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

[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

 

[Ray Stafford]

Hi Serfer

Please don't take offence, but from your posts its clear that you have just enough knowledge to be dangerous - either to life and limb, or more likely to your bank balance. Either settle down and do some serious (non-google) research, or take the guys advice and get an expert in.

 

[Gray0689]

I'm not a fan of thermal stores
There ok if a secondary heat source is being utilised but if not just an expensive cylinder

Where all different so we all like different things

But unless your house is very well insulated any and all will cost you to run

 

[Ray Stafford]

There ok if a secondary heat source is being utilised but if not just an expensive cylinder

Agreed. By far the best use for a thermal store is to integrate multiple heat sources, or (usually on a large scale) to dump the heat from an uncontrolled source.

For most domestic purposes they just add unnecessary complexity.

 

[SimonG]

As I mentioned in post #4.

Unvented direct cylinder, as long as static pressure, dynamic pressure and water flow are satisfactory. Needs to be installed by a suitably qualified engineer.
Amptec for rads.
Amptec for underfloor. This is a specific boiler that runs at a lower temperature for ufh. Theres no point using a normal boiler and overheating the water to kix it to lower temperatures.

The above will take very little room. I did a direct unvented and amptec for 10 rads in a small airing cupboard.

 

[serfer]

Hello again Simon, I remember the post. Would really need two boilers? Would one boiler running at low temp and feeding both ufh & large surface area rads suffice?

And Ray... The expert i got in suggested electric combi! I actually had a few in. Almost all just wanted to know what I wanted and didnt come with solutions.

 

[antdad]

The silence is deafening isn't it? Besides some confusion over electric combi storage heaters you've been given sound advice and even some basic calculations that you insist on ignoring, questioning or plainly just don't understand.

I'll try one last time, here's what you wrote...

I have been been investigating heat source and distribution since November and have resigned myself to having no option other than electric. Or 47kg bottled calor gas. I really don't have much room downstairs (trying to start running a business from home that needs equipment and loads of storage) and the loft is 350yrs old and cant take the weight of a tank up there.

Given that you say you have no outside land you can't use ground source but did you dismiss bottled gas because you thought you had to store the bottles inside (including those feeding the boiler)? A bottle cage will have the footprint of about four paving slabs and positioned against the outside wall of your home, all you need internally is space for a wall mounted system boiler and a high pressure vessel (which can be positioned anywhere given the right conditions) that will provide all the hot water you'll ever need for both bathrooms. I'd make room for these whatever it takes because frankly irrespective of your business acumen, if you continue to pursue an all electric course (if it's even feasible) whatever money you make will be going towards your electric bill.

 

[markfxy]

electric combis are so called because they combine an electric boiler and a cylinder in one unit hence the term combi they are not the same as a gas combi which is an instantaneous water heater (heat exchanger) combined with a heating boiler

 

[serfer]

So what do you think markfxy? Electric combi is cheaper to run than amptec and cylinder?

And anydad... You have a pretty poor attitude. If you read the above youll see i have explored all the ideas given, and pointed out some confusion and conflicting advice. Not ignoring anyone. I know i can store calor bottle outside, but at 16p per unit its the most expensive option there is. Thx for your time taken to contribute, and I'm sure you know your stuff, but its the least useful post i have had. I'm stuck with electric, just trying to figure out the best way to deal with this reality. Thx again to all!

 

[markfxy]

electric combi is amptec and cylinder! I just explained that part of it to you

 

[dancinplumba]

Have you considered Air to Water heat pump ?

 

[serfer]

Hmm... Yup. When i mention amptec above i meant boiler. Sorry! Electric flow boiler plus direct unvented cylinder costs around £1000 inc vat.
Electric amptec electromax combi has internal storage of 150 litres for example weighs in at around £1500...

so i guess i go with the separate boiler and cylinder. A bigger cylinder probably best.

 

[serfer]

Air to water heat pump costs around £10,000. Just cant afford it

 

[SimonG]

There are electric combination boilers which 'combine' an amptec, or similar electric boiler, and an unvented cylinder. Then there are electric combi boilers along the same lines as a gas combi, an elnur gabarron springs to mind. Looks like a gas combi and has a small hot water store.

 

[dancinplumba]

16p kWh for LPG, 10k for air to water ????? Where you live central London ?

 

[serfer]

Doh!> > 16p per unit of calor gas, keep up! LPG is 6 or 7p sure but I cant fit the tank anywhere. I've had loads of teams come to the cottage and 16kw high temp daikin or panasonic or mitsubishi is going to cost just under 10k inc vat. If you can do it cheaper, lets talk!

Simon! THANKS AGAIN! There seem to be some of us here who don't know too much about the electric side of things -or maybe i use the wrong terms or jargon gets in the way... whatever.

Still... I'm not sure whether to get the store and boiler together in one unit (what i call electric combi) - or go for a boiler and direct cylinder as separates.

3 beds, 2 baths, 2 kids under 10... underfloor heating of 75sqm, 4 large area rads and 2 little towel rads. i feel we almost have a resolution... ... ...!

 

[dancinplumba]

Doh !!!! Silly me......am sure Calor gas is LPG is it not ?

 

[serfer]

maybe lpg is calor... but i cannot fit a huge lpg tank on the property. i can dump a few47kg calorbottles outside = but then i pay about 16p a unit, which is just plain daft but there you go.

 

[dancinplumba]

Nope, Calor is LPG. Learn summat new every day

 

[markfxy]

Air source heat pump will be way cheaper to run and if you get an installer that's MCS registered you'l get the RHI payments reducing the payback considerably against an electric boiler

 

[rpm]

Could be being daft but .....

Can you bury a gas tank like you can an oil tank?