Gas boiler + water cylinder/ immersion heater

kayen

I'm waiting exchange on 2 BR terrace house and wanting to plan the initial works. 

Glow-worm Flexicon 18 HX gas boiler with flue is in ground floor kitchen.  Hot water cylinder with electric immersion heater in upstairs bathroom. 

#1 priority will be to install shower facilities (none currrently), so am guessing this would be an ideal time to change the water heating at the same time if it needs?

I'm unsure why there's a boiler plus a water cylinder/heater in the house- is this just an old -fashioned set up and/or is it needed these days?   Will just be me living there and possibly a lodger at some stage but not on a long term basis.

?Would a combi boiler be sufficient?

?Does anyone know ballpark costs to install a combi boiler downstairs and removing the immersion heater?

Total newbie here!  thanks for any help

FreeBear

The Glow-worm is a system boiler meaning that it does central heating and hot water via a tank. As a condensing boiler with an energy efficiency rating of 88.4%, it is perfectly serviceable. Using the boiler to heat a tank of water isn't the most efficient way of doing things (the immersion heater is just there as a back up). With a cylinder thermostat, it is fine during the winter months, but in the summer, probably best to turn it off and just use a kettle & electric shower for hot water.

It makes sense to have a combi in a two bed terrace as neither your heating or hot water demands are going to be particularly high, especially if you are the sole occupant. The space occupied by the HW tank could be put to better use.. If you have the funds for a boiler replacement, it may make sense. But only you can decide if the potential savings make it worthwhile.

greatcrested

It's a very common set up though less so these days.

With just one (maybe 2) people it tends to be more economic to heat water instantlay when needed, rather than storing hot water in a cylinder.

One advantage of a cylinder can be where more than one person wants hot water at the same time, putting strain on a combi boiler.

Having said that, I have the same set-up - also one person.

In winter I use the boiler for heating and hot water. My shower runs off the stored hot water in the cylinder (not an electric shower) and it's fine.

Add LOTS of insulation to the cylinder so when you use 30/40% of the hot water, the rest stays hot/warm for the next day.

In summer when the heating is off, I use the immersion heater to heat the cylinder water.

So yes, you could spend several thousand pounds removing the boiler and cylinder and install a new combi boiler and fancy electric power shower, or just learn how to make best use of the existing system.

kayen

thanks  @greatcrested and @FreeBear
Does having only a combi boiler mean that 1 person definately gets a cold shower if another person is using water in another part of the house? or 'might' depending on duration etc?

Switching between boiler and cylinder sounds complicated tbh.... And I like the idea of freeing up some space by removing cylinder.

dimbo61

There are a hundred and one things you can spend your money on when moving into a new home.
You will have lots of extra bills to pay once you move in so why not wait and see how the existing system works for a few months.
Have you got room in the bathroom for a shower cubicle ?
If not would you put one over the bath with a shower screen and electric shower.
Maybe you want a complete new bathroom with P shaped Bath so extra room for showering and curved glass screen 

Jeepers_Creepers

kayen said:

I'm waiting exchange on 2 BR terrace house and wanting to plan the initial works. 

Glow-worm Flexicon 18 HX gas boiler with flue is in ground floor kitchen.  Hot water cylinder with electric immersion heater in upstairs bathroom. 

#1 priority will be to install shower facilities (none currrently), so am guessing this would be an ideal time to change the water heating at the same time if it needs?

I'm unsure why there's a boiler plus a water cylinder/heater in the house- is this just an old -fashioned set up and/or is it needed these days?   Will just be me living there and possibly a lodger at some stage but not on a long term basis.

?Would a combi boiler be sufficient?

?Does anyone know ballpark costs to install a combi boiler downstairs and removing the immersion heater?

Total newbie here!  thanks for any help

Covered nicely in the posts above.

The best system for your needs is not a completely straight-forward choice; there are pros and cons for all systems. Your starting point will be 'how good/adequate is my existing setup for use with a shower?' It might well be ok, so does it make sense to rip the boiler and cylinder out and replace it at a cost of - ooh - £2-3k-ish? 

I take it that the hot cylinder in the upstairs bathroom is a conventional (vented) type with a domed top, covered in foam insulation and with a pipe coming out the very top? In which case this is supplied with fresh cold water from a cold water tank in the loft.

The shower this will give you will be as good as how high that cold tank is above the shower head, so a shower downstairs will be awesome but one upstairs might be just 'ok'. If the latter, then there are ways of improving it - adding shower pumps and possibly raising the cold tank further - but you may instead decide on a complete change.

Combis: these rely on a decent mains water supply - I'd say roughly 15 litres per minute minimum and 2bar+ pressure. With this you'll get a great shower, but as you suspect this will be for one shower running at a time. Running other taps at the same time will affect the shower flow, but a good thermostatic shower unit should prevent 'OOOOOH!"s and "AAAAAARGH"s.

To swap to a combi should be straight-forward, but involves a few additional bits the first time; the hot cylinder and cold storage tank need removing, and the pipes reconnected. Possibly you'll need a new - larger - gas supply pipe too, so that'll add a few £undred as well. What could be as little as £1.5k for a replacement combi will likely be more like £2k+ for the first time one's fitted with that extra work. 

Combis are usually a very sensible choice for smaller houses - 2 bed - like yours, and are fine for most other houses too. It's what we have - with 2 teenage kids - but it hasn't been a problem as we simply stagger our showering times. If you think that you and the potential lodger can also agree to shower at different times, then it's worth considering. Combis have three other advantages - endless hot water, you pay only for the water you actually heat and use, and it frees up room as you don't need a storage cylinder. Oh, and all your cold water taps will give potable water. Um, and all the water is delivered at mains pressure, so gushing taps. Cons? There's more to go wrong, so expect problems from around 10 years age onwards, and likely replacement in around 15. 

If your current setup works fine and will handle an upstairs shower ok, then the most financially practical advance is, I think, to live with it until it goes wrong, and then you consider other options. Is the bathroom upstairs? Does it have a shower attachment on the bath taps? If so, turn it on and lift the handset well above your head like a 'normal' shower. What's the flow like? That's you first step. If it's ok but a bit underwhelming, then see if the cold tank can be lifted - a couple of feet should give a significant improvement. I personally hate shower pumps - I dislike the noise, how frenetic they can be (turns on shower slowly... nope, nothing, hmm a trickle... now - HELLS BELLS!)

Finally there are options like mains pressurised hot tanks, but I can't see how that will make sense in a 2-bedder - they cost. 

FreeBear

greatcrested said: In summer when the heating is off, I use the immersion heater to heat the cylinder water.

You might want to rethink that strategy - Heating a tank full of water takes around the same amount of energy for gas or electricity. Gas is a quarter the cost of electricity.

I'd suggest turning off all the upstairs radiators and then see how long a tank takes to heat with gas. Then compare that to the time it takes with the immersion heater. Monitor the gas & electricity consumption and then do the sums.

Jeepers_Creepers

I'm inclined to agree with that, FreeBear. Gas is so much cheaper, and the control over it is effectively the same - a thermostat on the cylinder, whereupon it'll shut down. It'll also keep your system's pump and some valves active over the summer, to be hopefully ready to serve you again in the cold months ahead :-)

Most systems have their CH and DHW controlled completely separately, so there should be no need to turn off any rads - unless there's some flow easing through?

Nebulous2

I changed my boiler about 4 years ago, and decided to keep my hot water cylinder.  Heating is currently off, but boiler comes on morning and evening to heat water, a total of 4 hours a day. Three people in the house. We also have a gas hob. £6.53 for gas last month, 225 kWh which was pretty good I thought.

unfortunately the heating will need to go on soon! 

eddddy

kayen said:

Does having only a combi boiler mean that 1 person definately gets a cold shower if another person is using water in another part of the house? or 'might' depending on duration etc? 

With a combi boiler, it's not the duration of use that affects the water temperature, it's the volume of water being used at any particular time.

A combi boiler heats up cold water as it passes through the boiler on it's way to the shower. If only the shower is running, hopefully the water will get hot enough as it passes through the boiler.

But if somebody then turns on a hot tap (or another shower), the combi boiler and/or water pressure might not be able to cope:

• Twice as much cold water will be running through the boiler, and the boiler might not be able to heat it up fast enough - so the water reaching the shower won't be as hot, and/or
• There won't be enough water pressure to keep the shower and tap (or another shower) running at full speed, so less hot water will reach the shower.

The net result might be that your shower gets colder/hotter as a hot tap is turned on/off. A thermostatic shower valve might stop the shower water getting too hot, but it won't stop the water getting too cold.

Obviously, a more powerful combi boiler might be able to heat up a larger throughput of water.

macman

A lot of houses were originally plumbed with CH that did not allow you to heat the hot water without also having the CH on. Or, at the very least, it had to be manually turned off by way of a gate valve buried at the back of the airing cupboard. Most of these have now been modernised, but there are bound to be some still in use.
I would live in a property through at least one winter before ripping out a perfectly good system boiler and tank and installing a combi.