Steam questions, pressuretrol and LWC.

jgach11886

So first question, the low water cutoff on this weil Mclain boiler I worked on was not the float type but the electronic/probe type with the test button. The boiler isn't super old but only has 1 LWC so its wasn't installed that recently, not sure when 2 LWCs were implimented. Is it ok to have the electronic/probe type LWC on a steam boiler? It doesn't have anything to blow down, also the sight glass doesn't have anyway to blow down, I can only drain the boiler at the bottom spicket in order to blow it down.

Question number 2, so I installed a new honeywell PA404A pressuretrol, setting it to basically the lowest setting which is around .5psi, basically as low as I could before the adjuster screw started to lift off the body of the controller hopefully people understand that statement.

Also installed a new steam pressure gauge, so with these brand new parts installed setting the pressuretrol at the lowest it could be set, it ran at around 1psi of steam.

Is it normal for this controller obviously being mechanical and not super accurate, is it normal for it to not be set at the absolute lowest setting and expect it to be right on the money?

I feel like I've seen this before, but just wanted to see if anyone else has.

Thanks

EBEBRATT-Ed

The low water cutoff is ok for steam. Don't know about your location but in MA where I am 2 LWCO required over 200,000btu/hr

Pressure controls are not accurate. Best way to adjust is to put it on an air tank with an accurate gage. Do not run the pressure over 15 psi in the tank and use a bleeder valve on the tank to raise the tank pressure up and down to set the pressure control where you want. Then put the control back on the boiler

The gage glass usually has a pet cock or a nut on the bottom of the lower valve to blow it down

jgach11886

I was just thinking, they sell them with lower settings like ounces of steam pressure? Maybe I should have bought one of those instead so I could set it lower.

EBEBRATT-Ed

They do. They are called vaporstats and they are pricy. If your running 1 lb of steam and not short cycling the burner your ok as is

jgach11886

Oh another thought has come to me lol

So this boiler is in a residential setting, it only has the pressuretrol for controlling the system pressure, are vaporstats for if you have high and low fire, or if you plan to run everything less than 1 psi?


Another question, in commercial buildings I have seen the manual reset hi-limit pressure trols, I forget the name of them. Are these used in residential settings too? Should I recommend adding one to the boiler since it only has the pressuretrol? If I owned the home, I suppose I would sleep better at night knowing it was there lol

Jamie Hall

Ideally... one would have two LWCOs. One the regular one -- probe or float, they both work if you treat them properly -- which is automatic reset. The other one slightly lower (but still safe) which is manual reset, so it draws someone's attention... The automatic one can have a slightly higher setting, or at least some do, to control an automatic water feeder, too, if you aren't allergic to such things.

The same concept for pressure controls. Ideally two -- an automatic one; a vapourstat if you have a system which can or should run at under a pound, or a pressuretrol -- and a manual reset one at a higher, but still safe pressure, again to draw someone's attention. It should be on a separate pigtail, too...

Now. Often residential boilers -- particularly smaller ones -- only have the one LWCO and one pressure control. That is a code issue -- but as we all recognize, codes are minimums only...

Fred

@jgach11886 ,On the Pressuretrol, the scale on the front is the Cut-in scale. That is the pressure that the boiler will fire. Inside that model Pressuretrol, you will find a white wheel. That is the Differential. Set it to "1". The Pressuretrol is additive so Cut-in + Differential "1" will be the approximate Cut-out pressure, which is 1.5 PSI., unless the Thermostat is satisfied before it reaches that pressure.

jgach11886

@fred , that makes sense, I forgot to think of the differential.

Thx