Airtight electrical back boxes

[JohnW2]

Turn on the machine and cold water from the pipe flows in followed by water from the tank / boiler.

Intelligent designers specify a hot water loop circuit back to the hot water cylinder, with a pump connected to a motion sensor in the kitchen, with all pipes insulated.

That's a variant on a very old idea (the original Victorian plumbing in my house made much use of hot water loops) but I'm not at all convinced that it would improve efficiency. It's also worth pointing out that modern washing machines and dishwashers (at least in UK) use such ridiculously small 'puddles' of water to do the washing (and often very low temperatures) that I doubt that, efficiency/cost-wise', it makes a lot of difference how the water gets heated!

Kind Regards, John

 

[SimonH2]

... with all pipes insulated.

Just that bit would be a huge step forward in most cases

From what I've read, condensing dryers always release a certain amount of moisture into the air, which would be a big problem in an airtight house. From experience, houses with condenser dryers always have condensation and mould problems. Maybe this isn't always the case?

True. In our case the house is generally well heated and ventilated, so it's normally dry and the extra moisture doesn't cause a problem.

Also, having a 3kw heater running for hours, blowing hot air into a confined space such as a laundry room, small kitchen or closet might cause excessive overheating in an airtight house, making the immediate space unbearable to be in.

Again, it;s a large space so not a problem. I can see that it would be a problem for a small space.
But even if you vented it outside, a condenser would waste less energy than a non-condenser.

 

[JohnW2]

From what I've read, condensing dryers always release a certain amount of moisture into the air, which would be a big problem in an airtight house. From experience, houses with condenser dryers always have condensation and mould problems. Maybe this isn't always the case?

True. In our case the house is generally well heated and ventilated, so it's normally dry and the extra moisture doesn't cause a problem.

If a house is so poorly ventilated (aka 'airtight') that the residual moisture from a condensing dryer represents a problem, I wonder whether it is acceptable to have human beings (whose breathing and sweating represents a significant net input of moisture into the environment) living in the house, let alone cooking or taking baths/showers etc. in it?

Kind Regards, John

 

[viewer]

Intelligent designers specify a hot water loop circuit back to the hot water cylinder, with a pump connected to a motion sensor in the kitchen, with all pipes insulated.

Oh dear, yes, we've gone off on a tangent to electrical work, but still very interesting. However, the statement above needs cannot be left unchallenged. Pumped hot water systems are common in large or public buildings such as hospitals and need considerable care both in design and maintenance. Even with calorifiers, biocidal treatment and skin removing high temperatures, Legionella, iron bacteria and biofilms become a problem. These are serious concerns. I'm not sure how a motion sensor would help - if detection of someone in the kitchen turned on the pump then it would make the above problems worse. Insulation slows down heat loss and, again, could make matters worse as the water would stay at sub 60C for long periods before being returned to the store. I would suggest that they are not generally suitable for domestic situations.

 

[tew1]

If a house is so poorly ventilated (aka 'airtight') that the residual moisture from a condensing dryer represents a problem, I wonder whether it is acceptable to have human beings (whose breathing and sweating represents a significant net input of moisture into the environment) living in the house, let alone cooking or taking baths/showers etc. in it?

Kind Regards, John

well, in an airtight house, the MVHR system is designed to provide an adequate amount of ventilation to deal with moisture from normal respiration and bathrooms, but not the kitchen. The kitchen hood must vent outside as grease will clog up the system. I think the latent moisture from a condensing tumble dryer might be too excessive for the MVHR to deal with. Maybe not. Would be interesting to find out. All I can go by is my experience of old houses which develop mould around condensing tumble dryers due to the extra moisture. Maybe people don't empty the condenser tray regularly enough?

 

[tew1]

Insulation slows down heat loss and, again, could make matters worse as the water would stay at sub 60C for long periods before being returned to the store. I would suggest that they are not generally suitable for domestic situations.

domestic hot water loops are fairly simple. You have a pressurized hot water cylinder or plate heat exchanger. There is a return from the furthest hot draw-off point on the line back to a pump which returns the water to the bottom of the tank and heats it, killing any legionella (which is highly unlikely in a small domestic sealed system anyway). The pump is connected to a pipe thermostat on the return 'loop', meaning that when the water cools below 60 degrees, the pump pushes hot water around the loop, displacing the cooled water back to the tank for heating, meaning that whenever you turn on a tap, the water is always instantly hot. Therefore, you get no persistent cooling of water in the pipes. A motion sensor can be used inline with a thermostat, to only circulate the water when people are in the kitchen (prior to hot water being drawn off). It's very efficient, and prevents all that wasted water (turning a hot tap on and waiting for it to come out hot), and also great for hot-feed washing machines/dishwashers.

 

[tew1]

modern washing machines and dishwashers (at least in UK) use such ridiculously small 'puddles' of water to do the washing (and often very low temperatures) that I doubt that, efficiency/cost-wise', it makes a lot of difference how the water gets heated!
Kind Regards, John

That's a whole other story I won't get into regarding bacteria, chemical stain removers, extra concentrated laundry detergents, the contamination they cause in the environment and the effect of residual chemicals in fabrics on your health. You'd be better off using an eco-friendly detergent/softener and washing at a higher temperature.

 

[JohnW2]

domestic hot water loops are fairly simple. ... The pump is connected to a pipe thermostat on the return 'loop', meaning that when the water cools below 60 degrees, the pump pushes hot water around the loop, displacing the cooled water back to the tank for heating, meaning that whenever you turn on a tap, the water is always instantly hot. Therefore, you get no persistent cooling of water in the pipes.

I'm not sure I understand how that could be described as efficient. If there were no 'persistent cooling of water in the pipes', there would never be any 'cooled water' to be pumped back for re-heating - and constantly re-heating water which is not being used doesn't sound too efficient to me. However, you go on to add....

... A motion sensor can be used inline with a thermostat, to only circulate the water when people are in the kitchen (prior to hot water being drawn off). It's very efficient, and prevents all that wasted water (turning a hot tap on and waiting for it to come out hot), and also great for hot-feed washing machines/dishwashers.

Aren't there some potential flaws in that? Is it not common for people to turn on a tap soon after entering a (previously unoccupied) kitchen, and therefore probably still have to 'wait for it to come out hot'? ... and what about hot-feed machines which draw water when no-one is in the kitchen?

Kind Regards, John

 

[SimonH2]

Is it not common for people to turn on a tap soon after entering a (previously unoccupied) kitchen, and therefore probably still have to 'wait for it to come out hot'?

Can't think it's that common to walk into the kitchen or bathroom and immediately turn on the hot tap. Even so, the pump will be shifting hot water round fairly quickly so even if they beat it, the cold water will last a lot shorter time than without the circulation loop.

... and what about hot-feed machines which draw water when no-one is in the kitchen?

That is a fly in the ointment as it were.
Load sensor on the socket the washing machine runs from - but that's starting to get a bit complicated.

 

[EFLImpudence]

Seems to me a bit like 'filling the saucepan with hot water to save gas'.

 

[JohnW2]

Is it not common for people to turn on a tap soon after entering a (previously unoccupied) kitchen, and therefore probably still have to 'wait for it to come out hot'?

Can't think it's that common to walk into the kitchen or bathroom and immediately turn on the hot tap. Even so, the pump will be shifting hot water round fairly quickly so even if they beat it, the cold water will last a lot shorter time than without the circulation loop.

That's all true, and is advantageous in terms of convenience (fairly 'instant' hot water for those in hospitals, hotels etc.) but given that the cold water is being pumped back (however quickly or slowly) for re-heating (possibly not to be actually 'used' until it has been through a number of further cooling/heating cycles, I'm still struggling to see what is necessarily 'efficient' about it.

... and what about hot-feed machines which draw water when no-one is in the kitchen?

That is a fly in the ointment as it were. Load sensor on the socket the washing machine runs from - but that's starting to get a bit complicated.

Sure, if one considers it worthwhile, one can make it as complicated as one wishes, to cope with every 'fly in the ointment' one can think of.

Kind Regards, John

 

[tew1]

In a loop, the pump only needs to run for literally 30 seconds or so to replace all the water in the pipe with hot water from the tank, so the minute you walk in the kitchen, there will be hot water at the taps. It's more efficient with hot feed washers/dishwashers. Usually, you have to walk in the kitchen/utility to turn on the machine John! You also save a lot of water when there is instant hot water. I'm sure a lot of people can leave taps running for at least a minute waiting for hot water to come through. I'm not sure what any of this has to do with airtight electrical boxes, but hey!

 

[tew1]

Seems to me a bit like 'filling the saucepan with hot water to save gas'.

I always do that! I fill the kettle with hot water too

 

[EFLImpudence]

Seems to me a bit like 'filling the saucepan with hot water to save gas'.

I always do that! I fill the kettle with hot water too

You should not.

 

[tew1]

You should not.

why not?