Water suppy on or off?

Steve Goldstein_2

I do. The Baxi Luna HT monitors system pressure and shuts itself off as needed.

Steve Goldstein_2

Water suppy on or off?

I was reading the documentation that came with my pressure reducer valve, and it says that the water supply into the heating system should be shut off when not filling the system. My heating contractors have never told me to do this over the years.

Is this necessary, since the pressure reducer valve is regulating the system pressure anyway?

ALH_4

leaks

If there ever is a leak, at least the volume of the leak is limited if the valve is closed. Once the system is filled and all of the air is purged, there really is no reason for the valve to be open. If the system has glycol, I'm not sure an autofill makes sense anyway since all it can do is dilute your glycol concentration.

Big Ed

In a Perfect System......

....where there is no leaks it is recommended to shut off the feed incase of accidental future leak that could cause property damage or personal harm .

But most system have slight leaks that you may not notice .If the feed is closed , pressure will drop over time and loss of heat will result...

So if you opt to shut off feed you may need to check and adjust system pressure over time...

Joe Brix

AND...................

....you should have a low water cutoff safety device.

Brad White_9

Not quite the same thing

but is is better than nothing even though the internal pressure switch works too well sometimes...

A true LWCO device would be in addition to the internal controls. Sort of belt and suspenders.

ALH_4

flow switch

In these low-mass coil-type heat exchangers, is a flow switch not a better safety than a LWCO?

Robert O'Brien

If

you are going to shutoff anyway,why even have a PRV? Manually fill system and be done with it.Most systems a few years old with a tankless coil will lose pressure within days of shutting off a PRV.

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Brad White_9

I like both, Andrew

The internal pressure switch is more accurate, sure. If you meant flow, that is possibly another device to your thinking? The two are not interchangeable, not to put too fine a distinction on them.

A loss of pressure as the stack of water is coming down in a leak scenario will trip sooner than a wetted contact type for sure. Just that most practitioners and AHJ's do not consider an internal pressure switch to be a positive safety device.

ALH_4

oops

I was unclear. I meant a flow switch as an external device. The internal pressure switch is not acceptable here either. One of the Vitodens sizes has an internal flow switch that is acceptable in MT as a positive safety device. I cannot remember off the top of my head whether it was the 24/32 or the 44/60.

Lurkin' Murkin'

I think that a prv installed after the shutoff valve would prevent the homeowner from blowing the relief valve, during periodic refills. Especially when the piping was not done in a way to view the pressure gauge (which is not always too accurate or responsive) while filling.

Unknown

I would say if you have these leaks you don't notice, you want to know they are there so they can be found and fixed.

You don't want to keep bringing oxygen in with the fill water.

I would personally think leaving the fill valve open for a little while until the air separator finishes its job, and then closing it is the way to go.

Steve Goldstein_2

How long?

How long would normally expect a system to take before the air separator has finished its job? Days? Weeks?

Unknown

I think that would depend on a whole lot of factors (size of the system, quality of your initial purge, how much and how much OF the system runs...)

Personally I'd call it a month and look for evidence of "spittle" to tell me I'm wrong.

hot_rod

Some large radiant jobs

burp at the start of every heating season. Especially the rubber tube jobs, for some reason. Without an auto fill in the "on" position plan on some no heat call backs, worse case some pump change outs:)

hot rod

Mike T., Swampeast MO

Backflow

Can't believe nobody mentioned the potential for backflow if you leave the water on. If the domestic system looses pressure for any reason water from the heating system will flow into the domestic piping unless you have a functioning high-quality backflow preventer. I know from experience that swing check valves--particularly old ones--do not provide true backflow protection.

Most? all? states now require double backflow preventers on new hydronic heating systems, but at least here in MO there is no retro-fit requirement. The double backflow preventers are also, IMHO, a true pain in the a$$. They require annual inspection at rates that go up every year (now near $80 here), for whatever reason seem to require expensive replacement components every 2-3 years, and when installed indoors tend to occasionally discharge a "glurg" of water in some conditions.