From: John De Armond
Subject: Re: Honda EU generator for RV and house -which one?
Date: Fri, 14 Jun 2002 20:19:45 -0400
On Fri, 14 Jun 2002 13:30:29 -0700, "Rob C" <firstname.lastname@example.org>
>Very good inputs from all. I like the idea of trading off sound output for
>more wattage for the house backup power. I also need to check the
>circulating pumps on my furnace to see if they are 240V or 120V. I don't
>have a well water, so I don't need to start that huge beasty motor load.
>Because we are in blizzard country, I would like to run the generator(s) for
>house backup inside my attached garage. Any suggestions for venting the
>exhaust? Could I just run a line from the water heater chimmney tubes down
>and over the generator muffler? I would feel better with more positive
>ventilation, probably something like a kitchen exhaust fan mounted inline
>with the vent to the outside. Of course a monoxide detector would be used
>and has been used in my house/trailer/garage starting a few years ago. Kind
>of a pain when I start the lawn mower it goes off for a bit. I would store
>bulk fuel outside in a shed.
I set up an electric start mid-grade honda engines Genrac generator in the
basement of our family cabin in the mountains. (not my choice of generator -
my parents had already taken it upon themselves to buy it before I got
involved.) Here's what I did.
I ran the wiring upstairs so that the generator can be started, stopped and
transferred to the cabin's wiring without going to the basement. I used a
pair of mechanically interlocked contactors (normally used for reversing
service on cranes and such) that I had in my junkbox to do the connection.
These contactors mechanically prevent both from being energized at the same
time so backfeeding is impossible.
I rigged up an automotive electric fuel pump to pump gas from an outside tank
to the generator. I included the fuel pump switch on the upstairs control
panel so that I could shut the generator down by turning off the fuel and
allowing the float bowl to run dry. I made up an adapter that slides over the
generator's exhaust pipe and connects to a run of EMT that pokes through the
wall. This adapter is secured with a pair of self-tapping sheet metal screws.
I don't recall the size EMT I used but I went up a couple of sizes above the
exhaust pipe to minimize backpressure. My wall is block so I didn't have to
worry about heat. I simply drilled a somewhat larger hole and stuffed the
clearance space with fiberglass insulation.
To get the heat out and to remove any exhaust leakage, I installed a small
thorugh-the-wall exhaust fan and dampers (Dayton brand, Graingers.com) along
with a second air inlet damper. These are probably 6" square. The fan is
connected directly to the generator so it runs only when the generator does.
The generator makes sufficient heat to keep the basement warm even with this
ventilation operating in near-zero weather.
We've insulated the floors in the cabin with very heavy fiberglass batting,
both between the studs and stapled across them. This is sufficient to almost
completely muffle the engine noise. We know the generator is running but the
noise is not objectionable.
I used a white poly tank I bought at Northern for the gas tank. It holds 35
gallons. I have it under a little shed to keep the sun off the poly. The sun
both hardens the poly and polymerizes (gums) the gas. A shot of Sta-Bil keeps
the gas fresh. I normally only keep about 5 gallons or so in the tank so it
won't get stale despite the Sta-Bil. I keep about 40 gallons of gas in GI
Jerry Cans in the basement. These are air-tight and with Sta-Bil will keep
the gas fresh for years.
This is a good compromise between allowing a large quantity of gas to sit in
the tank on one hand and not forcing my elderly parents to lug fuel when I'm
not there on the other. The 5-10 gallons in the tank will run the genny for
the better part of a day. I have another automotive fuel pump (a high volume
Holly racing pump) hooked up with hose and gator clips for use as a transfer
pump. I just dump the jerry cans but I've showed my parents how to use this
pump to transfer gas from the Jerry cans when I'm not there. One thing nice
about those Northern poly tanks is the mouth is at least 6" in diameter so
there's a large hole to aim at with the Jerry cans :-)
This setup has worked well. I had one complication in that my well pump is
about 200 feet from the cabin and is fed from a separate utility drop which
comes from a common CT metering point on a pole. Since I could not power the
pump through the utility drop, I had to bury a wire and arrange relay logic to
cut the pump over to the buried wire whenever the power fails. That involved
a DPDT contactor with a 240 volt coil connected across the utility line.
Whenever the power fails, the contactor drops out and defaults to powering the
pump from the buried line which in turn is connected to the generator.
>Any chance that 2 EU's would start my trailer air conditoner? How do I
>figure this out without learning from the school of hard knocks? I just
>don't know how these things react to sudden temporary overloads?
Two should handle one easily. Reports we've seen here indicate that one will
start a Coleman 13,500 btu unit in moderate weather but won't run it in hot
weather. Maybe the high efficiency one would start. Only way to really know
is to talk to someone who's done it and to make sure their experience is in
weather as hot as you expect.
My Onan AJ is at the point of requiring an overhaul. I did some fairly
extensive testing last week to establish a "before" baseline. The engine is
weak enough that it can make 1.9kw max in 80 deg weather. It can start my
13,500 BTU Coleman AC but cannot keep it running once the weather gets above
about 85 deg. When I first got the rig about 3 years ago it COULD run the AC.
I'm sure it was then pretty close to its rated 3kw output.
Given that my degraded generator is operating at about the same output as a
single EU2000, I doubt that you'd be happy with just one but would find two in
parallel quite satisfactory.
The only thing I don't like about a pair of 2000's as opposed to a 3000 is the
lack of electric starting. I really like being able to crank the generator
whenever needed without having to go outside. I'm about 95% sure that I'm
going to modify my generator box so that I can install an EU3000 just because
it is so damned quiet and fuel efficient, particularly at low load.
From: John De Armond
Subject: Re: Enclosing portable gensets
Date: Fri, 25 Mar 2005 19:44:46 -0500
On Fri, 25 Mar 2005 18:27:26 -0500, HD in NY <email@example.com> wrote:
>If he has a reasonable explanation for his keeping gasoline
>in his basement, I'll apologize. On the other hand, I didn't
>call him any names or make any derisive comments either.
>HD in FL for 4 days
I thought your comments were gentle. After I read them I went back
and dug the original post out of the filter bin. I share your opinion
on everything except the gasoline storage. I have no problem with
that, assuming the proper container, say, an outboard motor tank.
I do have problems with installing a construction generator indoors.
The exhaust system isn't designed to be gas-tight. Briggs engines are
famous for their head exhaust flange gasket leakage. Given that he
didn't mention anything about ventilation, CO detection or all-welded
exhaust but did mention overheating which indicates a closed space, he
basically turned his house into a CO-based execution chamber. Unlike
you, HD, this is about what I'd expect.
Several years ago while I was out of town for extended periods, my
parents had a Generac 7kw construction generator (the one you can buy
at Home Depot) installed in the basement of our cabin. I had told
them on the phone to go to Home Depot and buy a Generac Guardian
standby generator. They heard the "home depot" and the "generac" but
missed the Guardian.
The next time I went to the cabin, I almost had a heart attack. The
backwoods handyman they'd hired had sat the generator next to a wall
and then hooked up the exhaust up with car flex hose. He'd removed
the muffler and welded on an auto exhaust stub. He'd not tightened up
the muffler-to-engine joint enough so it leaked profusely. Each joint
in the exhaust tubing had the split-swaged type of joint that left two
leaking openings. The tubing was way too small so the high
backpressure made the leaks even worse. The guy apparently had some
dim perception of the problem, for he had cut a 3X3" hole through the
block wall and installed a tiny fan.
I bought a NightHawk CO detector and brought it to the cabin. I
showed my folks that the thing would go into alarm in under 10 minutes
with the generator running. Then I disabled the unit so there would
be no temptation to use it until I could build an out-building to
The connection was as bad. There is a sub-panel in the basement. He
simply hacked one end off the twist lock cord that came with the
genset and then wired in an additional breaker to the cord. The cord
prongs were hot when the breaker was closed. He'd labeled "off" as
"normal" and "on" as "standby". No mention or instruction at all
about opening the main breaker in the main panel upstairs.
At least this guy didn't call himself an engineer.
An engineer would know that there are both NFPA and ASHRAE guidelines
for indoor installations of standby generators. One of the more
important specs is the required room air changes and the sealing of
room penetrations to control CO.
Someone who put any thought into the standby system would most likely
chosen an LP model or done a conversion (photos on my web site showing
just how simple the LP conversion is.) Even a 500 gallon propane tank
would ride through most any conceivable power outage while staying
fresh in the tank indefinitely.
Finally, I should note that it is not difficult to quiet a
construction generator sufficiently for standby duty. I've done it
and so have a lot of other folks. It's not hard but it does take an
understanding of what has to be done and it takes a systematic
From: John De Armond
Subject: Re: Creating Generator Exhaust Hose
Date: Sat, 17 Feb 2007 11:16:26 -0500
On Fri, 16 Feb 2007 18:17:57 -0500, MT <firstname.lastname@example.org> wrote:
>I've got a Coleman Powermate 8000 generator with a Kohler engine. I'm
>looking for a way to leave the generator in the detached garage when
>running, so it's out of the rain/snow, yet get rid of the exhaust
>I suppose I could just leave the garage door open, but even though the
>garage is a detached separate building, the roof of the garage is
>connected to the main house roof forming a small covered walkway
>(about 10 feet) between the detached garage and the house, which means
>I'm still a bit concerned about leaving the generator running in that
>garage, even with the door open, just in case the fumes could go up
>into the garage attic and across the connected roof and into the house
>during prolonged operation.
>The Kohler engine muffler has a 1 1/4 inch diameter exit fitting that
>looks like it's setup to accept some sort of connection. The
>connection sticks out several inches from the muffler, and has both a
>metal hose clamp and thin ring of increased diameter (to say 1 5/8
>inches) which looks like its meant to have a hose connect to it and
>then the hose clamp would be tightened down to hold it in place.
>However, I can't seem to find any kind of hose or fitting that would
>fit this connection. I emailed Coleman to ask about any accessory
>they might offer to do this, but they replied that they didn't have
>anything like that.
>What I would like is an adapter that would fit this connection and
>then on the other end fit a standard 3 or 4 inch auto exhaust hose,
>which I could vent outside around the corner from the garage door.
>I'm thinking that if I expand the diameter of the lengthy portion of
>the hose, versus the diameter of the exit connection on the muffler, I
>would lessen the chance of creating any kind of back pressure in the
>exhaust system that might damage the engine. I would probably need 10
>- 15 total feet of hose in order to get the fumes well around the
>corner away from the detached garage or the house.
My dad and one of his friends tried that on the same model generator.
It didn't work very well. His friend welded a length of tubing to the
muffler exit, then had a muffler shop make a slip fitting to slide
over the stub. They went up a couple of tube sizes and ran the
exhaust about 10 ft to the outdoors.
I didn't take a lot of time to analyze why it didn't work but I did
notice heavy resonance on a sub-harmonic of the operating frequency. I
also noticed hot and cooler areas of the pipe (indicating standing
waves) and significant soot coming from between the slip joint,
(indicating high pressure there). The engine was unstable and had
I made up a longer cord, welded on two more wheels so he could roll it
outside and insisted that he not try to run the thing in the basement.
If I were going to try this I'd copy what commercial repair shops do.
They generally have an overhead header with drop hoses to the stalls
with ends that couple loosely to the vehicle's exhaust pipe. At the
end of the header is a squirrel cage fan that provides suction to the
header and blows everything outside. There is inflow at the
intersection of the vehicle's exhaust pipe which both prevents exhaust
escape and pulls in cool air to cool the exhaust.
If I were given the task of getting the exhaust outside a small
building, I'd build the piping out of perhaps 3" metal duct (gas water
heater ducting would work well) with all the joints taped with ANSI
quality metal tape. I'd put a blower at the building wall that
applies suction to the pipe. At the generator I'd make an increaser
to bring the diameter of the muffler outlet up to the 3" pipe. I'd
also arrange some baffled openings into the pipe to allow in cooling
air so that the entire pipe doesn't get hot enough to become a fire
hazard. If it is possible for anyone to occupy the building then I'd
also install a CO detector and a vane-type flow proving switch in the
duct that would shut down the generator if the exhaust flow failed for
any reason. A vane switch, also known as a "sail switch" is a common
HVAC item, available anywhere HVAC parts are sold.