Got a heat EXchanger problem?

[Kevin in Ohio]

I've had my OWB online now for 15 years and have had a problem creep up on me. I have too much heat. LOL It started this year the opposite when I noticed on extreme cold days it wasn't heating as good as it used to. I attributed it a pump cartridge that had gone out years ago and the impeller had broken into pieces and were sent on down the line to the heat exchanger plate. I figured this year I would take it off and flush it because I though it might be plugging it some. With these warm temps this year, the house was staying warmer now even though the thermostat is set at 68. Lat night it was 83 degrees in the house and decided something is really wrong here.

I went down thinking the 3 way zone valve had stuck open as it was still sending heat out to the house. Used the manual lever and moved fine. Took the head off and plunger moves up and down freely. I always put a few drips of oil on it at the start of the season. Put it all back and still the same.

At this point I'll explain my system to give a better idea of what I have.

Hot supply is coming in the lower copper pipe. When not called for it U's through the 3 way zone valve and isn't allowed to go through the plate heat exchanger. When heat is needed in the house it goes through the plate when the valve opens. I run the boiler pump 24/7 and use the existing oil furnaces circulator pump(which also runs 24/7) and baseboard heat to distribute the heat throughout the house. Waters never touches each other in the systems if you will. Green poly pipes are to/from the house.

Last night before bed I decide to just turn off the circulator pump on the oil furnace to let the house cool down. I woke up this morning to find the house just as hot.

Am I correct to assume that my Heat exchanger has died and is allowing the water to cross over now and the boilers pump is pumping it through the house. It's the only thing I can see as the pipes are warm 1 story up after 24 hours! I check my water every year as well and it's still in range. I've only had to add condiitioner once to bring it back.

Can't turn wrenches now as I had shoulder surgery but want to see if you guys concurr with what I think has happened. Is this common? Thanks for any input.

 

[Erik B]

I've had my OWB online now for 15 years and have had a problem creep up on me. I have too much heat. LOL It started this year the opposite when I noticed on extreme cold days it wasn't heating as good as it used to. I attributed it a pump cartridge that had gone out years ago and the impeller had broken into pieces and were sent on down the line to the heat exchanger plate. I figured this year I would take it off and flush it because I though it might be plugging it some. With these warm temps this year, the house was staying warmer now even though the thermostat is set at 68. Lat night it was 83 degrees in the house and decided something is really wrong here.

I went down thinking the 3 way zone valve had stuck open as it was still sending heat out to the house. Used the manual lever and moved fine. Took the head off and plunger moves up and down freely. I always put a few drips of oil on it at the start of the season. Put it all back and still the same.

At this point I'll explain my system to give a better idea of what I have.

Hot supply is coming in the lower copper pipe. When not called for it U's through the 3 way zone valve and isn't allowed to go through the plate heat exchanger. When heat is needed in the house it goes through the plate when the valve opens. I run the boiler pump 24/7 and use the existing oil furnaces circulator pump(which also runs 24/7) and baseboard heat to distribute the heat throughout the house. Waters never touches each other in the systems if you will. Green poly pipes are to/from the house.

Last night before bed I decide to just turn off the circulator pump on the oil furnace to let the house cool down. I woke up this morning to find the house just as hot.

Am I correct to assume that my Heat exchanger has died and is allowing the water to cross over now and the boilers pump is pumping it through the house. It's the only thing I can see as the pipes are warm 1 story up after 24 hours! I check my water every year as well and it's still in range. I've only had to add condiitioner once to bring it back.

Can't turn wrenches now as I had shoulder surgery but want to see if you guys concurr with what I think has happened. Is this common? Thanks for any input.

Is the 3way zone valve the one with the green on top? Could that have failed and your hot water not being diverted thru that U? What controls the 3way valve, is that working? You could have something as simple as a broken control wire to that valve.

 

[Kevin in Ohio]

Is the 3way zone valve the one with the green on top? Could that have failed and your hot water not being diverted thru that U? What controls the 3way valve, is that working? You could have something as simple as a broken control wire to that valve.

Yes, the 3 way zone valve is what has the green on top with wires coming out. House thermostat(1 zone for whole house) controls the 3 way zone valve. I thought the same thing that the valve was bad TILL I turned off the circulator pump from the house and water is STILL getting pumped through, hot. I can't see any other answer to it.

 

[Erik B]

Yes, the 3 way zone valve is what has the green on top with wires coming out. House thermostat(1 zone for whole house) controls the 3 way zone valve. I thought the same thing that the valve was bad TILL I turned off the circulator pump from the house and water is STILL getting pumped through, hot. I can't see any other answer to it.

You mentioned that you had checked the mechanical operation of the valve but have you checked the electrical side? Have you put a meter on the wires to see if the correct voltage is getting there and can you hear the valve operate when someone else adjusts the thermostat?

 

[Jakers]

i think you're on the right track. im guessing the plates have failed internally. it potentially could be a case of thermo-siphoning but i doubt it. plate exchangers are cheap on e-bay. id get a new one and swap it out. looks like it should be simple the way you have things set up. great time to add any valves needed in the area too

 

[Kevin in Ohio]

You mentioned that you had checked the mechanical operation of the valve but have you checked the electrical side? Have you put a meter on the wires to see if the correct voltage is getting there and can you hear the valve operate when someone else adjusts the thermostat?

I have 24 volts on them so that is right. I takes about 2 minutes for it to work as I was told it heats up slowly to make it work. The thermostat does send/shutoff current.

 

[Kevin in Ohio]

i think you're on the right track. im guessing the plates have failed internally. it potentially could be a case of thermo-siphoning but i doubt it. plate exchangers are cheap on e-bay. id get a new one and swap it out. looks like it should be simple the way you have things set up. great time to add any valves needed in the area too

I did put valves and bleeder spigots in a lot of areas.

I've got spigots and valves at the top of the green lines from the HX too as you can see in the top left corner in this pic. Shouldn't loose too much and this is why I'm glad I listened to my stove rep! I shut one valve at the top of one of the green lines and house temp is coming down. Supposed to get cold tonight so may open back up then. I'll pressure test when I get able to take it off at the end of the season. If bad, I'll tear it apart and see what failed.

 

[Erik B]

Let us know what the problem turns out to be.

 

[Jakers]

Can never have too many valves or bypasses. I'm a firm believer in redundancy too. If you need 3 bolts to finish a project you don't just buy 3 from the store

 

[Kevin in Ohio]

The thing that has me confuse is why the open OWB side is not overflowing. The Oil furnace side of the system is a closed loop, pressurized with a self fill fitting tied into the house water. Oil furnace is running 12 PSI closed and the boiler is showing 15 PSI and is open. Zone valve may be not closing all the way too? Just don't know. I'll do the manual switching till the end of the heating season as long as their are no leaks or overflows. Plan of action is to take off HX, pressure test and clean. If it's okay then it has to be the valve. Can you take these apart or are they sealed? I've replaced the head side twice before from lightning and a surge but valve body is original. Piston rod moves smoothly. Does anyone know if it is a metal seat or poly? I may have a fragment from the impellor stuck in there from when the cartridge died. Just can't physically do it now with my shoulder so I will report back when I tear it down. Any other suggestions are appreciated. Thanks guys.

 

[Jakers]

this is an interesting problem. being the OWB is running 15psi of flow/head pressure its possible that you could be loosing water out of the OWB tank. have you checked it lately? could you bump up th oil furnace pressure to 16 and see if it goes the other way? im assuming the 15psi on the OWB is going to be just water weight and the bit of pressure from the flowing pump so not adjustable

 

[Kevin in Ohio]

this is an interesting problem. being the OWB is running 15psi of flow/head pressure its possible that you could be loosing water out of the OWB tank. have you checked it lately? could you bump up th oil furnace pressure to 16 and see if it goes the other way? im assuming the 15psi on the OWB is going to be just water weight and the bit of pressure from the flowing pump so not adjustable

Pressure is non adjustable as far as I know. In my mind it should go(flood) the other way. Reason I say that is the Oil furnace side of the system is sealed pressure wise as the OWB is open. Water level is still where it has been for 8 years now since I added it the one and only time. Got colder here last night and I woke up at 3 AM and checked the temps. House was 72 with the oil furnace loop closed and boiler temp was 186. My range is 178 - 185. Figured I'd better open it up to keep from going any higher on the boiler. At 8 AM The boiler is now at 178 and just opened to fire, house is at 73. Oil furnace circulator pump is OFF at the breaker(never turned it back on from 2 days ago).

 

[NSMaple1]

How much higher is the owb than your indoor system?

 

[Kevin in Ohio]

How much higher is the owb than your indoor system?

You mean the highest pipe in the closed loop oil funace loop in the house, main pump for the boiler(it's in the basement of the house), or?

 

[Henry Fuller]

Kevin,
I look over your pictures and see how your zone cir. pumps and oil boiler cir. pump are layout somewhat, are there flow check valves in your pump (if not, could it possible being gravity affect flowing by itself when you have the oil boiler cir. turn off during that moment). Do you have a spare 3-way taco valve like what you got now and compare the plunger height (after popping off the power head) setting to see that they are the same. I had one job that I took apart those taco valve body (was a 2-way valve) and had a solder slag piece that hung up the valve (unseated it). I use a C-clamp to compress the plunger down just a little just before you unscrew the valve cover plate (under spring tension) and slowly back it off and keep it centered while you are doing it. Even at 12 psi water pressure (indoor boiler sealed system) would over fill your outdoor wood boiler incase your HX is leaking internally into your outdoor wood boiler system. Get healing well soon Kevin, spring is just around the corner.

Henry

 

[Kevin in Ohio]

Kevin,
I look over your pictures and see how your zone cir. pumps and oil boiler cir. pump are layout somewhat, are there flow check valves in your pump (if not, could it possible being gravity affect flowing by itself when you have the oil boiler cir. turn off during that moment). Do you have a spare 3-way taco valve like what you got now and compare the plunger height (after popping off the power head) setting to see that they are the same. I had one job that I took apart those taco valve body (was a 2-way valve) and had a solder slag piece that hung up the valve (unseated it). I use a C-clamp to compress the plunger down just a little just before you unscrew the valve cover plate (under spring tension) and slowly back it off and keep it centered while you are doing it. Even at 12 psi water pressure (indoor boiler sealed system) would over fill your outdoor wood boiler incase your HX is leaking internally into your outdoor wood boiler system. Get healing well soon Kevin, spring is just around the corner.

Henry

I do not have a spare 3 way on hand here. I'm planning on seeing if I can buy the internal seat just to have a spare if nothing else. I've been told I can. That would save the unsoldering and such. I'm leaning towards a piece of the impeller got in there. Have no idea on check valves. I used what the dealer said to. Is it common to put a filter after the pump? Never considered it as I didn't know the pumps had plastic impellers. I'm used to metal ones on the old stuff. The more I think about it, I am leaning towards this valve being blocked or bad to the point of not sealing down closed. Still blows me away that convection could force it's way through an old style circulater pump and over a 200 ft run snaking it way around the first floor and up to the second, then back down. I use a sidearm on my water heater but never dreamed it could do this much. LOL I will post what I find when I'm able to verify and thanks for the well wishes.

 

[Henry Fuller]

Kevin,

Coming from your wood boiler system cir. pump after that installed the y strainer with the removable clean out bottom cap with screen to clean it out (scale, ect...) often. Example model Legend Valve 1" size #105-705NL with two pipe nipples installed between (after the pump) flange and ball valve shut-off (look it up under google search). I already put one on my system.

Henry

 

[NSMaple1]

You mean the highest pipe in the closed loop oil funace loop in the house, main pump for the boiler(it's in the basement of the house), or?

Maybe I misread or missed something & should read it all again - but if it's 15psi on the indoor system inside and the overflow point on the top of the OWB is more than 37' above where you're reading that pressure, it might not leak out the top of your OWB even if they were open in between. 1'=0.4psi, so 37.5' above 15 psi would be 0 psi. That's with no pumping action. If the OWB pump is pumping out the bottom, that might throw a couple psi's and a few feet less elevation difference into the mix.

Just a thought - could be off. If it's less than that, sure is a puzzler. I can't see a whole lot of heat being transferred through a plate HX just by convection on the load side - would need pretty optimum convection setup for that to happen (like pretty well straight up two floors right off the plate and no restrictions - but even then with much horizontal run before it goes back down to the HX and it will be pretty sluggish).

Try tracing all your heat flows with an IR gun?

 

[Henry Fuller]

Maybe I misread or missed something & should read it all again - but if it's 15psi on the indoor system inside and the overflow point on the top of the OWB is more than 37' above where you're reading that pressure, it might not leak out the top of your OWB even if they were open in between. 1'=0.4psi, so 37.5' above 15 psi would be 0 psi. That's with no pumping action. If the OWB pump is pumping out the bottom, that might throw a couple psi's and a few feet less elevation difference into the mix.

Just a thought - could be off. If it's less than that, sure is a puzzler. I can't see a whole lot of heat being transferred through a plate HX just by convection on the load side - would need pretty optimum convection setup for that to happen (like pretty well straight up two floors right off the plate and no restrictions - but even then with much horizontal run before it goes back down to the HX and it will be pretty sluggish).

Try tracing all your heat flows with an IR gun?

NSMaple1,

If I remember awhile back guessing 10 year ago or so, Kevin was showing on this ArboristSite his ODW boiler and his building that he put it in and while showing the surrounding area it's looking to be not much of a elevation. If possible Kevin's pictures could be that I didn't see it all correctly I can be wrong. I have work on couple of older houses that have gas fired hot water boiler system (not steam system type) that there are no cir. pumps at all (gravity flow) and both are 2 story houses and they are working fine the way it is. When I first read Kevin's OP was saying the weather is being much warmer and his place gotten too warm I'm guessing Kevin's outdoor weather is in the 60 degree F. they were having, and while here in New York it had gotten to 70 degree F. here, and ir sure feel like summer here. So I felt it could possible the 3-way valve is letting it by enough to notice this. On one of my service called, a customer home had one of the zone (in the living room) gotten too warm (78 degree F. and still climbing). They had an oil fired boiler with build in DHW maker itself alway maintaining 140 degree F. while all the room T/stats is not calling on heat at all, this is going up to 1 1/2 story split level ranch style house (gravity flow enough while cir. pumps is not running at all), and this was during mild fall season weather that I have fixed the problem. Since Kevin saying might have a broken piece of impeller and possible hanging up the valve also, it's not that hard to take the taco valve apart and put it back together, and just lube the O-ring when you put it back together.

Henry

 

[Kevin in Ohio]

Thanks guys. I will be installing a strainer after the main pump. To answer your questions: Top of boiler to pump in basement is maybe 20 ft. Second story baseboard is roughly the same height. I don't have an IR gun. Our weather was indeed in the high 60's when I shut it down. It made 74 afterward and then turned cold. Warming up again and I just turned the oil furnace circulator off as it's 74 in the house now. I'm leary about taking it apart while the heating season is still ongoing. It's working and keeping stuff warm, it's just not as handy having to control manually with turning on/off pumps and closing valves. I don't want to get caught if you know what I mean. My Dad just had 2 full knee replacements so we are both out for a while. I really appreciate your comments/suggestions and will report back. I never would have believed Henry that convection can work that well. Pushing through an idle pump and snaking it's way around a house floor level, up and around and back down. Amazing.