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Old 02-12-2021, 09:24   #1
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Join Date: Mar 2017
Location: Easton Maryland
Boat: LeBlanc trawler; 50 ft
Posts: 156
Air lock in ITR heating loop

I have a International Thermal Research boiler / heater on my trawler. This is a first rate piece of equipment however, from time to time it suffers from the dreaded "pilot error".
1. I had a long running leak which I absolutely could not find.
2. I finally found it in a leaking heater coil in the forward guest room; really buried.
3. Bypassed that heater coil by putting a piece of galvanized pipe in the "in" and "out" heater hoses and just eliminating that heat point.
4. Not sure the pump was circulating right so dropped the end cap on the pump to look at the impeller. Mistake. Drained about 7 gallons of antifreeze 'all over'.
5. The pump has a stainless steel impeller so that was a waste of time.
6. Filled the system.
7. It now goes through its startup cycle properly. The boiler fires and runs fine. The water gets hot and is circulated around to the coils where the fan(s) blow air across the warm coils and out into the space and heat the room Has worked a treat for many years.
The boat is 50 feet long and 24 feet wide. A Nova Scotia lobster boat built new as a yacht. There are three heating outlets in the upper salon and dinette and three below in the master bedroom, bath and guest room (guest room heat no more). There is heat in the upper spaces but no heat in the lower master bedroom or bath.
Obviously no hot water is making its way down to the coils in the master bedroom and bath.
The only thing left that I can think of is an air lock; likely somewhere near the top of the heater hose that turns down to the lower level.
These heater hoses (red 3/4 inch heavy duty heater hose) are really buried.
If I open up the splice where I bypassed the leaking coil I will make an unbelievable mess in a very bad place.
Blind hope leaves: time, circulating the pump hot / cold without the boiler. Waiting until I get offshore and get some rough weather to shake things up. As I said. Blind hope.
Right now my plan is to circulate every morning for 15 or 20 minutes with the boiler on and then leave it for the day or overnight. See if any air works its way out and try again.
I am leaving in about 4 weeks for the Bahamas (live in Easton Maryland) and do not have time to figure out how to redo the system so there is a valve or two to bleed it. I can be warm in the main level. Just use lot of extra covers until I get below Charleston or so.
Thanks in advance to anyone with the patience to read through this tale.
Any and all thoughts and suggestions are welcome.
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Old 02-12-2021, 11:17   #2
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Join Date: Jul 2005
Location: Bellingham
Boat: Outbound 44
Posts: 9,319
Re: Air lock in ITR heating loop

Did you do the bleed process defined in the manual? It basically disables the heater and runs the circulation pump continuously while you fill the system.. Alsom ITR tech support is good by email.
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Old 02-12-2021, 15:16   #3
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Join Date: Mar 2017
Location: Easton Maryland
Boat: LeBlanc trawler; 50 ft
Posts: 156
Re: Air lock in ITR heating loop

Thank you Paul.
Reading and reading manuals.
ITR support is great.
Just thought I would throw this out to the group and see if anyone had any "magic" ideas.
Big believer in magic - and luck.
I have two loops. At the point now of shutting off the 'good' loop - upper salon - and see if I can get it to circulate on the longer, lower loop.
Costs to learn. Just have to run hard to get south.
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