How many watts' conductive heat keep a pipe from freezing?

Short version:  I need to know the necessary wattage/btu's for keeping pipes in a (mostly unoccupied) synagogue from freezing in New England.


The whole story:

A congregation near me agreed that I can come blab at them for a bit at their pot luck.

They're super-progressive, the bulletin board has support for everyone of every identity and every cause.  But they also support National Grid, ConEd, or some other nefarious shenanigans, with a monthly campaign contribution in the amount of a thousand bucks (I'm guessing) in the winter.

I'm going to suggest we heat with christmas lights ("For example, a 100-count string of incandescent mini lights runs at 40 watts" from google search).  I think 4w per person is enough (10 lights on your lap), plus a blanket on top of your lap and a blanket on the seat you're sitting on.  

(The person next to you is a source of 100 watts too.)

 The lights can be put on before Shabbat on a timer.  

The obstacles/objections I'm sure I'll encounter is:
--what about the pipes freezing?
--this is a good idea, let's do it some day, once we've figured out ___ and __ and __ (and that day doesn't come till 2050)
--but we already switched to CFL's

I can kinda speak to 2 and 3, though it's hard I'll say look, we got a D- from the UN climate report, as Jews we have an ethical responsibility to "do not unto others as we wouldn ot have them do unto us," even if it's not %100 clear all the cause and effect there's a pretty clear line there. And why not save more money, be creative, explore, learn?

But the pipes, the pipes are freezing, oh danny boy...

The problem is Cambridge/Somerville is home to enough loonies already that people are burnt out and jaded about another new idea.  And I'm not the best at convincing anyone of anything.

So, again, I need to know the necessary wattage/btu's for keeping pipes from freezing in New England.

So, I found pipe-heating cables with a thermostat:

https://express.google.com/u/0/product/3336752598457051786_3478343239806312918_7472660?utm_source=google_shopping&utm_medium=tu_cu&utm_content=eid-lsjeuxoeqt,eid-ygcnqnyulq>im=CNC_0fak_MvRJhCJ7dLAv76Kj9oBGLC06Q0iA1VTRCigprPfBTCUjMgD&utm_campaign=7472660&gclid=CjwKCAjw6-_eBRBXEiwA-5zHab6agPfw2VBj5zxc_ficDEOcm4vLx6IoPe3Xmrx9hHOdE6nj9oXCjBoCFqYQAvD_BwE

that's smart, since you don't need to use any heat most of the time.

Does anyone know the carbon or toxic footprint of making a thermostat? power drain of an appliance with a thermostat when it's off?

(Leaving the water to trickle is not a sufficient option, by the way, because 1 that water goes to the sewage system, costs money and carbon, has one of the most energy-intensive processing processes in the state (Deer Island), and is wasting potable water.  Plus, things could freeze enough that even that wouldn't work, potentially...I don't know enough about plumbing in cold buildings.  I know of some pipes that froze in the south because they were exposed in teh underside of a beach house, and clearly they have different piorities from us Yankees.  Underground the water main should be at about 55 F year round, right? but then how well does that heat transfer to the water trickling through?

Thanks!

I am re-thinking the 4 watts per person.  For elderly people, we want to make it extra toasty. So maybe double it, 20 lights per person and 30 for an elderly person.  This may get too hot but better to err on that side.

That would come to approx:

10 w per person
50 people (capacity)
500 watts of energy used, and 1,250 holiday lights.  (That's a lot of embodied energy)


Anyone know of a good heat source that's on a long cable, like Christmas lights, that's low wattage and won't burn people?  max 10 watts in the whole appliance, I'd say, more than that would burn.

I don't want to use heating pads because they are too big--they part my body actually touches is quite small, and it's using 60 watts, why?

I'm going to watch Paul's video again and see if there's any other things in that I could use.  But I think Christmas lights are probably the likeliest bet just because thy are already here.  We have some lying around the house.

So, the search I did points out that insulating the pipes is generally enough (the internal heat from geothermal will stay for a while, water being an excellent thermal battery).  But then having something on a thermostat as a backup  is quite essential, you just don't want to risk something bursting.

The "leave it on" thing need only be a trickle.  It's so that the water backs up to the main from the frozen part, or can move out of the faucet if need be, but doesn't get stuck between the clsoed faucet and the frozen part.

In theory, you could capture all that dripping water in a bucket and save it for the spring.  Or water indoor plants.  Or wash with it.  

Hi Joshua, if I'm understanding you correctly, you want to heat the worshipers during services with something attached to an extension cord?  I'm sure they're progressive but that's taking it a bit far.  One elderly lady tripping on a cord and it's all over.

How many hours a week is the building heated?  I'm doing an energy improvement blitz at our church tomorrow and programmable thermostats are on the agenda.  Other than once a week for 2 hours, the place can be kept at 50 or 55.  

Regarding trickling water, you don't want to have the "frozen part" happen at all.  Trickling will help but once a spot freezes, it will probably progress in both directions and start to split pipes.  One pipe break in the wall and you'll be banned from the building.  Most churches I've seen have curious plumbing anyway and even running heat tape would be a challenge.

For our church we paid $200 for an energy guy to do an inspection and blower door test with thermal camera.  It gave us a laundry list of air leaks to seal.  And fire hazards to remedy.  And other nice finds.  Well worth the money.

The heaters to keep pipes from freezing need a thermostat  and pipe insulation in order to be enough watts to keep from freezing at small wattages. The thermostat limits temp and keeps the power off when not needed. Its a system. There are power supply/thermostat/circuit breaker modules and can run so many feet of heating cable or the thermostat goes on the cable, cant remember. There are several types.

The electric heaters for your application, local space heat and not building central heat, could be infrared quartz type heaters. They can be on the ceiling or walls and heat radiantly, meaning the air will not be heated, just the objects in line of sight of the heaters.

They can be turned on an hour or more before occupancy and shut off as soon as service is over without heating all the air in the building in order to have the air heat the objects. Also, doors can be opened repeatedly or left open at times without loosing all the hot air, or heat energy.

These type heaters are often used in warehouses (high ceilings, doors open often) and out on patios for restaurant.

We installed some for a customer. They work nice and can be bought in a range of beam angles and wattages wall or ceiling mount.

https://www.infraredheaters.com/quartz.html

All of the pipe exposed to cold might need to be covered and heated unless you add enough heat to keep the building and its plumbing frost protected, or drain it. Some areas might thermosyphon and some will not. A cirulator could help, but if its a labyrinth and has much built in plumbing....

Programable thermostats and an energy audit are the best advice for the building. Its really hard to get buy in when you are shivering. 10 watts per person is only 30 BTU which is roughly 1/3 of a candle per person... That is not much heat. A solution that cuts the majority of the waste and keeps people onside and actually gets implemented is better then a perfect solution that gets shelved. For the water lines You could try a recirculator like frank mentioned. They are made to maintain hot water at the tap so they pump the hot water line back into the cold supply until hot water shows up at the tap or the timer runs out. Its a great way to add heat to a hot and cold water line buried in a wall and involves very little retrofitting to implement. For exposed sections a thermostat controlled heat line and some insulation work well. Some links for ideas only...
circulator pump with built in timer  https://www.amazon.com/Watts-500800-Instant-Recirculating-Install/dp/B000E78XHG/ref=pd_sbs_60_1?_encoding=UTF8&pd_rd_i=B000E78XHG&pd_rd_r=97ab1e2e-e0b0-11e8-82a3-29f22d3591dd&pd_rd_w=R9YWW&pd_rd_wg=Bh07y&pf_rd_i=desktop-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=7d5d9c3c-5e01-44ac-97fd-261afd40b865&pf_rd_r=YJ67XBTXMX877EG09D0N&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=YJ67XBTXMX877EG09D0N
Heat line with thermostat: https://www.amazon.com/Easy-Heat-AHB-013-Weather-Heating/dp/B002YFAHAW/ref=sr_1_3?ie=UTF8&qid=1541391234&sr=8-3&keywords=water+heat+line+with+thermostat
Best regards,  David

Joshua Myrvaagnes wrote:So, the search I did points out that insulating the pipes is generally enough (the internal heat from geothermal will stay for a while, water being an excellent thermal battery).

In theory, you could capture all that dripping water in a bucket and save it for the spring.  Or water indoor plants.  Or wash with it.  

The insulation without heat tape in a building works best to keep the cold lines from conensing humidity and keeps the hot lines hot improving output temp in long runs or where hot water is used frequently or constantly.

For frost protection without tape in buildings i am more often than not, removing an insulating batt or sheet in order to make building heat available to the pipes!

It will keep pipes from freezing in tennessee or florida though.

Michigan is not alaska, but we see just about every type of frozen! Havent had square tires yet.

" its the temple with the gymnasium full of ibc totes storing drip water till spring" !

I kidd.

Heating with electricity that is made by burning gas at 30% efficiency might not be the best way to cut back on fossil fuel, in a state where only 10% comes from renewable.  https://www.eia.gov/state/print.php?sid=MA

The biggest thing that I would recommend is insulating the pipes both cold and hot water.

I do like the idea of getting a new thermostat and turning the heat down to 55F when no one is in the building and then back up when people are in the building.

If resources were not a problem. then recirculating the water in the house over a heating element would, keep the water mixed so that the outside does not freeze while the inside is still liquid. And if  the heating element could be set at 39F+ then one would not have to worry about it every freezing at 32F. And the heating element could be either gas or electric.

but maybe the problem is that you are forced to heat with electricity because centralized Natural Gas is not available.
I recommend getting a huge propane tank outside and have it refilled once a month.
Another option could be to get a Air Source Heat Pump. Maybe one of those newer CO2 refrigerant ones.  That is rated to work with a outside temp of 0F and a inside temp of 70F.