Advice on new CH system

[mrbutt]

Hi, I am new to the forum and would like some help from some of the knowledgable guys here. I have been lurking on here for some time, picking up certain things and have found the site very helpful.

I have a fairly large detached house with a detached garage/granny annexe. There are 2x combi boilers running this, one on natural gas and the other on LPG (located in the garage). All current pipework is on 22mm>15mm. I really need to do something with the heating system as the LPG boiler has packed in, and my other one is on its last legs.

My plan is to run all the place on natural gas and have the boiler(s) located in the house. I want a system boiler, preferably a sealed system. It will be simple for me to connect all the central heating to one location but DHW to the garage/granny annex will be difficult (requires lifting quite a fair amount of tiles which I am worried about doing as they are expensive, and lifting floor outside and digging).

I have calculated all the current radiator power outputs (which are adequately sized for the rooms and we dont want to change as they are ideal), which total 45kw (12kw dowstairs in living areas, 16kw downstairs in leisure rooms, 6kw upstairs bedrooms, 11kw garage/granny annex). There is no hot water cylinder as its on combis. There are 3x bathrooms (1st has electric shower, 2nd has power shower, 3rd has a power shower and jumbo bath/jacuzzi). The granney annex has 1 power shower at present.

My current idea in my head is for a sealed pressurised system, install a 500L hot water cylinder for DHW to the house, granny annex can have electric shower and electric hot water if I cannot plumb it to the main house. Boiler I am probably looking at a 40KW domestic or something like a 65KW commercial. I need your help people with devising a decent idea really. My current ideas include a Remeha Quinta pro 65, but I cant find a decent price on them.

To throw an extra spanner in the works, I am saving up for an extension to the upstairs of the house to be done in 10-15years time (as that is when my family will need it). I want to convert the current loft to make a 3rd storey, and a large part of my house is single storey which I would like to add an upstairs and 3rd floor too, all this would incorporate at least 3 more bathrooms. Do we need to include this in our current heating plans and boiler sizing, as 10-15years is a long time, a time in which the boiler may need replacing anyway.

I know that I really need some good heating engineers to have a look and survey everything, but I would like to hear ideas on here and take it from there. Im not too confident in inviting an unknown to me engineer to my house, with no decent ideas of what I could do as I may just get shafted!

Sorry for the long post, any help is greatly appreciated.

 

[D_Hailsham]

I have calculated all the current radiator power outputs (which are adequately sized for the rooms and we don't want to change as they are ideal), which total 45kw (12kw downstairs in living areas, 16kw downstairs in leisure rooms, 6kw upstairs bedrooms, 11kw garage/granny annex).

The rads may be "adequately sized", but that does not mean they are correctly sized, so using them as the starting point for sizing the boiler is going about it the wrong way.

Use the Whole House Boiler Size Calculator to find out what size boiler you need. You will have to do it in two parts: existing house and granny annex.

It doesn't matter if this gives a lower total that the 45kW of your existing rads. All it means is that your rads will tend to run cooler.

As for the proposed extension, it's worth taking into account as far as pipe sizing is concerned, but not for the boiler as your "new" boiler will probably need replacing in 15 years time.

 

[Dan Robinson]

Place your bets now people - 12 pages? Maybe 9....

 

[ServiceNumpty]

And I wonder will weather comp come up.

 

[mrbutt]

Use the Whole House Boiler Size Calculator to find out what size boiler you need. You will have to do it in two parts: existing house and granny annex.

Thank you for the response, good advice given there.

Here are the results of the calculator, I've broken them down;

Main House = 31.47kw
Granny annex = 12.55kw

I have put in a ZERO value for the "allowance for DHW" as I was unsure what to put. If somebody could advise, I could pop that in (currently thinking of a 500L cylinder).

Now onto the next step Mr Hailsham...

 

[ALEC1]

why wouldn't weather comp come up its a very viable control strategy, for people who want higher levels of comfort than on-off controls can offer!

0 is correct if you have a boiler with hot water priority..

 

[dcawkwell]

Two fairly standard 30kw boilers working as a cascade.
This gives a backup should one fail.
I would use combi boilers perhaps to supply some
of the house with hot water on demand.
The combi boilers can also heat an unvented cylinder(s) spread through
the house near to demand if required. Using acv cylinder that can keep
the size down as their re-heat times are fantastic.
Zone all the separate areas with thermostats to reduce running costs.

If you are anywhere near Doncaster let me know.

 

[mrbutt]

Im in Huddersfield mate, just off J25 on M62.

I have thought about using one combi and one system too and have thought of using two combis

If I have a hot water cylinder(s) and keep it permanantly on, would that not give instant hot water too, therefore eliminating the benefit of a combi?

One of my issues with using any combi is that they are thought to not be as reliable as a conventional boiler.

Good idea using more than one smaller cylinders as I'm sure 500L wont be needed all the time. Hardly anybody uses baths in our house, its all showers
That may be a good idea, having for example a 250L cylinder on all the time, with a back up 250L for when extra is needed (like prior to a bath).

 

[dcawkwell]

Im in Huddersfield mate, just off J25 on M62.

I have thought about using one combi and one system too and have thought of using two combis

If I have a hot water cylinder(s) and keep it permanantly on, would that not give instant hot water too, therefore eliminating the benefit of a combi?

One of my issues with using any combi is that they are thought to not be as reliable as a conventional boiler.

Good idea using more than one smaller cylinders as I'm sure 500L wont be needed all the time. Hardly anybody uses baths in our house, its all showers
That may be a good idea, having for example a 250L cylinder on all the time, with a back up 250L for when extra is needed (like prior to a bath).

Send me a personal message (top bar messages) if you like.
Don't mind coming over and giving a quote. Either over the weekend
or early next week.

 

[D_Hailsham]

Main House = 31.47kw
Granny annex = 12.55kw

Must be a very large house and possibly poorly insulated. Improving the insulation will reduce the size of boiler(s) required and give long term savings.

Check out Energy Savings Trust Grant Search.

 

[mysteryman]

Putting a new boiler without weather compensation in this day and age is sheer madness. There is no better form of control.

Don't get carried away by excess complication or mixing up combis and cylinders, you can't fit weather comp if you do that. Get someone you feel you can trust to design a good system for you to meet your requirements and needs. There's no point in fitting multiple cylinders with extra controls, unless some of the taps are a very long way away. The same applies to multiple boilers, you will need a proper cascade controller for effective control, and you've then got extra electronics as well as twice as much kit which can fail. Modern boilers are pretty reliable. Keep it simple!

 

[Agile]

Putting a new boiler without weather compensation in this day and age is sheer madness. There is no better form of control.

Alex, you have a new fan and follower on Twitter or wherever you tweet!


OP, are you sure your house is so large like 8-12 bedreeom and no loft insulation?

A 500 li cylinder is fine as any water not used today stays warm for tomorrow!

 

[mrbutt]

Send me a personal message (top bar messages) if you like.
Don't mind coming over and giving a quote. Either over the weekend
or early next week.

OK Mate, I will send you one in a bit.

Also, just to make it clear so I'm not wasting your time, I previously considered using a mixture of combis or combi/system but im not that way inclined. Im more inclined to using 1 single system boiler.

Must be a very large house and possibly poorly insulated. Improving the insulation will reduce the size of boiler(s) required and give long term savings.

Check out Energy Savings Trust Grant Search.

Thanks, I will have a look at that site, if its offering ways to improve insulation, I'm happy to take that

It is a fairly large house (3-3500 sqft downstairs, upstairs is a lot smaller), its not poorly insulated in most of it but 2-3 rooms have a fair bit of windows/french patio doors. The extension I spoke of was to increase the upstairs to a similar size as downstairs and create a third floor, but thats around 15 years yet, got lots of saving to do .

Don't get carried away by excess complication or mixing up combis and cylinders, you can't fit weather comp if you do that. Get someone you feel you can trust to design a good system for you to meet your requirements and needs. There's no point in fitting multiple cylinders with extra controls, unless some of the taps are a very long way away. The same applies to multiple boilers, you will need a proper cascade controller for effective control, and you've then got extra electronics as well as twice as much kit which can fail. Modern boilers are pretty reliable. Keep it simple!

I need to find somebody I can trust and who is also G3 certified (or whatever is required for sealed system boilers). Some taps are far away (in the granney annex, but I could possibly turn them electric), the rest are close and plumbed close to where I want the cylinder.

Simplicity is the reason I am favouring 1 system boiler and a 500L cylinder. Although I am not ruling out 2x smaller system boilers correctly cascaded.

OP, are you sure your house is so large like 8-12 bedreeom and no loft insulation?

A 500 li cylinder is fine as any water not used today stays warm for tomorrow!

I plan to use weather comp so no worries

It has loft insulation, those were the sums the calculator gave, I will try again to see if I get different results.


Could somebody explain what size boiler I require?
The calculations for the CH requirement were approx 44KW. Does there need to be an allowance for the hot water cylinder, or as stated before, is that dependant on the boiler I decide on?

Also, I am considering a Broag Remeha Quinta Pro 65, anybody know any good prices on this? Whats the cheapest I could get it?

Thanks for all the help so far people

 

[mrbutt]

If all I need is approximately a 45KW boiler, I had 6 in mind:

Atag Q38S
Vaillant EcoTec 46KW Commercial
Vaillant EcoTec Plus 37KW System
Viessmann Vitodens 200W 45KW Commercial
Broag Remeha Avanta Plus 39C (offer conversion to a system boiler)
Broag Remeha Quinta Pro 45

Could people offer comments on the above, with actual experience. Also open to other recommendations if you think there is better for the money.

Do people know the prices of the above boilers? Not RRP but the better deals

 

[Agile]

Its normal to add 2 kW for water heating to the radiator load.

44 kW is a massive heating load. Is it really 12-18 bedrooms?

Are you paying about £3000-£5000 per annum for gas?

You should never size a boiler for an extension planned for a long time into the future as thats inefficient until the extension is built.

Tony