Help with immersion water heating

[pistolpedro]

Hi

I have a BTL and my tenant has mentioned that they aren’t getting enough hot water, from what I can gather after 2 showers they are emptying the tank, they are also struggling to fill the bath.

The flat has no gas and the hot water is heated via immersion heaters, the tank has two immersion heaters one boost and one which comes on in the night which uses economy 7. The tank is on the same floor as the shower so the system is an indirect (?) with mains water passing through a coil inside the tank, this allows a good water pressure.

I’m not 100% sure but I’d guess that the system is approx. 20 years old, I have had an electrician out to inspect it and its operating correctly

I have little knowledge on this (or any) type of water heating but from reading around I think I may have 2 options to address the issue

1) Fit a larger tank – this is probably the most straightforward but at the expense of cupboard space
2) Fit an electric shower – not ideal as the fuse box is a good distance away from the shower and being an open plan duplex there is no ceiling to run cables through

I am looking for any advice or suggestions about any potential ways to fix this.

Thanks in advance, Pete

[mickmcpaddy]

Is this a thermal store as opposed to a standard immersion set up or is it an electric Megaflow type setup?

Thermal stores are over complicated things that always go wrong.

[pistolpedro]

not sure to be honest from the outside it looks like a bog standard hot water tank, foam covered copper (?) tank,

from what I understand the immersion heaters heat the water in the tank, the mains water then passes through this hot water inside a copper coil and the heat from the water in the tank is transferred into the mains water.

[jet_noise]

Is your tenant using the boost?
Or is he/she expecting unfeasibly large amounts of hot water from the overnight heat?

[TooMany2cvs]

jet_noise said:

Is your tenant using the boost?
Or is he/she expecting unfeasibly large amounts of hot water from the overnight heat?

I think we all know the answer to this...

User expectations do not fit the reality of the system's capabilities. They're probably used to a combi.

[pistolpedro]

I talked him through the boost (1hr) and also sent him the instructions (PDF) to the control panel

Or is he/she expecting unfeasibly large amounts of hot water from the overnight heat?

I suspect that this is issue, my electrician mentioned that when he spoke with them they mentioned that they are taking approximately two 10 minute showers in the morning, it’s the first complaint I’ve had in 10 years about it, but they are otherwise good tenants and with letting fees around £700 I’m thinking if I could try and appease them it would be best in the long run (£)

They're probably used to a combi.

This was my thought as well

[4Q]

One way to "increase" the amount of hot water without the expense of a new cylinder is to raise the temperature of the cylinder thermostat to 70 degrees and put a thermostatic mixing valve on the outlet to mix the temperature back down. This will give you an increased volume of water at the temperature you want. Don't raise the temp without fitting a TMV though as you risk scalding the user.

[pistolpedro]

Thanks, that’s a good point my electrician suggested upping the thermostats and I didn’t give it much thought as the volume is the issue rather than the peak temp but as the system is indirect a higher temp would give a greater volume, he is returning this week to increase them so I’ll keep an eye on that.

As a back up I had a quick look at a megaflow tank, (mentioned in an earlier reply) these look like a potential solution do they heat the water as and when it is required or is it just a more efficient immersion system (tank is heated then stored)

[mickmcpaddy]

I'm no expert but from what I've seen a thermal store is usually used where you cant get a blow off pipe to outside the building for the pressurised water, the ones I have seen have a small header tank sat on top of the unit to keep the volume of water topped up in it, with an expansion pipe back into the header tank. Mains pressure water is then fed round the coil to get heated by the volume of hot water. This is backwards to a conventional indirect cylinder where the coil inside the cylinder fed from the boiler heats the volume of water.

A standard electric Megaflow type would heat the volume of water directly via a couple of immersions, this volume of water is fed directly into the cylinder under mains pressure so would need all the pressure relief stuff to go with it including a blow off pipe to outside.

All the thermal stores I have seen have had a complicated PCB with relays on and several sensors to control the immersions and its usually the PCB or relays that fail due to the excess heat the thing produces.

I would choose a Megaflow any day over a thermal store, although you do seem to get problems with the thermostats in them tripping out occasionally.

[pistolpedro]

Thanks, that’s really helpful, the flat is located on the 1st floor and the boiler is towards the middle of the floor plan beneath the stairs so I think I’m right in saying that venting to an outside wall is not an option

[Flibble]

I have a flat with an electric megaflow fitted internally (pretty much in the middle in fact) - I'm not sure where the pressure valves vent to, but as it came originally fitted, there may be piping to the outside.
It seemed to work fine, plenty of hot water, the only issue being the thermocouples die every 5 years or so. They're about £20-30 online though and can be changed in about a minute, so not a huge deal.

[pistolpedro]

thanks that sounds interesting, this seems like the best solution as I wouldn't have to look at chasing wires and retiling for an electric shower, i'm speaking to my plumber in the next few days so i'll mention this to him,

thanks again for everybody's input got a few avenues to explore so fingers crossed i'll get it sorted out

[Bill]

It might simply be that the thermostat is on its way out and the hot water isn't getting as hot as it used to.

[pistolpedro]

yes thats true, the electrician mentioned that he'll put a new pair in just to make sure, as far as i know they dont cost much and they just slide inside the immersions so no big labour costs