Recommendation for replacing an old furnance

SD2000

My current furnace is 34 years old, and I currently have no AC, and my family typically don't need extreme comfort (aka we set thermostat at 66-68F in winter and 82-85F in summer). I live in San Diego, CA. I love some feedback on what I should consider as replacement. I have seen some discussions about heat pump being the most energy replacement for my central air. Is that the best energy efficient choice for heating the house? Would I be able to use the heat pump to also cool the house and skip installing an extra air conditioning system?

Hot_water_fan

Yes a heat pump handles both. It is the most efficient option. 

Jamie Hall

San Diego? Heat pump is definitely the way to go. Make sure that it gets sized correctly. Particularly in the air conditioning mode if it is too large it will have trouble controlling the humidity.

Jon_blaney

Is your current furnace failing? Furnaces are very long lasting and can frequently be rebuilt. You can usually add an ac coil to your furnace or cheaper still, window units. Is there some specific issue you are trying to address besides age.

SD2000

@Jon_blaney the furnace still functions ok, i thought they need to be replaced due to age but it seems like I can just riding it longer.

mattmia2

It depends on the installation and quality of the original furnace. My guess is that in san diego it gets very little use compared to say the midwest. If it is all rusty time for replacement. If it looks nearly new and someone competent tests combustion and draft and the safeties and that all checks out then it can go longer. There is still the question if it would make sense to spend money on making shee tmetal to put an AC or heat pump coil on a 35 year old furnace.

pecmsg

For the little if any use left in that furnace, scrap it. 

A heat pump with electric back up. 

Jamie Hall

I mentioned above that a heat pump is the way to go -- if, in fact, you need to replace it. But I completely agree with @mattmia2 -- that only applies if you really need to replace it. Furnaces age not by year, but by running hours -- and I'll guess that in San Diego your 35 year old furnace has about the same running hours as a one year old furnace in, say, New Jersey.

If it ain't rusty, and ain't broke -- don't fix it.

GW

You’ll get some good opinions here, but you really need a more local professional that’s familiar with your climate zone, and local/state rebates. If you’re in Massachusetts, I’m the man. If not, I can only opine. Good luck 

HVACNUT

Can you post some pics of the current setup?  Make and model?
If what you're calling a furnace, is in fact a gas fired warm air furnace, then it should at least have a maintenance done if it hasn't been done already within the past year. The maintenance should conclude with combustion and draft tests to show you how healthy the system is. 

SD2000

Thank you so much for all the great input. the house is currently rented out until April, I only have a pic from far away. perhaps I should stick with it until it dies

jplee3

Just wanted to note that electricity costs in CA are very high. If this is San Diego, presumably he's with San Diego Gas & Electric for the power company, which is reported to have the highest electricity costs in the nation. Natural gas is cheaper out here. Unless OP has a correctly sized solar array (which accounts for surge usage when it's hotter or colder than normal), wouldn't a heat pump be expensive to operate out here?

I am going through a similar situation where our furnace is seemingly on it's last legs - some portions of the heat exchanger appear to be well worn - no CO detected...yet. Other than that, I'm suspecting the flame sensor/thermocoupler is bad and possibly more but I'm not sure. The cost of the flame sensor is $100 and that won't guarantee that the issue is resolved. Even if it does though, the remaining life on the heat exchanger is a real concern. Anyway, most of the HVAC contractors I've had come out have all told me that unless I have solar, a heat pump is going to be run quite expensive so stick with a traditional natural gas furnace and condenser setup.

Hot_water_fan

@jplee3 higher rates, but who cares in that climate? It’s 1200 heating degree days. Solar is cheap there so makes sense either way.

jplee3

Hot_water_fan said:

@jplee3 higher rates, but who cares in that climate? It’s 1200 heating degree days. Solar is cheap there so makes sense either way.

1200 heating degree days? What does that mean?
Solar is cheap *if* you have it - we have a Spanish clay tile roof so there's no way we're having anything installed up there and breaking tiles or causing potential issues with roofing. I set the t-stat to 68F and during Dec-Jan our furnace kicked in multiple times throughout the night. Solar + heat pump makes sense out here.

Hot_water_fan

Heating degree days are one way to measure how cold a climate is, so a measure of how much heating a house would need in one place vs the same house in another. 1200/year is nothing, about 1 month in a cold climate. 

JUGHNE

I would keep using the existing furnace until it is dead....you need good CO detectors in the house.
If the unit fails in the "dead of winter" of San Diego, would anyone freeze or the piping freeze up?

A couple of space heaters would probably get everyone/thing out alive until you got a replacement.

If Fargo ND, then different situation.

Also as far as efficiency, if tenants pay the heating bill and it is not outrageous, there is no ROI on investment for you, the landlord.

SD2000

thank you for all the great feedback. final decision is to wait it out until the furnace dies or at least heat pump becomes affordable

hvacbro

SD2000 said:

My current furnace is 34 years old, and I currently have no AC, and my family typically don't need extreme comfort (aka we set thermostat at 66-68F in winter and 82-85F in summer). I live in San Diego, CA. I love some feedback on what I should consider as replacement. I have seen some discussions about heat pump being the most energy replacement for my central air. Is that the best energy efficient choice for heating the house? Would I be able to use the heat pump to also cool the house and skip installing an extra air conditioning system?

San Diego stays pretty warm throughout the winter season while summers can obviously get very hot, so a heat pump does make a lot of sense as you can have a highly efficient and inexpensive source of heat for mild SD winters. And, as you have already alluded to, you will also have cooling capabilities should you need it. Those long summer days in San Diego can get quite hot and uncomfortable.

Another benefit of a heat pump would be not having to buy two separate systems, as you get both in a single unit, meaning you can save money on the overall installation costs.