Can you run a Thermostatically Controlled Shower from an electric boiler system?

Leodogger

We have just bought a Grohe Thermostatically Controlled shower bar system with a twin handle bar.  We have an electric boiler and are finding that the temperature is not being controlled on the shower when we use it.   We have the boiler set at 48c and the shower is supposed to maintain 38c as standard but you can increase it to 45c through the thermostatic control valve, however we have increased it at the shower bar because it kept cooling down before we were out of the shower after a few minutes, but the shower still is not getting over 37c so we had to increase the boiler temperature to 55c which was plenty hot enough when we get in but then starts to cool after a few minutes. 

Does this mean that the thermostat is not working, or due to the electric boiler drawing in cold water and thereby reducing the temperature of the water to the shower bar to start with ?   I have written to Grohe but they keep saying it should work fine with the electric boiler.   I am not so sure because we had one previously connected to a combi boiler and it maintained the temperature perfectly as obviously the gas keeps the combi at the same temperature presumably.   So is Grohe lying when they say it works just as well off an electric boiler ?

grumpy_codger

Leodogger said:

 

Does this mean that the thermostat is not working, or due to the electric boiler drawing in cold water and thereby reducing the temperature of the water to the shower bar to start with ?  

This is easy to check with your palm by feeling the temperature of the outlet pipe of the boiler.

sheenas

Helpful to know what boiler we are talking about?

ComicGeek

Could be to do with the maximum flow rate provided by the electric boiler, which isn't enough for your new shower flow rate. Often there is a small amount of stored heat within the electric boiler, which might be why the shower starts off hot and then cools off once this stored heat has been used up - the flow rate from electric boilers is normally pretty low as instantaneously heating water uses a lot of power.

Sounds more like a limitation with the electric boiler than the shower to me.

Leodogger

ComicGeek said:

Could be to do with the maximum flow rate provided by the electric boiler, which isn't enough for your new shower flow rate. Often there is a small amount of stored heat within the electric boiler, which might be why the shower starts off hot and then cools off once this stored heat has been used up - the flow rate from electric boilers is normally pretty low as instantaneously heating water uses a lot of power.

Sounds more like a limitation with the electric boiler than the shower to me.

You could be right.   Grohe said there has to be a flow rate of 5l / minute but have absolutely no idea how to check that other than filling a 1 ltr jug 5 times from the shower head 😁

Leodogger

sheenas said:

Helpful to know what boiler we are talking about?

It is an Aparici boiler, manufactured in South Korea.

Leodogger

grumpy_codger said:

Leodogger said:

 

Does this mean that the thermostat is not working, or due to the electric boiler drawing in cold water and thereby reducing the temperature of the water to the shower bar to start with ?  

This is easy to check with your palm by feeling the temperature of the outlet pipe of the boiler.

How on earth can you check the temperature with the palm of your hand 🤔

grumpy_codger

Leodogger said:

grumpy_codger said:

Leodogger said:

 

Does this mean that the thermostat is not working, or due to the electric boiler drawing in cold water and thereby reducing the temperature of the water to the shower bar to start with ?  

This is easy to check with your palm by feeling the temperature of the outlet pipe of the boiler.

How on earth can you check the temperature with the palm of your hand 🤔

The same way as you feel the temperature of  water coming out of the shower.

ComicGeek

Leodogger said:

sheenas said:

Helpful to know what boiler we are talking about?

It is an Aparici, Spanish boiler.

That's probably an electric water heater (ie small amount of hot water stored in a vessel), rather than an electric boiler able to instantaneously produce lots of hot water. 5 l/min is a very small amount of water, a typical shower is more like 9-12 l/min.

How much water is stored in the heater? The largest Aparici unit I can see on a UK site (assuming that it's in the UK and not Spain?) is only 100 litres and takes 4 hours to reheat. 

Leodogger

grumpy_codger said:

Leodogger said:

grumpy_codger said:

Leodogger said:

 

Does this mean that the thermostat is not working, or due to the electric boiler drawing in cold water and thereby reducing the temperature of the water to the shower bar to start with ?  

This is easy to check with your palm by feeling the temperature of the outlet pipe of the boiler.

How on earth can you check the temperature with the palm of your hand 🤔

The same way as you feel the temperature of the water coming out of the shower.

I need to know if the boiler is working as it should and with the valve adjusted to its highest level, it should be 45c and should be able to maintain that temperature, how do I check that with the palm of my hand ?

grumpy_codger

Let's say you want 37. If the water from the boiler is hotter than 37 the mixer valve dilutes it with some cold water making it about 37. If the temperature of the water from the boliler drops below 37, you will feel it. If it remains hot, then the problem is with the mixer valve.