Towel Rail connected to hot water tank?! And Mixergy Tank any good?

[JohnD]

It takes about 4.5kWh to heat 100 litres of tapwater

So your cylinder should take around 15kWh to go from cold to hot in one go. Less on subsequent times when it is already partially hot.

Did you use any hot water during the day?

Did you heat it in one go then turn off?

How many radiators were on?

Is water running out of the Megaflow relief valve?

It is much easier to measure HW usage in summer when no heating is on.

It would be very unusual to use 300 litres of hot water in one day unless you like American style showers or have multiple hot baths. Not impossible.

Central heating can use much more gas.

 

[ndoubt]

We use hot water for the usual things - washing machine, dishwasher, washing up etc...
One blast of 45mins was only enough for a bath and quick shower.. i have to set up 3 separate blasts for 3 showers through the day..
No radiators were on, no central heating at all.
There is water running our of the relief valve when the system starts up yes

 

[JohnD]

There is water running our of the relief valve when the system starts up yes

Get it mended. It is wasting hot water.

 

[ndoubt]

Noted and on the case.

Is it normal for the pipe from the mains into the cylinder is warm when the hot water is on?
It looks like there is a return pipe maybe from the towel rails that joins back onto the cold pipe ..

 

[JohnD]

The towel rail would usually have one end connected to the flow (hot feed) and one end to the return (warmish) pipes that come from the boiler

The lockshield needs to be fairly well shut to prevent it stealing flow.

The cold water supply pipe to the cylinder, at the bottom, should be cold.

 

[ianmcd]

We use hot water for the usual things - washing machine, dishwasher,

washing machines and dishwashers dont have a HW supply unless very very old

 

[JohnD]

I love my old washer.

Uses hot water from cheap gas rather than expensive electricity.

 

[ndoubt]

John… more detail… the heating and hot water have been off for hours… but there is hot water circulating out from the megaflo *somewhere* … not rads or towel rails or any hot water using thing are on, no hot taps running. The water is circulating out from the top of the mega flow and looks like it’s coming back via this orange grundfos pump which pushes the hot water back into the cold inlet?! Pic provided. Is this pump just circulating hot water through the towel rail system maybe even tho the rads are off?or what could it be..

 

[JohnD]

The yellow pump is a Grundfos Bronze (very expensive)

Its purpose is to circulate hot tap water round and round between the cylinder and the bathroom, so you do not have to run the taps and wait for them to get hot.

How far away are your bathrooms?

When this is happening, the pipes act as long thin radiators, giving up heat to warm the spiders living under the floor and in other spaces.

So far as I can see the pipes are not even insulated.

This is very wasteful of energy.

 

[ndoubt]

When you say expensive do you mean expensive to run? The bathrooms are not far enough that I’m bothered if I have to run the tap for 30 seconds or so (or wld it be significant?) to get hot water. But we have one bathroom in the loft the other side of the house so I guess far. If I can change things so that the hot water is being conserved in the megaflo that wld be ideal.

Whats the solution here do you think? Take that pump out? Replace it with something? Would it only affect time for hot water to circulate to taps or would it affect pressure? And should I be concerned that it’s been plumbed to return into the cold water inlet?

Many thawks John

 

[JohnD]

I've had one like that. My preference would be to remove the pump, which will obstruct flow when it is not running

And put a gate valve on the return pipe (to prevent unwanted flow) and put up with the delay in the distant bathroom.

And of course insulate all the pipes.

If you wanted, you could control the yellow pump so it ran when the distant bathroom was occupied, for example with a PIR or off the light switch.

Don't throw away the yellow pump, due to its value.

 

[cdbe]

I have a 145l megaflo, 15kw boiler,2 towel rails run off the hw circuit. Two adults and 2 teenagers. I have the hot water timed for 30 mins in the morning and 5 - 9pm - we never run out of hot water. Obviously it doesn't run from 5-9pm - just fires up if someone has a shower. Secondary circulation probably unnecessary unless a mansion - I run my baths/showers in 15mm.plastic radials and the sinks in 10mm plastic radials - virtually on demand hot water everywhere. Compared with space heating our hot water gas consumption is pretty low.

 

[ndoubt]

Thanks for all this help guys. So if i took out the pump then the hot water wouldn’t circulate constantly right? It would just be on demand from the megaflo? The distant bathroom hasn’t been used for a year so feels a waste!

 

[JohnD]

When you say expensive do you mean expensive to run?

The pump was expensive to buy. I forget what mine cost. At least ten years ago in my previous house. Bronze, very resistant to corrosion and wear.

If you wanted the pump "on demand" you could fit it in the distant bathroom with local switching. It will cool the cylinder when running.

 

[ndoubt]

I suppose the other solution could be a timer on the pump? I have a spare Drayton timer.. would it be possible to fit that to the pump so it’s not running all the time? Would it mean I’d still get hot water even when it’s not running?