This is long. That's because it's not so much a technical fix that I need as a Wise
Opinion. I put a lot of details in the note.

I'm a new user here.. And I have a problem that's hopefully simple.
I'm a retired scientist with a background in electronics, chemistry and materials.
This is my first post. So be friendly and I'll do my best to be clear and to contribute.
Thanks
Andy.

Sorry this is fractured. I'll fill in the spots if you folks reply.

One of two units we have went out today an hour ago. I'm wanting the best choice for a
Dad who's 87 and has his own opinions based on what he heard 70 years ago or from the
Paperboy.

The house.
1940's 2200 sq foot , flat roof, 10' high ceilings.
Separate large lanai (room) on back with it's own heat/cool pump.
Main house unit went out. See how below.

Main Q. Can we reweld the flame box without creating a hazard or otherwise
Legally creating a problem? Was told it can't be repaired. I say it can be repaired
But not sure since I'm here asking you folks

The firebox has 2 - 1" cracks where the metal became brittle and simply crystalized.
The main blower probably presurizes the firebox slightly through the tiny hole although
there's a 2nd baffle behind the hole. As if it were a double wall. Although I know there
is a tiny bit of light from my flashlight that will go from the firebox to the air plenum(right word?)

Can we reweld a plate over the 1" cracks in the fire box without creating a hazard or otherwise
Legally creating a problem? I was told by the Carrier guys that it can't be repaired.
It looks simple to me. The entire unit looks almost new even though it's 50 years old.
It's worked exceedingly well.
I say it can be repaired but not sure since I'm here asking you folks

COST OF ENERGY:
The monthly bill in winter and summer is about $140. The house is
Well built.


Two heater / coolers:
1 An enclosed lanai on the back of the house about 500 sq feet has its
Own 3 year old heatpump which is very powerful and probably COULD heat the
Entire house. But the ducting is only in the lanai and it's on the roof. (ducts and compressor)

The rest of the house has ducts within the walls I think..
I had asked about tying the lanai heatpump to the ducting in the house and one of
The experienced repairmen said the labor cost would be too high compared
To simply putting in a new unit and using the old ducting.

2 Heater/ Cooler Carrier about 1940's . Water cooled compressor and
Large (unknown BTU) heater. Both parts are in the house in 20 sq foot area in a closet.
The heater and cooler work great. Even for the age. And it's water cooled compressor
For the cooling. We reuse the water on the lawn.

My Dad is 87 and in good health except for blindness.

The full size
Near industrial heater installed probably in 1945 went out.. that is
The heater box has two 1" long cracks in it. They are on either side
Of the heating flame and it's basically just metal that became brittle
Over 50 years of heating. (They picked the wrong kind of metal
Cause the deflector shield is 100%. Anyway..

The crack was found when the repairmen from Carrier came out to
Repair the thermostat and had to remove the plate / burner to access
Something ( I guess the thermocouple itself).

So now my Dad has this dillemma. Buy a new unit or live with just
One heat pump that is in the back part of the house. May he would use
The electric heat from the oven in the kitchen where he tends to hang out a lot.

The cost to replace was guesstimated at $8000.00

This was 1 hour ago they left. I found your site , signed up , and am asking for help.

My background is electronics and analytical chemistry. I understand about 99.99% of
Where we are with this problem. The only thing is the part about my Dad being 87.. and
I probably won't get this house for myself.

As always if anyone is wanting any kind of help with electronics, batteries, sciences of any kind, chemisty, or research help I'm glad to assist. Just PM me and ask away!
Andre

The Repair Guys - I pretty much trusted his opinion as I'm a retired laboratory instrumentation tech who's worked with many kinds of automation , cooling heating pumps, robotics, and much more. He knew his line of work and we talked a lot about
What all we could do , could not do, etc.

I would replace the system. If you have a crack in a cell in the heat exchanger the hole heat exchanger is weak. If you try to repair one crack it may only be a day or two before the next crack shows up. Plus the service tech may have stopped looking for cracks after the first two so you may have moore. It sounds like you got your moneys worth out of that unit if it is that old. Don't take a chance with your dads health replace it.