Leaking cylinder, time for a combi boiler?

exocet

Most likely.....I'm surprised that your system didn't have motorised valves to separate Heating and Hot Water.

If your house is 2000 build then at least the insulation should be pretty good, this helps the cause.

You can find "heating calculators" online - you basically type in room dimensions / state the insulation level and they come back with a figure for required heat output per room. You then go to a radiator manufacturer web site e.g. Stelrad and compare the rated heat output for any given radiator size. The main differences are single panel v double panel and single convector (fins) v double convector. The Stelrad site will give rated heat output for both old and new standards (82/71 v 50/30 or whatever the new standard is quoted at). If you do this for your main living room, you'll get a feel for whether there is a mismatch. 

In my house I replaced all radiators when I changed the boiler - upgrading such that every radiator had at least one convector on it. My house is a late 60's build so convectors on rads didn't exist then.

I run my system in condensing mode (flow temperature rarely goes above 58 deg) but to do this, I have to run the system for longer - In cold whether i pretty much leave it running 24 hours a day....but i have external weather compensator fitted so the system automatically adjusts for temp changes outside as well plus I can set different internal temperatures as well e.g heating at night runs at 16 degrees target room temp. I find that my bills are no higher than doing the more usual "set the heating to blast for 3 hours and then turn it off again" but my house is a nice comfortable temperature. My house is poorly insulated though by modern standards! 

Jalapeno

Do you mean the Hot Water Tank when you say cylinder ? If so I'd have though a new tank would be a lot cheaper than a new boiler.

Nowt wrong with a combi boiler, we have one AND a hot water tank AND a pump to keep the shower pressure up, even though the tank is on the floor above the bathroom(s). The ice-cold bast when somebody else flushes the loo or runs the hot tap was only ever an issue in gravity fed systems IME.

Roland

exocet said:

In my house I replaced all radiators when I changed the boiler - upgrading such that every radiator had at least one convector on it. 

Same here.

Jalapeno said:

Do you mean the Hot Water Tank when you say cylinder ?   If so I'd have though a new tank would be a lot cheaper than a new boiler. 

If the boiler is working well, and is reasonably efficient, then you might be better off just replacing the cylinder. Once you replace the boiler then you will probably want to replace the radiators, putting in a new control system and motorised valves. 

quarky

Jalapeno said:

Do you mean the Hot Water Tank when you say cylinder ? If so I'd have though a new tank would be a lot cheaper than a new boiler.

Yep I guess so! That is true about the tank, but with my boiler being so old, I don't want to fork out to replace the tank now, and then have to replace the boiler (and maybe the tank), if a couple of years.

quarky

My wife has already ordered a few new radiators anyway... Most (almost all I think) have convectors anyway. It honestly never feel like a struggle to heat the house, but by the sounds of it, it could be harder with the new boiler because of the lower temperature. I am pretty sure she placed the order yesterday though, but she did talk to the plumber about it first at least.

Perdix

The cylinder in the photograph is a thermal store. Big vessel of hot water heated by the boiler mains cold water passed through it in a separate pipe and comes out the other side hot. Gives balanced pressure to hot and cold taps. Not a very common system. Can be replaced by either a combination boiler or keep existing boiler and fit pressurised hot water cylinder in airing cupboard. Thermal stores are still available if you want to stick with what you have got.

quarky

Thanks @Perdix , that sounds exactly like it!

Jalapeno

Make sure any combi boiler is designed for hard water or you'll be servicing regularly (our first one needed the heat exchanger in the boiler de-scaling every year or so becuase it wasn't)

Snap

We have a Vailant gas condensing combi and it also has a reserve hot water tank in it. Its on the ground floor and is powering a 4 floor heating system, 100 year old house, that has a shower on the top floor. Pressure in the shower is huge, and we have almost instant hot water. It was new in 2016.

It works fine when other stuff is running like washers, sinks, but you find that hte pressure in the shower drops a bit if someone is running a bath and that.

The hot water reserve tanks aren't huge, but they hold enough water to givec you instant hot, whilst the rest heats up and runs through.

Prior to that we had a big worcester combi, dating to about 1990. That too had a tank, but it was rubbish in terms of hot water compared to the new one.

We are moving soon, and I am having a Grant oil fired combi in this one, again with a hot water reserve tank. Never had an issue with combis really. Big fan.

RandallFlagg

quarky said:

This is the recommended one. 
http://www.directheatingsupplies.co.uk/ideal-logic-plus-35-combi-boiler
Or a 33kw Worcester. The Ideal Logic comes with a 7 year guarantee compared with an "up to" five years with the Worcester, is 35kw, and cheaper.

The engineer has bene putting the Ideal Logic Plus in for several years and has one himself, so is fairly confident with them. 

The Ideal Logic+ 35 is the boiler we have. It's fine for us 3 bed detached, 4 adults. As you say 7 year guarantee. 14.5 litre flow rat at 35c rise. Our local fitter installs these and states that it's his preference as he's never had one go wrong yet.

We're 2 years in and no issues (only 2 years admittedly!)

exocet

Perdix said:

The cylinder in the photograph is a thermal store. Big vessel of hot water heated by the boiler mains cold water passed through it in a separate pipe and comes out the other side hot. Gives balanced pressure to hot and cold taps. Not a very common system. Can be replaced by either a combination boiler or keep existing boiler and fit pressurised hot water cylinder in airing cupboard. Thermal stores are still available if you want to stick with what you have got.

I hadn't looked at the photo! Yep, your current tank is a thermal store. The advantage of this set up is that it can give you better hot water performance than either a combi or standard gravity fed hot water tank. 

The thermal store can also be installed without specific accreditation (I think I'm right in stating this). The alternative is pressurised hot water tank (Mega Flow being one brand). This stores hot water in the tank at mains pressure. You need specific accreditation to install these.

exocet

Jalapeno said:

Do you mean the Hot Water Tank when you say cylinder ? If so I'd have though a new tank would be a lot cheaper than a new boiler.

Nowt wrong with a combi boiler, we have one AND a hot water tank AND a pump to keep the shower pressure up, even though the tank is on the floor above the bathroom(s). The ice-cold bast when somebody else flushes the loo or runs the hot tap was only ever an issue in gravity fed systems IME.

I've seen combi boilers used like this. The combi only feeds hot water to kitchen tap or other low volume requirements, the tank feeds hot water to high volume requirements e.g. bath / shower. When you have hot and cold water at mains pressure, no problems balancing the temp in a shower

boogieman

Jalapeno said:

Make sure any combi boiler is designed for hard water or you'll be servicing regularly (our first one needed the heat exchanger in the boiler de-scaling every year or so becuase it wasn't)

You don’t need a special boiler really, you can get an in-line filter to go in the cold water feed to the combi. That knocks the calcium out of the water. Any plumber worth his salt should advise fitting one in a hard water area. 

grungebob

Similar sized house 5/6 beds three bathrooms and we have a Worcester Bosch 40 something combi with a additional booster pump upstairs. We separated out the circuits though so it doesn’t actually work as a combi. 
The heated water goes to a tank and the boiler circuit remains almost as a closed loop but with an open header tank for the make up.  Plenty of heat for the rads and only need the hot water to come on once per day. 

grungebob

@quarky they may not be cheaper but BG fitted my Worcester 40 with mods to keep hot water tank and providing they service it yearly I’ve got a 10year guarantee. 
Due to the size of the boiler and mods it came to circa £4k tough yours may be cheaper as my house has a mix of pipe sizes due to originally being an oil fed system. 

ICBM

Ah bollocks... my hot water tank sprang a leak yesterday - or possibly well before that. Water coming through the downstairs ceiling. Took a while to find the source because it's basically running across the top of the plasterboard ceiling and coming down about ten feet away from the tank, but I've actually found the leak now, one of the pipe fittings has corroded. Probably not too surprising given that it's 37 years old, but still very annoying.

I'll definitely be replacing the tank, don't want one of the on-demand systems. The only question is whether I can get one with both indirect central heating *and* electrical heating, which is what the current one has - very useful. Anyone know? The ones I've looked at online don't seem to show electrical heating. Yes, I know electric is more expensive... that's not why I want it, it's so I can top it up without having to turn the whole heating system on, since electrical energy from renewables and nuclear is greener than gas.

Kittyfrisk

^ Sorry to hear that, it's a bugger & while there's never ever a good time for such things, winter really isn't it.
Can you temporarily seal the leak with something similar to these products? 
http://www.repairproducts.co.uk/page29.htm

 I may be wrong (it has been known) but it sounds as if you are describing wanting a system boiler or a 'regular' heat only boiler, supplemented by an electric immersion heater rather than a condensing or combi type?

exocet

ICBM said:

Ah bollocks... my hot water tank sprang a leak yesterday - or possibly well before that. Water coming through the downstairs ceiling. Took a while to find the source because it's basically running across the top of the plasterboard ceiling and coming down about ten feet away from the tank, but I've actually found the leak now, one of the pipe fittings has corroded. Probably not too surprising given that it's 37 years old, but still very annoying.

I'll definitely be replacing the tank, don't want one of the on-demand systems. The only question is whether I can get one with both indirect central heating *and* electrical heating, which is what the current one has - very useful. Anyone know? The ones I've looked at online don't seem to show electrical heating. Yes, I know electric is more expensive... that's not why I want it, it's so I can top it up without having to turn the whole heating system on, since electrical energy from renewables and nuclear is greener than gas.

As in a replacement Vented HW Cylinder that has CH Driven primary coil for heating water, backed up with a electric immersion heater ? These are pretty standard as far as I know - can’t see why they would remove the boss fitting in the top of the tank into which the element fits. Looking at Screwfix, some of the pictures show the hole in the top of the tank but then don’t refer to it in product specs.

ICBM

Kittyfrisk said:

^ Sorry to hear that, it's a bugger & while there's never ever a good time for such things, winter really isn't it.
Can you temporarily seal the leak with something similar to these products? 
http://www.repairproducts.co.uk/page29.htm

Unlikely, there's about an 8-foot head of water above the leak. Looking at the amount of corrosion on the fitting - which typically is round the back of the tank, although not too far - it's debatable if it would seal completely or (even semi-) permanently anyway.

I think it's probably better to bite the bullet and replace the tank.

The good news is that whoever installed the system in the first place did a proper job and there are separate outlets from the loft tank for the cylinder feed and cold, so now I've identified them and drained the hot water tank, that's all we don't have access to - all the low-pressure cold is back working.

And I have a mains-water electric shower elsewhere in the house, so the inconvenience is relatively mild...

exocet said:

As in a replacement Vented HW Cylinder that has CH Driven primary coil for heating water, backed up with a electric immersion heater ? These are pretty standard as far as I know - can’t see why they would remove the boss fitting in the top of the tank into which the element fits. Looking at Screwfix, some of the pictures show the hole in the top of the tank but then don’t refer to it in product specs.

Yes, I saw those. No mention of the heating element, but what looks like a fitting for it.

There's a further complication - the tank has *five* connections... I think the extra one is a dedicated outlet for the power shower in the bathroom, but it predates our ownership of the house so I'm not certain. It would be perfect if I could get a drop-in replacement of course!

boogieman

If one of the five outlets is feeding your shower you can get round that. There’s a thing called a Surrey Flange that screws into the top of the cylinder and provides a dedicated feed to the shower. Obviously it means adapting the pipework but it might get you out of a fix if you can’t find a matching cylinder.