Termovar not allowing enough warm water through?

[rcollman]

Does my termovar need cleaning and dare I do it? Thinking I need a plumber to do it with some replacement fittings on hand, here is backgrond. My questions are around a "cleaning screen" (where should it be?) and the effect of old antifreeze on a termovar.

Here is the longer story:
I have a Solo 40 plus installed in late 2008. It replaced a cira 1940 coal/coverted to oil boiler. The system had antifreeze in it and I decided for several reasons not to add any more after adding the Solo. Now I wondering if I should have drained all of it and flushed the system. Is it corrosive? I can still smell it when I bleed the radiators.

The symptoms: We are starting our heating season here in NH, most of the summer the Solo has given us hot house water and the heat is turned off. All night the boiler was/is at 175 and the cold return around 80. The house has called for heat since 6 and it is 11 AM. I have hot water past the backflow value between the hot water feed and house, so I am figuring the termovar is dirty and not enough. I do have a gas boiler backup and it is a balmy 45 today.

As the initial installer put it, the Termovar is "tender" and prone to leak if the cold return pipe is banged. This has happened in the past but the leak stopped. Leak being something hot water would take care of without any drips to the ground. Today it started up again but now it is a drip ever 10 seconds and as usually seems to come from the cold water side. The pipes/fitings below it appear mildly rusted, so I am afraid of putting a pipe wrench on it Or even trying to turn off all the values if I cool down the Solo to look at the termovar. So I am thinking better pay someone take the temovar a part, with some new fittings on hand.

I don't remember the installer mentioning a screen to keep debris out of the termovar and rest of the system. We did have major work done on our town water system and while we tried to be careful, it is possible something got into the furnace loop.

Otherwise I am happy with my Solo. Comments? I see a similar closed post back in 2010, so started a new one.

 

[rcollman]

Does my termovar need cleaning and dare I do it? Thinking I need a plumber to do it with some replacement fittings on hand, here is backgrond. My questions are around a "cleaning screen" (where should it be?) and the effect of old antifreeze on a termovar.

Here is the longer story:
I have a Solo 40 plus installed in late 2008. It replaced a cira 1940 coal/coverted to oil boiler. The system had antifreeze in it and I decided for several reasons not to add any more after adding the Solo. Now I wondering if I should have drained all of it and flushed the system. Is it corrosive? I can still smell it when I bleed the radiators.

The symptoms: We are starting our heating season here in NH, most of the summer the Solo has given us hot house water and the heat is turned off. All night the boiler was/is at 170 and the cold return around 80. The house has called for heat since 6 and it is 11 AM. I have hot water past the backflow value between the hot water feed and house, so I am figuring the termovar is dirty and not enough. I do have a gas boiler backup and it is a balmy 45 today.

As the initial installer put it, the Termovar is "tender" and prone to leak if the cold return pipe is banged. This has happened in the past but the leak stopped. Leak being something hot water would take care of without any drips to the ground. Today it started up again but now it is a drip ever 10 seconds and as usually seems to come from the cold water side. The pipes/fitings below it appear mildly rusted, so I am afraid of putting a pipe wrench on it Or even trying to turn off all the values if I cool down the Solo to look at the termovar. So I am thinking better pay someone take the temovar a part, with some new fittings on hand.

I don't remember the installer mentioning a screen to keep debris out of the termovar and rest of the system. We did have major work done on our town water system and while we tried to be careful, it is possible something got into the furnace loop.

Update: I left the house and returned at 1:30 PM House return is now 105, Solo is 170.

Otherwise I am happy with my Solo. Comments? I see a similar closed post back in 2010, so started a new one.

 

[maple1]

Do you have Wye strainer in your system? If not, you should - although even they are farily coarse, strainer/filter wise.

It shouldn't 'need' cleaning, talking regualr maintenance, but maybe there is a bit of dirt in it. Another possibility is the thermostat has gone wonky in it (there is a recent thread on similar problem).

If I understand the issue - it's a bit unclear in what you wrote, and not much accompanying info (or pics). How has you system pressure been behaving?

Once your system is up & running, town water shouldn't make it into your system water unless you've got system leaks. The one you mention sounds minor, but not sure. I & many others keep our fresh water feed valved off & only open it to replenish if system pressure goes down - but that shouldn't happen with a tight system.

Just read you have no storage - is heat getting to the loads at all? Could it be that the loads just aren't circulating for some reason?

 

[boilermanjr]

If the element in a termovar valve fails, it fails closed. This means that there will be no flow away from the boiler to the load, only recirculation back to the boiler. The symptom is like that of a near boiler circulator that is not operating properly. The element inside the valve can be replaced without removing the valve from the system. Although, it reads as though your valve is not well sealed and could use new union gaskets, which would require valve body removal anyway. Give me a call and I'll walk you through it you'd like. 603-795-9100 Scott

 

[heaterman]

I should be noted that if the valve/fitting leaks with water or mostly water in the system, it will for sure leak with antifreeze in it. Believe it or not, the molecules of antifreeze are smaller than a water molecule and will pass through places water will not.

 

[rcollman]

Sorry for delay in repling. Now that the cold weather is upon us, I only had to do my magic tricks once.

Last week I woke up one morning, outside was about zero F and living room was 55 degrees, min it should be is 64. Radiator water being recirculated was about 80 degreee, boiler was 175 and the hot water feed past theTemovar loop was 140 degrees. The 80 degrees is my concern.

I did notice that the pressure in my system was 15 pounds and last year it was around 18 pounds. (re Maple1) I opened the valve which lets town water into my system until the pressure was just under 20. Then I shut the valve before the Temovar for 5 seconds and opened it for 5 seconds and returned it to the semi closed position. Within 5 minutes I saw the radiator water temp start to rise and within 30 minutes it was over 120 degrees.

Scott, I think I do need to check the valve by pulling it. However, it aint really broke, so I am leary of fixing it along with the seals. Think I will call in a professional plumber

Heaterman: Antifreeze molecules smaller than water Interesting and believable.

Now that we are in heating season, the joints do not show any dampness below them.

I would really like to believe that the physics of 5 lbs more pressure in my system will cure my ills.

Thanks again. Chris
Franconia NH

 

[maple1]

I think what really happened was you had an air bubble that was air-locking your flow. Likely the 2psi difference is not that significant. My system runs at 12psi tops with no issues, I don't really thing anything more than 15 is needed. Do you have air traps/scoops/bleeders at the high points of your piping?

 

[rcollman]

Appreicate all the comments on this thread. My son came home for Xmas and gave me a raspberrry pi. This is a $40 computer with $40 dollars of attachments. For about a week, it was making a decisions and storing data every two minutes about temps. One temp sensor is on the pipe before the temp value (boiler side) and the other is on the pipe before the temp value (cold water return). He created a webpage where I could see the two graphs, that I could change the timeframe via a webbrowser.

Here is a schema of our forced hot water system (we were discussing placement of gages) and part of a graph. The blue is the house the red the boiler. It is best thinking of the lines as relative temps. The gage on my Solo is 10 to 15 degrees higher and does not appear to vary much.

What I now realize is that the the aquastat that turns on my backup is not taking the tempurature in the right place. Currently it measures the boiler temp and goes on when that temp drops (150 by the boiler temp gage on the front, not the temp on the graph) AND the house wants heat. However when it comes to heating my house, the cold water return is what counts, not the boiler.

That is what a raspberry pi will do for you. We programmed it to turn on a relay that started the gas backup when the cold water temp dropped and the house wanted heat. My ah ha moment was that I realized I didn't need no stinking computer to add another relay to the system. All I needed was the or another aquastate to measure the cold water return.

But then I would not have the pretty graphs, the potential for email alerts and have more fun with the data. Thought I would share. Chris

 

[henfruit]

Send him down here and I will give him Prime Rib!

 

[maple1]

What the heck is a raspberry pi?

 

[rcollman]

LOL henfruit, well I will tell him about the offer of Prime Rib. He has gone back to the left coast doing his neuroscience thing,

Maple1 and others: a raspberry pi is a small computer, about the size of two decks of cards laid side by side. Robot builders and DYI'ers (Do it yourself) use it. It has places to put an HDMI (video cable), RCA (video cable), 2 USBs, Memory card, RJ 45 (internet cable), powersupply and at least 3 ribbon cables. It has 0.5 gig memory and we started with an operating system on a 4 gig memory card. A basic pi cost around $40. You can find them online and probably at a serious hobby store. www.raspberrypi.org developed the open source (free) software and has lots examples and support for semi experienced users. Another unit to use might be an Arduino see www.arduino.cc. The $25 model has been around for years. Both units will need someone unafraid of programming and a knowledge of electronics on the level of hobbyist.

My system's design probably did not take a degree in Physics and a doctorate in brain research but it helped. I watched him put it together. The webpage/graph required knowledge of Linux, MySQL, Apache, Python and Mathlab programs, plus some network administration thrown in. IMO, that required some real experience. However, the physical electronics knowledge would be something would be something a robotic hobbyist would understand, along with the programming. So if you just wanted to control pumps, valves and switches based on temperature, pressure, time, motion, circuit status information, that would be a lot simplier project than addiing the over the top interactive webpage.

More than you wanted to know.

 

[webie]

Does my termovar need cleaning and dare I do it? Thinking I need a plumber to do it with some replacement fittings on hand, here is backgrond. My questions are around a "cleaning screen" (where should it be?) and the effect of old antifreeze on a termovar.

Here is the longer story:
I have a Solo 40 plus installed in late 2008. It replaced a cira 1940 coal/coverted to oil boiler. The system had antifreeze in it and I decided for several reasons not to add any more after adding the Solo. Now I wondering if I should have drained all of it and flushed the system. Is it corrosive? I can still smell it when I bleed the radiators.

The symptoms: We are starting our heating season here in NH, most of the summer the Solo has given us hot house water and the heat is turned off. All night the boiler was/is at 175 and the cold return around 80. The house has called for heat since 6 and it is 11 AM. I have hot water past the backflow value between the hot water feed and house, so I am figuring the termovar is dirty and not enough. I do have a gas boiler backup and it is a balmy 45 today.

As the initial installer put it, the Termovar is "tender" and prone to leak if the cold return pipe is banged. This has happened in the past but the leak stopped. Leak being something hot water would take care of without any drips to the ground. Today it started up again but now it is a drip ever 10 seconds and as usually seems to come from the cold water side. The pipes/fitings below it appear mildly rusted, so I am afraid of putting a pipe wrench on it Or even trying to turn off all the values if I cool down the Solo to look at the termovar. So I am thinking better pay someone take the temovar a part, with some new fittings on hand.

I don't remember the installer mentioning a screen to keep debris out of the termovar and rest of the system. We did have major work done on our town water system and while we tried to be careful, it is possible something got into the furnace loop.

Otherwise I am happy with my Solo. Comments? I see a similar closed post back in 2010, so started a new one.

This sounds like a similar issue that I had with my setup a solo 60 and termovar and antifreeze . I beleave what I figured out is has a bit to do with everything the pipeing the return temperature and the antifreeze and the pump . What I think happens is Cavitation inside the the termovar that creats an airlock situation . I changed out my pump to a larger pump and that took care of it . This situation happened to me about 5 years after I had everything in service and before that everything was fine and worked great . It worked great after the pump change too .

 

[rcollman]

This sounds like a similar issue that I had with my setup a solo 60 and termovar and antifreeze . I beleave what I figured out is has a bit to do with everything the pipeing the return temperature and the antifreeze and the pump . What I think happens is Cavitation inside the the termovar that creats an airlock situation . I changed out my pump to a larger pump and that took care of it . This situation happened to me about 5 years after I had everything in service and before that everything was fine and worked great . It worked great after the pump change too .

Webie: that makes sense to me. I have a 3 speed motor, Wonder if Mr. Cheapo (aka The Bald Idiot), turned it down years ago because it "only circulated the boiler water and wasting electricity". When I go home I will make sure it is on high. If nothing else this should increase the volume through the Termovar from the cold water side, allowing more hot water to enter the system, very important on COLD days.

Humm gets me thinking about my value magic trick. I shut then open the value after the backflow, and shut the valve just before the Termovar and return it to the 45 degree position. . This might distrupt the 'cavitation' phenom and sort of allow the pump to set up the perfered flow. I like your theory about my system.

I also think the "cold start" aquastat should be on the cold water return, not the boilder. But that is another story. Thanks

 

[rcollman]

This sounds like a similar issue that I had with my setup a solo 60 and termovar and antifreeze . I beleave what I figured out is has a bit to do with everything the pipeing the return temperature and the antifreeze and the pump . What I think happens is Cavitation inside the the termovar that creats an airlock situation . I changed out my pump to a larger pump and that took care of it . This situation happened to me about 5 years after I had everything in service and before that everything was fine and worked great . It worked great after the pump change too .

THANKS. Looks like both Webie and Maple1 got it right !! Short version: came home, turned the boiler recirculating motor to high. Immediately heard some small tinkeling noises, wondered if it was air. I started to unscrew the top of the the "air scoop" on the boiler out line and it hissed for a good 5-10 seconds. The air was not there before.

SOLUTION THEORY OF MOMENT: i am going with an air lock (aka cavation near the Termovar valve) caused by an underpowered pump (setting). It happens, no reflection on my Solo nor Bioheat.

Still need to see if this is it, but it sure beats my "magic" theory. Only sorry that I have taken down my pi until upgrades arrive to see what the temps say. Goodnews is that all the previous data is there, so we can compare data. Who would have known a raspberry pi would be so much fun AND eductional.

BTW: My son asked me to check that air scoop when I was explaining the system to him two weeks ago. I did the same thing as I did 30 minutes ago, even pressed the valve to allow water to escape. There was no air from that point, nor from any other point I can release air in my system at that time. Sure was tonight. After posting initially, I went back and unscrewed the cap and pressed the relief valve until smelly antifreeze water came out. An upstairs radiator that tend to catch air had none. I conclude there was a lot of air in or near the boiler that went away when the pump speed increased.

I will report back if my "problem" has gone away. Then I can change my kudos to gold stars to Webie and Maple1.

 

[webie]

Humm gets me thinking about my value magic trick. I shut then open the value after the backflow, and shut the valve just before the Termovar and return it to the 45 degree position. . This might distrupt the 'cavitation' phenom and sort of allow the pump to set up the perfered flow. I like your theory about my system.

I did the same thing with the shut off valve before the termovar and it did blow out the air lock for the time being but it would return the bigger pump in my case or speeding up your pump may take care of it . I actually have small marks on the valve to aid in the 45 degree adjustment and have found certain points in the setting of that valve were more prone to create cavitation . You could hear noise in the termovar that sounded kinda similar to water boiling or air in the termovar . In my case the quieter that I could get the water going thru my termovar the less issues that I had . Ideal for me was to try to keep that mixed return water to the boiler 140 or slightly above the closer I got to 160 the more issues I had . The bigger pump inabled me to help run cooler water back to the boiler because of an increase in pump head pressure and volume thus taking care of the issue .

 

[rcollman]

If the element in a termovar valve fails, it fails closed. This means that there will be no flow away from the boiler to the load, only recirculation back to the boiler. The symptom is like that of a near boiler circulator that is not operating properly. The element inside the valve can be replaced without removing the valve from the system. Although, it reads as though your valve is not well sealed and could use new union gaskets, which would require valve body removal anyway. Give me a call and I'll walk you through it you'd like. 603-795-9100 Scott

I did the same thing with the shut off valve before the termovar and it did blow out the air lock for the time being but it would return the bigger pump in my case or speeding up your pump may take care of it . I actually have small marks on the valve to aid in the 45 degree adjustment and have found certain points in the setting of that valve were more prone to create cavitation . You could hear noise in the termovar that sounded kinda similar to water boiling or air in the termovar . In my case the quieter that I could get the water going thru my termovar the less issues that I had . Ideal for me was to try to keep that mixed return water to the boiler 140 or slightly above the closer I got to 160 the more issues I had . The bigger pump inabled me to help run cooler water back to the boiler because of an increase in pump head pressure and volume thus taking care of the issue .

Webie: Interesting. I have never got air like that before. I have heard some noise at the which I took for air. And tried to move it along with opening and closing valves quickly. Last night it was -19 F and currently is a balmy +14. My wife tells me there is rain in the forcast for Sunday night....perhaps another opportunity to see if pump speed avoid the issue.

Spent the morning with the latest schema from BioHeat. Turned page 9 into a png file and then started to erase things and create some new lines. At this moment not trying to get every valve and every electrical system correct. I have a cold start boiler control that controls both the circulators and the backup propane boiler and that was too much work at one sitting But it looks better than my hand sketches and shows more detail that the simple google drawing my son did.

I really like install book that came with my Solo Plus and the above pdf. Thanks for the followup comment. Chris

I tried to correct errors which I mentioned in a later post. I basically deleted the old file and put up the new now V6.

 

[Bob Rohr]

Webie: Interesting. I have never got air like that before. I have heard some noise at the which I took for air. And tried to move it along with opening and closing valves quickly. Last night it was -19 F and currently is a balmy +14. My wife tells me there is rain in the forcast for Sunday night....perhaps another opportunity to see if pump speed avoid the issue.

Spent the morning with the latest schema from BioHeat. Turned page 9 into a png file and then started to erase things and create some new lines. At this moment not trying to get every valve and every electrical system correct. I have a cold start boiler control that controls both the circulators and the backup propane boiler and that was too much work at one sitting But it looks better than my hand sketches and shows more detail that the simple google drawing my son did.

I really like install book that came with my Solo Plus and the above pdf. Thanks for the followup comment. Chris

Not sure about the green and purple lines, are you trying to pipe the boilers in series?

Really one expansion tank connection is ideal. By putting expansion tanks in two different locations you are trying to establish two PONPC points of no pressure change. that could complicate air removal from the system.

Unless the two boilers are able to be 100% isolated from one another with valves, I don't see a reason for the two exp tank locations?

 

[rcollman]

Not sure about the green and purple lines, are you trying to pipe the boilers in series?

Really one expansion tank connection is ideal. By putting expansion tanks in two different locations you are trying to establish two PONPC points of no pressure change. that could complicate air removal from the system.

Unless the two boilers are able to be 100% isolated from one another with valves, I don't see a reason for the two exp tank locations?

Hi Bob and others. There are two images. The second is the one came from the BioHeat pdf. I thought it came closest to describing my system and I then altered that one. The Solo replaced and existing woodboiler with propane backup. I have no storage. The curved green and purple lines were added by me so my changes to the BioHeat drawings would be obvious. And so I could get useful comments about what seems odd about them I did not do the install and my understanding of plumbing and the physics of it all is in the learning stage.

It is another day and I am looking at "my" drawing that used the Bioheat drawing as a starting point. Bob's comments had me looking at it more closely and seeing errors. I will spend an hour or so tweaking it with software not designed for that task and repost. I am using two different image editing tools (GIMP and Snagit) to do this and it took me a couple of hours to get to version #5.

Short answers: the boilers are in series. Errors I now see in my drawing. The check valve after the propane boiler is actually on or near my curved green line. There is no feed at the expansion tank before the circulators. I am not aware of backcheck valves shown on the two zones after the circulators. There is no seperate emergency cooling circuit, it is connected to the largest cooling loop. I need to put an aquastat at "C" with an arrow, after the Solo, and maybe copy the C so it points at the alternative aquastat sites of 1 and 2. The electric controls are not right. The aquastat at "C" goes to what I will call a cold start boiler control (when boiler temp is below X degree, house wants heat, propane starts) that also controls the circulators. Yikes, I apologize for posting something so incomplete.

Off to fix everything except the electrical controls in the drawing.

Chris

 

[rcollman]

Hi Bob, Had some other projects that came first I made the corrections, including showing that the propane boiler was controled by the same control box as the circulators. It has a name. Which ever aquastat is the switch for the low temp that triggers the propane connects to that box. Removed the old picture and put up the new in the post your commented upon.

Also I am not sure about the difference between a weighted backflow valve and other types. Apparently I have two. The one from the boiler is about 3 times the size as the one on the other side of the P2 circulator pump. There maybe other devices outside my furnace room such as backflow valves. There are several bleeds on the radiator and even one on a pipe that is buried under a crawl space in a knee wall.

Appreicate you comments. Time for dinner. Chris

 

[Bob Rohr]

THANKS. Looks like both Webie and Maple1 got it right !! Short version: came home, turned the boiler recirculating motor to high. Immediately heard some small tinkeling noises, wondered if it was air. I started to unscrew the top of the the "air scoop" on the boiler out line and it hissed for a good 5-10 seconds. The air was not there before.

SOLUTION THEORY OF MOMENT: i am going with an air lock (aka cavation near the Termovar valve) caused by an underpowered pump (setting). It happens, no reflection on my Solo nor Bioheat.

Still need to see if this is it, but it sure beats my "magic" theory. Only sorry that I have taken down my pi until upgrades arrive to see what the temps say. Goodnews is that all the previous data is there, so we can compare data. Who would have known a raspberry pi would be so much fun AND eductional.

BTW: My son asked me to check that air scoop when I was explaining the system to him two weeks ago. I did the same thing as I did 30 minutes ago, even pressed the valve to allow water to escape. There was no air from that point, nor from any other point I can release air in my system at that time. Sure was tonight. After posting initially, I went back and unscrewed the cap and pressed the relief valve until smelly antifreeze water came out. An upstairs radiator that tend to catch air had none. I conclude there was a lot of air in or near the boiler that went away when the pump speed increased.

I will report back if my "problem" has gone away. Then I can change my kudos to gold stars to Webie and Maple1.

Really should not need to choke down a valve to make the mixer work properly.

When you choke down a valve you can cause cavitation. Basically the velocity increases in the closed off section and causes the cavitation, which then moves down to the mix valve. IF you need to balance it should be with a valve designed to restrict flow. A ball valve in not a good balance valve as it presents a sharp edge to the flow and has very little authority to make accurate adjustments. A globe valve, ideally one with a tapered plug is perfect if you need to make fine balance adjustments.
Also the higher the temperature the more apt to get cavitation, the system may be quiet when the temperature is low, but the system will be more prone to cavitation as temperatures increase. Cavitation often presents itself as an air problem, you bleed and purge, it goes away then reappears when the system heats again.

Cavitation is mostly commonly thought of as pump related, or caused issue, but in fact valves misapplied can also cause cavitation problems.

 

[Bob Rohr]

Really should not need to choke down a valve to make the mixer work properly.

When you choke down a valve you can cause cavitation. Basically the velocity increases in the closed off section and causes the cavitation, which then moves down to the mix valve. IF you need to balance it should be with a valve designed to restrict flow. A ball valve in not a good balance valve as it presents a sharp edge to the flow and has very little authority to make accurate adjustments. A globe valve, ideally one with a tapered plug is perfect if you need to make fine balance adjustments.
Also the higher the temperature the more apt to get cavitation, the system may be quiet when the temperature is low, but the system will be more prone to cavitation as temperatures increase. Cavitation often presents itself as an air problem, you bleed and purge, it goes away then reappears when the system heats again.

Cavitation is mostly commonly thought of as pump related, or caused issue, but in fact valves misapplied can also cause cavitation problems.

Another good article on cavitation, causes and solutions.

http://www.pmmag.com/articles/85124-look-mom-no-cavitation

 

[rcollman]

Thank you both. Increasing the pump speed has made a big difference. I am reading more about cavatation. In my distant past I worked with a group on a low head hydro project with a long penstock. So I am vaguely familiar with friction and head. Cavataton is something new for me to think about. Love these forums!

 

[webie]

Really should not need to choke down a valve to make the mixer work properly.

When you choke down a valve you can cause cavitation. Basically the velocity increases in the closed off section and causes the cavitation, which then moves down to the mix valve. IF you need to balance it should be with a valve designed to restrict flow. A ball valve in not a good balance valve as it presents a sharp edge to the flow and has very little authority to make accurate adjustments. A globe valve, ideally one with a tapered plug is perfect if you need to make fine balance adjustments.
Also the higher the temperature the more apt to get cavitation, the system may be quiet when the temperature is low, but the system will be more prone to cavitation as temperatures increase. Cavitation often presents itself as an air problem, you bleed and purge, it goes away then reappears when the system heats again.

Cavitation is mostly commonly thought of as pump related, or caused issue, but in fact valves misapplied can also cause cavitation problems.

Question ? I do understand how the ball valve can cause cavitation but by changing the ball valve you really dont change your head pressure just the volume of heated return water going to your mixer correct ? . The other question is could the actual thermovar be causing the cavitation which is what I beleave was happening in my case because when I would get the cavitation and airlock was when my radiant in floor would run for a long periods . The boiler would be up at operating temp and the house would be getting cold as there would be little to no return water from my zones returning .The really funny part about this was as the OP stated his return temp was at 80 degrees my water temp return was also at 80 degrees when it would air lock . I myself thought my Termovar was shot but that was not the case some 5 years later . I have used 5 different pumps as the primary pump a taco 007 was the original pump and ran for about 5 years before the problem appeared , no noise in the system just little to know heated water to the house . I thought my termovar was shot too . I too am concerned about how much electric I am using . I changed out the pump to a Bell & gosset NRF 25 and the problem remained . I then got a Bell & Gosset NRF 36 and that took care of it running on any of the 3 speeds . This year I added in pressurized storage with my unpressurized along with changing some piping and removing the antifreeze . I started the system up and it worked great but part of my changes was in hope of being able to down size the main pump and this pump was a bit noizy because of pump velocity . I then this year replaced the NRF 36 with a Grundfos alpha and guess what the temp lock appeared again , not as bad as it was but still very apparent . It was really interesting having the alpha in there as I could adjust the ball valve and see what it did to the gpm on the alpha and there were some magic points on the ball valve that worked better then others But that pump was just not big enough. The pump that I am now running and luv is a B&G Vario running wide open , Problem solved.
Rcollman My suggestion is if you can get your hands on a bigger pump try that if you can .

 

[Bob Rohr]

Question ? I do understand how the ball valve can cause cavitation but by changing the ball valve you really dont change your head pressure just the volume of heated return water going to your mixer correct ? . The other question is could the actual thermovar be causing the cavitation which is what I beleave was happening in my case because when I would get the cavitation and airlock was when my radiant in floor would run for a long periods . The boiler would be up at operating temp and the house would be getting cold as there would be little to no return water from my zones returning .The really funny part about this was as the OP stated his return temp was at 80 degrees my water temp return was also at 80 degrees when it would air lock . I myself thought my Termovar was shot but that was not the case some 5 years later . I have used 5 different pumps as the primary pump a taco 007 was the original pump and ran for about 5 years before the problem appeared , no noise in the system just little to know heated water to the house . I thought my termovar was shot too . I too am concerned about how much electric I am using . I changed out the pump to a Bell & gosset NRF 25 and the problem remained . I then got a Bell & Gosset NRF 36 and that took care of it running on any of the 3 speeds . This year I added in pressurized storage with my unpressurized along with changing some piping and removing the antifreeze . I started the system up and it worked great but part of my changes was in hope of being able to down size the main pump and this pump was a bit noizy because of pump velocity . I then this year replaced the NRF 36 with a Grundfos alpha and guess what the temp lock appeared again , not as bad as it was but still very apparent . It was really interesting having the alpha in there as I could adjust the ball valve and see what it did to the gpm on the alpha and there were some magic points on the ball valve that worked better then others But that pump was just not big enough. The pump that I am now running and luv is a B&G Vario running wide open , Problem solved.
Rcollman My suggestion is if you can get your hands on a bigger pump try that if you can .

Pumps need to be sized to move the adequate gpm against the head, or resistance the piping system provides at the required flow rate. No more, no less. That is the beauty of multi or variable speed pumps, dial them in to what the system requires.

Changing pumps to mask other problems is not a good idea, it may reward you with other problems down the road. if you hear rushing water or fluid, and the system is purged and air free, good chance you are over-pumping and have high velocities. Really the only way to know for sure is add a flow indicator of some sort.

Circ pumps move fluid by creating a delta P (pressure difference) adding a larger pump, or bumping up the speed would show as an increase in the pressure at the discharge of that pump if you were to install a pressure gauge there. So this added pressure could help supress a cavitation problem if one exists. Lowering the fluid temperature also does that. But a properly piped system should not have cavitation issues to begin with.

Another thought is the valve has too low of a Cv for the flow you are trying to move thru it. Or something inside has reduced the flow passage..

Don't trust the GPM readout an any of the ECM circs. They can be off 60% or more. it's not an actual measured reading, but a calculation the microprpcessor makes based on energy consumption.

An automatic, thermostatic valve should perform properly without imposing an artifical restriction on the ports. The thermostatic element should open and close the various ports so the indicated flow rate is always able to move thru without causing a high pressure drop condition. if you close down the bypass line with a valve while that port is 100% open, asking for full flow, and the return port is closed down to protect the return, you have forced the valved to do something it was not designed to do.

it's like jumping in your truck, jamming the accelerator pedal to the floor, and using the brake pedal to adjust the speed, as you travel down the highway Adding a bigger engine doesn't add much improvement to that driving methods, probably causes the driveline or brakes to fail sooner.

 

[maple1]

To the OP:

(I didn't want to quote a previous post & duplicate the reading material).

What do you have for an expansion tank, where is it located, and where is it tied into your system at w.r.t the boiler circ pump & termovar?