Central heating idea

[normspanners]

Or i could use it to warm up the water entering the tank which would solve the overheat issue as once the tank comes up to temp it will shut off the heating circuit via the motorised valve.

how about putting the PHE in the hot line from the hot water tank, therefore boosting the temp of the already hot water to near boiler temp,( NOT BOILING btw) then you would not have to use quite so much hot water, as you would be mixing more cold to attain the same hot shower, as said I run my immersion at 80 deg and can get 5 showers out of it, one after the other plus modified hot fill washing machine! and doing it that way it wouldnt affect any other circuit, yes you have to be careful in the basin and sink but we are well aware of it, I placed my DHWT centrally when I designed the system and the longest hot run is about 12/15 ft of 15mm and 5ft of 22mm, It also means when we run a bath you turn both the taps on equally and start getting undressed etc and by the time you are naked got your towell ready etc the bath is full of the correct temp water ! I can come in freezing enter the bathroom and be in the bath in 4/5 mins.

 

[Barlidge]

HEHE a few weeks ago I went in the shower and it was VERY hot, scalding so I tried to adjust it down and it was making no difference now I thought that is strange coz it has an anti scald, solenoid valve thats weird it must have stuck so there I am in my birthday overalls with screwdriver etc off came the cover of the pump housing to check out whats wrong screwed the valve all the way to the cold and it was still scalding hum seems like its plumbed up wrong, its been there 20 yrs so cant be ?? so I clamped off the silicone hose for the hot and it was still ridiculous, so clamped off the cold and it obviously stopped ?? suddenly had this horrible feeling, AH!!! shouted to the wife get the bidet and bath turned on cold , she thought I had gone mad, it was the eureka moment when I realized I had a 60/70 gals tank full ish of absolutely boiling water in a plastic tank in the loft !! ---------as well as a hot tank full. She was shouting the taps are the working the wrong way whats happening
WOW how lucky that we found out and hadnt left it !!
Off to the shed for a spare stat, not in birthday overalls BTW
Any views on safety clamp-on trip stat on the vent pipe ? it would have to stay tripped though once tripped, otherwise its a new complete immersion ?

Had exactly the same experience about 10 years ago when the immersion thermostat stuck on, very scary and it wasn't long after a couple had lost their lives when a tank collapsed while they were in bed.

 

[normspanners]

yes you have to be careful in the basin and sink

just found an anti scald mixing valve https://www.heatandplumb.com/acatal...MIvIH39qjG2QIVr7ftCh0zsQwUEAQYAiABEgI4vvD_BwE , now thats an Idea for the sink, hand basin and bidet coz especially the bidet that can be a bit .

 

[normspanners]

tank collapsed while they were in bed.

The cold tank I assume ?

 

[normspanners]

I'm struggling to understand how you have the immersion and boiler running

it depends how big the coil in the tank is, some coils are only 5KW and immersion 3 ish ? thats 8 kw most electric showers are 10 to 12 kw so there is maybe a bit of a short fall, if heating cold water.

 

[Kayos]

Saying the coil is “only” 14kw shows a lack of understanding

I don’t think adding the plate will work, if it does you will be feeding the unvented with an uncontrolled heat source so it’s in contravention of part G3 of the building regs

There’s a reason you have to be qualified to work on those cylinders

 

[thinfourth]

Saying the coil is “only” 14kw shows a lack of understanding

I don’t think adding the plate will work,

The max amount of heat the coil can transfer is 14Kw

If you fill the tank with cold water it will take X amount of time to heat up

If instead fill the tank with warm water from a plate heat exchanger then that time will be reduced as have to stick in less energy to reach the temperature.

If i could magically replace the 14Kw coil with a 36Kw coil then would you have an issue with that?

if it does you will be feeding the unvented with an uncontrolled heat source so it’s in contravention of part G3 of the building regs

There’s a reason you have to be qualified to work on those cylinders

How is it an uncontrolled heat source when the heat exchanger is going to be fed from the outlet of the tank heating coil which is controlled by a zone valve?

The boiler itself has a normal thermal cutout for operating and an over temp cutout so that is another 2 layers of control.

 

[thinfourth]

how about putting the PHE in the hot line from the hot water tank, therefore boosting the temp of the already hot water to near boiler temp,( NOT BOILING btw) then you would not have to use quite so much hot water, as you would be mixing more cold to attain the same hot shower, as said I run my immersion at 80 deg and can get 5 showers out of it, one after the other plus modified hot fill washing machine! and doing it that way it wouldnt affect any other circuit, yes you have to be careful in the basin and sink but we are well aware of it, I placed my DHWT centrally when I designed the system and the longest hot run is about 12/15 ft of 15mm and 5ft of 22mm, It also means when we run a bath you turn both the taps on equally and start getting undressed etc and by the time you are naked got your towell ready etc the bath is full of the correct temp water ! I can come in freezing enter the bathroom and be in the bath in 4/5 mins.

Thought about that and it won't work as well

As when the boiler is off then i am potentially sticking energy into the central heating circuit

A heat exchanger isn't fussy it will transfer energy either way

Also it bypasses the temperature switch on the tank which controls the zone valve so you could have 80C water coming out of the taps in the kitchen so its a nope

 

[thinfourth]

I'm struggling to understand how you have the immersion and boiler running and you are running out of hot water. Surely you just need to run the water cycle on the boiler for longer. Our boiler does the hot water and central heating and the immersion has onlyu every been used when we didn't have a boiler up and running. There are 4 of us in the house all having showers and we don't have a massive tank. If it looks like theres going to be a rush then I just put the water on advance.

As the cold water is fed by a pretty big pump so our flow rate is somewhere between very good and now you are getting stupid.

The same pump can fill an IBC in under an hour with ease

 

[normspanners]

As when the boiler is off then i am potentially sticking energy into the central heating circuit

only a small amount because the pump would be off so only the small amount in the boiler side of the HE would get warmed. If plumbed so there was no thermosyphon effect the amount would be negligible

so you could have 80C water coming out of the taps in the kitchen so its a nope

we do and its fine for us , but as said you can get the inline anti scald mixer valve to regulate hot tap temperature to what ever you want so the hot tap would never exceed the preset temp because it would mix it with cold.

 

[armalites]

I fully understand what you are saying about the heat source not being able to keep up with the flow but that would only matter if the shower was running all day.

My point is surely the easiest/cheapest resolution here is a bit courtesy/communication/planning? IE "Please don't spend 20mins in there as I need to have a shower" How long are you guys staying in there? 200L should be easily enough for you both to have a 15-20 minute shower every day

The shower will only flow what it flow no matter how big the pump is.

 

[the snooper]

Heat exchangers, immersion heaters hot water running, out the simple answer is, buy a shower

 

[Barlidge]

The cold tank I assume ?

Yes it was, bit longer than 10 years.

https://www.telegraph.co.uk/news/uknews/1434588/Woman-killed-by-boiling-water-pouring-on-to-bed.html

 

[knighty]

Saying the coil is “only” 14kw shows a lack of understanding
I don’t think adding the plate will work, if it does you will be feeding the unvented with an uncontrolled heat source so it’s in contravention of part G3 of the building regs
There’s a reason you have to be qualified to work on those cylinders

I'm the one who said my hot water tanks only have 14kw coils, not op

what about that shows a lack of understanding ?


OP said he's going to fit the phe to the cold feed into the boiler, heated by the return from the coil in the tank... so it'll only be heated when the tank is, it'll start/stop with the tank coil feed as the tank stat calls for heat

also, it's an oil boiler so I can't see how it counts as uncontrolled ? (not like a wood burner etc.)

 

[knighty]

p.s. not sure about old ones, but modern immersion heaters (should) have 2 stats in them... the normal one you set for the temperature you want and another stfty stat which should tick out at 90'C and needs resetting before it'll cut in again after cutting out

I'm not sure if this is a 'rule' for them... just all the immersion's I've seen lately have two

 

[CompoSimmonite]

Get an instantaneous electric shower ?

 

[tlovatt]

Either you or the wife change to showering in the morning / evening or just take a longer break between having showers.

To raise the temperature of 200l of water through 50 degrees C in under 1h only requires a 12kw heat source, with both the boiler and immersion heater I am surprised you need more than 40mins or so to have another tank of hot water ready to go even if all of the hot water was fully depleted?

 

[thinfourth]

Get an instantaneous electric shower ?

NOPE, NOPE and nope again

I have to meet an electric shower that is anywhere close to the output of our current shower.

Either you or the wife change to showering in the morning / evening or just take a longer break between having showers.

To raise the temperature of 200l of water through 50 degrees C in under 1h only requires a 12kw heat source, with both the boiler and immersion heater I am surprised you need more than 40mins or so to have another tank of hot water ready to go even if all of the hot water was fully depleted?

While a completely reasonable suggestion

I prefer a complex over engineered solution mainly to prove that it can be done

 

[tlovatt]

3 other possibilities:

1 - create a hidden cupboard in the shower, fit a low flow shower head for the wife to use and keep your existing shower head to yourself.
2 - fit a smaller tank, in the time it take someone to get out of the shower and dry off, the tank (allowing for some time for the second person to undress etc) would be hot again.
3 - Shower before the wife - its her problem then?

 

[thinfourth]

3 other possibilities:

1 - create a hidden cupboard in the shower, fit a low flow shower head for the wife to use and keep your existing shower head to yourself.

The wife would notice and it would result in my death

2 - fit a smaller tank, in the time it take someone to get out of the shower and dry off, the tank (allowing for some time for the second person to undress etc) would be hot again.

At some point the wife will be in the shower and run out of water

This would result in my death

3 - Shower before the wife - its her problem then?

This would also probably result in my death

Or worse

She might sulk and stop cooking

Which would result in my death