Hot Water LWCO on Steam Boiler

Rusty18

The oil company installed a Guard Dog LWCO labeled for use on a hot water boiler when they put in our new steam boiler the other week. Is this safe or does it need to be replaced with a LWCO designed for steam (we do not have a secondary LWCO, just this one)? It does not have any labels on it so I am not sure of the model, but it does have a manual reset.

EdTheHeaterMan

There are different models for hot water and steam.   I’m not sure if that makes a difference in the ability to safely control the burner in the event of a low water condition or if the internal wiring has the ability to operate a water feed device.  One made for hot water boilers would not need to have a set of normally open contacts to operate a water feed valve one might need on a steam boiler that has a regular cycle of dropping water level and adding small amounts of water.  

Another thought is that a LWCO made for a water boiler would not normally cycle as a limit control on a regular basis, while a steam rated model would cycle more often.   

I’ll need to look up more information on this topic 

do you have the model number from the actual control?   Not the cover but the actual control.

 (Last month a home owner purchased a wrong control based on a sticker in the cover that was not the correct cover for the control)

JUGHNE

I thought all new steam boilers came with a LWCO as part of the "steam trim".

Where is the probe of the LWCO in relationship to the sight glass water level.

If you had slow returns and the LWCO was activated and with manual reset, there would be no heating when and if the return water made it back without doing the manual reset

EdTheHeaterMan

JUGHNE said:

I thought all new steam boilers came with a LWCO as part of the "steam trim".

Where is the probe of the LWCO in relationship to the sight glass water level.

If you had slow returns and the LWCO was activated and with manual reset, there would be no heating when and if the return water made it back without doing the manual reset

I think the OP had a no heat call and the original LWCO was replaced.

model number PSE801-120 would be my choice for a replacement.

It appears that you have a PS-851 in the picture. It also appears that it is a discontinued model. Still available NEW from suppliers with old stock. Nothing wrong with that. It may be discontinued as a result of a newer plastic model that is very popular due to the lower price.

Still researching the compatibility issue.

JUGHNE

"New steam boiler the other week" it says above.

EdTheHeaterMan

It appears the one you have will be adequate for your system unless there is short cycling of the burner. the Hot water model does not have the same time delay function as the Steam model

here is the literature that comes with the part.

https://www.alpinehomeair.com/related/McDonnell & Miller 153875 PS-801-120 Installation Instructions.pdf

This is the difference (in the red box) on page 2 of the instruction sheet

ethicalpaul

JUGHNE said:

I thought all new steam boilers came with a LWCO as part of the "steam trim".

Exactly this. Reference @Rusty18's first thread where you can even see a hot water autofill valve on the makeup water line of this steam boiler. I think they bought a boiler trimmed out for hot water and put steam controls (mostly) on it. They don't know steam is my theory (shocking I know)

JUGHNE

I look at pictures of the old boiler.....there is an aquastat on the right side with some switching relay....but no piping for water heating or indirect.
Does Rusty know why those are there?

Also on the raw water feed is a pressure reducing valve as you would have on a water boiler. Sometimes they are installed on a steam feeder so the city pressure does not over come the feeder control. Or to reduce the gallons per timed fill cycle.
Rusty, do you have very high city water pressure?

The model number on the label of the boiler might tell if this was shipped with hot water or steam trim.

I share Paul's suspicion that this was a water boiler, not steam trim.

Or in wiring hacking/confusion they let the smoke out of the steam LWCO and used this for a replacement.

JUGHNE

Also the actual part number may be inside on the cover or the internal control parts.

Rusty18

Thanks everyone for all the helpful input. First, @EdTheHeaterMan was spot on and it is a PS-851; @JUGHNE, thanks yes the part number was on the inside of the cover (assuming it's the correct cover on the unit). It sounds like I am safe with the LWCO even if it's for a hot water boiler. I am fine having to manually reset it and that will actually give me a heads up if I am losing water.

As for the boiler itself, it is a steam boiler according to the label and model number. To "save us money", the oil company just ordered a new block and jacket and reused other parts. Looking at an old order book online, it seems the LWCO is included in the burner package. If this is true then because we did not get a new burner, we did not get a new LWCO. The old LWCO was busted, so I think they just used what they had around, which happened to be the PS-851. My biggest concern now is that while I was just looking at the model number, I saw that this is a KSZ150 (the only place I see this is on the energy star label), not the KSZ125 it was supposed to be. Any thoughts on how to deal with this are most appreciated....

@JUGHNE 's question about the aquastat on the old boiler raises more suspicion. The aquastat was connected to a relay but we never had an indirect heater or used the boiler to make hot water. I was a kid when that boiler was installed (this is all at my parent's house), but the oil company had told my parents that the boiler would maintain an internal temperature and fire occasionally even during the summer to "clean" itself. Is there any truth to that or did they just install all that so we would use more oil?

I have no sense of whether or not we have high city water pressure but it has never been a problem elsewhere. They repiped the supply line and put in a manual shutoff just above the flowback preventer but did not replace the pressure reducer. But, they did leave the shutoff partially closed, so maybe that was done intentionally because the pressure was overcoming the feeder control now that there is no pressure reducer? Seems pretty bush league if true.

JUGHNE said:

Where is the probe of the LWCO in relationship to the sight glass water level.

It's in the same spot as on the old boiler:

JUGHNE

Serial number: SHORTY...........??
Does that mean anything to someone?

ethicalpaul

Wow I would say yes, that auquastat on the old boiler was nothing but a money grab. Hopefully your folks just shut it off during summers. This company is scummy 

EdTheHeaterMan

Serial number SHORTY from crown boiler means you have a label that will refer to the previous boiler for warranty purposes.   The warranty on the replacement cast iron block assembly is 2 or 5 Year or the balance of the original boiler that failed.   

EdTheHeaterMan

If this is not replacing a failed crown boiler then you have a full warranty from the manufacturer.  
I just got a Text from The CEO of Velocity Boiler Works (the new name of crown boiler)
The burner and controls are not covered by the manufacturer of course/  the contractor would go to the supplier of any part that fails.   If the burner is new then the burner has a different warranty,   

Your system is just fine with the control you have

EdTheHeaterMan

As far as the KSZ004 model number, this covers 3 sizes.  the 090, the 125, and the 150.  The energy star label must be included to let the boiler leave the factory.  So the label for the largest one is used.  

If you purchased the burner package there would be a label to put over the SHORTY label with the 125 designations and the lower BTU and Sq. Ft. of steam rating.   

In order to get the performance you want, the installer just needs to put the proper nozzle size in the burner to get the 125,000 BTU firing rate.    You got the correct boiler!  ...and the installer probably did the correct nozzle.   Someone should take a Sharpie and write the correct nozzle size on the label for future reference.

EdTheHeaterMan

Here is my conversation with Yale S. 

Rusty18

Wow thank you @EdTheHeaterMan, above and beyond with this information! That all makes sense now as the boiler was bought separately from the burner.