low water cutoff, manual vs auto reset

wesPA

I am looking for some input. I installed a boiler around 6 years ago for a customer. Peerless Pure fire 399 mod con. It was a full building renovation (apartment building) at the time, so the boiler was inspected at completion and has been inspected ever since. During the past inspection, the inspector noted that the low water cutoff (McDonnel Miller RB-24E) is an auto reset and needs be changed to a manual reset type. I am good with swapping it out, it was just interesting how it was only now noted. The auxiliary high temp switch that was installed was a manual reset type. I was just curious as to what is standard for some of you for that type of application and to make sure the proper controls get added for future jobs. Thank you!

Alan (California Radiant) Forbes

You will get a few different answers. Ultimately, it depends on your local code. I would ask the inspector to provide the code requirement.

wesPA

Thanks Alan, appreciate the quick response. Good advice

Jamie Hall

Many AHJs require two low water cutoffs for a commercial installation, which usually includes an apartment building. One can be automatic. The other, set lower, must be manual reset.

HomerJSmith

The automatic reset is not a low water condition, but a loss of power condition.

Automatic reset feature resumes operation after a power outage when water is on probe

I would like to know what happens when there is a low water condition and water is replenished.

exqheat

The low water control should ad water automatically when it falls below the safe level set at installation. (mid glass or lower by 2 inches. Steam is evaporated water. If there is a one pipe system with radiator vents, water vapor will escape and the water needs to be replenished. Manual is usually done after water loss..during maintenance. You do not want to rely on manual fill. The guy will go away for a week and the boiler will fail from lack of water. $30,000 booboo. Check the operation of the fill by blowing down the device once per week. Read instructions.

Jamie Hall

Whoa whoa. First, we are talking about a hot water boiler here, not a steam boiler. Second, an automatic low water cutoff will reset -- automatically -- if the water level returns above the cutoff level. No user action is required. A manual reset, on the other hand, must be reset manually -- as the name suggests -- if it has tripped. The hope is that someone will be curious as to why it tripped.

Neither one has anything to do with a power failure.

JUGHNE

We are talking about a ModCon with limited water content.

If there is truly a low water condition you would want shut down quickly and with manual reset required by someone to realize there is a problem.

On Lochinvar's I put the LWCO up in the piping above the boiler.

I can't see an inspector condemning anything because it had a manual reset. IMO

JimP

Where I’m at both the high temp and low water protection device must be a manual reset.

wesPA

Thanks all for your input. In this particular case, the boiler is a floor mount in the basement with 3 floors of cast iron rads and all piping above. Existing LWCO is on the boiler riser, just above the top of the boiler. I will swap out the auto reset with a manual reset model and go from there. There is also a flow switch on this one as well.

JohnNY

Unfortunately, the factory LWCO provides a soft lockout E31 error condition. But I've had inspectors accept the flow switch as a substitute for the MRLWCO providing it initiates a hard lockout on the boiler control, which it does on the Purefire. So maybe that's something.

EBEBRATT-Ed

Mod Cons are a whole other issue in this regard and the codes in most cases havent caught up to the "modern" now 20 year old technology.

Some inspectors will accept a flow switch some will not. Some accept what the MFG says some will not. Differs by location

wesPA

Thanks all, really appreciated everyone's thoughts. John, I forgot about the Purefire having that LWCO contact, but you are correct. If configured for the LWCO, it is an auto reset. For a flow switch, it is a hard lockout. I've had issues with those particular boilers with nuisance trips if the flow switch is wired to those contacts. The boiler jogs the pump briefly when firing, and if the switch doesn't respond quick enough, it goes into a hard lockout. I am replacing the existing control as is with a manual reset model.

clammy

Residential can be a auto reset lwco while commercial around these parts they want a manual lwco and a manual hi limit been code as long as I can remember but some times inspector miss it and the insurance co pick up on it or in your case the inspector at a later date . Personally on larger mod cons a flow switch is a great idea and even on a low mass copper fin boilers which lochinvar at least used to show in the piping diagrams as required and some know why . Even so I don’t think a flow switch is required by code but some manufactures suggest but the others are definently required . It funny that guys not familiar w doing commercial boilers always complain about having to purchase separately and why it isn’t included I always suggest may be they should bo more due diligence in selling there jobs and knowning there business . No?
Peace and good luck clammy