Pressure relief valve and expansion tank replacement.


  #1  
Old 08-25-17, 06:27 PM
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Pressure relief valve and expansion tank replacement.

Next weekend I plan on replacing my pressure relief valve and expansion take on my furnace. I have 3 zone baseboard heat and an Amtrol hot water tank. That’s 4 zones coming from by boiler. I’ve watched videos on how to make the replacement and the most time consuming part seems to be draining all 4 zones and then bleeding the system. This led me to wonder why there is no water shutoff installed just before the relief valve and the expansion take. This would avoid draining and then bleeding the system, I think. There must be a reason that there are not shutoff valves installed just before the relief valve and the expansion take.

Any explanation would be appreciated. Thanks.
 
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Old 08-26-17, 05:20 AM
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Pretty sure no shut-off valve is allowed before the relief valve so there's no possibility of shutting off a safety feature. I installed a valve at my expansion tank the last time I changed it. Now the next tank replacement will be a snap. No valves in other key locations is usually just to save $. Steve
 
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Old 08-26-17, 08:07 AM
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I am a believer in “worst case” design and plan for things on a freezing cold winter day when things go wrong with the heating.

All zones can be isolated with valves so if one is bad the others can still provide heat. Each zone has a drain valve.

Valves on either side of water regulator safety valve assembly (with unions) to easily remove it for servicing.

Circulaltor has valves to isolate it for service or removel.

Expansion tank has shut off valve for easy replacement or to make depressurizing system easier.

There are always pro's and con's in design. I focus on having heat when needed.
 
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Old 08-26-17, 10:55 AM
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Theres almost always a way to isolate the zones so all dont have to be drained.

Pics would help..

If there is indeed no way to isolate now would be the time to add some valves...
 
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Old 08-26-17, 12:03 PM
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If there is a “usual” design in US residential hydronic heating systems I have not seen it. As pictures on DIY show there are endless configurations.

Normally the fresh water feed valve to regulator is kept open. It is should only be closed when regulator is being serviced.

The safety issue comes when hydronic water leak turnes it into steam boiler. Use of a separate burner shut off control set at 190F max is a better way to eliminate that threat.

I use a second channel on the control to turn off circulator when return water is below 137F to avoid condensation.
 

Last edited by doughess; 08-26-17 at 02:37 PM. Reason: Spelling error
 

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