Radiant Heat System Question

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TheFerretman

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Howdy All:


I have what I guess may be a silly question but I don't really know the answer.

I have a Triangletube boiler (the Solo) driving my radiant heat system. The radiant heat uses glycol rather than water since part of it is outdoors to act as a snowmelt system.

Right now I'm having a problem with my LWCO switch....I'm actually not 100% sure it's reading low, or if the system itself is actually low.

I assume that if I go to replace the switch and unscrew that sensor (it basically bolts into a standpipe) that I'll get some glycol coming out, yes? That's not actually water in there since the system is glycol?

As I said, probably a dumb question but I figured I should ask to see if anybody knows.

Thanks in advance!

Steven in Colorado
 

Jadnashua

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The system is pressurized (common value range is 12-16psi, but can vary based on system needs), so, yes, if you open up the pipe without doing anything, the heating fluid will come out under pressure (and hot, if the system has run recently). FWIW, 100% ethylene glycol is almost never used, so it's a mix of water and antifreeze, just like when you put antifreeze into your car (but it is NOT the same, and don't use automotive antifreeze in a boiler!). If you're lucky, you have some valves nearby that can be closed so you don't lose much of anything when you open things up to replace the sensor.
 

TheFerretman

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The system is pressurized (common value range is 12-16psi, but can vary based on system needs), so, yes, if you open up the pipe without doing anything, the heating fluid will come out under pressure (and hot, if the system has run recently). FWIW, 100% ethylene glycol is almost never used, so it's a mix of water and antifreeze, just like when you put antifreeze into your car (but it is NOT the same, and don't use automotive antifreeze in a boiler!). If you're lucky, you have some valves nearby that can be closed so you don't lose much of anything when you open things up to replace the sensor.

Thank you! I had after carefully looking at the way all the pipes were routed figured that it must be glycol, and it is/was indeed. And don't worry, it's all propolyne glycol (food safe)...originally it was pink but this new bucket I have is kinda purple.

The reason I'm fiddling with this at all is that I realized (a couple of days after the fact, as I'd put the cover back on the display of the boiler unit) that I had a Low Water Cut Off (LWCO) error. The last time I had that (two years ago), there was visible air in some of the radiant tubing and I ended up calling somebody in to fix it. He said he didn't think the installers had properly flushed all the tubing and that over the couple of years the system had been running the air finally collected together enough trigger the LWCO. He pumped a more glycol into the system, carefully flushed each set of loops, and things were great.

This time around there's no air at all in any of the tubing I can see. I popped off the top of the standing tube that the LWCO switch is on and took a look, then poured in a tiny amount of glycol...it's definitely full, nearly all the way to the top.

So the system is running right now but it's only registering (at present...cold start) between 3 and 4 psi. Which is of course a great puzzle to me.

Now I admit I didn't ever really look at the pressure when it was running just fine so I suppose it's possible that maybe a glycol system runs at a lower pressure? That doesn't seem right though. But if that column the LWCO is attached to is full then what'd going on -- could the switch just be bad?

Most puzzling.


Steven in Colorado
 

TheFerretman

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An update and more puzzling things.

Okay, I was very careful to watch the boiler spin up this morning and it never, during the entire day, registered more than 5 psi according to the pressure gauge. I checked at several points over the day and while the system says it's at 3-4 psi it is running fine.

Then in the evening I checked and it was running while reading 0 psi. Well that just seemed wrong, so I tapped the pressure gauge -- and it promptly jumped up to 5 psi.

I'm now beginning to suspect both the LWCO switch (for sending a low signal when there appears to be plenty of fluid) and the pressure gauge itself (for apparently getting stuck).....do these typically both go bad together?


Steven in Colorado
 

Jadnashua

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Just like your car's cooling system has a pressure cap, your boiler needs some pressure in it so that you don't get things flashing into steam. Most LPCO switches usually want more than 3-5psi...more like 10-12 or sometimes, even more. How much pressure the system needs is partly a function of how much height variation there is...water pressure will drop about 0.43-lb/foot of elevation, and you want it to still be under pressure at the highest point. In a typical 2-story house with the boiler in the basement, you'll often see 12-16psi static pressure at the boiler and if you're expansion tank is fully functional and sized properly, it won't vary much as the temperature changes. Now, I'm not a pro, but I think 3-5psi is not enough. TO get that, you need either a pump, or a makeup feed where you can use your potable water supply to raise the pressure (which will dilute the mix depending on how much you need to add). If you have a makeup valve, it must also have a backflow preventer on it so you can't get antifreeze into your drinking water. If there are no leaks, you should never have to add anything to it again until you need to service something like say a circulator or valve.
 

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Just like your car's cooling system has a pressure cap, your boiler needs some pressure in it so that you don't get things flashing into steam. Most LPCO switches usually want more than 3-5psi...more like 10-12 or sometimes, even more. How much pressure the system needs is partly a function of how much height variation there is...water pressure will drop about 0.43-lb/foot of elevation, and you want it to still be under pressure at the highest point. In a typical 2-story house with the boiler in the basement, you'll often see 12-16psi static pressure at the boiler and if you're expansion tank is fully functional and sized properly, it won't vary much as the temperature changes. Now, I'm not a pro, but I think 3-5psi is not enough. TO get that, you need either a pump, or a makeup feed where you can use your potable water supply to raise the pressure (which will dilute the mix depending on how much you need to add). If you have a makeup valve, it must also have a backflow preventer on it so you can't get antifreeze into your drinking water. If there are no leaks, you should never have to add anything to it again until you need to service something like say a circulator or valve.

Yes I agree, but that doesn't explain a.) the filled level of fluid in everything I can open and b.) the weird behavior of the pressure gauge (well, it's a dial).


Steven in Colorado
 

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You have to pre-pressurize the system with a fill-valve from the potable side to 12psi (either when cool or warm). You can't just POUR fluid in and fire it up. The expansion tank should be pre-charged to the intended system pressure before pressurizing the system.

Most boilers at 2-5 psi would complain audibly if fired at 2-5psi, with sizzling popping banging since there isn't sufficient pressure to keep the micro-boil on the heat exchangers from going macro, with the larger bubbles collapsing with a pop once the flow moves them off the heat exchanger.

If you don't trust the existing gauge, buy one that can be screwed onto a standard hose tap, and use that for pre-pressurizing the system after filling. If there is a lot of air in the system that eventually gets purged by vents you may have to add a bit more water later, but you'll at least be starting out somewhere near the right range.

Most boilers are shipped with 30psi pressure relief valves, so don't fill it to anything like 25 psi cold unless you really know what you're doing and why. Almost all 1-3 story systems will do just fine with a 12 psi pressure measured near the bottom level of the system. If somebody opted to set it up to pump away from the Triangle Tube instead of toward it you may need as much as 15 psi to fully suppress the sizzle, but probably not.
 

TheFerretman

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You have to pre-pressurize the system with a fill-valve from the potable side to 12psi (either when cool or warm). You can't just POUR fluid in and fire it up. The expansion tank should be pre-charged to the intended system pressure before pressurizing the system.

I believe it is...there's certainly no reason to think it's lost its charge or anything.

Most boilers at 2-5 psi would complain audibly if fired at 2-5psi, with sizzling popping banging since there isn't sufficient pressure to keep the micro-boil on the heat exchangers from going macro, with the larger bubbles collapsing with a pop once the flow moves them off the heat exchanger.

I wouldn't say there's anything like that....there's the normal sounds of the system coming online but nothing like that or different from what it did from the beginning. It's louder right now because I have the cover off but I wouldn't say there's anything unusual. Not sure how to check this any better though.

If you don't trust the existing gauge, buy one that can be screwed onto a standard hose tap, and use that for pre-pressurizing the system after filling. If there is a lot of air in the system that eventually gets purged by vents you may have to add a bit more water later, but you'll at least be starting out somewhere near the right range.

There are a couple of things in your sentence that don't make sense to me:
  • "pre-pressurizing" the system after filling -- what/how? running the fill pump to drive up the PSI on the gauge (which again I think might be faulty)?
  • "screwed into a standard hose tap" -- where? There are a half dozen places I can attach something like that, but none inside the boiler itself.
Most boilers are shipped with 30psi pressure relief valves, so don't fill it to anything like 25 psi cold unless you really know what you're doing and why. Almost all 1-3 story systems will do just fine with a 12 psi pressure measured near the bottom level of the system. If somebody opted to set it up to pump away from the Triangle Tube instead of toward it you may need as much as 15 psi to fully suppress the sizzle, but probably not.

I haven't done anything to any of the pressure valves other than to take the one off to check the fluid level.

Don't know what "suppress the sizzle" means however?


Steven in Colorado
 

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Expansion tanks usually come pre-pressurized to some nominal value, but that should ALWAYS be checked during installation. The lose air over time (it's just a tire-type air valve, after all), and the bladders develop leaks etc. Checking the charge on a tank is a pretty standard-maintenance type of thing to verify at least every few years.

Most systems have a nominal connection to the potable water system in the house. Are you saying that yours can only add fluids a port with a fill pump to pressurize the system?

Any hose type tap near the boiler and/or the fill-port/valve would be a good place to check the pressure. Test it only with the system off, since pumping pressures can skew the result a few psi.

If the pressure is too low there is usually at least an audible sizzle type of sound at the boiler when it's firing, a sound that goes away when you raise the pressure. If the system is pumping away from the boiler it's lowering the pressure at the boiler a few psi, making it more susceptible to flash-boil sizzle. This is more than an annoyance factor thing- bubbles big enough to hear are insulating the water side of the heat exchanger, lowering the heat exchange efficiency.

A few pictures of the near-boiler plumbing and where/how you are adding fluid to the system might make the discussion more fruitful.
 

TheFerretman

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Expansion tanks usually come pre-pressurized to some nominal value, but that should ALWAYS be checked during installation. The lose air over time (it's just a tire-type air valve, after all), and the bladders develop leaks etc. Checking the charge on a tank is a pretty standard-maintenance type of thing to verify at least every few years.

Most systems have a nominal connection to the potable water system in the house. Are you saying that yours can only add fluids a port with a fill pump to pressurize the system?

Any hose type tap near the boiler and/or the fill-port/valve would be a good place to check the pressure. Test it only with the system off, since pumping pressures can skew the result a few psi.

If the pressure is too low there is usually at least an audible sizzle type of sound at the boiler when it's firing, a sound that goes away when you raise the pressure. If the system is pumping away from the boiler it's lowering the pressure at the boiler a few psi, making it more susceptible to flash-boil sizzle. This is more than an annoyance factor thing- bubbles big enough to hear are insulating the water side of the heat exchanger, lowering the heat exchange efficiency.

A few pictures of the near-boiler plumbing and where/how you are adding fluid to the system might make the discussion more fruitful.

Ah, I think you're saying there should be an air valve on the tank to replenish the air? I can check that easily enough.

Remember this is gycol, not water, but I assume it works the same.

Again I don't hear anything out of the ordinary (what I believe to be ordinary anyway) when it fires up. Are you saying there should be NO sounds of popping and "ramping up" (not sure how to describe it).

I can easily provide a couple of pics and will do so once I get home. Again, remember I've not added anything other than the tiny amount at the very top of stack that the LWCO sensor is in.

I'm intrigued by the thought the expansion tank might have lost air pressure.




Steven in Colorado
 

Dana

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The addition of some glycol doesn't dramatically affect the boiling characteristics of water very much, unlike it's freezing characteristics.

You should hear the burners when it fires up, but the plumbing should be pretty quiet.

If you haven't been pressurizing the system and firing it at low pressure that could easily explain a sensor reading that indicates low water levels, depending on how that sensor works.
 

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The addition of some glycol doesn't dramatically affect the boiling characteristics of water very much, unlike it's freezing characteristics.

You should hear the burners when it fires up, but the plumbing should be pretty quiet.

If you haven't been pressurizing the system and firing it at low pressure that could easily explain a sensor reading that indicates low water levels, depending on how that sensor works.

Well now, some interesting findings last night.

I took a gander at the boiler's expansion tank last night, following up on Dana's suggestion that perhaps it had lost pressure. Took me a while to find the air port -- it's located directly on the bottom of the tank and I didn't see it until I got down on the floor to look (it's mounted a good foot and a half up but you can't see the bottom standing normally). I put my pressure gauge on it and wouldn't you know -- it was reading 3 psi!

Well dang.

So I got out my handy air tank and aired it up to 12psi. The tank says it's pre-pressurized for 12psi and the max it can handle is 240psi (this information is on a nice sticker that's handily positioned exactly facing the wall--sigh). Fired the system back up and it was running smoothly enough, though the gauge on the boiler didn't jump up to 12psi....he went to ~8psi. I figured maybe the system needed to heat up so went to bed.

This morning the boiler's gauge said 5psi again! Frustrated I tapped it as before--and it jumped to 10psi.

So now I'm thinking that a.) the tank was definitely under-pressurized (thanks Dana!) and b.) I'm really starting to doubt that pressure gauge in the boiler itself.

Since my house is two stories (well, there's a small room on a third floor) I'll probably air it up to ~16psi tonight when I get home. If that gauge continues to misbehave I'll probably replace it--it definitely should NOT "stick" like it's doing. I'll also check the tank's pressure again to see if it's actually keeping pressure or losing it (perhaps thru the valve, perhaps thru the membrane inside) and see if that need replacing.

More when I know it.....


Steven in Colorado
 

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You don't set the system pressure with the expansion tank, you pre-pressurize the tank to the anticipated/designed system pressure before pressurizing the system, so that it has sufficient expansion range.

Firing up the boiler with the system pressure at 8 psi is just plain silly- the boiler needs more than that to function properly. At 12 psi system pressure measured in the basement it's good for 99% of all houses with 2 above grade stories. If the highest radiation in your 3rd floor room is ~35' above the pressure gauge you would need at least 15 psi just to get the water up there, and should be running it at ~18 psi to manage pressure fluctuations from the pumping head. If you're starting out at 8 psi the water measured at the bottom of the system, the water pressure the top of your system is at negative pressure relative to the room air at the top of the system.

Buy yourself a replacement gauge before screwing with it further and properly pressurize the system before firing up the boiler. The way you're going at it you're apt to break something rather than fix it.
 

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You don't set the system pressure with the expansion tank, you pre-pressurize the tank to the anticipated/designed system pressure before pressurizing the system, so that it has sufficient expansion range.

Firing up the boiler with the system pressure at 8 psi is just plain silly- the boiler needs more than that to function properly. At 12 psi system pressure measured in the basement it's good for 99% of all houses with 2 above grade stories. If the highest radiation in your 3rd floor room is ~35' above the pressure gauge you would need at least 15 psi just to get the water up there, and should be running it at ~18 psi to manage pressure fluctuations from the pumping head. If you're starting out at 8 psi the water measured at the bottom of the system, the water pressure the top of your system is at negative pressure relative to the room air at the top of the system.

Buy yourself a replacement gauge before screwing with it further and properly pressurize the system before firing up the boiler. The way you're going at it you're apt to break something rather than fix it.

I will be getting a working gauge, but I may also have to replace that expansion tank if it's leaking. I'll know more when I can check it tonight.


Steven in Colorado
 

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I will be getting a working gauge, but I may also have to replace that expansion tank if it's leaking. I'll know more when I can check it tonight.


Steven in Colorado

I am confused over what I'm seeing between the Triangletube documentation and what is at the parts supply outlets.

I have a Solo 175 box....here's a diagram of the inside:

http://www.manualslib.com/manual/754107/Prestige-Solo-175.html?page=15#manual

Looking at the diagram, the gauge that I'm suspecting is faulty is the one on the lower right, not the one indicated as Item #10 in the diagram. I honestly don't remember anything at the spot where Item #10 is indicated though I'll verify that when I get home.

However, my confusion stems from when I started looking around for who has this part and found this:

http://bostonheatingsupply.com/PSRKIT17.aspx

Right part number, but nothing at all like what is indicated in that diagram. This instead very much looks exactly like the gauge on the lower right of the above diagram. If you zoom in you can even see the black millibars measurement and the red psi measurements, just like on the gauge I'm suspecting is bad. I hadn't actually looked at how it's connected in my system (I just started looking at this), but that appears to be a screw in fitting towards the back. I'll check that when I get home.

So my assumption is that the Triangletube documentation is what's in error here? Which surprises me.

Secondary questions, once I get a couple of photos of the system how do I post them here? I don't see anything for including an image that isn't on a URL somewhere....maybe I'm missing it?



Steven in Colorado
 

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You can't tell if the expansion tank is leaking unless you fill it when the system is depressurized, and re-test it when the system is depressurized. If it's leaking at the bladder it'll fill up over a few days, and would thud rather than ring when you tapped on it on the half with the air-valve. If it's leaking at the valve you'd be able to test that with soapy water.

Is your boiler really the Solo 175, or the older version? The MINIMUM fire output on that at sea level is 48,000 BTU/hr and even with derated output for 10,000 feet of altitude would be well over the whole house heat load of my ~2400' sub-code insulated house at -10F. That's at it's minimum fire output. At max fire it could heat all my abutting neighbor's houses AND my house at -10F.

All of which imlies you either have a very large and barely insulated house, or a ridiculously oversized boiler. Which is it?

What's the location/elevation of this house?

Post the pictures on some web-hosting side, and post the links here.

A system pressure and temperature monitoring gauge doesn't have to be the one inside the boiler. Installing one (permanently or temporarily) on some near-boiler plumbing would be good enough, or even better. A cheap 200 psi or 100 psi full-scale hose-bib type would be accurate enough for measuring when pressurizing the system to 12-18 psi, though it's good to have a permanently mounted pressure & temperature type plumbed in where it can be easily monitored.
 

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You can't tell if the expansion tank is leaking unless you fill it when the system is depressurized, and re-test it when the system is depressurized. If it's leaking at the bladder it'll fill up over a few days, and would thud rather than ring when you tapped on it on the half with the air-valve. If it's leaking at the valve you'd be able to test that with soapy water.

Yeah, that was on my list of things to check. It's rather like any other gas valve that way.

I'd say at 3 psi the system was pretty close to depressurized when I filled that bladder. Heck, it might have been zero for all I was getting off that pressure gauge.

Is your boiler really the Solo 175, or the older version? The MINIMUM fire output on that at sea level is 48,000 BTU/hr and even with derated output for 10,000 feet of altitude would be well over the whole house heat load of my ~2400' sub-code insulated house at -10F. That's at it's minimum fire output. At max fire it could heat all my abutting neighbor's houses AND my house at -10F.

Yes, it's a Solo 175, I'd say the older one if only because it looks like the diagram in that link. I don't recall seeing "TriMax" on it anywhere. It was installed mid-2011 as part of the construction. Very powerful, yes much more than I needed. Price was virtually the same as the lower end unit (which I thought was weird).

All of which imlies you either have a very large and barely insulated house, or a ridiculously oversized boiler. Which is it?

The house is ICF, new construction, 13" thick walls. It's very well insulated (17" concrete floors between first and second floor, R-60 fiberglass in the attic). I went for overkill. My builder at the time said it was the warmest house he'd ever built.

What's the location/elevation of this house?

8000 feet on the nose.

Post the pictures on some web-hosting side, and post the links here.

Ah, so that's how we do it. I'd figured I'd have to do something like that.

A system pressure and temperature monitoring gauge doesn't have to be the one inside the boiler. Installing one (permanently or temporarily) on some near-boiler plumbing would be good enough, or even better. A cheap 200 psi or 100 psi full-scale hose-bib type would be accurate enough for measuring when pressurizing the system to 12-18 psi, though it's good to have a permanently mounted pressure & temperature type plumbed in where it can be easily monitored.

I like the way you're thinking there, and I can probably just pick that up over at ABC Plumbing. I guess I"d just ignore the Triangletube one then.

Did you understand why I'm confused over the diagram vs. the problematic gauge? It's very definitely the gauge to the right (white circle in their diagram) that seems wonky; as I said I don't actually think there's anything at the position the diagram indicates. But of course if I circumvent that and just stick my own on there it wouldn't matter if their documentation is wrong.




Steven in Colorado
 

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The house is ICF, new construction, 13" thick walls. It's very well insulated (17" concrete floors between first and second floor, R-60 fiberglass in the attic). I went for overkill. My builder at the time said it was the warmest house he'd ever built.

It forgot to mention that it's also 7000 square feet and I ran a loop (currently turned off) outside to act as a snowmelt system. That might help with why I sized as large as I did.

Here is a link to the pics of the boiler (hope I'm doing this right):

http://theferretman.imgur.com/all/

You'll see I have insulation on most of the piping though I pulled some of it off for the pics. That insulation helps keep that utility room for getting as warm as it can otherwise.

On the views "under" it, to the right is the return system and to the left is the supply system (above the expansion tank). The expansion tank is under the supply pipework and presumably those valves above it are where I'd shut off the expansion tank, hook up a hose, and pump some more glycol into the system to pressurize it properly?


Steven in Colorado
 
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The picture link comes back with the error: "TheFerretman's images are not publicly available."

IIRC the Solos have to be tweaked to work entirely properly above ~4000' or so (it's probably in the manual).

A 7000' house with an R20-ICF construction (2.5" + 2.5" EPS) with slightly better than code-min windows & R60 (really not much higher than current code min) would come in at a heat load in the neighborhood of 75,000 BTU/hr @ -10F, and would have to be put together pretty poorly to exceed 100K. If it's a sprawling ranch house with a very complex shape it could have a higher heat load than 100K, but that would be rare.

Never up-size the house boiler for a snow melt system unless you're trying to clear the snow off the back yard regulation sized soccer pitch or something. If it's just managing a driveway and some stairs and maybe 400 square foot patio it doesn't really take very much capacity.
 

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The picture link comes back with the error: "TheFerretman's images are not publicly available."

Well smeg.


IIRC the Solos have to be tweaked to work entirely properly above ~4000' or so (it's probably in the manual).

Yes, it was.

A 7000' house with an R20-ICF construction (2.5" + 2.5" EPS) with slightly better than code-min windows & R60 (really not much higher than current code min) would come in at a heat load in the neighborhood of 75,000 BTU/hr @ -10F, and would have to be put together pretty poorly to exceed 100K. If it's a sprawling ranch house with a very complex shape it could have a higher heat load than 100K, but that would be rare.

I actually have no idea what you're saying here or, more precisely, why, but it's mox nix to the issue so I'm moving on.
Never up-size the house boiler for a snow melt system unless you're trying to clear the snow off the back yard regulation sized soccer pitch or something. If it's just managing a driveway and some stairs and maybe 400 square foot patio it doesn't really take very much capacity.

Yes....it's a rather larger driveway than you are probably thinking. And regardless it's bought and done.

Either way, I'll see about getting those pictures public...hmmm.............

EDIT: I think it's good now.


Steven in Colorado
 
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