Boiler condensate pipe freezes in prolonged cold weather

[Bankrupt]

The trace heater was made using nichrome wire sleeved with silicon tubing and run inside the pipe. The power source was a few volts from a low cost toroidal transformer that provided safety isolation of the heating wire from the mains. The hardest part was threading the nichrome wire into the silicon sleeving.

Thanks Bernard. I don't suppose that you could list a quick " Bill Of Materials " for the bits that you used, particularly the transformer ? I like the idea of the trace heating being lower voltage if it is inside the drain pipe. You should manufacture and market them on eBay or Amazon - I would buy one !

 

[bernardgreen]

a quick " Bill Of Materials "

It was about 25 years ago so this is a new provisional BoM from memory

Silicone sleeving 3mm ID
LINK

NiChrome heating wire JPR Stock code 845-356
LINK

The voltage required will depend on the length of the trace heating wire. It was a trial and error process.

The wire was installed doubled back on itself so that both ends came out of the pipe at the top end via a T joint in the pipe.

 

[bernardgreen]

I cannot recall for sure how many Watts per metre were used.
The value of four Watts per metre is what I recall but it seems low compared to trace heating tapes.

That said I have set up one metre of the JPR 845-356 NiChrome in a test rig and got the following results

V= 3.2V I=1.8 W=5.7
V= 4.3V I=2.4 W=10
V= 5.0V I=2.8 W=14

V= voltage across one metre of NiChrome wire
W= calculated Watts per metre

The amount of heat was that heat necessary to keep the temperature inside the pipe at least X°C greater than the ambient temperature outside. X being the number of degrees below freezing for which protection was needed. I recall this experiment involved a length of internally trace heated pipe in a bath of cold water.

 

[ianmcd]

or just buy one straight off the shelf

 

[bernardgreen]

Off the shelf is good. but not always possible to retrofit if access to the pipe at risk is restricted

 

[Harry Bloomfield]

Off the shelf is good. but not always possible to retrofit if access to the pipe at risk is restricted

..and the heaters I have seen, are intended to be installed around the outside of the pipe, then have insulation added over the top. No reason not to fit Bernard's version inside the pipe - I think with one leg insulated with silicon tubing, the return leg uninsulated. The difficult part for many, might be the transformer, or power supply. An old laptop power supply might fit the bill, depending on the length of pipe/wire. They are double insulated.

20v will run a 6m long heater, if you use copper for the return leg, providing around 6w of heat per meter. Add an outdoor mechanical switching stat.

 

[bernardgreen]

The return leg would have to be insulated to prevent the erosion of the copper by the acidic condensate liquid.

Good idea about using a laptop power supply to power the heater, simple and easy to set up.

I have found that connecting copper cable to the ends of the NiChrome can be achieved using crimp ferrules and adhesive lined heat shrink covering the joint and extending onto the silicone sleeving and the insulation of the copper cable.

20 volts over 6 metres of heater ( 6 Watt / metre ) sounds good. If the pipe is longer than 6 metres then the heater could be assembled as

copper----NiChrome---copper---NiChrome---copper----NiChrome---copper----NiChrome----copper