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Old 02-07-2009, 10:43 AM   #1
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York PM9 Mod Furnace, Aux Fan Question


I have a York gas mod furnace that I installed in the fall. Due to the layout of the house, I have one room at the end of the duct distribution that is hard to heat. It has a large glass sliding door on one end and a large bay window on the other. I have balanced the system as best I can to make certain that I get the warm air I need, however the room loses heat quicker than the room with the tstat. I installed a 115V inline booster fan that dumps an additional 500 CFM into the space. This is controlled via a simple on/off switch mounted on the wall in the room.

I would like to find a (simple) way to have the fan come on when the furnace comes on. One idea was to power the fan with the Aux line voltage contacts on the furnace that were provided for the humidifier (only provide power during a call for heat). Unfortunately, this set of contacts is limited to 1 Amp. I can not find the amp rating on the fan in all the literature I have, but I have to believe that it is more than 1 Amp.

Any ideas?
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Old 02-07-2009, 11:34 AM   #2
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York PM9 Mod Furnace, Aux Fan Question


Have the hum contacts pull in a small fan relay and have the relay power your booster. Or get or borrow a amprobe and check the amprage. or they make a air pressure switch/ sail switch for booster fans that sense the air movement in the duct work when blower is on.
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Old 02-07-2009, 11:36 AM   #3
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York PM9 Mod Furnace, Aux Fan Question


Just noticed 500 cfm Isnt that really noisey?
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Old 02-07-2009, 11:39 AM   #4
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York PM9 Mod Furnace, Aux Fan Question


Another way to do it is buy a 110 volt thermostat that is used for electric baseboard heaters and use it instead of the wall switch. Probably available at HDepot. A 220 one will work also, ignore one set of contacts.

Last edited by yuri; 02-07-2009 at 11:41 AM.
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Old 02-07-2009, 12:06 PM   #5
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York PM9 Mod Furnace, Aux Fan Question


thanks for the quick replies!

1. yes, 500 cfm is quite noisy! Added to the problem is that the room is over a crawlspace, has two 8" ducts feeding it, so The fan is in the further of the two, roughly under the center of the room floor (living room). However, I find that when the furnace calls for heat and I turn on the fan, it warms the room very quickly! so I can turn it off soon.

2. Actually, I am looking at a booster fan duct tstat right now. It is based on warm airflow sensing to operate. My only concern with this is that I also have my furnace setup to have the fan run periodically (30 minutes/ hr) for a cleaning mode, that also helps to balance out the temps in the house. I can not find in the literature for the duct tstat what the temp needs to be to operate the fan, but I am looking!
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Old 02-07-2009, 12:14 PM   #6
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York PM9 Mod Furnace, Aux Fan Question


A booster fan?

Some how with such a high tech furnace that seems like a stone age remedy. )no offense guys)

There are ways to get that room heated right with out a booster fan.

And in this situation it probably wont work anyway.

Who installed this Mod Furn for you? I might have a few solutions.
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Old 02-07-2009, 12:48 PM   #7
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York PM9 Mod Furnace, Aux Fan Question


Use a thermostat with fan circ/recirc ability.

Or just run the fan 24/7

Fan circ is probably quieter and better.
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Old 02-07-2009, 12:53 PM   #8
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York PM9 Mod Furnace, Aux Fan Question


Been my thinking here is about the same as you propose. But if the duct just isn't up to the job even "Fan On ' won't help.
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Old 02-07-2009, 01:22 PM   #9
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York PM9 Mod Furnace, Aux Fan Question


The York furnace replaced a 50 year old oil-fired unit. There were no duct mods to the system other than a slight tweaking of RA for the new furnace. I used to design HVAC systems and quickly realized the reason for the cool room is poor duct sizing. Rather than rip out 50' of ductwork and upsize the main, it was easier to install the booster fan to one of the branches that feeds the room. The Tstat I am using for the furnace is a LUX CAG1500, which has settings for Auto, Clean and Fan operations. Auto is simple, fan runs when there is a call for heat. Clean mode allows the fan to run for X minutes per hour (currently set for 30 minutes per hour during the day). The fan mode is simple 24/7 fan operation. Fan speed based on the fan speed jumper position on the furnace control board.

To add some complexity to the system, I have an add-on wood furnace installed with the ductwork ducted to the furnace system RA and SA mains.

The wood stove does provide nice aux heat to the system, however due to the duct sizing restrictions, living room gets very little heat, which is another reason for adding the fan.

My answer to this problem is to install a duct mounted tstat for the booster that will only come on when it senses a worm airflow (adjustable). Additionally, I will have a cut-off switch that will allow me to kill the power in the event that we want to shut off the fan, due to heat or too much noise.

Oh, FYI, I installed the furnace myself, but again, did very little work on the ducts. Additionally, I also considered moving the tstat for the furnace to the living room, but I am fighting the boss on that one. Plus, I could see the system short cycling do the high amount of glass in the room.

Last edited by javan; 02-07-2009 at 01:27 PM. Reason: more
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Old 02-07-2009, 01:24 PM   #10
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York PM9 Mod Furnace, Aux Fan Question


His post suggest implies that it may not warm up enough at all, or that room may be getting enough heat while the system runs. But then cools off faster then the rest of the house.

A little hard for me to tell which.

But, if its not warming up enough while the furnace is heating. I'd add an dditional supply, and still use teh blower in circ, or fan on, instead of a add on fan.
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Old 02-07-2009, 01:32 PM   #11
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York PM9 Mod Furnace, Aux Fan Question


It is duct restriction. See above.

Additionally, The room in question was definitely an addition to the house. the previous owners had a kerosene heater (piped through the wall to a tank), to take care of the need. However, we got rid of it since it took up so much floor space.

Obviously, in hind-site, we learn that the reason for the aux heater was that the existing duct system was never modified accordingly for the new room.
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Old 02-07-2009, 02:17 PM   #12
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York PM9 Mod Furnace, Aux Fan Question


Constant circulation isn't going to be of much help if you have poor duct work.

Neither is a booster fan. It can't push what isn't there (ie; lack of warm air at that run).

Somebody can correct if i am wrong, but since the furnace is a modulator even with constant circulation the room is going to have bad heating not just because of the duct issue, but the control location of the stat. The main structure will warm to comfort level but always leaving the addition far behind before it even gets a chance to warm up.
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Old 02-07-2009, 02:50 PM   #13
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York PM9 Mod Furnace, Aux Fan Question


Quote:
Constant circulation isn't going to be of much help if you have poor duct work.

Neither is a booster fan. It can't push what isn't there (ie; lack of warm air at that run).

Somebody can correct if i am wrong, but since the furnace is a modulator even with constant circulation the room is going to have bad heating not just because of the duct issue, but the control location of the stat. The main structure will warm to comfort level but always leaving the addition far behind before it even gets a chance to warm up.
The following "tweaks" have worked so/so

1. Run the booster fan when the furnace fires. Downside is that you can quickly overheat the room. Tstat calls for 72 degress, living room can get to 78 degrees.
2. with a wood-fire going, put the furnace in either clean mode (30 min fan operation / hour), or continuous mode and run the booster as needed. this usually will keep the room around 68 to 70. But I do not have a wood fire all the time.

Additionally, to add insult to injury, this living room is over an un-insulated crawl space, which is typically very cold. One thing that has helped this year is to blow in warm air from the basement into the crawl space, when there is a fire in the wood stove.

too many variables in this problem!
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Old 02-07-2009, 03:23 PM   #14
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York PM9 Mod Furnace, Aux Fan Question


Didn't get the rest of what you posted. Sorry, i just read "booster fan" and thought about the general failure rate they have. But, yes, as you said they can work in SOME apps. Yours is one, obviously.

There are ways to average out the temp diff you have in the areas.

i think the most important one is getting some insulation in the necessary places is job one.

A zone control system might help too. It will close dampers to the rooms already at set point and (theoretical) keep the addition form over or under shooting set point. I am not that well versed in them to advise you further and I think it would likely require an on site evaluation, but it seems to be a good place to start.

Hope this helps.

Sorry for the first misunderstanding.
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Last edited by hvaclover; 02-07-2009 at 03:30 PM.
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Old 02-07-2009, 07:58 PM   #15
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York PM9 Mod Furnace, Aux Fan Question


Why not spend the time and money and insulate the crawl. Save energy dollars and increase comfort. If the problem is a cold crawl space dont put a band aid on the problem fix the problem itself.
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