Pump Timer

smithy1982

Hi

I have a house built in 2009 the plumbing is a pressurised system. All plumbing is in the garage including the pump.

What i have discovered to be the problem with this is when i need hot water i have to run a good bit of cold water

down the drain which isnt good.

My question is would it be possible to add a timer to the pump so it would circulate water at set times ie: when we get up in the morning and before we go to bed

sydthebeat

so youre saying the hot water cylinder is in the garage and when you need hot water youve to clear the line of colder water before you get to the hot?

how many litres on average do you need to run off? how far is the garage from the house?

the pump on a timer will only work if you have somewhere to dump the "run off" water to ie an outside gully (unless you can think of a more sustainable direction for this run off?)

smithy1982

Not sure if that would work. in that situation i could potentially run hot water down the gully.

i kinda thought it would circulate round till it was called for by a tap or shower, but that could be just crazy talk.

garage is about 30m away so a lot of water being wasted

when i turn on my tap weather it be cold or hot a pump in the garage comes on?

sydthebeat

30 meters is nuts!

You can't circulate it round as there is no return back to the cylinder. The cylinder refills from the cold water system.

What's your heating source? Oil boiler beside the garage?

I am assuming it's also doing your space heating, which is also nuts having heat losses over 30 meters before the pipes enter your house. Hopefully the builder didn't scrimp on costs and installed those pipes in a district heating conduit

The Continental Op

The way to do this and not be running water down the drain is to have a loop in the pipe system, the trade off is heat loss. So you have a pipe go most of the way into the house to a point that is central to the taps and showers that require hot water. From the end of this you create a loop by taking a pipe back to the hot water tank. Then your timer pumps hot water around the loop at times you know there will be demand. Now whenever at tap is turned on the water in the loop that goes into the house is already hot and only has a short distance to travel. The plumbing of it does take a bit of thought but I have seen it done in massive old houses where the pipe run from the nearest hot water tank could be 50 meters or more. Obviously lag the pipes as much as possible.

10-10-20

I don't know why this is in the building regulations forum, it really belongs in plumbing & heating.

Anyway, this can be done. It's called a secondary re-circulation loop. All hotels have them and that's why you never have to wait for hot water at the sink or shower.

It's not always possible to retro-fit these systems as it requires that a second pipe follow the existing pipe so that a loop is created, and the hot water can be set to circulate around this system as needed. The problem being, this new piping arrangement then acts like a radiator and looses heat as it circulates, so your overall losses are large for a moderate gain. In theory you could loop the system with a smaller return pipe, such as microbore 10mm (or even 8mm), this may make it more practical overall.

sydthebeat

Alternatively design a system with a secondary hwc in the house and install a larger buffer tank in the garage.

If you're going to the rounds and costs of digging up 30 meters to install circulation pipes on the dhw system, I'd bite the bullet and get all the hot water closer to the house. Move the boiler and get a new hwc into the house somewhere.

sydthebeat

ps i calculate nearly 10 litres being held in a 22mm dia pipe over 30 meters, assuming its a 22mm pipe

10-10-20

https://www.boards.ie/discussion/comment/120418512#Comment_120418512

Yes, or deploy an under-sink water heater...

smithy1982

from what i was told at the time of build there is 1 degree of heat lose from garage to house.

i dont know much about it but the pipes going in did look well insulated came in a roll with insulation already on it.

what i did do was put a 4inch duct in from the manifold in the house to the garage. so running a pipe to the garage might not be

to crazy once its big enough for a well insulated pipe.

10-10-20

That quoted "1 degree loss" is a blunt instrument when talking about domestic hot water piping if the content of the pipe needs to be displaced every time there is demand for hot water at the remote tap. It would have been valid if they were talking about central-heating pipe over a long fetch. Nice statistic, invalid in the context provided by them.

smithy1982

https://www.boards.ie/discussion/comment/120418883#Comment_120418883

if you were to put a number on it what would be a reasonable figure.

10-10-20

https://www.boards.ie/discussion/comment/120419385#Comment_120419385

That's what I'm saying - with the standard non-circulating pipe setup when you're operating a hot tap you're only interested in getting the hot water out of the cylinder, anything that's been in the pipe is now cooler than the cylinder so must be purged to obtain the hotter cylinder water. So it's an invalid metric to say that the loss is only 1C from cylinder to tap if all of the loss is coming about while the water is static and you weren't utilising the water. It's really only valid to do quote this metric when the water in the pipe is actively flowing from origin to destination.

But as pointed out above, the better that the pipe is lagged the better efficiency will be had if you were to implement a recirculation loop.