Furnace OK on shore power, no-go on battery
Jack MacDonald
works properly when plugged into shore power, but the burner does not
ignite when running on battery power. The blower fan works properly,
but the flame does not come on. In both cases, the furnace follows the
correct startup procedure, with time delays between the thermostat-up
signal and the startup of the fan. Similarly, there is a time delay
from the thermostat-down signal and the stopping of the fan.
Checked for voltage at the furnace connection. Shore power: 13.36
volts, battery power 13.26 volts. I understand there is a safety sail
switch that prevents the gas from flowing when there is insufficient
airflow, but I am not sure whether this is the root of the problem.
The furnace is (probably) original equipment. HydroFlame model 8232,
32000 BTU installed in 1986 General Coach Corsair motor home.
Can anyone offer advice to a do-it-yourselfer, or is it time to take
it to the shop for a professional to work on?
**********************
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Scott McPhillips [MVP]
> I recently purchased a 19-year old Class-C motor home. The furnace
> works properly when plugged into shore power, but the burner does not
> ignite when running on battery power. The blower fan works properly,
> but the flame does not come on. In both cases, the furnace follows the
> correct startup procedure, with time delays between the thermostat-up
> signal and the startup of the fan. Similarly, there is a time delay
> from the thermostat-down signal and the stopping of the fan.
>
> Checked for voltage at the furnace connection. Shore power: 13.36
> volts, battery power 13.26 volts. I understand there is a safety sail
> switch that prevents the gas from flowing when there is insufficient
> airflow, but I am not sure whether this is the root of the problem.
>
> The furnace is (probably) original equipment. HydroFlame model 8232,
> 32000 BTU installed in 1986 General Coach Corsair motor home.
>
> Can anyone offer advice to a do-it-yourselfer, or is it time to take
> it to the shop for a professional to work on?
Were your voltage measurements taken with nothing running, or while
under load? An old or weak battery will drop the voltage just when it
is really needed, but the shore power is unlikely to drop under load.
bob
Jack MacDonald wrote:
> I recently purchased a 19-year old Class-C motor home. The furnace
> works properly when plugged into shore power, but the burner does not
> ignite when running on battery power. The blower fan works properly,
> but the flame does not come on. In both cases, the furnace follows the
> correct startup procedure, with time delays between the thermostat-up
> signal and the startup of the fan. Similarly, there is a time delay
> from the thermostat-down signal and the stopping of the fan.
>
> Checked for voltage at the furnace connection. Shore power: 13.36
> volts, battery power 13.26 volts. I understand there is a safety sail
> switch that prevents the gas from flowing when there is insufficient
> airflow, but I am not sure whether this is the root of the problem.
>
It could well be if battery power only is dropping under load and not
running the fan fast enough.
cheers
bob
shape
> I recently purchased a 19-year old Class-C motor home. The furnace
> works properly when plugged into shore power, but the burner does not
> ignite when running on battery power. The blower fan works properly,
> but the flame does not come on. In both cases, the furnace follows the
> correct startup procedure, with time delays between the thermostat-up
> signal and the startup of the fan. Similarly, there is a time delay
> from the thermostat-down signal and the stopping of the fan.
>
> Checked for voltage at the furnace connection. Shore power: 13.36
> volts, battery power 13.26 volts. I understand there is a safety sail
> switch that prevents the gas from flowing when there is insufficient
> airflow, but I am not sure whether this is the root of the problem.
>
recently (1-4 hours) been taken off a charger. You must give a battery
time to rest after charging before checking voltage. Then it will not
read above 12.6 volts. Even so, it doesn't sound like a battery
problem. My furnace is 12 yrs old, and I have problems all the time
with it igniting. I have found that the procedure in the owners manual
(wait 5 minutes and retry) works.
Also, it takes a lot of battery juice to run the furnace. I haven't had
nearly as many problems since I added an extra battery and wired them in
parallel. I can now make it thru the night without getting cold. If
your furnace works like mine, it's strictly off the battery. Both the
fan and the ignitor run off DC only. So does the thermostat.
It could also be the LP regulator. Does the pilot on the oven light
well? Do you have sufficient gas supply? There must be adequate
pressure for a pilot to light regularly.
Hope this helps.
Jack MacDonald
I fully charged the battery on Saturday morning, and it sat idle until
today (Monday night). No-load voltage was about 9 volts. AFAIK,
nothing in the motor home was switched on. Not good... FWIW, I used
the motorhome for 3 nights on battery power in late May. It *seemed*
OK then.
So I plugged it back into shore power for a couple hours and the
no-load voltage returned to 13.2 (I understand that I should let it
rest for 1-4 hr, but it's getting late and I want to get this done
tonight...)
Then ran the fan on battery power. Voltage dropped to about 9.5 volts.
Plugged it back into shore power. No-load voltage was 13.2 volts. Run
the fan, and the voltage was about 11.5 volts.
Does this sound like the battery is dying? Sticker on the battery says
it was purchased in 2002 (Actually, it says '2', and I am pretty sure
it's not 1992!!!)
Thanks in advance for any advice.
Frank
> OK - lesson learned -- measure voltage under load.
>
> I fully charged the battery on Saturday morning, and it sat idle until
> today (Monday night). No-load voltage was about 9 volts. AFAIK,
> nothing in the motor home was switched on. Not good... FWIW, I used
> the motorhome for 3 nights on battery power in late May. It *seemed*
> OK then.
>
snip
> jackmacM...@telusTELUS.net
> remove uppercase letters for true email
> http://www.geocities.com/jacksonmacd/ for info on MS Access security
You should get a hydrometer to measure the specific gravity of each cell in
your battery. They can be purchase for about $10 at autopart stores. The
procedure for this can be had at:
http://www.ehow.com/how_5923_check-rv-battery.html
Since the furnace fans usually use about 7 to 8 amps, they consume the most
energy a device can use in an rv, with the exception of large inverters. So
is this battery a true deep cycle battery or a pseudo conventional battery
masquerading as one? Deep cycle batteries are designed to be discharged up
to 80% of their capacity. Auto starting batteries on the otherhand are
designed for shallow discharges at high amperage. If you drycamp for more
then 3 days in cool weather, one house battery might not be sufficient.
--
Frank Howell
www.fphowell.com
shape
> OK - lesson learned -- measure voltage under load.
>
> I fully charged the battery on Saturday morning, and it sat idle until
> today (Monday night). No-load voltage was about 9 volts. AFAIK,
> nothing in the motor home was switched on. Not good... FWIW, I used
> the motorhome for 3 nights on battery power in late May. It *seemed*
> OK then.
>
> So I plugged it back into shore power for a couple hours and the
> no-load voltage returned to 13.2 (I understand that I should let it
> rest for 1-4 hr, but it's getting late and I want to get this done
> tonight...)
>
> Then ran the fan on battery power. Voltage dropped to about 9.5 volts.
> Plugged it back into shore power. No-load voltage was 13.2 volts. Run
> the fan, and the voltage was about 11.5 volts.
>
> Does this sound like the battery is dying? Sticker on the battery says
> it was purchased in 2002 (Actually, it says '2', and I am pretty sure
> it's not 1992!!!)
>
> Thanks in advance for any advice.
>
>
state should read 11+ volts. If you had charged it recently, not put a
load on it, and it read 9 volts, the battery is bad. Check the water in
the cells. I think it still should be replaced.
I'm sure this is why your furnace isn't working properly.
Rich256
"Jack MacDonald" <jackMACm...@telus.net> wrote in message
news:mhvod11v8dgof0ldf...@4ax.com...
> OK - lesson learned -- measure voltage under load.
>
> I fully charged the battery on Saturday morning, and it sat idle until
> today (Monday night). No-load voltage was about 9 volts. AFAIK,
> nothing in the motor home was switched on. Not good... FWIW, I used
> the motorhome for 3 nights on battery power in late May. It *seemed*
> OK then.
>
> So I plugged it back into shore power for a couple hours and the
> no-load voltage returned to 13.2 (I understand that I should let it
> rest for 1-4 hr, but it's getting late and I want to get this done
> tonight...)
>
> Then ran the fan on battery power. Voltage dropped to about 9.5 volts.
> Plugged it back into shore power. No-load voltage was 13.2 volts. Run
> the fan, and the voltage was about 11.5 volts.
>
> Does this sound like the battery is dying? Sticker on the battery says
> it was purchased in 2002 (Actually, it says '2', and I am pretty sure
> it's not 1992!!!)
>
> Thanks in advance for any advice.
>
>
Bad Battery. When plugged into shore power your converter was trying to
charge it raising the voltage into the 11.5 to 13.2 volt range. You need to
check the battery with a hydrometer to see if all cells are functional.
For information about batteries and their maintenance go to:
Jack MacDonald
wrote:
Wow -- a huge amount of information there!
Purchased a new battery, and the furnace ran immediately. Thanks to
all for the help.