Combi boiler woes

seatbeltnoob

Hi I always lived in houses with cylinders all my life. It's slightly more expensive but you get hot water from the tap instantly when you need it.
I've moved to a flat (renting) with a combi boiler. It had issues where we wouldn't get hot water without having central heating on. Landlord sent a boiler engineer who fitted a new divertor and cleaned out the heater exchange.
He changed those two parts, and now we get hot water without central heating but it's nothing like homes with a hot water cylinder. You have to run the hot water for a good 30 seconds to have hot water. It's such a waste of water. Also the temperature varies, you can see it going from lukewarm to scalding hot and after you run it for a long time the temp dips from scalding hot to lukewarm.

The gas engineer told me this is normal with combi boilers. Just need a second opinion on this.
I get that it's cheaper than conventional boilers to use a combi, but for the sake of £200 a year energy savings I would take the convenience and reliability of hot water on top any day!

The boiler is a old main combi 24. It's old and has no digital display and a pressure gauge dial. The timer feature looks like something out of the 80s

Talldave

Welcome to the world of combi boilers - been there, hated it.  When we were renting a flat the system boiler with a tank died and was replaced with a combi.  For sure the gas bill went down, but because we spent half our lives staring at water running out of a tap waiting for it to get hot, the water bill leapt up and overall our costs went up!  So if you're on a water meter, prepare for a shock.

Fortunately, we're now renting a house with a lovely 300 litre tank.  During summer, gas consumption was around 50kWh a week for just the water (this week with heating on, it's 1100kWh!).

matelodave

we had one for about eleven years and as far as I was concerned it the next best thing to sliced bread. We gained space in the kitchen where the old boiler was, space in  the airing cupboard where the tank was and space in the loft where the cold water tank was situated. I can't see whats not to like.

We've got a tank at this place because we've got a heat-pump but I'd have a combi if we had mains gas. 

Neil_Jones

seatbeltnoob said:

Hi I always lived in houses with cylinders all my life. It's slightly more expensive but you get hot water from the tap instantly when you need it.
I've moved to a flat (renting) with a combi boiler. It had issues where we wouldn't get hot water without having central heating on. Landlord sent a boiler engineer who fitted a new divertor and cleaned out the heater exchange.
He changed those two parts, and now we get hot water without central heating but it's nothing like homes with a hot water cylinder. You have to run the hot water for a good 30 seconds to have hot water. It's such a waste of water. Also the temperature varies, you can see it going from lukewarm to scalding hot and after you run it for a long time the temp dips from scalding hot to lukewarm.

The gas engineer told me this is normal with combi boilers. Just need a second opinion on this.
I get that it's cheaper than conventional boilers to use a combi, but for the sake of £200 a year energy savings I would take the convenience and reliability of hot water on top any day!

The boiler is a old main combi 24. It's old and has no digital display and a pressure gauge dial. The timer feature looks like something out of the 80s

It is normal for the water to run cold initially and then go hot as water passes the heater in the boiler and comes to the tap.  That's always been the case with them.

Water tanks that live in places like the attic tend to attract unpleasantries in the water, which may make it unsafe to drink:

https://www.youtube.com/watch?v=HfHgUu_8KgA

Hence if you eliminate that from the equation, all the water can only come from the mains and is safer.  Of course whether it's better for on-demand hot water is always up for debate.

roddydogs

Doesn't the water from any heat source run cold to start with.?

tacpot12

roddydogs said:

Doesn't the water from any heat source run cold to start with.?

It depends how far the tap is from the hot water source and the amount of insulation on the pipes. In situations where the taps are a long way from the source, circulation pumps keep the hot water flowing around all the distribution pipes so that you get near instantaneous hot water even from a cylinder. 

Combi boilers can be ok if they are sized adequately. I preferred them because I wanted hot water for baths very occasionally, and used an electric shower the rest of the time, so I only need to heat a full tank on odd days. The trick is to learn how much flow they can supply, and to turn the tap down to just that flow after you turn it on enough to get the boiler to light.

roddydogs

Thanks, but never heard of a circulation pump for the HW, obviously CH.

matelodave

Circulating the hot water is something they tend to do in very large buildings or where there are very long runs to the sinks/baths from the boiler room or even multiple bathrooms like in hotels or other multiple occupancy situations where the boiler house is remote from the point of use. The pipes need to be well insulated to reduce the heat loss from the long double runs.

They don't often do it in your average 3-bedroom house.

Even though we've got a HW tank, there's over 12 metres of pipework between it and our shower and so we still waste quite a lot of cold water before it runs hot so we avoid using using hot water for short draw downs. to save the waste, not only of cold water but then 10 metres of hot which sits there to get cold.
.

Ectophile

I have a hot water tank.  I also keep a water carrier in the kitchen.  If I want to do the washing up, I run through about 3 litres of cold water before it starts getting warm.  The water carrier is so I don't waste the water - I can use it for watering plants or flushing the loo.

The biggest problem a combi boiler has is that it needs to heat the water from cold almost instantly.  That's not so difficult in summer, when the mains water is relatively warm.  But summer is now gone, and the ground is cooling down.  Mains water is getting colder and colder.  Unless you have a really high power boiler, you've got a choice of lots of warm water, or turning the tap down and getting a lower flow but hotter water.  Newer boilers should have a water temperature control on them, but they can't work miracles if the water flow is too high.

RelievedSheff

We had a boiler with hot water tank in our old house. It still ran cold water through the pipes before the hot water arrived.

We have a combi now and our gas bill is much less than in the previous house. For our use the combi works much better.

JohnB47

Yes, combi every time for me now. Had hot water tanks in bedrooms, two header tanks in the loft, each with ballcocks (invented by the devil, I think). Never again.