Replacing old boiler for new to save money in the long run

Golden_Holden

Okay, this is good information. Essentially I just want a more efficient way of heating the house/water and I don't need to change the system's current footprint (the tank and cylinder could stay where it is) so looking for the most cost efficient option. 

Bendy_House

Golden_Holden said:

Okay, this is good information. Essentially I just want a more efficient way of heating the house/water and I don't need to change the system's current footprint (the tank and cylinder could stay where it is) so looking for the most cost efficient option. 

Ok, could you tell us what type of hot cylinder you have? Is it in a useful airing cupboard? Do you have reason to think it's losing too much stored heat? Why do you needs pumps - what are they supplying, just a shower?

FreeBear

A like for like replacement is probably going to be the cheapest option assuming the tank & plumbing can be retained. A new combi will need modification to the hot water pipe - Depending on where your boiler is currently located in relation to HW pipe (and assuming a combi is going in the same place), it may just need a short run of pipe. And the pipework to/from the tank will all need to be disconnected.

Having to go through the same exercise here with a boiler replacement. Will be putting in new plumbing for heating & hot water.

BUFF

& a powerful combi (for high DHW flow rate) may need a gas pipe upgrade.

Golden_Holden

Bendy_House said:

Golden_Holden said:

Okay, this is good information. Essentially I just want a more efficient way of heating the house/water and I don't need to change the system's current footprint (the tank and cylinder could stay where it is) so looking for the most cost efficient option. 

Ok, could you tell us what type of hot cylinder you have? Is it in a useful airing cupboard? Do you have reason to think it's losing too much stored heat? Why do you needs pumps - what are they supplying, just a shower?

Yes, it's in an airing cupboard. The pump is under the bathroom sink and supplies the taps, shower and bath. 

My only reason to think the system is inefficient (either losing heat or taking too much gas to heat up) is the steep increase in usage that appears on my smart meter when it is on. 

For info, I have the hot water programmed to come on twice a day (a couple of hours in the morning, and a few hours at night) and am only using heating on an ad hoc basis at the moment. Should I only be heating my water once a day? 

FreeBear

Golden_Holden said: For info, I have the hot water programmed to come on twice a day (a couple of hours in the morning, and a few hours at night) and am only using heating on an ad hoc basis at the moment. Should I only be heating my water once a day? 

Unless you really need a full tank of hot water (e.g. for a bath), then just boiling a kettle or two for washing up may well prove to be more economical.

I just fire up the boiler for a bath as/when I need one. The rest of the time, a kettle (and electric shower) provides all the hot water I need.

[Deleted User]

Golden_Holden said:

Bendy_House said:

Golden_Holden said:

Okay, this is good information. Essentially I just want a more efficient way of heating the house/water and I don't need to change the system's current footprint (the tank and cylinder could stay where it is) so looking for the most cost efficient option. 

Ok, could you tell us what type of hot cylinder you have? Is it in a useful airing cupboard? Do you have reason to think it's losing too much stored heat? Why do you needs pumps - what are they supplying, just a shower?

Yes, it's in an airing cupboard. The pump is under the bathroom sink and supplies the taps, shower and bath. 

My only reason to think the system is inefficient (either losing heat or taking too much gas to heat up) is the steep increase in usage that appears on my smart meter when it is on. 

For info, I have the hot water programmed to come on twice a day (a couple of hours in the morning, and a few hours at night) and am only using heating on an ad hoc basis at the moment. Should I only be heating my water once a day? 

Most domestic boilers are massively oversized for the properties that they are installed in. All boilers modulate: for example, a 24kW boiler should modulate down to at least 7kW. Even at 7kW, when the boiler is at its set temperature, the boiler will cycle on and off. Yes, usage will be high initially but fall off markedly as the home heats up. The graph below shows 30 minute usage. The early period is cylinder reheating.

Heating hot water by gas is inefficient. A gas boiler is inefficient compared to electricity and the piping between the boiler and the HW cylinder acts as a mini radiator. We have a 250L unvented cylinder with 2 adults. Reheating the cylinder once per day is enough. Using gas, it requires about 6kW but electricity reheating requires about 50% less. That doesn’t mean that electricity should used in preference to gas: it depends on the 2 unit prices.

BUFF

Golden_Holden said:

For info, I have the hot water programmed to come on twice a day (a couple of hours in the morning, and a few hours at night) and am only using heating on an ad hoc basis at the moment. Should I only be heating my water once a day? 

You could try cutting back the heating times - either only once a day or shorter, twice a day - & see how you get on?.

Bendy_House

Golden_Holden said:

Yes, it's in an airing cupboard. The pump is under the bathroom sink and supplies the taps, shower and bath. 

My only reason to think the system is inefficient (either losing heat or taking too much gas to heat up) is the steep increase in usage that appears on my smart meter when it is on. 

For info, I have the hot water programmed to come on twice a day (a couple of hours in the morning, and a few hours at night) and am only using heating on an ad hoc basis at the moment. Should I only be heating my water once a day? 

The airing cupboard doesn't feel excessively warm? The existing cylinder is well insulated - but could always have an extra jacket fitted, particularly in Summer when you are unlikely to appreciate the additional heat given off!

Why is a pump needed for this bathroom? Is it on an upstairs floor? The CWS in the loft cannot be raised, repositioned or replumbed to provide a better flow instead? Usually only a shower needs a boost - the basin should be fine with gravity. In which case, a powered shower (wee built-in booster pump inside the unit) can be very effective, and get the hellish pump sound gone for all other uses - but that's a separate issue.

Your hot water heating times are excessive, unless someone is having an all-day shower? A tank should be fully heatable from cold in, what?, one hour? So, for the usual already-warm tank, a half-hour would normally do. A 'few' hours at night?! Lawdie! I'd suggest, again, try a half-hour before hot water is required - say for evening dishes - and leave it on afterwards if folk have showers and baths. But have it going off as the last use is required - there should be plenty nicely-warm water left for use until the next morning when it's given a boost again. But no point at all having a 'hot' tank sitting there all night - that's a waste.

Try and reduce the heating times to what is 'needed'. Try just a half-hour before wake up, or 45 minutes, and see how that goes. Have it turning off as folk will be getting ready to leave the house - no point having a hot tank sitting there all day. So, if the last morning shower is at, ooh, 7am, have it timed to be off by then - there should be plenty of hot water for the shower, and the house will be left with a 'warm' tank instead = less loss during the day.

Your Potterton is a beast - a floor-mounted jobbie? The size - 60, 80, whatevs - is the btu output in 1,000s, but roughly ties with around 17kW for the '60'. The replacement heat-only boiler will be almost certainly wall-mounted, half the size, and TONS more efficient. For example, the Pottie seemingly loses around 1kW just to the air!! Um, you don't have a classic car in the garage, do you?!

If the new boiler will remain in the garage - and it's a sensible place for it to be - it will already be better insulated, but I'd still have it built in to a cupboard with a snug-fitting door - that should reduce heat loss even more (and offer it more protection against frost, for example). And make sure the pipes from the boiler to the house are superbly lagged...

In your situation, then, I would personally just fit a new heat-only boiler. (Ideally a 'system' type which won't need a small F&E tank in the loft). This should come in at around £2k - £2.5k, so a nice saving already.

If the existing hot tank is reasonably well lagged (does it have a make and model on it?), then I'd consider keeping it, but adding an extra jacket, certainly for Summer use (you might want to keep a nice warm 'airing' for winter).

I'd then try and lose that pump. I know it has now't to do with the general thread, but I hate em, and it's personal.

If you want a generally improved supply in the house, with no need for pumps, then another possibility is to replace the hot tank with an unvented type. That would have the additional bonus of being insulated to current standards (I guess?), and you'd lose the CWS in the loft. BUT, it wouldn't make financial sense if the current one is ok.

Finally, do you anticipate adding another renewable energy source such as PV in the future/? If so, def do not lose the hot tank :-)

Golden_Holden

Thank you Bendy_House that’s really help. 

I will definitely adjust my hot water times accordingly.

I’m also going to replace the boiler on this advice too. Still undecided on which type but I guess an engineer will be able to tell me more once they have eyes on the setup/pipe work etc and will be able to give me more info on pressure too. 

Totally agree about the pump - it’s so noisy and feels unnecessary for the sink. 

And also agree on the tank - will keep it regardless so I can future proof.