Combi Boiler and Cylinder

[sk09]

Hi

We've just done a renovation at our house and added a 210L unvented cylinder powered by 2 3kw immersion heaters. The cylinder provides water for two showers and three sinks.

We've also got a combi boiler that runs UFH, a couple of radiators, kitchen tap and a bath.

The boiler is downstairs in the kitchen and cylinder on first floor.

The issue:

We're finding that we're running out of warm water in the cylinder towards late afternoon and heating the cylinder up could take a couple hours to reach temperature providing no one is running water. Because it's late afternoon/evening warming the cylinder up is probably not worth it as overnight prices are considerably cheaper. It just means the bath needs to be used instead of the showers if anyone wants to use it.

As a layman:

I don't know much about plumbing - I'm hoping you guys do . Does such a valve exist where I can have the output of the cylinder pipe and the output of the boiler pipe connect together and a lever can be moved either side to divert the water source. If the cylinder is cold then I can flick the valve to close the cylinder output and open the boiler output and vice versa.

If this is possible then I'll look for plumber to help get this sorted.

Thanks!

 

[Elsa TLC]

Have the combi Flow & Return pipes been used as primary's for the hot water cylinder, or are you just using the Immersions?

 

[sk09]

Combi and cylinder are not linked at all. Immersion is solely heating the cylinder.

 

[Elsa TLC]

Combi and cylinder are not linked at all. Immersion is solely heating the cylinder.

Maybe that's worth looking at doing.

Only if the cylinder in indirect.

 

[Johntheo5]

As a layman:

I don't know much about plumbing - I'm hoping you guys do . Does such a valve exist where I can have the output of the cylinder pipe and the output of the boiler pipe connect together and a lever can be moved either side to divert the water source. If the cylinder is cold then I can flick the valve to close the cylinder output and open the boiler output and vice versa.

Technically/plumbing wise possible but almost certainly against regulations IMO, you could disconnect one shower from the HW cylinder and plumb in the combi boiler to permanently supply HW to this shower.

Measure the HW temperature from the HW tap after a overnight reheat, if its say 60C, then assuming 200L of HW and a showering temp of 40C means (from mains at 10C) 333L of 40C water available but if the cylinder stat is increased to max which I think is ~ 70C then 400L of 40C water is available, nearly 70L more which might meet your requirements but may need the installation of a thermostatic mixing valve on the cylinder outlet, especially if young children in the house.
Otherwise install a bigger cylinder (300L?) with or without a coil for indirect heating from the boiler (also requires new programmer) but if you go down this road ensure that two heating elements can still be installed with the bottom one below the heating coil otherwise you can't heat a full cylinder electrically.

 

[sk09]

Ok thanks for your advice. I will not go down this route if it's against regs.

I do have smart immersion elements that tell me the temperature of the water at both the bottom and middle of the cylinder. So knowing how much warm water is left we can sort of guage.

I think best bet is to plumb one of the bathrooms with direct connection to the boiler as a fail safe. New indirect cylinder will almost mean additional pipes and devices to control flow of warm water.

However, I think such a device should exist!

 

[Johntheo5]

What kind of temperatures are you seeing, have you a link to this smart immersion.

 

[sk09]

I can set the temps max 70 using the immersions. Immersions have an app and a display that show temps. Water temperature is not the issue.

I can automate turning on and off immersive using separate services.

What my overall goal was to power on a valve of some sort to divert the water coming from the cylinder and use the boiler instead depending on the temperature of the top immersion. Then overnight flick back again.

Immersion is from a company called Tesla (UK one not the car company)

Immersion Heaters & Thermostats | Plumbing and Heating Manufacturer

International Distributor of Plumbing and Heating Product. Specialising in Immersion Heaters, Cooker Hoses, Towel Rail Elements,

www.teslauk.com

Probably pick it up from Amazon cheaper.