Sizing/Specifying cold water supply pipes in very hot environments

[EnOm]

Hi,
Where I live temperatures get really hot in the summer, around 110°F, and during summer if a cold water supply is opened the water that comes out is too hot to touch. This lasts for around 3 months out of the year. Does this mean that the "cold" water supply network inside the house should be designed (sized/specified) for hot water, unless some module in the system cools the water down? Or is the 3 month period not long to justify this?
I'm thinking even if a water chiller was used to cool down the cold water supply before it enters the pipes, the pipes should still be sized/specified for hot water because what if the chiller fails, or for some reason the owner wants to remove the chiller all together in the future.

Am I thinking in the right direction?

Thank you
Regards.

 

[PEDARRIN2]

Is the temperature in the house/building that hot? The water in the pipe should reach ambient temperature, but, unless there is no air conditioning in the building, the ambient should not reach that temperature.

I would not design/size the cold water as hot, I would not use the water from the water heater during those months and save some energy.

You could put thicker insulation on the cold water so it stayed cooler longer between uses.

If you are not concerned about water conservation, you could slightly oopen a faucet and let cooler water into the system. I don't really recommend this, but it is an option. You could use the extra water for some other purpose.

You could install a water to water heat pump (much like an air conditioner except you are taking the heat out of water instead of air) that would use the latent heat of vaporization and expansioon of a refrigerant to cool the water, but you would want to make sure the evaporator portion was outside - otherwise you are rejecting the heat inside.

 

[EnOm]

PEDARRIN2,
Thank very much for all the help you have been offering.

-What I can conclude is that the water reaches those temperatures from direct sun radiation and not from heat transfer from ambient air. Water storage tanks over here are usually placed on buildings' roofs and are not shaded in most cases. You must've heard about places where you can fry eggs on pavements, its kind of the same thing.

-Water heaters are turned off during those months.
-Thicker insulation on the pipes would not do much since the water is getting hot at the source (water storage tank).
-Opening a faucet is a solution, albeit not a good one. I don't think its a good idea can't ask the owner of a building/house to keep a faucet open during the summer months to protect the piping system.
-A water to water heat pump would work, but like I said in the original post, the heat pump can be removed from system for one reason or another and I think the piping system should be designed to function well without it.


So the issue has come down to: Will a system designed for cold water (pipe sizes, materials...etc) work properly when hot water flows through it 3 months a year? I mention materials because we use plastic pipes (PP-R) here, and some are suitable for hot water, others are not.

 

[PEDARRIN2]

Pipe sizing would be as for cold water, even if the temperature is not too cold.

Plastic piping (PP-R) would work since it is rated for domestic hot water.

http://brochure.luisid.com/piping/PP-R-Eng-Sep-2008.pdf

is a resource I have used for this piping.

One thing to consider - plastic pipe will expand more than metal pipe - so you would have to design for that expansion/contraction. I think it would be a gradual expansion, but the piping would be longer at 110 F than it would be at 40 F. So you would want to be aware of the ambient temperature during installation.

The above resource has some good guidance for this.

 

[EnOm]

PEDARRIN2,
Thank you for your response. Understood.
As for the expansion issues, installation is outside my scope of work.

Regards