Side Arm Heat Exchanger Help Please (Set up has worked for 19 Years)

[HoosierBoiler]

Looking for some help from fellow OWB owners. I have a Central Boiler 6048 feeding a 50gal electric hot water heater and then heating approx 3,000sf home. I run the OWB at 185-190° and for 18 years, never had a problem with my side arm heat exchanger. I fire up the OWB in October and run is non-stop until May. For 18 years, I have never used the electric hot water heater when the OWB was firing.....I actually throw the breaker at the main just to make sure it isn't pulling any electricity. Well.....about this same time last year with little warning we were surprised with a cold shower one day. I drained the hot water heater and had very little mineral build up flush out but I flushed out what I could and it still didn't help. Of course I thought I lost my thermal siphon so I opened my bleed valve and let some water flush out. Still didn't fix the problem. Called the plumber who originally installed the set up when we built the house, only to find he was semi-retired and really not too excited to come out and work on it. We flipped the breaker on so we could get some hot water from the electric water heater....waited a few days for another plumber and to our surprise, we suddenly got a scalding hot shower (we don't run a mixing valve...maybe not the safest but our youngest is 13 and we all know to be careful)......so what must have been an air lock, worked itself away and we were happy, flipped the breaker again to off, and enjoyed "free hot water" until May. This past October we fire up the stove, everything is great, "free hot water" all fall and all winter.....until 2 days ago! I repeat the steps as I did this same time last year, flush out very minimal mineral deposit flakes, bleed the valve, and then hope for the best. Hasn't helped.

• Do you think it is a thermal siphon issue with an airlock?
• I know at least the outer jacket of the side arm is working because it is almost too hot to touch. After 19 years is the inner tub maybe plugged?
• If I try to force water with the garden hose to push out the air lock, I assume I run it into that valve on the "bottom right" of the lower unit picture, keep the bleeder valve closed, but do I need to have other valves or hot water faucets open to let that "hose water" flow through and go somewhere?

I thought about doing a plate exchanger, etc. but this exact setup has worked for 19 years so I am confident it is a proven concept but just something minor is preventing it from working properly. Please share your suggestions! Thank you!

 

[salecker]

When i built my system i wanted free hot water as part of it.
The guy who designed it told me right off the bat there is no free hot water.The BTU's that you use to heat the water has to come from somewhere,ie your wood pile.
Sorry i can't help on your issue,just wanted to address the misconception of free hot water from a boiler.
I had two good reasons living in my house not to have the hot water from the boiler,my wife and daughter.With unlimited hot water they would have showers for hours.
Cheapest hot water is an electric heater,if you are really cheap insulate the heck out of the heater.

 

[HoosierBoiler]

Thanks! Considering I have an unlimited supply of ash trees (no thanks to the Emerald Ash Borer invasion), and I have 3 daughters and a wife, and my house is all-electric (which means I wouldn't have warm feeling air coming out of the registers with a heat pump), I consider burning the OWB as a sunk cost. I need the chainsaws, log splitter, tractor, and other tools to upkeep our property anyway, so although I fully appreciate the laws of physics that energy cannot be created nor destroyed, I do consider the free firewood and my free labor to stoke the OWB different than when I pay the electric company $0.12/kwh to heat my water. If I am throwing 8 logs on to heat my house, might as well throw a 9th log on to heat my water. Would love any troubleshooting suggestions from anybody!

 

[hedge wood]

Hoosier Boiler Welcome to the forum. It has to be a flow issue. So it comes from the OWB to the side arm first and then to the device your heating the house with? Is the device that's heating the house working right? If it is then the flow on the OWB must be working right or if that side was no flow or air locked your house heating device wouldn't be working. Next is the side arm plugged on the domestic side? I have put in a couple side arms and not much to go wrong. I run a plate with a pump on both sides and a thermostat for my domestic hot water off my Garn.

 

[HoosierBoiler]

Thanks Hedge Wood! The heat exchanger at my air handler, which does properly come after the hot water heater, is still plenty hot and my side arm is hot as well as my supply and return lines of PEX that is exposed so I am with you, if it isn't an actual air lock, the side arm might be plugged on the domestic side. Do you think I can fish a piece of wire up from that valve I talked about putting a garden hose on? I guess I would just shut off the main, drain the tank again, and then start running something like a small brand new drain snake up in there? Is that worth a try or do you think after 19 years it's just time for a new side arm? If I am "plugging up" a side arm, how many years can a guy expect to get our of a plate? Seems like the plates will clog up much quicker?

 

[mark cline]

Following in earnest , I will be putting in a side arm before next winter.

 

[Case1030]

I agree with getting your DHW working again.

When spending 10k plus on a boiler (without install). It's definitely worth it to add everything you can onto your system. Sure you need extra wood... but all boilers do better when being worked rather than idling. So more heatload the better in my opinion. (Still need to load it every day)

I run my unit all the way into mid to end of May. Start it end of September. I'm going to use it regardless. Soon I'll have it hooked up to my pool in the summer as well, which means even more use out of my investment.

 

[maple1]

I think after that many years I would just get a new one. Last years issue could have been build up flaking off temporarily blocking flow.

And while I was at it, plumb in with unions and add isolation valves and hose bibs to make future flushing and servicing easy.

 

[brenndatomu]

I think after that many years I would just get a new one. Last years issue could have been build up flaking off temporarily blocking flow.

And while I was at it, plumb in with unions and add isolation valves and hose bibs to make future flushing and servicing easy.

Could be...but you'd think you'd see the lack of flow somewhere else...or be able to flush some junk out.
I wonder if he has a worn out pump impellor that is not moving water well anymore...which allows air lock to happen easily.
I recall reading on another forum about a fellow with a similar issue...he ended finding that one of his pumps had a plastic impellor that was about shot and it was actually starting to spin on the shaft sometimes...seems to me it had an intermittent weird noise too.
I dunno...just a SWAG...this stuff is hard enough to diagnose in person, let alone remotely.

 

[maple1]

Could be...but you'd think you'd see the lack of flow somewhere else...or be able to flush some junk out.
I wonder if he has a worn out pump impellor that is not moving water well anymore...which allows air lock to happen easily.
I recall reading on another forum about a fellow with a similar issue...he ended finding that one of his pumps had a plastic impellor that was about shot and it was actually starting to spin on the shaft sometimes...seems to me it had an intermittent weird noise too.
I dunno...just a SWAG...this stuff is hard enough to diagnose in person, let alone remotely.

From my interpretation, it's the DHW side that isn't flowing. That loop should be natural thermal convection- no pump. Which wouldn't really take much to block.

 

[hedge wood]

Looking at the pictures it looks like there is a union on the bottom of the side arm on the domestic side. I would disconnect it and flush the side arm both ways and see if there is a mineral build up in one of the ninety degree elbows or the side arm it self.

 

[HoosierBoiler]

I agree with Maple1........and you're darn right, while putting a new one in, for certain I will be adding isolation valves and hose bibs to make flushing and servicing easy!
Thanks everyone for your help. Feel free to add more comments and I will be sure to report my results once I tackle the project and do an inspection of the almost 20 year old side arm.

 

[HoosierBoiler]

It might be this summer before I report the results. It started heating the water again, so there was either an air-lock or some sediment cleared itself and I regained by thermal siphon again. I will wait to tear into this summer when I have more time. Very odd that it was similar in timing to last year and the duration of about 7-10 days was the same as last year.

 

[yooperdave]

It might be this summer before I report the results. It started heating the water again, so there was either an air-lock or some sediment cleared itself and I regained by thermal siphon again. I will wait to tear into this summer when I have more time. Very odd that it was similar in timing to last year and the duration of about 7-10 days was the same as last year.

Something else to consider is the way the side arm reconnects to the water heater. I thought I had read somewhere that after leaving the side arm assembly, it should be no more than a 4" drop back into the water tank.

But, then again, it's been working the way you have it plumbed in for almost two decades; kind of hard to argue with success, no?