Radiant closed loop pressure shot up

[Flexia]

Hello all. Please help diagnose my closed loop system. I have a navien boiler and my pressure shoot up to over 35psi the other day and the relief valve opened. The boiler does have an auto fill valve that I am wondering if it is stuck open. Has anyone seen pressure shoot up? Usually it operates around 15psi.

 

[LXCam]

If it has an auto fill valve, I’d assume it also has a regulator before or after that valve. Or the valve is controlled off a internal pressure switch.

What doesn’t make sense to me is why would you have a auto fill feature on a closed loop system?

 

[dfiler2]

You have to have an auto fill on all closed loop systems, it's actually code. It may be that that valve is malfunctioning.

It's also possible that your expansion tank bladder failed.

 

[LXCam]

You have to have an auto fill on all closed loop systems, it's actually code. It may be that that valve is malfunctioning.

It's also possible that your expansion tank bladder failed.

Why is that?. Being I've always lived where AC was the call of the day I've never dealt with a hydronic system. It would seem to me a autofill function would make it difficult to troubleshoot a leak that isn't obvious. And being a sealed system....where does it go if it there isn't a leak?.

 

[dfiler2]

The auto fill is a safety device, if there isn't a leak the auto fill just keeps his 15 lbs of pressure. If there is a leak it keeps the boiler full of water, what can and did happen without the auto fill is a leak in the boiler, which could go undetected, which would cause a loss of water around the heat exchanger, then the boiler would fire heating the heat exchanger, then a pump would kick on and shoot a cup of water on to a red hot exchanger. At that point you turn a cup of water to steam which is a very violent thing to have happen. I don't remember the exact numbers but I think a cubic inch of water grows instantly to 15000 times larger and that makes really bad things happen. I know he is just using a hot water boiler and is not intending to produce steam and the video is of a steam boiler explosion.

 

[LXCam]

Thanks D, after asking the question I did the research. But thanks for taking the time to explain.

 

[fitter30]

Check the ex tank pressure bottom of the tank with a 0 -50 lb tire gauge. Water comes out tank is bad needs replaced. Set pressure the same as cold system pressure use a tire pump or be vary careful with a compressor they don't hold much air.

 

[Firebrick43]

Most autofill valves sized for hydronic systems incorporate a backflow preventor. A backflow preventer are required by law by nearly all AHJ.

Of course an autofill valve makes it a breeze to purge air with just one person so they are very common but most systems I see for warm water heat have a ball valve in front of the autofill valve(that is closed) as a leak could cause flooding of the house.

I think this bundling of functions is why autofill valves are normally installed, I think a back flow prevent is all that is actually required by law but I would still highly suggest an autofill as it makes maintaining the system. For example, glycol systems don't have one at all. They just have two hose bibs(at the low point of the system) with a ball valve between them to fill/purge air.

Some AHJ require a Low water cut off that has a sensor, if uncovered, kill power to the boiler and some sound an alarm. I use safguard boxes for this. By their lit its required in NYC now. This would be the safety in a warm water heating system.

I could see it being a requirement in a steam boiler and left open by dfiler on an attended system in a steam system. I do not deal with steam so I will defer to him on those systems. Of course many places my require them, codes vary greatly from one AHJ to another.

Fitter30 makes a good comment about the expansion tank. It does seem like a likely culprit in this situation.

 

[Jackfre]

The wall Hung’s which I am familiar with have electronic low water cut-offs. Some jurisdictions won’t accept that because you can’t tell or explain anything to them. I may have missed this but you have a Pressure Reducing & relief valve combination like the Watts T1450F?