Replacement Boiler - large house - two boilers?

[Ptolemy1978]

HI there.

I just wanted to say this is my first post and I am seeking info so I can form a view of what I need or what’s best for the house before I start talking to the professionals for quotes......so please go easy!

We bought a large four story Georgian house with mostly single glazed windows and solid brick walls - we have managed to have the whole loft insulated to current standards (but thats about it). Its over 4000 square feet and there are 23 radiators (some new but mostly 20+ years old with a variety of TRVs) and 2 bathrooms with pumped showers.

The heating system to me is a little bit of a mystery to me but the boiler is an ideal Mexico RS100, its based on the raised ground floor level with one pump (believe its an open system as there are two tanks in the loft - one small and one large). There is no thermostat and no valves to separate the heating and hot water system (the hot water only comes on when the heating is on) which means that we mostly heat our hot water using an immersion electric heater. The tank appears to be of a smaller size than needed too as it empties after two showers - there are only two of us here so we can live with this most of the time but when we have guests and they use the bathroom on the top floor its not remotely enough.

None of the radiators on the sub ground floor get warm at all and the boiler and the radiators all seem to have varying effectiveness across the house.

So thats the picture - I hope its enough....

So to the point of the email... clearly the boiler and the whole system has seen better days and I contacted good old British Gas who came out with a view to giving me a quote to replace the boiler. Unfortunately, the nice chap told me that the house is too large for their boilers and the pipework is in such a state it would be easier to start from scratch with a commercial boiler (40-50kw), with a mains hot water tank that had something that increased water pressure.....

I am thinking that as the main living accommodation, kitchen and two toilets with sinks are on the sub and raised ground floors it would be worth separating this from the old system and installing a separate combi to supply the heating and the hot water to the sinks, etc. The hwt is currently on the 1st floor so it takes ages to come through....

I was then thinking of doing the next stage of the replacement in a couple of years and installing a separate system boiler to supply the upper floors heating, a replacement hw tank in the place of the current one and installing a brand new hot water tank at the top for the guest bathroom (zoned somehow so it only came on when we had guests).

I was thinking that the zoning of one new commercial boiler and various hot water issues would be complicated and expensive to install. I have poor mains pressure so still want to retain the hw tank and do not lack space so thought a second tank would solve my sporadic need for hot water on the top floor.

Now, how does that all sound? Is it feasible?

 

[boilerdoktor]

you can cascade two domestic boilers easily

you can get a water collector that collects and stores incoming cold water.

you could go for a small commercial boiler

if you do either of the above may need a u16 gas mtr if your gas useage is more than 6m/hr. They are all costly implications.

I think you need quotes from experienced professionals who can get on site and look into all avenues and discuss your individual needs

 

[D_Hailsham]

We bought a large four story Georgian house with mostly single glazed windows and solid brick walls - we have managed to have the whole loft insulated to current standards (but thats about it). Its over 4000 square feet and there are 23 radiators (some new but mostly 20+ years old with a variety of TRVs) and 2 bathrooms with pumped showers.

There is a tendency for installers to recommend a boiler which is larger than actually required. So the first thing you should do is use the Boiler Size Calculator to find out what size you really need.

 

[OwainDIYer]

Zoning a system for multiple heat and hot water circuits is not complicated. However you require a heating engineer with experience of hotel or country house installations.

Two smaller boilers do offer the advantage of redundancy which can be important if you have paying guests.

 

[mysteryman]

... however, it is more difficult to fit weather comp effectively to paired boilers. Weather comp on a job like this will save a packet on gas bills.

 

[mickyg]

I find it highly unlikely 23 radiators will need over 40kw. You can get 40kw domestic boilers. There are various ways of tackling a job like this and most haven't been mentioned, you should get some highly recommended installers to give advice. British Gas are rubbish at anything thats not completely simple and the packages need to be on their little laptop else they get very confused.
Lots of people will recommend you this and that on a forum, but its quite easy to do when your not doing the job.

 

[dcawkwell]

I would be inclined to start with the whole house boiler calculator.
Once you know the size of boiler I would estimate around the 30 to 35kw mark.

The system will need flushing out with at least a mains flush. I suggest
draining and refilling the central heating a couple of
times and then adding some cleanser before the new boiler goes in.

I would go for a system boiler and therefore remove the need for any
central heating header tank in the loft. You will definitely need
and extra expansion vessel.

You might want to replace older radiators with new ones and add thermostatic valves and wall thermostat. I would definitely zone upstairs and downstairs so that they can be controlled separately saving
the costs of heating the whole house when only the downstairs is in use.

In future look to replacing the hot water tanks with unvented cylinder if flow and pressure ok.

 

[Agile]

There is an extremely effective German boiler from their light commercial range.

I do not mention the name because I will be accused of advertising - however, if you like you can ring their Technical helpline in ****!

That sounds like the Vaillant Ecotec 46 kW !

But they are based at Rochester, Kent rather than at **** where it is said there are five boiler makers based.

 

[hansthebear]

I find it highly unlikely 23 radiators will need over 40kw. You can get 40kw domestic boilers. There are various ways of tackling a job like this and most haven't been mentioned, you should get some highly recommended installers to give advice. British Gas are rubbish at anything thats not completely simple and the packages need to be on their little laptop else they get very confused.
Lots of people will recommend you this and that on a forum, but its quite easy to do when your not doing the job.

bitter ex BG members from the service department should be banned from commenting on aspects of central heating installations.

 

[mickyg]

I find it highly unlikely 23 radiators will need over 40kw. You can get 40kw domestic boilers. There are various ways of tackling a job like this and most haven't been mentioned, you should get some highly recommended installers to give advice. British Gas are rubbish at anything thats not completely simple and the packages need to be on their little laptop else they get very confused.
Lots of people will recommend you this and that on a forum, but its quite easy to do when your not doing the job.

bitter ex BG members from the service department should be banned from commenting on aspects of central heating installations.

Sorry do you have something constructive to say? Bitter? About what exactly? don't be insane. If you want to learn something I'm happy to help

 

[mfarrow]

with a mains hot water tank that had something that increased water pressure.....

That sounds like a Megaflow they're trying to sell you.

The hwt is currently on the 1st floor so it takes ages to come through....

You can get a bronze pump that will constantly pump a loop of hot water from your tank and down through the rest of your house, so you get instant (ish) hot water when you turn on the tap.

I have poor mains pressure

Then a Megaflow probably won't do a lot, as it relies on having good mains pressure in the first place.

Some will try to sell you one all the same, but as they say, you can't polish s**t.