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  1. #1
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    Default Hyd gen set engagement

    I would like to hear from other FD that are using Harrison Hyd. Gen sets. In peculiar how they are engaging them. At the present time we have 7 of these units in the 7-10Kw range. These trucks use approximately 60-70% of there load for scene lighting. We have a policy that we can engage the PTO at less than 1600 RPM and then activate the genset while under load (flood lights turned on at the breaker panel). This has given both Chelsea and Harrison companies a great deal of heart burn… Has anyone experienced problems with the failures of PTO hot shift, inlet hydraulic leaks or collapsed genset field? We like having the scene lighting as we are pulling up and ready to go.


  2. #2
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    I'm not overly familiar with generators and their operation, but from what I do understand is when you put a load on a generator that's not fully warmed up and ready, you're causing damage to the unit.

    Our policy (we've got a Harrison 10kW hdyraulic) is that we engage the PTO and allow the PTO and pump to get to speed before putting it in high-idle. At that point, we don't turn on anything until it hits 60 Hz and 240 volts or more. It usually only takes a couple of minutes, which is the amount of time it takes to get everything off the truck and ready to work.

    Even on our gas/diesel-powered generators, we allow them to sufficiently warm up prior to putting a load on them.

  3. #3
    Forum Member Rescue101's Avatar
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    On the New Ladder we have a 15k Onan.Instructions SPECIFICALLY state under 1000 to engage pto and the genset is to be "spun up" to operating speed before any load is put on the system(lights).We put rocker switches in the cab so we can turn the lights on while pulling up AS LONG AS the above conditions are met. T.C.

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    Forum Member FIREMECH1's Avatar
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    I can see why Chelsea and Harrison are having problems with your actions.

    First off is the rpm activation. It should be 1,100 rpms, or less. Unless you like metal shavings, or the splines on the drive shaft to be completely smooth and sheared off, 1,600 rpms is way too high.

    Secondly, never start it with the load already engaged. This will burn up the brushes in the genset, as well overload the regulator. You need to make sure you have had it running/spooling up long enough to be able to accept the load that your going to put on it. As said, a rocker switch to activate the load is a good idea, and works.

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  5. #5
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    You probably received a Harrison generator manual when your truck was delivered. I would imagine the manual would give you the proper instructions for the start up sequence.

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    We have a Harrison (Model MAS I Believe) 10KW hydraulic generator. Its referred to by the manufacturer as "constant mesh" PTO. We spec'd it to be ale to engage at any speed. As we were told by the MFR, its safe to start it at any speed. They told us that the PTO is always engaged, and that the switch for the gen only initated fluid flow to the unit. We never start it under load.

  7. #7
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    We have a Harrison on our new engine and out truck that is currently being built. We have 2 swtches...an "ENGAGE" switch and an "Energize" switch. We can engage at any rpm, but if they rpm's are too high it will automaticaly wiat untill the rpms are low enough before it engages. Once it's engaged, you can "engergize" they system which turns on the actual powere generating part of the generator.
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    Roof -

    Is that standard for harrison?

  9. #9
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    Quote Originally Posted by rm1524 View Post
    Roof -

    Is that standard for harrison?
    I don't think it is. Ours is on a GMC 5500 quick-attack and is set up where we have to kick on the PTO to engage the hydraulic pump, then to kick up the hydraulic pressure to where it needs to be we put it in a high-idle mode by hitting the cruise control button. From there we have to kick on the breakers or switch, depending on what we're turning on.

    How they're set up on larger apparatus, I don't know.

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    Forum Member Fyrtrks's Avatar
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    I would never suggest that any load be "dumped" onto the generator. The addition of 12-volt switches and 120 or 240-volt relays is cheap insurance. You can control your scene lighting and save a great deal on generator wear. If you don't want to control your loads at the circuit breaker box then spec switches near each load.

    As far as Regular PTOs and Hot Shift I think it comes down to two things 1. Apparatus Type and 2 Operational Procedures.

    A regular pto would be best suited for a rescue vehicle that coulde be easily returned to idle.

    Hot Shift is best suited for an apparatus that can't be returned to idle easily like an engine company, or a unit that needs to be high idled like a breathing air compressor truck.

    You can also set up your operational procedures so that the PTO is engaged before the truck leaves the station. You may get some PTOs that would overspeed and disengage when driven at highway speed.

    You also should determine what speed you want your unit to run at. You can have the unit running at different engine speeds, some units are programed so that the clutch fan engages with the PTO. If you don't want alot of noise then you would want a PTO ratio that is differfent than the most likely standard. Now with LED warning lighting you don't have to worry about the vehicles 12-volt charging system so much.

    Check with yor prefered builder and others to see what thier ideas are. They might have something that works for other people. Don't listen to just one person.
    Last edited by Fyrtrks; 07-26-2009 at 11:24 AM.
    Fyrtrks

  11. #11
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    Default

    Quote Originally Posted by tburandt View Post
    I would like to hear from other FD that are using Harrison Hyd. Gen sets. In peculiar how they are engaging them. At the present time we have 7 of these units in the 7-10Kw range. These trucks use approximately 60-70% of there load for scene lighting. We have a policy that we can engage the PTO at less than 1600 RPM and then activate the genset while under load (flood lights turned on at the breaker panel). This has given both Chelsea and Harrison companies a great deal of heart burn… Has anyone experienced problems with the failures of PTO hot shift, inlet hydraulic leaks or collapsed genset field? We like having the scene lighting as we are pulling up and ready to go.
    tburandt,

    First off I would be interested who gave you that information? Sales person?

    Second, Any generator should never be engaged under load, unless you want to shorten the life of the generator! Unless you have a hot shift PTO I would not recommend engaging the generator PTO unless you are under 1000 RPM's unless you want to shorten the life span of the PTO. Most PTO's are designed to engage under 1000 RPM's, most have so type of safety (Relay) built in that will not allow them to engage above 1000 RPM's. I would suggest that if your apparatus does not have that, it might be worth looking into!

    I would echo Fyrtrks, statement about controling everything from the Panel box.

    chief1ff
    Mark

  12. #12

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    Default Recommended Generator Usage

    Engaging the generator: This is what Harrison teaches at all its service schools:

    Use a hot shift PTO when you can to reduce the wear on the hydraulic pump. Many failures of systems are do to Hydraulic pumps running all the time, even when the generator is not engaged. The PTO manufacturers recommend below 1100 RPM...you may never get a letter telling you that...they are cautious about that information.

    Never idle the tuck for extensive amounts of time with the hydraulic pump engaged. Due to the 2004 EPA, the engine manufacturers have fueling strategies at idle that cause PTO fretting. If you have a constant engaged PTO, it will see this potential damage anytime the truck is at idle. This is most true for 6, 8 and 10 kW ratings as they are direct mounted and driven by spline shafts. Larger than 10 kW is typically have a remote mounted pump with a key shaft and are much more resistant to these issues.

    All loads should always be off before you engage the generator. Remember, engaging the pump does not mean the generator is engaged. You may have two separate switches. If you leave the loads on when you engage the generator, the loads will see voltage from 0 to 240 VAC. It will damage your equipment over time. Essentially you are browning out the attached lights, etc every time you start the generator. This is true of ANY generator.

    Turning off the generator: All loads should be turned off sequentially...turning them all off at once will cause over speed of the generator and eventually damage the alternator. Leaving the loads on will take the load through 240 VAC to 0 VAC, again giving you the brown out conditions. ALWAYS TURN LOADS OFF SEQUENTIALLY WHEN SHUTTING DOWN THE GENERATOR.

    Follow these rules and your Harrison will out last your apparatus...most damage occurs from these issues rather than engaging the PTO at too high of an RPM. Most Firetruck Manufacturers don't have any interlocks to prevent you from engaging at higher RPM...a few do but the majority don't.

  13. #13
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    Default

    Wow, just Wow. i had to re-read your OP a few times and after reading the replies i guess you are really engaging the PTO at, up to 1600 rpms? That is a very bad idea. i dont care who told you that you can, even if the PTO is designed to engage at any rpm speed you should never engage above 1000. you should engage at idle. Having replaced many PTOs myself if i were the mechanic of a truck and was replacing a PTO because you engaged at 1600 rpms i might want to slap you.

  14. #14
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    Default genset info

    Our first gensets dating back to 1991 were Onan 7.5 KW diesels on our ladders and pumpers. We owned 5 of these from 91- 98 and the crew’s liked the fact they could light up the scene on there way in or even light up streets and addresses. At first Onan company had a major problem with starting the genset under load.
    • You will collapse the field!!
    • It very hard on the starting system!!
    • You will shorten the life of you genset!!
    My reply was explain to me how much damage is occurring. At the time we were using them this way about 5-6 times per month. What is the likely hood of collapsing the field and what will it cost to fix the collapsed field. Risk / Benefit.
    After some more discussion with Onan in Minnesota It was decided that we had been using it this way for 2 years and over the life of the unit, the product would hold up. Along the way we have been running more and more calls, some crew’s were lighting up the trucks genset on every call. Bottom line we ran these genset hard for the fire service. I personally do not believe we ran them as hard as the rental companies or the oil field companies run them. Not one failure.
    Fast forward around 2004 I purchased my first of 5 Harrison gen set. I’m at the Pierce factory and the operation instructions on the dash state.
    • No PTO engagement while moving
    • Not to energize the unit under load.
    • Park brake must be set.
    I called back to the Harrison factory and talked with one of the owners at the time. I told them you sold me one of these, but I’m moving back to the Onan Company the one that took me to the prom all these years. Then the covering your butt started. Well our units will handle the hydraulic fluid shock due to the way our stators are built and the heavy duty inlet flange... You are doing some damage to the winding and brushes, but in comparison to the oil fields units we have in-service this wear is minimal.
    The PTO is the weak link in the chain.
    So I call Chelsea spoke with a technical service manager “explain to me why you call it a hot shift and you will not allow me to engage unless it is stopped? This is where the 1500 RPM ceiling came from this manager stated our product will stand up to the load, just done be maxed out on the governor and drop it in or there will most likely be parts and pieces on the highway.
    Bottom line is we have been running these units this way for more than 18 years and 5 years with the hot shift. We have not had one failure. These companies will not put anything in writing because they are afraid they will have to warranty something. For the most part I feel the crews are safer and can have a more rapid deployment on scene and that is a bigger benefit then the small risk or damage we take with our operation. Due to the message boards input I most likely will change the procedure to 1100 RPM for the PTO shift and give the unit time to react before energizing the genset. Maybe reduce the flood lights to 50% of the rated KW capacity of the unit.
    Pierce is way too proud of the relay switches to be able to sequence the lights in the cab via relays.
    I have the names and numbers I contacted back at the companies but I never receive anything in writing. There only ½ a million dollar trucks you cannot expect everything…thanks for all the input Tim B.

  15. #15
    Forum Member retiredtruckman's Avatar
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    Default

    People get told different things from the salesman, dealer, manufacturer, etc.

    We took delivery of an Arrow XT with a Harrison 10KW gen and a Chelsea Hot Shift PTO.

    Brow lights and side floods are switched from the cab. They are also switched from the engineers panel. Pole raised lights and rear flood are turned on at the breaker panel and are normally off. All outlets in the vehicle are live when the shoreline is plugged in and switch over to genset when engaged.

    You can go down the road, engage the PTO, engage the generator and turn on the front and side lights with absolutely no problem.

    This operation was approved by Pierce and Harrison as it was included in the vehicle specification document and works flawlessly.

    Our 1999 Dash 105 ladder is similar operation but the original generator (no longer in business) was replaced with a Harrison.

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