New system advice

[DavidH1983]

Morning, wondering I could ask a a few questions regarding a replacement system we're having installed potentially this week.

We've just moved into a property (Victorian style 3 floor + a cellar). We're a family of 4 with two boys under 3. The house has a ground floor toilet with basin, a shower room on the 1st floor and a bath in one of the bedrooms. The 2nd floor wer'e looking at installing an en suite as we're looking to convert this into either our son's new room or a guest room.

The existing system consists of a Vaillant Thermocompact boiler which I believe is getting on for around 25 years old and a Megaflow h/w cylinder.

We've had a couple of quotes to replace the system like for like but I'm wondering if a combination boiler is the way to go. We asked both plumbers whilst they were surveying and both suggested we keep with the cylinder/vented boiler setup.

I'm worried, along with plenty others i imagine about the rising costs of energy and particularly electricity. Would opting for a large combi boiler both a; improve efficiency and b; provide lower energy costs. Is there much between the running costs of say a Megaflow and a combi boiler?

I know a lot of this depends on usage. I'd say we are fairly average when it comes to our hot water and central heating habits.

Any advice would be very helpful and apologies if I've missed anything out.

Cheers

 

[bernardgreen]

Combi boilers were "invented" and developed specifically for small houses where there was no space allocated for a hot water cylinder ( or there was space allocated but the owners wanted more storage space ).

With a combi boiler each time a hot tap is turned ON the boiler has to go through it's firing up sequence which adds wear and tear to the boiler.

After turning the hot tap ON the person has to wait until the boiler has reached temperature before the water from the hot tap becomes warm. Water is wasted.

When the hot tap is turned OFF the hot boiler shuts down, The heat in the boiler now goes to atmosphere and is wasted.

 

[vulcancontinental]

A system boiler was found to be the sightly more efficient when a comparison of many systems was carried out by the BRE but overall efficiencies were equal once pipework heat losses between the boiler in cylinder were factored in.

Stick with what you have.

 

[flameport]

Would opting for a large combi boiler both a; improve efficiency and b; provide lower energy costs.

Neither.
The cost of hot water is directly related to how much of it you use.
Whether it's heated on demand or heated and stored in a cylinder makes very little difference.

A combi will tie you in to using gas with no option for any alternative such as solar or a heatpump at a later date as both of those require a hot water cylinder.

 

[Agile]

The Megaflow should not need replacing and a system boiler is a little cheaper than a combi.

Cylinder systems are a lot better to live with.

Higher flow rate and a back up electric immersion heater.

 

[DavidH1983]

Thank you for all the replies - really helpful.

We estimate the boiler to be around 30 years old. It's a Vaillant Thermocompact. Unsure on the size but it'll be replaced like for like size-wise.

Also not sure how old the megaflow is but it does look to be best part of 15 or maybe 20 years. I don't know. Parts on the outside have certainly corroded and the various valves and pipes don't look great. We may as well replace it whilst we're getting the boiler done.

Silly question but can cylinders be wall mounted? I'm guessing not due to their sheer weight

 

[DavidH1983]

Thank you for all the replies - really helpful.

We estimate the boiler to be around 30 years old. It's a Vaillant Thermocompact. Unsure on the size but it'll be replaced like for like size-wise.

Also not sure how old the megaflow is but it does look to be best part of 15 or maybe 20 years. I don't know. Parts on the outside have certainly corroded and the various valves and pipes don't look great. We may as well replace it whilst we're getting the boiler done.

 

[ianmcd]

Unsure on the size but it'll be replaced like for like size-wise.

No dont do that, get an installer who will do a proper heat load calculation and fit what is required , your existing boiler will almost certainly be over sized as nearly all boilers were way back then

 

[DavidH1983]

Quite right, I asked him earlier to send me a link to our replacement and it is indeed a lot smaller in physical size. Capacity is 210lts. 4 bed house. Low to average consumption. Using some of the calculatros online this seems sufficient I think.

Cheers.

 

[ianmcd]

Quite right, I asked him earlier to send me a link to our replacement and it is indeed a lot smaller in physical size. Capacity is 210lts. 4 bed house. Low to average consumption. Using some of the calculatros online this seems sufficient I think.

Cheers.

I was talking about the boiler not the Cylinder

 

[oldbutnotdead]

Cylinder all the way to have any hope of running 2 showers and a bath. If you want to, you can have a combi and a cylinder (use the combi hot water in say the kitchen and the ground floor shower assuming boiler is on the ground floor, use cylinder for the 1st & 2nd floor hot water). This can reduce the volume of wasted hot water from having to run the taps and allow you to run all 3 bathrooms at once. As above, cylinder can work with solar, heat pump, immersion heater.....

 

[DavidH1983]

Boiler is going to be an Ecotec 37kw. Not sure what's in there at the moment but we have rads spread over four floors and 2 kids who in a few years will no doubt be needing showers at the same time etc.

 

[DavidH1983]

How viable is a solar solution? Do the savings make running a cylinder off say a 4kw solar panel substantiate the installation costs?

 

[JohnD]

Boiler is going to be an Ecotec 37kw.

why?

 

[oldbutnotdead]

How viable is a solar solution? Do the savings make running a cylinder off say a 4kw solar panel substantiate the installation costs?

Are you talking solar PV or wet solar?
Either way, financially probably not.
Have a look here Discussion on eco energy...