Heat Exchanger Water Text & Conflicting Advice

[SombraAla]

Some background before I begin:
I'm a (relatively) clueless homeowner when it comes to furnaces and whatnot. Bought our first house 1 1/2 years ago, house is old - built in 1939. Current furnace is ~10 years old (Lennox WhisperHeat), 125k BTU. Not sure just how well it was maintained before we acquired it, but suspect not that well. Both times we had it serviced the serviceman mentioned cracks in the heat exchanger.

Ok, now the first question:
About a week ago we had a tech come in and perform a 'Water Test' (we were given a coupon for a free one at the last service call) on the heat exchanger. Apparently 2/5 cells failed the test, at which point the tech said he was 'supposed to turn the furnace off' but, since it was 10F outside, instead I signed a paper which said I was aware that the furnace was potentially unsafe. He then set us up with an appt. with a sales rep from his company.

I then decided to read up a bit on what this water test is all about and found No links to other forums allowed discussion on . The folks there seemed to have very mixed opinions on the issue, so I posted No links to other forums pleaseforums at which point someone directed me here.

So the first question is - what do you all feel about this test? It's my feeling that it will most likely find issues if they are there (if there's a big gaping hole in the thing, yes, water will pass through) but I have no idea what the false positive rate might be, etc. The whole thing with signing the acknowledgment t that the furnace might be unsafe - I see how that could be a legit limitation of liability type of thing but also see how it could be used as a pressure tactic to sell new furnaces. I do trust the company, for the most part, but after reading the alt.hvac thread I did start to question whether or not a new furnace was absolutely necessary or not.

As for the second question:
Some more background relevant to this question: Our house is a 2 story house and we do have a heat pump. Heating switches to the gas furnace at 45F. The house is ~2000 sq ft., and we live in Kansas City.

Despite waiting to hear more about the water test stuff, we went ahead and met with the sales rep, she looked at what we had and walked through the options - 1 stage, 2 stage and variable speed. She indicated that variable speed would benefit us, they had a sale going for a 2 stage for 1 stage price or Variable for a 2 stage price, whatnot.

To test out some more options, my wife called two other companies and described our situation. While talking to one of them, the person she talked to said that a variable speed furnace would have problems in a 2-story house, and also seemed to think that a 2 stage would not be worth the additional cost for our situation. This seems to be in direct contention with the first set of information we were given.

One thing that my wife was unable to tell the gentleman (apparently he kept interrupting) is that we are able to control which rooms receive heat/air through manual damper controls on the duct work in the basement - we (mostly) close the 1st story vents in the summer and the 2nd story vents in the winter. I'm not sure if that makes a difference in the case or not.

Its also my understanding that variable speed will be more energy efficient while we are on the heat pump heat(?)

So basically, the 2nd question is - would a 2 stage or variable speed furnace be advantageous or disadvantageous in our house?

Also, if you want to go for a bonus, would it be much/any more efficient to have variable speed with a heat pump?

Thanks for any help you folks can give me, sorry that I write so much but I figure it's (generally) better to have too much information than too little.


Don't post links to other forums. Please read site rules, Thank you.

[beenthere]

Variable speed blowers work well in single, and 2 story houses.

Closing the dampers as you are, may be the cause of your heat exchanger problems, if it indeed does have holes or cracks in it.
Since closing those dampers, decreases the amount of air over the heat exchanger.

Do not close the dampers, adjust them to lower air flow, but not stop it.

If you do that with a variable speed blower, it will make the blower work harder. Use more electric, and could be harmfull to the motor.


Depending on type of heat exchanger cell you have, failing a water test, means nothing.

A visual inspection should be done.

Before you just replace that furnace.
Have a load calc done, to determine what size equipment you need.

A proper sized furnace, will have longer run times then an oversized one. And give you a more even heat in the house.

Same with A/C.

[SombraAla]

Variable speed blowers work well in single, and 2 story houses.

Awesome, good to know

Closing the dampers as you are, may be the cause of your heat exchanger problems, if it indeed does have holes or cracks in it.
Since closing those dampers, decreases the amount of air over the heat exchanger.

Do not close the dampers, adjust them to lower air flow, but not stop it.

Well, there were cracks on the heat exchanger before we realized that we had the opportunity to use the dampers, but definitely good to know. Might have exacerbated those issues though.

Depending on type of heat exchanger cell you have, failing a water test, means nothing.

A visual inspection should be done.

Yea, I do think that the water test was prompted by a visual inspection... does this mean that the water test necessarily doesn't mean anything? Does it work on certain types of heat exchangers?

Before you just replace that furnace.
Have a load calc done, to determine what size equipment you need.

A proper sized furnace, will have longer run times then an oversized one. And give you a more even heat in the house.

Same with A/C.

Well, the sales rep had said that she thought the current furnace we have was too big for our house (and that it being too big could have caused premature wear on the heat exchanger, whatnot) and was moving us down to a 100k BTU furnace, at least with what she was offering us. She definitely didn't do any calculations though. How long would that take and who would be able to do it (tech, sales rep, etc)?

Thanks very much for your help, I appreciate it.

[beenthere]

Yea, different types, can fail the test, when there is nothing wrong.

You can do you rown load calc.
http://hvaccomputer.com/talkref.asp

The salesman/person, should do the load calc.

[cmajerus]

the water spray test works very well on the whisper heat clam shells, they are welded seams, so any leakage is bad leakage. Get your estimates and get a new system.

And I think that your furnace is older than 10 yrs, what is the serial number?