Gas and Oil Home Heating Furnaces - A few gas furnace ??'s

Hi

I just purchased a "completely renovated" home in the District of Columbia.

Its a small 2.5 bdrm 900 sq ft brick 2 story, no basement row house built in 1913 and there are two chimneys. The rear one is being used to vent the gas furnace and HWT. The furnace is a power vented type. Currently there is naught but an old terra cotta liner in the chimeny with a a few cracked missing tiles. Additionally, the single wall exhaust duct extends only about 1/2" into the horizontal section of a terra cotta tee leading into the rest of this chimney. The appliances draw their make up air through a roughly 6 x12 vent to the outside of the house. Return air to the furnace is through a similar sized grate in the exterior wall of the closet in which the furnace is located (which grate attaches to a 8 x 8 duct then to the furnace) and also though two 8" round ducts leading to the upstairs.

I have several concerns regarding this arrangement;

1. venting improper. It seems (clearly) I should have a metal flue kit in the chimney. I'm not sure if this need be a type b double wall or will single wall standard galvanized duct suffice since it is within a masonry structure? also I cannot seem to find full info on flex duct attachement from the bottom of the rigid sections insidde the chimeny rahter than using a rigid tee which would involve breaking up the masonry somewhat.

2. Return inadequate? why they ran these two 6" ducts from the upsstairs (btw both begin and terminate in the same location, so why not just use inside of drywall channel in which they reside?) the one return in the downstairs seems pitiful, a single room register leading to an even smaller duct. the main supply duct leading from on top of the unit is about 10 x 14, with a total of perhaps 8 or 9 room registers throughout the house.

3. make up air inadequate or posssibly would be better to come through house, to avoid having cold air come into house?

4. thermostat (ac/heat type, manual) "fan on" setting does nothing. also the ac thermostat wiring is only connected to the unit outside the house, it then hangs free inside the closet. I guess it was too difficult to figure out for the jokers that did this installation.

btw, this is kind a mess but so far the CO detector isn't going off (yes it has batteries), the house is realtively warm ( 2 degrees cooler than thermostat setting 4' from a drafty window downstairs and 2 degrees warmer than thermostat setting at the thermostat (actually this somewhat concerns me although the thermo is right on the outside of the furnace closet wall)

I am quite capable at putting things together and making them work but this is my first house. sorry for lack of more detailed info on furnace but I'm not sure how ciritcal it is for these questions...ok...I'm shutting up now...

thanks
Dave in DC

daves_trip:

Gas heating is not my specialty so I'll save the liner question for someone else.

Return air:
You can get a rough idea if your return air ducting is adequate by slightly opening the fan compartment door on the furnace.
If there is fairly strong suction and the panel wants to snap back then you have some return air issues.
Caution: Be carefull and watch your fingers. The cover could in extreme cases snap back unexpectedly and leave you with a pinched finger!
This will tell you if you have a return air volume problem.
Return air distribution problems will leave some rooms without enough air flow.

Combustion air:
In all cases it is better to have a separate air supply for the furnace.
A high efficiency furnace will have a hook-up for an outside air line and a mid and standard unit can have the air drop in near the burner end of the furnace.
Check your local codes on this.

Thermostat wiring:
The fan switch at the stat needs to be connected to a fan relay.
Depending on your furnace it may already have one or if older one, will have to be added.