Fill Valve Open or Closed?

mdreyer93

OK, I've searched this on the site and have seen both answers depending on the situation so I thought I'd give the details of my situation and get your advice. We have a two-pipe forced hot water system with old cast iron radiators in our home. The piping is all old black steel and our boiler is a Bryant 234C-6PW and is probably 30 years old. From what I can tell there is no low water cutoff and our fill valve is just a normal gate valve with a newly installed backflow preventer before it.

We bought the house in March and there was a hard freeze which ruptured some pipes and a couple radiators. We've replaced the leaking sections and filled the system and don't see any more leaks.

I'm concerned that if we fill the system and it appears to hold and we fire up the boiler and start running it we may spring a leak somewhere while we're away/asleep and either flood the house if we leave the valve open or let the boiler run dry if we leave it closed.

What should we do?

Thanks in advance

SWEI

Valve off the autofill when you plan to be home for at least a week. Run the system and check the pressure gauge once a day. Make sure the pressure gauge is good. If it holds for a week, try a month. Closed loop hydronic systems are supposed to stay closed. Adding a bit of water once per season is generally OK, though some systems can go for years with none.

mdreyer93

Thanks SWEI, so leave the valve open if I'm not going to be home for a week?

DanHolohan

Just the opposite. Leave it closed to see if the system holds pressure.

Gordy

Is there a pressure reducing valve? I did not see that in your discription of the piping. Only gate valve and back flow preventer?

If not there should be one set to system fill psi usually 12-15 psi for average system elevation. Maybe you forgot to mention it.

mdreyer93

No pressure reducing valve that I can see unless it's built in to the new backflow preventer (see photo).

So, to make sure, I should fill the system, bleed everything, etc., then close the fill valve and fire the boiler and run the system (even if I'm going to be at work for the day) check the pressure gauge once a day to make sure it is holding. If pressure doesn't hold I should shut it down I guess and try and find the leak?

Thanks all for the help so far!

DanHolohan

That's right. You don't have an automatic fill valve. Your boiler should have a low-water cutoff to stop the burner is the system springs a leak. That could save your life.

Dan

Gordy

What psi is the boiler reading? You don't have a prv / auto fill valve so if you leave the fill valve on your hydronic system will have city pressure. As Dan said a Lwco is good insurance and install a prv

Jean-David Beyer

Where I live, you cannot have a hot water boiler without a LWCO. My W-M Ultra 3 control unit is said to have the smarts that some jurisdictions consider a LWCO unnecessary, but my AHJ says I must have one. (I do.)

I prefer to leave my supply valve off, but my service contractor prefers to have it on. So I turn it part way on before he comes, and turn it off when he leaves. I do check the pressure gauge every few days. When I first tried this, I checked it twice a day, but pressure does not go down. Sooner or later, I will put a 3" pressure gauge on it, but there really is not enough room, so I still use the tridicator gauge that comes with the boiler.

j a_2

Why does he want it on?

Jean-David Beyer

I suspect "There is no reason for it; it is just our policy." I think he is worried about dry firing even though there is a LWCO (probe type) on there and the controller itself acts as a LWCO that is accepted in some jurisdictions, though not mine.

I do not know how long my aluminum heat exchanger would last if it were dry fired. But for both the controller board to fail and the LWCO to fail at the same time, seems remote compared to the cost of continually feeding water into the system if there is a leak in the walls or floor.

Ages ago, a badly soldered joint pulled apart after I had gone to work, and it sprayed LOTS of water all over my garage, and running out under the door down the driveway. Luckily, it caused no damage, wasted a lot of water, and was a big pain in the @$$ to fix around midnight when I got home. It is tough to solder copper pipe when the water is still in it with a Bernz-O-Matic torch, I did drain it, but there is 64 feet of horizontal tubing above where the soldering needed to be done, and it never stopped trickling. I used up my entire stock of swear words.

j a_2

I see no reason to ever leave it open…once the system has been completely full….I am sure you will get the opposite opinions…People don’t ride around with hoses attached to there cars radiator…Its foolish not to look at your system every couple of days…Why wait for it to call you,that usually means trouble…Pretty simple

Jean-David Beyer

I do look every few days. It is in my garage in plain sight. So on any day when I use my car, I look at the pressure, and if it is running at the time, I look at the control panel to see the supply, return, and goal temperatures, the firing rate, etc.

I also look in a bucket I have to see if the drain pipe from the condensate pump has frozen up. If it is frozen up, the water goes into a bucket. This has never happened.

hot_rod

I prefer open. With todays low water content boilers and pressure cutout switches there is a potential for the system to drop pressure and lock out causing some no -heat calls, possibly frozen pipes. A small burp of air is enough to put a low water content system into a low pressure condition. Some of the new boilers hold less that 1 gallon or so of water.

Once the system has been running and pressure tested you really should not have connections or pipe joints coming apart causing a flood.

Notice most cars now have small flash tanks to handle over pressurization or allow fluid back into a system if the radiator cap pops.

Or an Axiom feeder or a expansion tank pressurized with a fill valve to make sure there is always a reserve.

The usually fail when you are out of town, nit the days you have a chance to look at them.

Just my thoughts.

j a_2

I agree mod/cons may be a bit different, i believe most of the good ones have freeze protection…but not sure…I know Rinnai does…I see no need, at all, for an older system with a good old conventional cast iron boiler to leave the fill valve open…Makes no sense to me...

Jean-David Beyer

My mod-con has no pressure detector in it. It holds 0.69 gallons of water.

It does have freeze protection. If the heat exchanger goes below 40F, the burner goes into low fire and runs the specified circulators. I specified the boiler circulator and the two heating zones, but not the domestic hot water. The circulators turn off when the temperature rises above 45F. I assume the boiler stops firing then too, but the manual does not say so.

It does check things and resets for some conditions automatically, and locks out for others.

For example, if the supply water temperature in the heat exchanger rises faster than 2F per second during the first two minutes the burner is on. It will reset after a one minute delay. If this happens five times in a row during a single call for heat, it must be manually reset.

If supply 58F > than return it will reset after a 30 second delay. After 20 of these, it will lock out and need a manual reset.

There are lots more, but since they are boiler-specific, I will not bore you with the rest.

None of these have happened since I got the boiler in late spring 2009. If I am home, I can easily reset these things. Of course, If I am away, it will not get reset until I come home. Unfortunately, that could be a week or two once in a while.

SWEI

I like 'em sealed. So much so that we're starting to experiment with a portable fill rig that we disconnect once the system is fully proven. Not ready to make any big decisions yet, but gathering information.

mtfallsmikey

Been a long time since I've posted...Always leave them on, and adjusted properly. If I shut one off, it was just another reason for my Irish dad to kick my butt... Thanks goodness for the Dead Men!

j a_2

I prefer to close it….Yup, it is a closed system….It would look awful funny if we all drove around with hoses hooked up to our cars coolant system….just because it might leak….Makes no sense to me….But that is just my opinion…Your home heating system has the power to destroy your home and sadly cause death, so why not maintain it like it should be….

hot_rod

on a new or retrofit installation you need to keep an eye on that static pressure for days or weeks. With the high efficiency air separators which are now being built into many of the hydraulic separators also, micro bubbles and entrained air may come out of the system for several days or more.

If the boiler has a pressure switch it need to maintain pressure, as air burps out. Large radiant systems with 10's of thousands of feet of tube can take some time to de-areate.

A couple thoughts;
Leave the fill valve open for the first month
Use a fill system like the Axiom
Build a fill "pig" with an expansion tank and fill valve
Over size the expansion tank and fill several pounds over the pre-charge. i've found if you pre-charge a #30 tank to 12 psi, static fill the system to 15 psi, the tank will hold about 1 gallon of fluid. Confirm you still have the required acceptance capacity if you over fill exp tanks.

I think Viessmann refers to this as a "safety seal" and it is important on solar thermal systems as they can see a huge delta tee from ambient outdoor to 130F or more on a cold winter day. The over charge make sure pressure gauges don't drop to 0 and you get a call back.

Yet another option is to just crack open the valve on the Autofill to allow a trickle flow, but not the full 5 fpm if a pipe breaks.

But if you are sure you system is 100% leak free, does it really matter if the valve is open or closed?

A burst from a no heat condition, frozen line will be a lot more problem with the potable water piping compared to a hydronic leak at 12 psi.

Or add one of those new flow monitoring shutdown system, that they use to shut down the main water if a toilet leaks, flapper hangs up, etc.

If you leave the fill off a LWC should be included. I've found them to be more call backs than an issue with a fill valve left on.

Really a personal choice, not unlike pumps or zone valves Ford or Chevy?

WayneMech

It seems, to me, that the problem is not so much the water valve, as it is the water hitting a red-hot hunk of metal. If the fill valve is left on (with a slow makeup rate), and the boiler employs a LWCO and a direct mounted high temp limit switch, then the likelihood of catastrophic failure is reduced to almost nil. Most existing residential systems have neither safety feature. In those cases, I give the owner an option: Either leave the valve shut, or I can install the safeties. Their wallet (read: mind-set) tends to dictate their answer. Either way, the ball is in their court, and the paperwork verifies that ( and my, er, liability).

billtwocase

I like them open. Like Waynemech stated, many older boilers out there have no low water cutoffs, and it is like pulling teeth for upgrading to at least a Hydrolevel. If the homeowner is lucky and happens to experience the loss of heat with low or no pressure, a tech will be called. If not there, eventually the boiler will steam out whatever water is left, and self destruct. Seen it on a few occasions. Even worse when a greenhorn gets there and starts feeding cold water into a glowing mass of iron.

Jamie Hall

I knew there was a reason I like steam heat...

I can see (for that matter, have seen) both sides of the problem. Two examples: (both hydronic). In both cases the house was unoccupied for a time. In one case, there was a power failure and the house froze and pipes burst. When the power came back on, the house warmed and the autofeeder obligingly fed the frozen pipes -- and the house was a total constructive loss (the domestic plumbing also froze, which added to the mess). In the other, there was no autofeeder and there was a small leak and the boiler shut off. In that case it was the domestic plumbing which froze and... the house was a total constructive loss.

Which leads me to a question: is there such a thing as an autofeeder which will feed only a very small flow? In many steam systems, the autofeeder will feed only a specified amount -- say a gallon -- at a time.

Just thinking...

SWEI

Some kind of a time/volume limited feed system would be nice.

On DDC jobs, we monitor system pressure and alarm on drops (typically >4 PSI, but it depends to some extent on system volume and emitters.)

hot_rod

This Autofill valve allows you to regulate the flow rate with a knob on the bottom.

It will automatically fast fill the system at 5-1/2 gpm without the need to flip any levers, turn screws, etc.

After the system is filled and purged, you can throttle the valve to allow only a very small flow rate.

field_engineer

I have been doing Hvac service for 25 years and have never had a problem with leaving the autofill valve open, as long as you have the proper safeties to protect the appliance then there shoild be no issues. I work in one of the coldest, snowiest climes (Cleveland, Ohio), where it's not uncommon to get 12 invhes of snow in 6 hours. I would rsther waste water than have a house freeze, or worse yet, bhst a radiator, they are too hard to replace.

unclejohn

I say leave it open. I say that because one time my wife and I went up to Woodstock to see Levon Helm. It was the a couple years ago when there was only a dusting of snow up there, we got back to back snow in dc and had about 4 feet of snow. My Daughter called and said the boiler was out. I shut the fill valve before I left for some reason I still don't know. I told her to look at the gauge and she said it was at zero. I told the shut off is mark with the word FEED right next to it on the wall. She said I see it and she was so proud of her self for fixing the boiler. It's been open ever since.

DanHolohan

unclejohn said:

I say leave it open. I say that because one time my wife and I went up to Woodstock to see Levon Helm. It was the a couple years ago when there was only a dusting of snow up there, we got back to back snow in dc and had about 4 feet of snow. My Daughter called and said the boiler was out. I shut the fill valve before I left for some reason I still don't know. I told her to look at the gauge and she said it was at zero. I told the shut off is mark with the word FEED right next to it on the wall. She said I see it and she was so proud of her self for fixing the boiler. It's been open ever since.

Sure sounds like you have a leak, Uncle John.

Gordy

I think this boils down to system integrity no. If you got leaks leave the fill valve open instead of fixing. Strictly speaking hot water heat. If the system is tight leavening on or off really should have no consequences unless you have a real special situation that's improperly piped, and the suction side of the circ is causing the fill valve to activate until you have a,relief valve pop or a compression tank water log.

If there is a extended power outage, and your away you will be dealing with domestic burst, and hydronic, or just domestic unless that was shut off to. Either way collateral damage.

DanHolohan

How about when the fill-valve manufacturer insists it be closed and disclaims any damage that may take place if the valve is left open? Contractor holds the bag, right?

hot_rod

DanHolohan said:

How about when the fill-valve manufacturer insists it be closed and disclaims any damage that may take place if the valve is left open? Contractor holds the bag, right?

If you believe in the integrity of your system, and that adequate safeties protect it, and you want to leave the valve on... Time to switch to a brand that lets you decide

j a_2

If its a tight system leave it closed,if its not a tight system,leave it closed, and fix the leak…Pretty simple

Zman

unclejohn said:

I say leave it open. I say that because one time my wife and I went up to Woodstock to see Levon Helm. It was the a couple years ago when there was only a dusting of snow up there, we got back to back snow in dc and had about 4 feet of snow. My Daughter called and said the boiler was out. I shut the fill valve before I left for some reason I still don't know. I told her to look at the gauge and she said it was at zero. I told the shut off is mark with the word FEED right next to it on the wall. She said I see it and she was so proud of her self for fixing the boiler. It's been open ever since.

Uncle John, as Dan said, you have a leak. I think you are making a strong argument for leaving it closed.
I have had that conversation a few times where you instruct someone to open the fill valve over the phone. It should always start with "is the the boiler glowing? is it hot to the touch?". It is important to remember that the problem could be low water with the boiler still firing. Blowing up (most) customers or relatives is bad business.
Carl

Gordy

Yes Uncle John your daughter could have been a statistic if the boiler would have been as Zman said glowing.

hot_rod

got any statics on how many "glowing boiler" calls there have been compared to no-heat, low pressure lock out calls? And freeze ups caused by boiler lock outs. Poll the contractors, wholesalers and reps to get an idea.

A number of failures need to take place to get a glowing boiler, LW condition, boiler drained, operating temperature control failure, high limit failure, LWC and pressure switch failure if equipped, possible stack temperature switch failure, flow switch failure common on copper tube boilers? Usually this is a series circuit and any one should drop out the fuel source.

For a lockout on a typical mod con, a few lbs pressure drop. In a small content fluid system, a dripping air vent could cause a drop in pressure quickly. Or a air bubble that collected and burped weeks after start up. We sell several million air vents a year, I'd guess most are for replacements. Float vents are a sensitive device, often installed in harsh dirty operating conditions. A grain of sand under the seal will cause them to drip.

Really that's what micro bubble separators do so well. They slowly collect micro and entrained air, or air displaced everytime the fluid is heated. It could take a week or more for a large bubble, collected from the system finally drops the float in the air vent and burps the system to a 2- 3 psi pressure drop.

I've seen a lot more dripping or seeping air vents over the years, and rubber tube fitting seeps, relief valve seeps, etc than glowing boilers.

Agreed you should know or determine if the system has a leak, a fill valve isn't intended to mask a leak. That should be one of the first steps in a yearly check, confirm the system still holds pressure, especially large under slab or any radiant where the tube is covered and always in harms way. Bb and panel rad leaks tend to be discovered by the HO.

Gordy

I'm sure there are more older boilers than new out there. With no LWCO, pressure cut offs etc. so you got prv, roll out,gas valve proving, damper proving, high limit. You can still have a hot boiler getting doused at the right moment with cold fill water....can't be good.

Take uncle johns event that boiler could have been firing to high limit, and off when his daughter went down to turn the fill valve on. Hot boiler cold water. Would the prv been enough if it were actually functioning properly?

DanHolohan

hot rod said:

got any statics on how many "glowing boiler" calls there have been compared to no-heat, low pressure lock out calls? And freeze ups caused by boiler lock outs. Poll the contractors, wholesalers and reps to get an idea.

A number of failures need to take place to get a glowing boiler, LW condition, boiler drained, operating temperature control failure, high limit failure, LWC and pressure switch failure if equipped, possible stack temperature switch failure, flow switch failure common on copper tube boilers? Usually this is a series circuit and any one should drop out the fuel source.

For a lockout on a typical mod con, a few lbs pressure drop. In a small content fluid system, a dripping air vent could cause a drop in pressure quickly. Or a air bubble that collected and burped weeks after start up. We sell several million air vents a year, I'd guess most are for replacements. Float vents are a sensitive device, often installed in harsh dirty operating conditions. A grain of sand under the seal will cause them to drip.

Really that's what micro bubble separators do so well. They slowly collect micro and entrained air, or air displaced everytime the fluid is heated. It could take a week or more for a large bubble, collected from the system finally drops the float in the air vent and burps the system to a 2- 3 psi pressure drop.

I've seen a lot more dripping or seeping air vents over the years, and rubber tube fitting seeps, relief valve seeps, etc than glowing boilers.

Agreed you should know or determine if the system has a leak, a fill valve isn't intended to mask a leak. That should be one of the first steps in a yearly check, confirm the system still holds pressure, especially large under slab or any radiant where the tube is covered and always in harms way. Bb and panel rad leaks tend to be discovered by the HO.

No stats, HR, but some experience. There were these events: https://heatinghelp.com/systems-help-center/why-your-boiler-needs-a-low-water-cutoff/

And another, where the feed valve was keeping the boiler going. The people were at work. The Water Company shut off the main to fix a leak. The boiler dry-fired. When they turned the water back on, the boiler leveled the house.

Made me a believer in low-water cutoffs and shutting the feed valve.

Docfletcher

I used to have it open which for me was a mistake. One of the upstairs air bleeders was leaking and I did not know it for a long time. I keep the valve closed now, relying on the pressure gauge to tell me if there is a leak somewhere.

hot_rod

DanHolohan said:

hot rod said:

got any statics on how many "glowing boiler" calls there have been compared to no-heat, low pressure lock out calls? And freeze ups caused by boiler lock outs. Poll the contractors, wholesalers and reps to get an idea.

A number of failures need to take place to get a glowing boiler, LW condition, boiler drained, operating temperature control failure, high limit failure, LWC and pressure switch failure if equipped, possible stack temperature switch failure, flow switch failure common on copper tube boilers? Usually this is a series circuit and any one should drop out the fuel source.

For a lockout on a typical mod con, a few lbs pressure drop. In a small content fluid system, a dripping air vent could cause a drop in pressure quickly. Or a air bubble that collected and burped weeks after start up. We sell several million air vents a year, I'd guess most are for replacements. Float vents are a sensitive device, often installed in harsh dirty operating conditions. A grain of sand under the seal will cause them to drip.

Really that's what micro bubble separators do so well. They slowly collect micro and entrained air, or air displaced everytime the fluid is heated. It could take a week or more for a large bubble, collected from the system finally drops the float in the air vent and burps the system to a 2- 3 psi pressure drop.

I've seen a lot more dripping or seeping air vents over the years, and rubber tube fitting seeps, relief valve seeps, etc than glowing boilers.

Agreed you should know or determine if the system has a leak, a fill valve isn't intended to mask a leak. That should be one of the first steps in a yearly check, confirm the system still holds pressure, especially large under slab or any radiant where the tube is covered and always in harms way. Bb and panel rad leaks tend to be discovered by the HO.

No stats, HR, but some experience. There were these events: https://heatinghelp.com/systems-help-center/why-your-boiler-needs-a-low-water-cutoff/

And another, where the feed valve was keeping the boiler going. The people were at work. The Water Company shut off the main to fix a leak. The boiler dry-fired. When they turned the water back on, the boiler leveled the house.

Made me a believer in low-water cutoffs and shutting the feed valve.

Seems the issue has more to do with the LWC or lack of? A LWC is a safety device, listed, tested, approved, sometimes code dictated. It's intent is to protect the system from the conditions you mentioned.

A fill valve or feed valve is simply a pressure reducing device, not a listed safety, tested, approved or even code required as far as I know.

If there is a meltdown caused by cold water hitting the hot surfaces, not really fair to blame the fill valve. It leads a fairly simple life, reduce that pressure to this pressure

Many homes have PRV (pressure reducing valves)to reduce and regulate the incoming city water pressure, if one fails and overpressurizes a DHW tank, for example, the protection mechanism is the T&P valve not the main line PRV.

When water heater fail and explode due to over-pressurization, you don't blame or sue the PRV manufacturer, it's the failure of the pressure relief and or safeties to perform it's function. Which is why that is a listed, tested, approved device mandated by code and probably insurance.

If it's piece of mind, or redundant protection, that you leave the valve off, that's fine.

You could save every homeowner 80 bucks or so, plus labor cost, and not even install a fill valve then all this becomes a mute point. Connect a garden hose to the boiler drain, fill and pressurize, disconnect, roll up the hose, walk away knowing you will never flood or explode their investment.

LWC would be a must, of course.

j a_2

Yup agreed LWC a must

Zman

I have seen a couple boilers that were running in the "glowing hot" condition. Both were a result of installation or service errors. I have seen far more homes totally destroyed by lack of heat in the winter.

I really think Vacation homes in cold climates should have low temp sensors and a water monitoring device like flow logic.http://www.flologic.com/Automatic-Water-Shutoff-System.html

I personally like leaving them open because it avoids service calls due to very minor system leaks.

I totally see the other side of the argument as valid.

Carl