I am a new member, and live out in Jackson NJ. Just recovering from Hurricane Sandy and the Nor'easter. I have a water furnace geothermal heating/cooling unit. I am trying to determine the surge watts needed for a backup generator. My unit was just installed 2/2011. I tried to find the info everywherem but have not had any luck. Even Water Furnace said they can't tell me what that info is. I found a post online, taht was from this web site. However it was from 2007. From these posts I did learn what to look for. My info is: Volts: 208/230 LRA: 960 RLA: 21.1 PH:1 I come up with 22,080 surge watts. I presently have a 10kw surge, 8kw running portable generator. It does well with a good part of my home, but the biggest draw is my well. If my info is correct I would probably need a 28kw generator, if not larger, to do what I have now PLUS the geo. I found in the post a response from a member stating he had a 15kw generator running his 3 ton geo and well pump, plus a good part of his house. I am assuming, with the info I have, that I have at least a 3 ton, if not 3 1/2 ton geo unit. I am trying to find anyone who has a backup generator that does work their geothermal unit (and what the tonage is), what other circuits, etc it may also run, such as the well pump, fridges, freezer etc. brand name, fuel type. This info woulkd be greatly appreciated. I have people around me now hooking up regular gas furnaces on a 6250-6500 watt generator. It is killing me that I may need a 28-30k watt generator to power what my portable is doing now, plus the geo. Again, thanks to all who read/respond to this.

I found this generator sizing sheet, it shows the reduction in generator size if you have Intellistart.

Intellistart: http://www.waterfurnace.com/literat...1629MW.pdf

Hope that helps, I am in RI, wish I had a generator to run my 4 ton GSHP, maybe someday, if I hit the lottery.

ChrisJ

Post the full model number of your WF unit.  It should be on the same label that you read the specs on.

Double check the LRA.  It may be 96.0, not 960.  Your unit may be a 4-ton unit, need the model number to tell for sure.

I agree with ChrisJ.  If you don't have IntelliStart, get it (the model number may indicate if you already have it).  If you don't have it, your WF dealer may be able to install it for about $400 (a guess based on our experience.)

We have a 20kW air-cooled automatic standby generator which runs our 3-ton and 2-ton WF Envision units (both with IntelliStart) just fine.  Some transfer switches have load management/load shedding, which can help keep the generator size down.  Note: the generator may not be able to handle the electric heat strips (if any) unless you get a very large generator.  There are ways to lock out the heat strips while on generator power.

WF, would you lend a hand here and confirm that the attached spreadsheet applies to Richg635's WF model (with IntelliStart) after he posts this information?

Posted By Richg635 on 20 Nov 2012 02:28 PM
I am a new member, and live out in Jackson NJ. Just recovering from Hurricane Sandy and the Nor'easter. I have a water furnace geothermal heating/cooling unit. I am trying to determine the surge watts needed for a backup generator. My unit was just installed 2/2011. I tried to find the info everywherem but have not had any luck. Even Water Furnace said they can't tell me what that info is. I found a post online, taht was from this web site. However it was from 2007. From these posts I did learn what to look for. My info is: Volts: 208/230 LRA: 960 RLA: 21.1 PH:1 I come up with 22,080 surge watts. I presently have a 10kw surge, 8kw running portable generator. It does well with a good part of my home, but the biggest draw is my well. If my info is correct I would probably need a 28kw generator, if not larger, to do what I have now PLUS the geo. I found in the post a response from a member stating he had a 15kw generator running his 3 ton geo and well pump, plus a good part of his house. I am assuming, with the info I have, that I have at least a 3 ton, if not 3 1/2 ton geo unit. I am trying to find anyone who has a backup generator that does work their geothermal unit (and what the tonage is), what other circuits, etc it may also run, such as the well pump, fridges, freezer etc. brand name, fuel type. This info woulkd be greatly appreciated. I have people around me now hooking up regular gas furnaces on a 6250-6500 watt generator. It is killing me that I may need a 28-30k watt generator to power what my portable is doing now, plus the geo. Again, thanks to all who read/respond to this.

Your Locked Rotor Amps (LRA) of 960 looks suspicious.  That is probably 96.0.  Locked Rotor Amps for most electrical motors is on the order of 5 to 6 times the Full Load Amps (FLA) or Running Load Amps (RLA).  Your RLA is 21.1.  5 times that is 105 A, so locked rotor is likely 96.0 A vs. 960 A.  Inrush watts is essentially LRA x supply voltage or 96 A x 230 V = 22,080 W or 22 KW.  That is a pretty big unit.   I looked up a Climatemaster Tranquility 20 single stage geo heatpump and a 4 ton unit has a RLA of 20.5 A, so I would estimate yours it at least a 4 ton unit.

I have been asking the same question myself lately. I am looking at a 13kw generator that runs off the pto of my tractor. I have a 4 ton system, closed loop. I also want to be able to run my well pump, electric dryer, tankless hotwater, and such. My installer said a 13kw would run my house well. He is going to install the intellistart for me.

Wow! Thank you to everyone who not only responded with great info, but for the unbelievably fast response. I messed up and forgot the decimal point. The LRA is 96.0. My full serial number is NDV049A111BL. Thanks to ChrisJ for his generator sizing sheet. It lists my NDV049 as a 4 ton unit. I thought my old FHP was a 2 1/2 ton unit and was replaced with a 3 ton. Anyway, another thanks for the Intellistart info. That looks amazing, and I am just waiting until 9 am to call my installer. I don't believe I have it because I do get the occassional loud noisy startup, etc. Thanks to geome, for your info, and the insert to WF. Do they actually read/respond to anything posted? I called them after out 2011 hurricane, just prior to buying a generator. They were absolutely useless, unfortunately. It would be great to get a response from them. Thanks to arkie6 for your input, also. Good luck johnny1720. Hang in there ChrisJ, you'll get there. Thanks to "Sandy" i have to replace my roof, also. Well, that's what they make loans for. Still way better off then the Jersey shore 12 miles away, and many other places. Hopefully none of you were hit to hard. Thanks again to all.
Rich G

WF may respond - if they see this post. You may get better results if you PM them (typically better than calling them.) Their user name is "WF_Inc." with the period, but without the quotes. They defer to their dealers on some questions for liability reasons, but they may be able to answer other questions.

Based on your model number, your unit does not appear to have IntelliStart as a factory installed option, but your dealer should be able to install it for you.

The NDV049A111BL does not have a factory installed intellistart, it would be 141 if it did.
If you install intellistart it will bring your LRA down to 34 instead of 96 a HUGE savings on startup.

24 kw 1800 rpm Generac starts my WF 038 (no intellistart) without missing a beat...virtually indistinguishable from utility power

Thanks Skyheating. Thats great info, just what I needed. Just talked to my installer last night. Will be installing an intellistart next week. Then, have to pick my standby generator, then find a propane place to install a tank.
Hey, engineer. I am guessing that you have some other circuits on your generator, also. Thanks for your info too.

Yup - whole house. One day I manually transferred and then started clothes dryer (5600 Watts), oven, water heater, heat pump, etc. I didn't detect so much as a change in generator noise with those loads added.

96 LRA corresponds to a 4 ton WaterFurnace two stage, and since CM uses same compressors, I'll bet yours is a 4T as well.

My off-the-cuff guess is that a 4 ton with Intellistart would start with a 10kW surge genny, and once running, other loads could be added

If you have natural gas service, consider a 14 kw or thereabouts NG-fired standby genny.

A premium option is an 1800 RPM 22 kW Generac liquid cooled unit.

A water-cooled generator with a water-to-water heat exchanger in place of the radiator might allow you to recover some waste heat and put it to good use inside your house. A stainless water-air HX on the exhaust pipe would extract some heat too.

Of course there's some cost for piping and controls but it seems a shame for all the waste heat from the genny remain outdoors when you have it available.

might allow you to recover some waste heat

In the case of the Generac 22kW unit Curt mentioned above, it is 99,000 BTU/hour. Not insubstantial.

Anyone here recovering generator waste heat via fluid circulation?

Posted By ICFHybrid on 26 Nov 2012 11:48 PM

might allow you to recover some waste heat

In the case of the Generac 22kW unit Curt mentioned above, it is 99,000 BTU/hour. Not insubstantial.

Anyone here recovering generator waste heat via fluid circulation?

Expensive generator + non-approved modifications = voided warranties (on both ends of the mod) and possibly code violations and voided homeowner's insurance in the event of a related claim.  Not in my house.

Thanks to everyone for their answers. You have all helped greatly. I don't know where any of you live, except ChrisJ in RI, but I hope we don't ever have to experience another "superstorm" followed by a 12 - 13" snow from a nor'easter ever again. In, fact, I would rather just get to "play" with the generator (run it once a month for a few hours) then actually NEED it. Thanks again to all

Expensive generator + non-approved modifications = voided warranties (on both ends of the mod) and possibly code violations and voided homeowner's insurance in the event of a related claim. Not in my house.

I'm not too worried about it. Only has a two year warranty anyway. My buddy thinks it's a great idea.

Posted By ICFHybrid on 28 Nov 2012 01:40 AM

Expensive generator + non-approved modifications = voided warranties (on both ends of the mod) and possibly code violations and voided homeowner's insurance in the event of a related claim. Not in my house.

I'm not too worried about it. Only has a two year warranty anyway. My buddy thinks it's a great idea.

At what point did 'not worrying about something' become the standard for 'something being a great idea'?

There was no beer involved, honest. The conduit and fittings are already laid. I need a pump, though. I'm thinking something bronze, something rated for high temperatures.......

I wouldn't rule out a well considered plan to recover heat from generator coolant. I'd want a double walled heat exchanger or similar redundancy to be certain genny coolant could not contaminate potable water.

I can't imagine this worthwhile for a standby genny that runs only a few hours per year.

I don't know how you came up with the idea that a 22 kW genny has 99 kBtuh waste heat available. Available waste heat is highly dependent upon the load placed on the genny, its efficiency, ambient temp, etc.

Here are mfg propane burn rates for my genny. Know that propane contains about 92 kBtu per gallon.

ENGINE FUEL CONSUMPTION (Propane)
(gal/hr.)
Exercise cycle 0.65
25% of rated load 1.53
50% of rated load 2.40
75% of rated load 3.27
100% of rated load 4.15

W-e-e-l-l-l-l.....I seem to remember from my salad days in engineering school wading through what seemed like thousands of endless problem sets, some of which dealt with just this sort of thing. And, if I recall correctly, they still haven't gotten internal combustion engines to be much more efficient even now. Rule of thumb is about a third efficient, so you've got 2/3 of the fuel being lost in heat and other things. If you calculate the total energy available at 75% and 100% generator output, it is 300 kBTU and 380kBTU respectively for the fuel consumption figures you provided. 2/3 of that is 200 kBTU and 250 kBTU. Total heat rejection is important for bigger generators, because it turns out that people want to put them inside of weather protection shelters and they have to provide for cooling and whatnot. In this case, however, we are just looking at the heat available in the coolant. Roughly, it can be split equally between heat lost to exhaust gases and air cooling and the coolant. So, let's further reduce those numbers by a factor of 1/2. That gets you in the ballpark with 100 kBTU and 125 kBTU, respectively. So, I'd say that the 99kBTU number represents what is available in the upper end of the power curve.

When folks get a bigger generator like this at home,it is often because they want to run their home heating plant with it. If you are running a heat pump with a COP of 3 or so, you are putting, say, 150 kBTU into the home, while at the same time losing 99 kBTU of heat from the jenny engine. In a long run situation or a situation in which fuel is VERY different to come by, reclaiming that extra energy might be important. Or, it might just be important to someone looking to increase efficiency of the system as a whole. So, for $2 grand worth of heat exchanger, tubing and pump, you might be able to add quite a bit of efficiency to your $10 grand propane generator.

BTW, if you look more closely at the engineering specs in the Generac Owner's Manual, you will probably find the 99 kBTU number as heat rejected to coolant. There is a reason they provide that, even for a residential type generator.