GMP125-4 Heat Exhanger - Worth Replacing?

deccher

I have found multiple cracks on a heat exchanger in a Janitrol GMP125-4 furnace. I believe this is now a Goodman-owned product.

Is it worth replacing this heat exchanger vs. purchasing a new furnace?

The furnace is only 11 years old...

greghvacguy

I would not. dont care for janitrol (jan it junk). Just my thought....

hvaclover

As you were informed at the other forum: better to replace furnace.

Dr Heat

Change the heat exchanger if it is still warranted. All you will pay is labor and maybe shipping. But if you cannot find a tech who wants to do a little labor and only wants to sell new or if you want to spend extra money then get new. The new one will be shinny.

Wait in this economy you should spend spend spend. So buy new new new.

It sickens me that HVAC professionals would flatly say replace an 11 year old furnace.

Even janicrap should last 20 years.

You should look at other parts also venter motor blower motor etc to see if they are original or replacements.

MechAcc

Find out why it cracked.

Check total External Static Pressure. Is airflow correct. Returns a 125,000 may need two returns. Both sides or bottom and one side. Check the install manual.

Found a GMPN100 this week with a - 0.625 inch WC on the return without the filter - 1.15 with the HO super efficient 16 x 20 x 1 filter. Heat exchanger cracked. Two 6 inch round returns to the return trunk. There seems to be more and more folks in this trade doing things they shouldn't do.

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hvaclover

Hi Guy!

The reason most HVAC guys would suggest replacing the furnace is because the amount of money to change out HT EX is a considerable portion of a new one. And in 11 years there has been so many more benefits added and improve made to current models it just makes good economic sense.

Dr Heat

I charge on average $400 to replace a heat exchanger plus parts. If the exchanger is under warranty the cost of shipping can be $50 to $100, if it is a Heil then I don't get charged shipping. So the total cost to ho is around $500 to $600 the cost of a new unit $2000 to $3500. I cannot think of any improvements in the last 11 years worth $1500 to $1900.

Its not like the old days when changing a heat exchanger could take 5 or 6 Hours. I have changed primary and secondary in less then 2 hours.

I think the real issue is do most techs know how to do it.

Do we sell the customer life time warranties that we have no intention of honer ring?

flashheatingand

10-4 Doc!!! This may not be a good thing, but I like your style.

I don't think things have changed drastically since furnaces made in the mid 90's. Everything is case by case. Sometimes it is beneficial to just replace the furnace and start afresh. Sometimes, replacing just the h.e. is justified. The key is giving the h.o. the options and letting them decide.

Dr Heat

If more of us considered the HO and informed them of their options our rep. would be much better as a trade. Tomorrow I am rring an old Heil 90 I put it in 22 years ago I will replace it with a new Heil H9MPD050 I would prefer the H9MPT050 (two stage) but the HO chose (after much educating) the single stage he whanted an N series (Builder model) but I was able to upsell.

hvaclover

You can't think of any improvements in the last 11 years that makes it worth while to consider a new furnace?

If you are are happy with $400 with a ht ex change out than I am happy for you.

Each of us knows our own worth and will price accordingly. Around here $400 buys a 1/4 hp blower motor.

Must say i have not seen any one worth his salt claim a 90% furnace is not worth investing in cause the difference it an an 80% is not enough to consider. Another argument that the 90% would eat up what ever gas savings you you banked in repair cost. You pay once for a 90% but gas prices keep raising.
There is no diff between the 80an the 90 except a secondary heat ex so how can the incident of repair be higher than the 90.

Dr Heat

do the math it is not a no brainier to go to a 90
now all our new work is 90% and the majority of our change outs but there are times when the 80% is the better choice.

As far as pricing I would get $400 or there abouts for a blower motor it can be a more time consuming job also you will make a smaller profit on a four hundred dollar motor then I will on a $400 HE just a thought

hvaclover

You are in the minority if you think 80s are better investments that a direct vent 95 2 stg vs. There is 15% saving right off the top with the furnace alone, than there is the saving of reducing the btu usage of the over sized furnace being replaced.

Apples to apples: Original furnace is 100kbtu at 60%, really needs only 60 or 75Kbtu but was oversized cause at the time of build gas was cheap and bigger was considered best, Assuming a 100kbtu furnace in a home that needs only 60kbtu, just replacing a 60%er with the right size furnace would be a 40% saving in gas used.

Rplace that 60k with a 95% is a saving of 55%. Then there is the comfort aspect that a 80 cannot deliver over a 95%.

If all you can sell in your neighborhood is 80s than that is just your market limiting you.

But if you aren't offering 90s as a sales option to your customer than i think you are leaving a whole lot of money on the table.

Dr Heat

This all started because the original poster said he had a unique install where the new vent was impractical.

Also I stated that the vast majority of our work is 90% we only put in maybe 40 80% last year and most of those were in three four or six story loft buildings were the side wall vent is against code because of adjoining structures. We also run into cases where association rules will not permit side wall vents.

All of this not withstanding there are single family homes where because of finished basements second stories etc. It makes no cents, or dollars.

hvaclover

Misread your post. My bad.

So I guess you didn't post this in DIY?

Quote:
Once you have subtracted these non heating fuel costs you simply take 15% if that is the efficiency difference and wella you approximate savings.

I have not found a case where the payback in my area warrants the 90 over the 80
Bare in mind we need to consider interest you will pay on financing or interest lost by withdrawing savings.

Consider how long you expect to stay in your home

Dr Heat

yes I did post that on diy and stand buy it. I should edit that to say I have not found a case using na gas on a retro

hvaclover

i think this post you made contradicts what you just said





Join Date: Jan 2009
Location: Northern Central IL
Posts: 49

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Why a 95 it may well be that an 80 would be a more cost effective choice.

What is the fuel source LP or NA

How much pvc will be needed to run a new flue

Is the existing flue small enough to handle just the water heater or will you need to instal a liner for the water heater?

Where are you located?

hvaclover

and this one




Quote:
Originally Posted by beenthere
If your getting a 90% plus, make sure they pipe it up as a direct vent.

If its properly sized, its worth the savings.

Unless you own stock in the gas company.

Dr. Heat Quote:
If you have combustion air in the mechanical room does a two pipe really increase efficiency by that much

Dr Heat

I am not sure what the contradiction in the earlier post. I have never said that an 80 is always the best choice

mo-flo

goodman has a replacement program for the gmp models i believe,will run out soon though....proper sizing of furnace is key.If you replace heat exchanger there will only be one year warranty....in my opinion i would have load calculation done first,then make decision...