pressure regulators on hydronic systems

[John Arnold]

Can someone 'splain to me why I keep seeing hydronic heating systems with pressure regulators and a water supply valve that is turned off. Seems that would defeat the purpose of the regulator.

[wayne soper]

That would also cause the boiler to self destruct if a leak were to occurr, since the water supply would eventually run out.
Was a backflow preventer installed?

[Bob Harper]

John, I've seen this too and here's what I'm finding: the pressure regulator goes bad allowing full house pressure into the boiler. Since the PRV is 30 psi, it pops open causing a flood. The 'cure' is to simply shut off the water feed. Sure, it defeats the purpose of the automatic feed but it is far cheaper at the moment than calling a boiler tech or plumber. Also, a lot of older hot water boilers do not have automatic feeds or low water cutoffs. You will almost always find LWCOs on steam boilers because they are required by ASME and the codes. Until recently, the mechanical codes did not require LWCOs on hot water boilers. BTW, according to the insurance industry, the number one cause of boiler failures is dry firing.

All boilers, whether steam or hot water, should have an automatic feed regulator with a strainer and bypass feature, backflow preventer with shutoffs on either side of it for easy service AND LWCOs. On steam systems, I recommend a water feed monitor such as the Hydrolevel VXT-120, which measures water consumption. If your steam boiler is using too much water, you need to call for service. In addition to measuring water consumption, it can manage water filling cycles to prevent other problems.

HTH,