Help OWB losing too much heat at exchanger

[absrio]

My husband got home and went out to check to see what was going on and temp is fine. Everything was right with the boiler. Temp settled. He checked gasket and blower and everything was good. Thinking maybe a piece of wood or ash fell down when blower was running and wedged it open. Possibly it fell loose when I opened the door. Not sure, but all seems fine now. Will keep an eye on it!

We have a continuous loop, so water flows 24/7 through the system regardless of whether furnace fan is on or off. We notice that when not calling for heat (thermostat controlled fan on furnace) the temps in and out at the stove are within 10 degrees typically usually around 7 or so. But almost instantly when the fan kicks on the gauge out at the OWB drops down. It literally happens within seconds while you are watching it.

On the air lock/air bubble note how much water should you be running through it to check? We ran 6 gallons out of it when we first noticed it felt a little sluggish. There was a little air that came out but this was right after new pump install so we expected to see a little air. And like I said we only are maybe 30ft in and then 30 feet back to OWB. Should we try running even more through it?

And 120 was return temp when stove was up at 210, with furnace fan running.

We just installed a Taco 007 pump. It's what the dealer had (I've heard bad things--maybe it's ok). We did have Grundfos UPS 15-58FC prior to this and it was set to low initially so we tried it on its highest (3) setting and it didn't change our heat output inside the house so then we thought the pump was just bad but we probably didn't even need to change it out to begin with.

This is our first winter with the OWB and it just feels like it's heating less than when we first started out.

you didn't answer my questions. here they are again. did you install the boiler yourself? or did it come with the house? did you have this problem last year?

Also did you bleed the air from the lines by cracking loose the bolts at the pump manifold when you installed it? cause if you didn't then you have air trapped in your pump. and its possible you already damaged the fins of your motor. its POSSIBLE, I didn't say it happened. but its possible. it sounds like you have air trapped in your system. do you have an air separator in your system? cause if not then you need one. it could be a number of problems. we are trying to help you narrow down the problem. but if you don't answer our questions then we can't help you. here is a heat temp gun for about 10 bucks. http://www.ebay.com/itm/Digital-Tem...614385?hash=item3f668f69b1:g:xXIAAOSwAPlXgxWa
spray paint the spot you check with FLAT BLACK PAINT before you take a temp reading. and hold the gun right on the BLACK spot. also check it on a METAL surface. DO NOT CHECK IT ON THE PEX LINES. and do not check it from a foot away. hold the gun right on the flat black metal spot. another possibility is that your heat exchanger could be plugged. please let us know if your boiler overheats again. thanks.

first thing you need to do is tell us when the system was installed and post a couple pics of the pump and heat exchanger. if you just recently installed the system and the pump is mounted in the house. and the pump is mounted too high it could be trapping air in the pump and not flowing the water. or the pump could be mounted wrong and be trapping air. or it could be countless things. we need more specs and info.

 

[Kevin in Ohio]

you didn't answer my questions. here they are again. did you install the boiler yourself? or did it come with the house? did you have this problem last year?

Also did you bleed the air from the lines by cracking loose the bolts at the pump manifold when you installed it? cause if you didn't then you have air trapped in your pump. and its possible you already damaged the fins of your motor. its POSSIBLE, I didn't say it happened. but its possible. it sounds like you have air trapped in your system. do you have an air separator in your system? cause if not then you need one. it could be a number of problems. we are trying to help you narrow down the problem. but if you don't answer our questions then we can't help you. here is a heat temp gun for about 10 bucks. http://www.ebay.com/itm/Digital-Tem...614385?hash=item3f668f69b1:g:xXIAAOSwAPlXgxWa
spray paint the spot you check with FLAT BLACK PAINT before you take a temp reading. and hold the gun right on the BLACK spot. also check it on a METAL surface. DO NOT CHECK IT ON THE PEX LINES. and do not check it from a foot away. hold the gun right on the flat black metal spot. another possibility is that your heat exchanger could be plugged. please let us know if your boiler overheats again. thanks.

first thing you need to do is tell us when the system was installed and post a couple pics of the pump and heat exchanger. if you just recently installed the system and the pump is mounted in the house. and the pump is mounted too high it could be trapping air in the pump and not flowing the water. or the pump could be mounted wrong and be trapping air. or it could be countless things. we need more specs and info.

It does become frustrating doesn't it? I don't know how her system is but with my Central Boiler is is a non pressurized system. Boiler is open meaning there is a non sealed cap over the top of the boiler that you add water into. She said she had steam coming out with the overheat so I'm assuming it is the same style but not sure. Generally, once they are primed and moving water you are good to go. I may be way off base but that is my experience on it.

If it is an open style system do you need an air separator? I put several hose spickets on mine and bleed that way with one more at the highest point in the basement. just wanting to learn here as well but I will answer your questions.

 

[NSMaple1]

We have a continuous loop, so water flows 24/7 through the system regardless of whether furnace fan is on or off. We notice that when not calling for heat (thermostat controlled fan on furnace) the temps in and out at the stove are within 10 degrees typically usually around 7 or so. But almost instantly when the fan kicks on the gauge out at the OWB drops down. It literally happens within seconds while you are watching it.

Here is something basic & simple you can do & report back on: along with the underground pipe size (diameter) question asked earlier - can you also measure the exact distance (feet) from the furnace heat exchanger, back to the boiler return fitting where the return thermometer is. And, time it exactly - the time it takes from turning on/off the furnace fan, to the time the big change in temp is seen at the thermometer. Do it a few times, both turning fan off & on, to get a good repeatable number if you have to. To the second or two. Should be able to get a rough idea on how the pump is or isn't doing, with results of that (with accurate distance & time numbers) and pipe diameter.

The 007 isn't as capable as the 15-58 is on high, and won't pump as much, if the head gets above the 7' or so area. And if the head is 10', the 007 won't pump at all while the 15-58 will still be pumping 9gpm. We don't know what your head is, can't see everything in the loop (fittings etc) & don't know pipe size. The heat exchanger itself will also present quite a bit, but we don't know anything about that either - the manufacturer specs should tell.

At this point, I also think the furnace & ductwork are likely causing issues too. Maybe most of them if we can determine the pump is doing OK. And we don't know anything about that part - lots of pictures would help. Is any of it insulated? Air sealed? Where all is it in the house? In heated or unheated spaces? Was it designed & installed by a pro? Where does the furnace return suck air from - is it ducted right from room inlets, or is it not ducted & sucking off a basement floor?

 

[morewood]

For the boiler temp issue check the thermostat on the boiler itself, had one going bad and had the boiling issue since everything the boiler does is based off of that temp. Also, unlike Kevin, I have had occasional issues with the cartridge with my Taco. The impeller blades can become brittle and break off, bingo, no water or little water being pumped. As far as the heat loss, I would expect that in a decent sized house in Minnesota with average insulation. I can tell you if the lines are un-insulated under the house (mine are) you will have more heat loss. My parents have a system similar to your set up and even with the fan off the heat coming up through the ducts can cause you to open windows in the coldest days (mid-teens). Mind you, these are only my experiences with our two stoves over the last 20 years.

Shea

 

[absrio]

It does become frustrating doesn't it? I don't know how her system is but with my Central Boiler is is a non pressurized system. Boiler is open meaning there is a non sealed cap over the top of the boiler that you add water into. She said she had steam coming out with the overheat so I'm assuming it is the same style but not sure. Generally, once they are primed and moving water you are good to go. I may be way off base but that is my experience on it.

If it is an open style system do you need an air separator? I put several hose spickets on mine and bleed that way with one more at the highest point in the basement. just wanting to learn here as well but I will answer your questions.

lol. sorry if I was coming off like a jerk. I'm just trying to be thorough. you are correct that they are generally good once they are pressurized. however, pex and boilers in general can get air in the systems over time. but it depends on your system. some boiler systems need to be bled every 5-10 years. some don't. just depends. air is present in a boiler system fluid in different ways;
Free air or, the large visible air bubbles, or that cannot escape from the system collect and create problems in curved piping, dead end risers, controlled zones, radiators, and radiant floor areas.
Entrained air is present as tiny microbubbles that travel at the same speed as the water and are transported by the flow of the liquid. they can remain in the system as microbubbles or combine and become larger.
Dissolved or Absorbed air is always present in water to some degree, because water (H2O) is part oxygen. you did it right installing those spigots. that way you can bleed the system should the need ever arise.

every time you add water to top off a boiler, you are also adding air to they system. fresh water is full of dissolved air and when you take pressurized water from your house (80psi~) and put it into an open wood boiler system (0psi~) the air particles expand. then the water mixes with the boiler water (180*F) and heats the water causing the air to expand even more. hence giving you air into your boiler system. that's if you have a fill valve plumbed into your wood boiler system inside your home.

also like ns-maple said it could have a problem with not having enough head pressure. she hasn't said whether its a new install or if its an old install. so its really hard to pin point the problem, at this point.

 

[Kevin in Ohio]

lol. sorry if I was coming off like a jerk. I'm just trying to be thorough. you are correct that they are generally good once they are pressurized. however, pex and boilers in general can get air in the systems over time. but it depends on your system. some boiler systems need to be bled every 5-10 years. some don't. just depends. air is present in a boiler system fluid in different ways. the large visible air bubbles or free air, that cannot escape from the system collect and create problems in curved piping, dead end risers, controlled zones, radiators, and radiant floor areas. entrained air is present as tiny microbubbles that travel at the same speed as the water and are transported by the flow of the liquid. they can remain in the system as microbubbles or combine and become larger. Dissolved or absorbed air is always present in water to some degree, because water (H2O) is part oxygen. you did it right installing those spigots. that way you can bleed the system should the need ever arise.

every time you add water to top off a boiler, you are also adding air to they system. fresh water is full of dissolved air and when you take pressurized water from your house (80psi~) and put it into an open wood boiler system (0psi~) the air particles expand. then the water mixes with the boiler water (180*F) and heats the water causing the air to expand even more. hence giving you air into your boiler system. that's if you have a fill valve plumbed into your wood boiler system inside your home.

also like ns-maple said it could have a problem with not having enough head pressure. she hasn't said whether its a new install or if its an old install. so its really hard to pin point the problem, at this point.

In no way saying you were coming off in a brash way. I, like you, get perplexed when someone asks for help but won't help the helper by answering direct questions. Like asking a mechanic to tell them what's wrong with a car over the phone without giving details. Perplexes me at times.

In 13 years I've added water once which most, along with I, find hard to believe. One issue I do need to address is that it seems my HX is not transferring heat as well as it was. When I assembled mine I was VERY particular to only use brass, copper.poly or stainless in the system to avoid any rust issues. The reason was, as you say, I knew small amounts of air means corrosion on mild steel/cast and can lead to build ups or plugging. What my guess is that when my impellor died on my Taco those poly shards worked their way to the HX. In any event, I will pull it off and flush the Summer to at least check it.

 

[absrio]

In no way saying you were coming off in a brash way. I, like you, get perplexed when someone asks for help but won't help the helper by answering direct questions. Like asking a mechanic to tell them what's wrong with a car over the phone without giving details. Perplexes me at times.

In 13 years I've added water once which most, along with I, find hard to believe. One issue I do need to address is that it seems my HX is not transferring heat as well as it was. When I assembled mine I was VERY particular to only use brass, copper.poly or stainless in the system to avoid any rust issues. The reason was, as you say, I knew small amounts of air means corrosion on mild steel/cast and can lead to build ups or plugging. What my guess is that when my impellor died on my Taco those poly shards worked their way to the HX. In any event, I will pull it off and flush the Summer to at least check it.

[imghttp://photos.imageevent.com/kevininohio/rugermini14/large/MVC-012S_3.JPG[/img]

man that is such a clean install!! it impresses me every time I see it. very well done!!!!

 

[NSMaple1]

Yep.

Attention to detail.

Which comes down to patience - which I usually run out of before the project is finished.....

 

[Henry Fuller]

That would be awesome if we felt like we were getting the whole 40-50 degrees out of our vents...but air just feels lukewarm at best, and often cool. Also, it just seems concerning because I have read so many forums and I can't seem to find anyone who pulls that many degrees off at the hx. I see tons who get 5-20 degrees off but we just think 40-50 seems crazy, especially since we don't run anything else with our OWB.

Another concern would be return temp affecting life of the OWB. I have read return temp should not be below 140 due to risk of cold spots causing creosote and corrosion, and right now we dip below that set at 185 and at some point (spring/fall) we had thought we would probably reduce somewhere between 165-175. So then if we still have those dips we would get down between 115-135. We want to make our stove run as long and efficiently as possible. Thank you so much for your response!

Maddieg7,

Could you tried an simple thing first, check the return air temp. at the furnace/air handler to see if this near the same temp. coming from inside your living space. I've been on service call saying their furnace using too much oil than normally. What I found was that the return air fiberboard trunk had came apart (sucking outdoor cold air in uninsulated crawl space) underneath their place.

Henry