Electric combi boiler for underfloor heating and rads - off the grid

[serfer]

I'm just confused as there are different models mentioned above, one mentions a a smallish amptec would suffice, another mentions having 2 inline, one serving each distribution method. Another mentions not even a powerful gas combi would cope. So its a bit confusing!

 

[Masood]

Heating water instantly?
I was hoping to find a combi with an internal store of 50-150 litres that is kept ticking over at a good temperature...

Guess what you've just described? Yep, you got it - a cylinder!

 

[serfer]

If a combi has an internal store - then why would i go for a cylinder? Or rather, if I want a cylinder, then why is the combi a bad idea? I was lead to believe by a plumber not on this forum that a combi would have a store... So i dont know what to make of it all!

 

[Deleted member 64964]

Guess what you've just described? Yep, you got it - a cylinder!

No its a electric combi boiler with thermal store and an immersion to heat it, its completely different to a cylinder. This think you can get in different sizes and is cylindrical in shape. :blush5:

 

[serfer]

thanks Therm! can you sense my confusion? Masood tells me I'm talking about a cylinder. you like his comment, then you say i'm talking about something completely different.

I'm going to look into the cylinder option, unvented direct, as suggested above, but then chris' comment worries me! Chris seems to be saying that i don't have the electricity supply to deal with an electric boiler of any type?

:disappointed:

 

[SimonG]

The irony of it.

 

[Deleted member 64964]

thanks Therm! can you sense my confusion? Masood tells me I'm talking about a cylinder. you like his comment, then you say i'm talking about something completely different.

I'm going to look into the cylinder option, unvented direct, as suggested above, but then chris' comment worries me! Chris seems to be saying that i don't have the electricity supply to deal with an electric boiler of any type?

:disappointed:

Direct unvented cylinder is your best option. Don't worry about any other posts about hot water. That's your best option without doubt.

It's the most cost effective way and once it's hot it's just a matter of a tickle ro get back to temperature.

 

[chris watkins]

Direct unvented cylinder is your best option. Don't worry about any other posts about hot water. That's your best option without doubt.

It's the most cost effective way and once it's hot it's just a matter of a tickle ro get back to temperature.

I know, I know, I said I was out of here but just a word of warning serfer what you have been told a number of times is correct storing hot water in a cylinder is the way to go cos you can use the energy over a longer period & so it doesn't have to be so powerful, most immersions are 3kW you just have to have em switched on for a good fuse hours.

You started by saying you are on a tight budget but you must understand that the installation of an un-vented cylinder (well any actually) is subject to the Building Regulations AD Part G & as such it is both illegal & dangerous to try to install one yourself "YOU HAVE BEEN WARNED"

Get a plumber in who has their ticket & can self cert the install, they can advice you of the best options & limitations.

Bye CW

 

[cr0ft]

If a combi has an internal store - then why would i go for a cylinder? Or rather, if I want a cylinder, then why is the combi a bad idea? I was lead to believe by a plumber not on this forum that a combi would have a store... So i dont know what to make of it all!

I will try my best to explain. As far as electricity goes you have 2 options available to you. Use cheap off-peak electricity to heat your house (last time I checked this was available for as little as 6p/KWh compared to around 15p/KWh for peak rate electricity). There are even Economy 10 tariffs now available that give you 3 off peaks in the afternoon. Use this electricity to power immersion heaters during this time to heat the largest hot water cylinder you can fit in your property. The energy in this is then stored and used when required to run normal central heating, underfloor heating (plumbed not electric) and heat hot water on demand. These modern cylinders are very heat efficient and will retain nearly all of their energy over a 24 hour period.

As you've mentioned already, cylinder installs are more expensive so you would save money initially by not purchasing a cylinder. This saving will be eaten away in no time at all by paying 15p/KWh vs 6p to heat all your hot water and run your central heating. I can't really make this any clearer so I hope it makes sense!! Effectively your cylinder is like a giant energy battery that stores up off-peak energy and uses it in the peak times.

This is the only cheap way to run an all electric house. If you size the cylinder correctly it will be cheaper than any other fuel type except mains gas. If the cylinder is too small you end up using peak rate electricity and the system costs a fortune to run.

My experience in this? We fit these systems fairly regularly and so I know they work and how cheap they can be to run.

At present a 60A incoming supply to your house isn't sufficient to run one of these systems though (they nearly all draw 52A, running 4 immersion heaters at once usually) which doesn't leave enough left to boil a kettle. Ask your supplier to upgrade you to a 100A supply. This is often free if you can demonstrate why you need it.

 

[village idiot]

Phone up any of the major underfloor heating company manufacturers (Uponor, WarmUp, etc) and provide them with your scenario. They are better able to assist you. Good luck

 

[serfer]

Thanks croft! Really useful and very much appreciate your time and patience!
I was lead to believe that economy 7 or 10 would increase my peak rate by quite a lot. So instead of 10p per unit 24/7. I pay 6p for 10hrs and 15p for 14 hrs. My business will be using quite a lot of electric to power the equipment so i wasn't sure about going economy 7 or 10...

 

[serfer]

also, one more question: why direct cylinder? If i am getting a boiler, wouldn't an indirect be an good option?

 

[SimonG]

Have you ever heard of the horse, the water trough and the two bricks?

 

[serfer]

Not yet, no!

 

[Chalked]

Not yet, no!

dont mean to be blunt but! For example.
Why would you use a 3kw boiler to heat a cylinder with pumps etc. that you can heat with a 3 kw immersion heater?

the op needs to realise that electricity is 100% efficient, but costs 3 times per kw than natural gas.

 

[serfer]

Aha. Gotchya! So boiler is eg 9 or 12kw. And immersion in a direct cylinder is 3kw. I see i see . Thx chalky and all

 

[serfer]

so.. is an immersion heater the same thing as a direct cylinder? last question i promise. probably.

 

[Gray0689]

The direct cylinder is heated by immersions
Indirect by a boiler or the like

 

[cr0ft]

also, one more question: why direct cylinder? If i am getting a boiler, wouldn't an indirect be an good option?

No need to get a boiler. You only need a boiler if you are going to be on mains gas. Off-peak electricity is cheaper than all the other fuel types. You just need the cylinder to be sized correctly so it holds enough hot water (i.e. stored energy) to satisfy your hot water/heating demands in the peak rate times. The cylinders in question work in reverse to normal cylinders. The immersion heaters heat the water in the cylinder. The heating circuit water passes through a heat exchanger in the cylinder and takes energy from the cylinder water itself. Make sense?

You can run underfloor heating off these no problem in fact a UFH system works better on these than a normal radiator setup due to the lower temperatures UFH runs at.

Take a look at this system - this would be perfect for you: -

THERMAflow

Make sure you get someone who knows what they are doing to size and install it for you or it will be the most expensive system to run you could imagine.

 

[cr0ft]

dont mean to be blunt but! For example.
Why would you use a 3kw boiler to heat a cylinder with pumps etc. that you can heat with a 3 kw immersion heater?

the op needs to realise that electricity is 100% efficient, but costs 3 times per kw than natural gas.

Off peak electricity is much closer than that to the cost of natural gas though. If he doesn't have access to natural gas in the street an off-peak electric system is cheaper to run than LPG or oil.

 

[serfer]

Thanks for the info croft... The thermaflow link is selling me electric combi boilers... Which was my first plan. But the consensus seemed to be to avoid the electric combi due to run it costs.

What at does anyone else think? Is a direct unvented cylinder enough to run 6 rads, 75sqm ufh and dhw? Would a boiler be needed too? Would 9 or 12kw be best... Loads of fun this plumbing malarky! A fair bit to get me head around and thx again for helping

 

[chris watkins]

Can you have yourself taken off of a thread ???????? this is starting to do my brain in.

serfer please for the sake of god get a local guy to come in explain the options & give you a quote, you are getting yourself all tied in knots & it is certainly not fun, in fact I am starting to think this is a windup.

You keep using the term "combi" a combi to us is a boiler (gas or oil fired) that heats water instantaneously you turn on a tap and we have done that one haven't we??

What croft has suggested is an electrically heated thermal store, the heat is stored in the primary water & can be used to provide heating for the house &/or domestic hot water (taps) via a plate heat exchanger.

An un-vented hot water cylinder can not be used to provide heating for your house only hot water from your taps.

You are right about the cost of peek rate electric when on an Economy 7 tariff it tends to be higher than if you were just on a standard rate but we can't help you with that can we ?? You need to look at you day time usage & get some quotes.

One thing you have found out is just how much "FUN" it is living & working in a small old property in deepest darkest Devon & if you think you are poor now wait to those bills start to roll in.
There was a good reason why they stuck to logs burners !!!!
Now for the very last time bye.

 

[serfer]

electric combi boilers are common place - they appear all over the internet, and in Croft's link.. it clearly mentions 'electric combi' on the first page...

these electric combis (their word NOT mine) have an internal store of 150 litres or so. so to me it seems like they call it an electric combi, and you guys call it an electrically heated thermal store and thats fine by me, just want to use the right terms to make sure i'm on the same page as you all.

so i want an electrically heated thermal store AND a plate heat exchanger? never heard of a plate heat exchanger, is that a seperate bit of kit, or does it come inside the thermal store?

 

[Gray0689]

Get a plumber in to talk to you direct on the job and explain as you are not either listening or grasping the concept

Get an electric boiler to do the heating side
And a direct cylinder to do domestic water

 

[serfer]

Thx Gray. I bet this must be painful for everyone and its great this community exists to help folks like me. Electric boiler and direct unvented cylinder. Yes. Got that agree! Sounds great. I understand.

But chris and croft have mentioned a thermal store.

A) you don't agree with their advice
b) a thermal store is another way of describing either a boiler or cylinder...

Theres so many terms its confusing. I dont know if everyone is using different words to talk about the same things or if you actually have fundamentally different solutions to the problem.


Thx again all, you guys are awesome