Need a food safe waterproof insulator to repair Buffalo water heater

[Robert Hill]

Hi There,

I have one of these:

I opened it up because the plastic tap needed replacing and found that the inside was full of limescale.

I cleaned all the limescale off including what I thought was limescale on a three pronged sensor. The sensor had a brownish coating on it. When I put the boiler back into use it only filled a tiny amount and stopped when the water reached the bottom of the longest metal probe. The brown coating was obviously meant to stop the probes getting wet until the 10l mark had been reached and then turn off the valve letting the water in. The probe looks almost exactly like this one (except mine had the brown stuff on):

I may or may not be able to get a spare part so looking into a material that I can use to repair the probe by recoating the metal to the correct height to make it fill correctly again.

The material needs to be:
Food safe (people drink the water from this boiler)
Waterproof
Able to withstand up to 100 degrees C
Able to be poured or molded onto the metal probes
Able to withstand being submerged in water and have a flow of water around it.

Any help appreciated,
Cheers,

 

[shrtrnd]

You'll have to decide if you can utilize this idea.(My first idea is to just try to get a factory replacement)
When we installed thermocouples in corrosive media, we used 'thermo wells' to protect the thermocouple probes.
A thermo well is just a sleeve or casing to isolate the probe from the media. Heat transfer itself was minimally affected.
A stainless steel or teflon sleeve should work. There's one idea for you.

 

[Alec_t]

If you want electrical insulation of the probe you could try a few layers of polyurethane varnish (limited googling suggests it's food-safe and good up to 110C), or perhaps heat-shrink tubing (don't know if that's food-safe).

 

[Bluejets]

Think you will find the three probe system works this way....

long probe common
short probe stop
medium probe start

In effect, water fills until it reaches the shortest probe and stops.
As level falls, it turns on again at the medium level, until it again reaches the shortest probe.
We used to fit heat shrink on the probes so just the tip was visible, eliminating any floating particles giving false readings.
(in my experience anyhow)

 

[Martaine2005]

eliminating any floating particles

That is my daily nightmare!!

 

[Martaine2005]

Ok, for the serious gear. Pourable, moldable, potable and flippin' expensive!!!
Lm60...A liquid based waterproof insulator. I know it's good for lining water tanks. But I can't remember who manufactures it! Or the temp limitations.
But worth a look..

Martin

 

[Robert Hill]

Thanks, looks like food grade heat shrink is the way to go. Anyone know a uk supplier of it? Will need it in a pretty small size.

Bluejets, why do you think the water is stopping as soon as it reaches to bottom of the longest probe?

 

[Bluejets]

Without any diagram or photos of the setup, only guessing, perhaps if the scale build up was everywhere, maybe it's causing false probe readings somewhere.
I'm hesitant to advise your bypassing/ isolating of particular sections as this is a mains powered device and you could quickly get into dangerous territory.

 

[Katie Eells]

I think you will get that spare part.You can contact the professionals at the Commercial HVAC service, they either replace or repair the spare part of the system according to the need.