What size Weil-Mclain cast iron replacement boiler with indirect water heater?

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Old 09-18-19, 07:01 AM
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What size Weil-Mclain cast iron replacement boiler with indirect water heater?

Hi,

We are considering finally replacing our Weil-Mclain CGA5 cast iron boiler that I posted on here two years ago that has served us very well for 27 years but has been making boiler knocking/percolating type noises during fire stage. After evaluating a few contractor proposals we have decided we are not comfortable with mod-con units with our micro zones, contractors experience, higher cost, etc. so we are planning to go with a similar type cast iron boiler but add in an indirect water heater as part of the project.

We had a Manuel J performed which indicated around 68000 BTU heat loss. I also did the dry bulb approach last year that Dana outlined in an article a while back using my actual numbers and it arrived at around 62500 BTU/hour @ 60F.

One contractor indicated that the Manuel J heat loss number was on the borderline between a CGA3 (59000 BTU out) and CGA4 (88000 BTU out) but thought it was too close for comfort so wanted to go with the CGA4. The CGA5 is 117000 BTU out which the numbers show is oversized but our existing one has served us quite well for 27 years but some short cycling at times with our micro zones.

One contractor who we like is indicating that he will put in the CGA4 but indicates he would personally stick with a CGA5 with the Aqua Plus 45 indirect water heater as part of the solution. As indicated, we have had great success in our home with our current CGA5 but based on the heat loss/dry bulb numbers it shows the current boiler was way oversized.

Obviously we are a little confused and not sure if we should still tell him to go with the CGA4 or go with what has worked and what he would personally go with, especially in light of the addition of the the new 45 gallon indirect water heater.

Any Thoughts would be much appreciated.
Thanks in advance.

deeMatrix
 
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Old 09-18-19, 09:58 AM
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I wouldn't be replacing the boiler just because it's kettling, have you tried to treat it with cleaners? I had a kettling issue with my 20 year old boiler that I was able to solve using Rhomar products. I used their cleaner for several weeks and then followed by a flush and refill with their water treatment. It's been several years now and the kettling has never returned.
 
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Old 09-18-19, 05:36 PM
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Hi Tom, thanks for your reply. Yes I tried the Rhomar red cleaner that you install, run for a while and then flush followed by the blue conditioner two seasons ago. At first it quieted the system down but then the noise slowly returned.

Last season, based upon additional input on this forum I tried the Oatey Hercules boiler cleaner and it too initially quieted the boiler down but then the noise once again returned. That one wasn't a flush and readd though. I recently added some more to the system this year getting ready for the cold season as I had another quart and I've been running the system to remove some of the introduced air through the process and so far running well but waiting to see if noise returns.

Someone recently recommended trying the Fernox F1 cleaner or F3 which requires flush as another potential before replacing out the boiler. I just am a little paranoid with having a heat exchanger leak develop during the heating season and having to then react versus a planned replacement. Not sure just yet so getting ducks lined up just in case.
 
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Old 09-19-19, 07:41 AM
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I agree that you don't want to have any issues mid season, but kettling isn't going to kill a cast iron boiler, albeit annoying at times. I would try an aggressive cleaning again, followed by a good flush and refill with a treatment to help soften the water. Another thing that comes to mind is the firing rate. Being you now realize that you only need ~70K BTU, you might want to see what the firing rate is currently set at and if you can down fire it a bit and still achieve the required BTU capacity to head the home. That will help quiet it down some too. Cast iron boilers can last a long time before needed replacement and at 27 years, it really isn't that old. Good luck !!!
 
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Old 09-19-19, 11:24 AM
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Thanks Tom once again for your thoughts. I added the Oatey cleaner again this past week as had another quart and right now it's very quiet but don't want to get too excited as last times it was the same and then noise returned after a bit. I do agree that if noise comes back again though that it does make sense first to try one more aggressive clean/good flush and then refill with treatment protector before shelling out $$$ for a new boiler.

As for firing rate, that's something I need to look into more to better understand. Thanks again for your perspectives.

 
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