays that both myself and Yankee have used are 80A with two change-over contacts. You switch both live and neutral, the diagram in post 3 shows how it's connected (K3).

It's important to realise that the connection to J? changes if we are using a full-auto genset as opposed to simply stopping a unit without electric start.

a. To implement stop only you just need the ATS described in Post 3, connect the magneto 'stop' wire to J? pin 2 and genset ground to J? pin 3.

b. For full auto all the generator control is handled by a genset controller, either the simple 555 based unit in post 26 or the more complex GTR-17 based design in post 33. Both these require a relay contact in the ATS, closed to run, open to stop. This would be provided by J? pins 1 and 2. There are only two control wires between the genset controller and the ATS.

The genset controller determines the time that the starter operates, the 555 based unit runs the starter for 5 seconds or so, if the engine starts before that time the Starter Inhibit relay (see post 26) will disconnect the starter. The GTR-17 has it's own internal arrangements to determine that the engine has started and doesn't need the Starter Inhibit (but it does no harm).

As to why the separate power source. The GTR-17 does consume power when the genset is not running, so the battery would be discharged if no float charging was arranged, hence the power supply. The separate battery isn't really needed as the GTR-17 does have cranking protection (so it doesn't die when the battery voltage is low during engine start) but I included it as a belt and braces approach (and I happened to have the battery in stock).

[getout]

Ok so with my rudimentary understanding of what I'm doing I have crafted an even more rudimentary diagram of a system I think might work. I found a device that is relatively cheap that can do the job of the ATS (I feel much better using something like this than making it myself.)

http://www.electusdistribution.com.au/productView.asp?ID=11768&CATID=Search%20all%20Categories&keywords=rich+electric&SPECIAL=&form=KEYWORD&SUBCATID=

To enable my geni to stop and start when needed I have built on what Crossy has shown me with regards to using relays, although from what I've read Contactors might be better if I'm dealing with 240v coil inputs .In my diagram the Invertek ATS-20 has mains power, the geni power and the output load all connected.

On the geni I have the key start which if left in the centre does nothing, if turned clockwise starts the engine (then springs back to centre) and if turned anticlockwise stops the geni by earthing out the magneto. Just like Crossy mentioned I think I can use some relays to close and open the circuits to the starter motor and the earthing out of the magneto to get the desired result.

In my diagram you can see one of the relays has its input connected to the Mains power. The Normally Closed connections of this relay are used between the starter motor and the battery positive. The Normally Open connections of this relay are used between the magneto and earth. So if the mains has 240v power flowing through the relay's input coil then the starter motor circuit will be open and the magneto circuit will be closed (earthing out the magneto). If the 240v power from the mains fails then the magneto circuit will be open and the starter motor will be closed. This will engage the starter motor to start the engine but I need another relay to disengage the starter motor and let the engine run on the magneto.

The second relay has its input connected to the generator power. The Normally Closed connections on this relay are used to disable the starter motor circuit once the geni starts producing power. Once the Geni engine starts up and the generator starts producing power the relay then opens the circuit to the starter motor releasing it from the flywheel.

This seem like a fairly safe design for my purposes. Firstly I have the Invertek doing the isolation of the power feed. Even if I start the geni when the mains is on it shouldn't do anything. Secondly I will be using this setup for a server rack which already has a large UPS that can supply enough power for around 30 minutes so cut over time or issues with existing load during geni startup isn't an issue (the UPS will simply be plugged into the wall outlet in my diagram).

From what I can understand I might need some way of limiting and/or repeating the engagement of the starter motor. Say the fuel tank was empty, the starter motor would never disengage as no power has started to flow out of the geni to the second relay. This wouldn't be as much of an issue if there was a way to have, say, 10 second intervals of engaging the starter, even if it ran the battery dead it's not as bad as continually running the starter until the battery died.

Please let me know where my mistakes are and what else I should consider.

http://postimg.org/image/m9n2sry7t/

[Crossy]

A couple of comments, more later when I'm home from work.

1. That ATS does not appear to have a generator control output, it would be far easier to get a unit intended to connect to a remote start/stop genset than to try and cobble together something.

2. How do you intend disconnecting the starter motor once the genset starts (EDIT or to prevent the battery running down if it doesn't)? I've used a 555 timer in my simplest controller.

EDIT For your ATS one of these http://www.ebay.co.uk/itm/Automatic-Transfer-Switch-control-module-Build-your-own-change-over-panel-/251603839784?pt=UK_BOI_Industrial_Tools_Generators_ET&hash=item3a94c1eb28 and a 220V 80A relay like I've used will do the job. Modifying the application diagram in the manual to work with a relay rather than contactors is not rocket science.

EDIT2 My experience with trying to use relays as main-failure sensing wasn't good. It works fine if the mains fails 100%, but the relay will stay energised when the supply is down below 120V but not actually off (at which point you would want the genny to be running). I had to use a proper under/over voltage switch to make things function reliably.

[getout]

Hi Cossy and thanks for the reply,

"1. That ATS does not appear to have a generator control output, it would be far easier to get a unit intended to connect to a remote start/stop genset than to try and cobble together something."

That's correct it doesn't have any other power output other than the final load output. This ATS is designed for use with a related inverter product. It has some ports on the front that connect to an inverter in the same product line. This is the best priced ATS that I have seen @ AUD$199. I just thought it might be piece of mind using an existing ATS than make my own.

It also struck me that with my current design I might be able to use some of the power indicators on the front of this ATS to run the relays instead of using the actual 240v feed. I would then only require small automotive relays. I have not seen inside this ATS so maybe it can't be done but it seems like a better solution to me if possible.

"2. How do you intend disconnecting the starter motor once the genset starts (EDIT or to prevent the battery running down if it doesn't)? I've used a 555 timer in my simplest controller."

In my diagram (with next to no experience doing this - so let me know if I'm way off) I have the second relay's input connected to the 240v feed from the geni and the output connections that are Normally Closed are wired into the circuit which the first relay uses to engage the starter motor on mains failure. E.g. when the mains fails the Normally Close outputs of the first relay engage the starter motor. Provided there aren't any problems with startup the generator starts supplying 240v to the second input of the ATS and this is where the second relay with its inputs connected to the geni 240v feed gets energized and then opens the connections which are intersecting the circuit between the first relay and the starter motor

One catch that I can see, as you said is if there is an issue on starting the geni. There may need to be some sort of "retry" or intermittent attempts to deal with that but I'm not sure if it can be done.

In regards to power dips, I have a big APC 5000 watt UPS sitting in the bottom of the rack which pretty much is designed to smooth out most hiccoughs in the power supply. So there is some leeway available in this design.

I have no idea if I'm completely wrong with my assumptions in my design so please let me know if what I just said is fundamentally flawed.

Cheers.

[yankee99]

I used this one

http://www.ebay.com/itm/DEEPSEA-Generator-Auto-Start-Control-panel-DSE710-/301182695261?pt=LH_DefaultDomain_0&hash=item461fe3375d

It does about everything at a low cost using the relay Crossy linked.

[Crossy]

When designing a control system like this it's very important to design for how the system will fail as well as for how it will work. You must protect your genset at all costs. What happens if the 220V output does not come up (breaker open perhaps)? Would you keep the key turned on your car once the engine starts, let alone drive into town like that? How about if the fuel tank is empty?

Also, I'm not certain that the ATS being proposed by getout is going to do the job. Yes, one could use the indicators to send a 'start' signal to the genset, but you're not going to be using an automotive relay. Those indicators will be supplied from a 5V logic output via a limiting resistor, an ultra-low power relay (probably a reed relay) will be needed in order to avoid frying the LED driver output. Also, exactly how does that ATS handle the aux input, how long will it wait for that input to come up?

By the time you've done the modifications and added relays it could be just a simple to build a transfer switch, if you're not confident to design it (or build my design) use a unit like the DeepSea one Yankee is suggesting which will work by adding just one relay (others like it at lower cost).

[getout]

Hi Crossy,

I have taken more time to study your diagrams (and electronic fundamentals in general!) and now feel much more confident using the GTR 17 and all of the other components you suggest for making this system from scratch.

I see more clearly now how the timer relay will switch connectors and energize the coil on one of the three relays (labelled ATS) which are used in conjunction with the GTR 17. This relay (labelled ATS) will close the circuit that will connect to No 12 on the GTR. I presume this is providing the internal microcontroller of the GTR with an earth at the No 12 connection, since the GTR has power supplied at connection No 1 the No 12 earth completes a circuit in the microcontroller and tells the GTR that the ATS says "mains fail" which in turn prompts the GTR to internally close a circuit to energize the relay labelled "Start" and have that relay close the circuit to the starter motor.

Side-Note: The ignition circuit used with the relay labelled "Ing" I assume will be opened on mains fail? The term ignition confused me at first as I was thinking of "creating" ignition but am I correct in thinking that this is actually the "removal" of ignition from the geni so as the shut it down? If this is the case then as I mentioned above about the internal microcontroller of the GTR closing a circuit to energize the relay labelled "Start" during mains failure the microcontroller should also energize the relay labelled "Ign" to open the circuit which was earthing out the magneto.

Q1. How "smart" have you found the GTR in your configuration? If there is a problem with starting the geni will it attempt a second time etc?

Q1. Is the output sensing circuit connected to No 12 & 13 on the GTR directly connected to the full output of the geni? Not a reduced voltage but the full 240v? If so where on your generator would you suggest to get the power from (if you were installing the GTR directly on the geni not in a wall cabinet)?

Q2. In your design you have provided the GTR 17 with its own battery and charger. I was planning on connecting my generator's battery to a charger to keep it constantly topped up. I presume there is no foreseeable problem in using this existing battery with the GTR 17?

Q3. How reliable is the 80amp 240v relay in your opinion? Would replacing it annually make a more reliable system or is it a matter of the initial build quality (or quality control) of the relay that's the concern. Have you used other brands that you feel are more reliable?

It has been such an interesting process to learn all about how these things work, especially with a real-world requirement as I have in this case. It's like all the pieces start to come together and you can see more clearly what is actually going on ("Once I was blind but now I can see"!).

Thank you again for your time I appreciate your sharing your knowledge and expertise.

[Crossy]

Download the GTR manual from the link I provided in Post 33, it tells you much of what you need to know.

Q1. There's quite a bit on the net regarding the GTR family of controllers, with the switches configured as in the photos it tries three 10 second cranks of the engine before it gives up and lights the 'overcrank' indicator. There are various options for pre-heat and cool-down if you have a diesel genset.

Q1a Yes, you connect the 220V direct to those terminals. Connect it to the output of the genset, either the back out the output socket, or, if there's a second outlet, plugged into there.

Q2 That should be fine provided the genset battery is in good condition, the GTR does have crank voltage protection, but if the supply is very low for long it will 'forget' what it's doing.

Q3 The relay does not have a hard life, in normal operation the coil is not energised so everything is nice and cool. Ours takes the full domestic load except the water heaters, aircon and garden pumps without flinching. I would only replace it if it failed.

EDIT The 'IGN' relay is energised on mains fail, it's intended to open the fuel valve on a diesel, or turn on the ignition on a petrol engine. We are using the normally closed contacts to ground out the magneto and stop the engine when mains returns.

[Crossy]

For those interested in building this system, here is a complete diagram of what I have as of today.

Notes:

1. I've not included the generator output Volt/Amp meter as it doesn't form part of the control system.
2. I have removed the internal battery in the controller and added a 'Charge' connection to the genset to keep the genset battery fully charged, the genset battery powers the controller when the mains is off, this works fine.

Here we go:-

If anyone else actually builds this, or something similar, please post here, it's good to see how others address the same problem.

[Crossy]

Update on the genset controller.

I was having issues with the generator not stopping when the power returned, in fact it wouldn't stop even when the 'Off' button on the GTR-17 was pushed (and the 'Off' lamp illuminated).

Investigation showed the 'Ignition' relay was still energised, the GTR had locked up. The only way to reset it was to kill the power (unplug and disconnect the battery). Not a good situation.

Reading the manual (yes finally) showed that, (unlike the other relays) the Fuel Solenoid had a suppression diode shown.

So I fitted one, and to the 'Start' and 'ATS' relays too for good measure.

I also added 0.1uF and 1000uF decoupling capacitors right at the DC power terminals of the GTR.

Finally I connected the negative battery rail to the incoming earth on the power supply.

Updated diagram:-

So far (touch wood) the lockups seem to have been eliminated.

[IMHO]

What about a good old fashioned manual transfer switch, that breaks before make? Any leads on decent quality & price?

[IMHO]

No-one? OK, what should I be looking for then?

From what I can figure, a 2nc/2no 2 or 3 position switch? How do I insure that it's break before make (what spec to look for - 3 position I guess)?

[Crossy]

Yeah ^^^, something with a centre-off position will ensure it's break before make.

I've seen some really low cost 3 position knife switches that would do the job perfectly such as http://www.ebay.co.uk/itm/New-63A-2-Pole-Double-Throw-Knife-Safety-Disconnect-Two-Direction-Switch-HK1-63-/181750980811?pt=LH_DefaultDomain_3&hash=item2a5133e0cb

Also look at 3-phase 'reversing' switches, many can be re-wired to provide the desired function, like this http://www.thaivisa.com/forum/topic/542125-make-yourself-a-cheap-and-safe-generator-transfer-switch/?p=6392573

Or a 3 position rotary isolator like this http://www.ebay.co.uk/itm/Craig-Derricott-Ltd-20A-Changeover-Switch-Md23-P-Coi-SWITCH-DISCONNECT-/201350688665?pt=LH_DefaultDomain_3&hash=item2ee16faf99

EDIT Or you could use the 80A relay noted earlier, if you connect the 220V coil to the generator output then it will switch over when you start the genset, but if you're going that far you might as well make the auto-stop version

[IMHO]

I'm not great at reading electrical spec sheets (especially the X|O|X|O charts for contactors) - can someone help confirm whether this switch will do the job?

http://th.rs-online.com/web/p/non-fused-switch-disconnectors/3307708/

Form what I can see, tech specs are on p16 of this doc (FS 684 / T3-2-8211) : http://docs-asia.electrocomponents.com/webdocs/081d/0900766b8081d179.pdf

Note, the genset is a 6.5kVA / 5kW unit, so assuming the half-priced T0-2-8211 wouldn't be good enough right? - it's rated as 20A AC on the RS website, but only 14A in the spec sheet.

[Crossy]

Yes, the T3-2-8211 will do the trick, I would oversize any transfer switch for peace of mind.

You need to consider the load when running on mains rather than the genset, particularly if you are manually load shedding (turning off your water heaters when on genset). That 32A switch should have a 32A (or thereabouts) MCB between it and the mains supply to avoid overload and potential fires.

Are you intending switching your whole house or just essential items through the switch?

[IMHO]

Yes, the T3-2-8211 will do the trick, I would oversize any transfer switch for peace of mind.

You need to consider the load when running on mains rather than the genset, particularly if you are manually load shedding (turning off your water heaters when on genset). That 32A switch should have a 32A (or thereabouts) MCB between it and the mains supply to avoid overload and potential fires.

Are you intending switching your whole house or just essential items through the switch?

I have 3x CU's - one of which is setup with breakers for the essentials only (3x inverter fridges, 1x 12K BTU inverter AC, a few LED lights, 1x power outlet for LCD TV+STB, and a water pump). The genset runs/starts it all fine, so a 32A switch should do the trick - thanks Hot water is all solar, with electric boosters off at the breakers, so the AC is the biggest single load (~950W).

[carlyai]

My mistake, in that I bookmarked the gen set thread a long time ago but did not read the new bits until now.

Hope to get started on this beautiful project after .........

[Crossy]

Since this thread has re-surfaced an update is in order.

The genset has been moved to a more remote location for noise reasons. I decided that the controller should stay accessible without having to go out in the rain so some modifications were required.

I added a couple of relays at the genset so I could use a 3-core control cable (readily available), since it only carries 12V at low current (to operate relays) you can use the thinnest cable you can find commensurate with the environment and how vulnerable it is to damage. I've used some 1mm² 3-core flex which was in-stock. Power cable from the genset is 2.5mm² (6kVA generator).

I've also reverted to completely separating the GTR power supply from the genset battery.

The updated drawing is below :-

A larger (readable) version of the drawing is here http://www.crossy.co.uk/Handy%20Files/With%20GTR-17%20Controller%20-%20Update%20for%20longer%20cables.jpg

The original TinyCAD file is here if anyone needs to modify for their own use http://www.crossy.co.uk/Handy%20Files/With%20GTR-17%20Controller%20-%20Update%20for%20longer%20cables.dsn

[carlyai]

I like port Naam, sadly I'm not you neighbour

Anyway, the bump reminded me that I was going to update when my pukka generator controller arrived.

I bought one of these http://www.ebay.co.uk/itm/New-Generator-Controller-GTR-17-Auto-Start-Stop-Function-/221390800443?pt=LH_DefaultDomain_0&hash=item338beb863b

$(KGrHqF,!osE9dH8uIEKBPbYTj8PJg~~60_12.JPG

As well as the controller you will need:-

• 3 off 12V car relays with change-over contacts
• A 12V 1.2Ah sealed lead acid battery
• A 12V 1A switching power supply (or a linear PSU) needs to be adjustable to about 14V.
• A 1N400x 1A rectifier diode
• A box to put it all in

Assorted crimps, wire connector blocks etc.

The manual for the controller is here http://www.monicon.com.tw/03products/PDF/GTR%201X/SG17V08E.pdf

This is the circuit

With GTR-17 Controller.jpg

I also bought one of these http://www.ebay.co.uk/itm/Digital-AC-100-300V-50A-Blue-LCD-Amp-Volt-Ammeter-voltage-Panel-Meter-gauges-/231046353676?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item35cb6f930c

$(KGrHqUOKooFIwwKDIGJBSP9!KBLHg~~60_12.JPG

To monitor the genset output during operation.

Some photos of the completed unit including the settings of the DIP switches on the controller.

Image00900.jpg Image00901.jpg Image00902.jpg Image00903.jpg

As shown in the diagram it works with the modified genset shown earlier in this thread.

I notice a lot of your buys are from ebay uk, was wondering is it because the quality or price is better than what can be sourced on web sites here?

Like I bought an android box to watch iptv from the L web site, and the specs were good, write up good, but the finished product, connectors, positive switch throw, etc were poor. Think they just buy the same chipset and put it in the cheapest hardware.

So, buying the volt/amp meter, gens set project etc from ebay uk would be better quality?

Or, is it that you have a great like for a country that can't beat Aus in rugby?

(There again, my UK friends continue to remind me of the Aussie record in the cricket).

[Crossy]

I use Ebay UK coz I'm a Brit and have always used that particular portal. Much of the stuff I buy does actually come from Chinese sellers anyway.

I have noticed that many sellers on ebay.com (the US site) are reluctant to ship overseas, often quoting ridiculous postage costs, annoying when they are the only ones with a particular item

The US site also uses the system whereby you can (have to) pay duties in advance and they then refund any overpayment. I'm quite capable of managing any duty to be paid myself

[carlyai]

I use Ebay UK coz I'm a Brit and have always used that particular portal. Much of the stuff I buy does actually come from Chinese sellers anyway.

I have noticed that many sellers on ebay.com (the US site) are reluctant to ship overseas, often quoting ridiculous postage costs, annoying when they are the only ones with a particular item

The US site also uses the system whereby you can (have to) pay duties in advance and they then refund any overpayment. I'm quite capable of managing any duty to be paid myself

OK thanks.

I was wondering why the US sites charge such high postage rates, I thought it was to make more money, now I know. Me to on the duty, I just love to pay it and try and pay as much as possible.

I bought a water pressure guage from the States that was sooo expensive, I think $17 postage, (before I knew what to look for over here, and not to ask the shop assistants), now I know what to look for and now I see them everywhere, in little boxes, on second to bottom shelves. They're about the only thing they hide in little boxes.

I drove to Mukdahan to get a pressure switch for my pump from the tractor agent there, and asked him how he tested the pumps as he is also the Mitsubishi agent, he showed me his set up with a water pressure guage and told me where to buy it at Mukdahan Shutters, (they've got everything). That was when I discovered that the guages iive in little boxes and cost about B 150. [ I include this for anyone who is near Muk and needs a pressure guage].