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Probe vs. Float low water cut off
georgede54
Member Posts: 50
I’m looking to hire a contractor to install a new oil - fired steam boiler. I want it equipped with a low water cut-off. I believe there are two types: float or probe. Are there any other types I should consider? From what I have learned, I think I should go with the probe, but I’d like some input.
First of all, I have to be away from the house for weeks at a time and there is no one in the house to do the 7 – 10 day maintenance that I have read the float type requires. I have read that the probe type only requires maintenance on an annual basis. Even if the probe requires more than annual maintenance, it seems like my best, possibly my only, choice.
Second, I have read that adding water to the boiler causes oxidation, which in turn shortens the life of the boiler. So as the float requires more frequent adding of water, the probe would seem to be the better choice in terms of boiler life.
As I think about the second reason, I’m having a hard time finding a reason for anyone to install a float mechanism. The probe seems to be clearly the better choice, but there is a lot I don’t know.
I will be grateful for all comments.
Thanks.
George
First of all, I have to be away from the house for weeks at a time and there is no one in the house to do the 7 – 10 day maintenance that I have read the float type requires. I have read that the probe type only requires maintenance on an annual basis. Even if the probe requires more than annual maintenance, it seems like my best, possibly my only, choice.
Second, I have read that adding water to the boiler causes oxidation, which in turn shortens the life of the boiler. So as the float requires more frequent adding of water, the probe would seem to be the better choice in terms of boiler life.
As I think about the second reason, I’m having a hard time finding a reason for anyone to install a float mechanism. The probe seems to be clearly the better choice, but there is a lot I don’t know.
I will be grateful for all comments.
Thanks.
George
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Comments
The probe type, on the other hand, doesn't require much maintenance or attention, which may be a real advantage in some settings -- although leaving any boiler, steam or water, unwatched and unobserved for more than a few days at a time is a rather poor idea, in my opinion. Properly installed, they are reasonably reliable, as solid state circuits go. They can be fried by power surges, though, and completely defeated by incorrect installation.
All that said, again -- in my opinion -- a steam boiler should have two independent low water cutoffs, on independent tappings on the boiler (the float type is usually connected to the sight glass). So why not install one of each? And make the probe type the lower of the two, and manual reset, so if it does trip you know that you have a problem.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
An automatic water feeder is a good idea if you are away often. A water meter installed with it is a good idea to monitor usage. It's better if you add water yourself and check the boiler occasionally........but if you away the feeder provides back up
What model boiler are you considering?
Where are you located?
"Reducing our country's energy consumption, one system at a time"
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Baltimore, MD (USA) and consulting anywhere.
https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
1) I'm planning to add water whenever I'm around, but I'm still wondering about the cold water in a hot boiler problem. Are there certain times I can't put water in?
2) I'm located in New Rochelle, NY, which is slightly above the Bronx.
3) I'm not going to think about boiler models until after I have figured out how many BTUs the boiler should crank out.
4) Mikeg said he had a float but needed the tapping for a aquastat so he went back to a float. I'm not completely clear on what that means and I'm wondering whether that's a problem I could be running into.
Thanks again.
George
On number 4 -- Depends a lot on what tappings are available on the boiler, and what they are used for. Many boilers have a tapping which is rather specifically meant for a probe type low water cutoff -- it should be noted in the installation manual. Most if not all boilers will have two tappings meant for the sight glass -- one quite near the top, and one lower, below the operating water level. Those two are commonly used for a float type low water cutoff, which needs two tappings spanning the operating water level. There may well be other tappings in the boiler -- indeed, there should be. On a boiler which is already installed, they may well be hidden under the cosmetic shroud. Your boiler installation manual should note them all -- and often, helpfully, suggest what they might be used for.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
And I imagine it's in the boiler manufacturer's best interest to install a decent one that's not going to end up destroying their boiler. Not that boiler manufacturers don't do crazy things sometimes (like give you a pressuretrol set to 10psi on a pigtail that can't be easily disassembled for annual cleaning, but I digress)
PS: my homeowner opinion is that I don't want any part of dealing with a float-type LWCO
Paul, I really think it's whatever you get use to. Both the probe type and the float type are very reliable (I would avoid the Cyclegard like the plague because of its shutdown feature). I have the Float type and I think nothing about blowing it down periodically. I often wonder where the crud goes with the probe type; just settles on the bottom of the boiler, I guess, and if you have to drain some water out of the drain valve, periodically, it is not much different than the attention given a float type LWCO. In my case, the boiler lacks a properly placed tapping to place a probe type LWCO and the float type mounts right off of the sight glass fitting. There are pros and cons to both styles. JMHO
EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/15
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If it puts your mind at ease, mine is 10 y.o. but I'm knocking on wood as I type this!
I'm 80% sure that I know what size I need. I posted information and pictures of my radiators on a different discussion titled, "Computing the EDRs of my house radiators . . . " Someone got a chance to look at the EDR of my upstairs radiators and his computations agreed with mine. I then posted information and figures on the downstairs radiators (I had to get into the tenant apartment), but no one has gotten a chance to check over my work. Thus, I'm only 80% sure of the boiler size I need.
Now I have turned to finding out what it should look like post install. I figure the more I know of that the better chance I have of finding the right person to do the job.
Thanks.