The House Projects Thread

[Simon]

I’m always amazed by the large percentage of heating engineers who have no clue at all when it comes to wiring up heating systems

Yep. We had a boiler recommissioned after a heroin addict sold all the pipework to the radiators and I'd removed the power lead from the fused switch until everything had been checked out. The guy wouldn't even reconnect the power to the switch to test his work let alone replace the RF Thermostat.

We had to get the electrician back for those bits as our usual plumber understandably wouldn't sign off the other guys work.

It seems to be a younger plumber's problem along with absolutely no idea what to do with a back boiler other than condemn them lol

They also have no idea how to fit anything other than a combi boiler, system boilers and even more so regular boilers confuse hell out of them.

I can always tell when an electrician has wired up a heating system- everything terminates in its own slot in a wiring centre and then there’s a million and one links, just makes it confusing as hell

OK, I know a combi boiler, but I didn't know there were 2 other types? What's the difference between a system boiler and a regular? I have an S-plan system, cold water tank, hot water tank etc, so thought that was just a system boiler? Edumacate me.

[mik]

Combi boiler does instant hot water.

System boiler has hot water tank.

Old boiler = MIL

[Jobbo]

System boiler is pressurised, has a gauge on the boiler. Normal one has a header tank. So you need a system boiler with an unvented system.

Our Grant oil boiler can be turned into a system boiler very simply; I think the kit is basically just the pressure dial.

ETA: a system boiler will also include the pump, usually - not sure that’s the case with my Grant if converted though.

[jamcg]

Regular boiler is literally just a burner and heat exchanger- usually open vented/tank fed but can be sealed system/pressurised- would require an external expansion vessel, pressure gauge and pressure relief valve. Also requires an external pump. Usually seen on y plan but sometimes on s plan. Mostly seen with open vent hot water cylinders but can run unvented too

System boiler- integrated expansion vessel, integrated pressure gauge, integrated pressure relief valve, integrated pump- basically a combi boiler but with the hot water section deleted. 99% will be on an s plan system, very rare to be seen on a y plan. Not compatible with open vent hot water cylinders as the cylinder coils aren’t able to be pressurised, so will be installed in combination with an unvented hot water cylinder

@Simon from the sounds of it you will have a regular boiler on an s plan system, with an external pump and an open vent hot water cylinder

[Carlos]

Sadly this stuff is voodoo to even professionals

[Simon]

Think I got it. Thanks all!

[Simon]

Regular boiler is literally just a burner and heat exchanger- usually open vented/tank fed but can be sealed system/pressurised- would require an external expansion vessel, pressure gauge and pressure relief valve. Also requires an external pump. Usually seen on y plan but sometimes on s plan. Mostly seen with open vent hot water cylinders but can run unvented too

System boiler- integrated expansion vessel, integrated pressure gauge, integrated pressure relief valve, integrated pump- basically a combi boiler but with the hot water section deleted. 99% will be on an s plan system, very rare to be seen on a y plan. Not compatible with open vent hot water cylinders as the cylinder coils aren’t able to be pressurised, so will be installed in combination with an unvented hot water cylinder

@Simon from the sounds of it you will have a regular boiler on an s plan system, with an external pump and an open vent hot water cylinder

Yup, 30 y/o boiler, pump, 2x2 way valves, CW tank, HW tank. Pretty standard I think.

[jamcg]

Regular boiler is literally just a burner and heat exchanger- usually open vented/tank fed but can be sealed system/pressurised- would require an external expansion vessel, pressure gauge and pressure relief valve. Also requires an external pump. Usually seen on y plan but sometimes on s plan. Mostly seen with open vent hot water cylinders but can run unvented too

System boiler- integrated expansion vessel, integrated pressure gauge, integrated pressure relief valve, integrated pump- basically a combi boiler but with the hot water section deleted. 99% will be on an s plan system, very rare to be seen on a y plan. Not compatible with open vent hot water cylinders as the cylinder coils aren’t able to be pressurised, so will be installed in combination with an unvented hot water cylinder

@Simon from the sounds of it you will have a regular boiler on an s plan system, with an external pump and an open vent hot water cylinder

Yup, 30 y/o boiler, pump, 2x2 way valves, CW tank, HW tank. Pretty standard I think.

Your boilers probably running about 40-45% efficient, you should see a massive change in gas bills by changing to something modern. Definitely worth considering at some point as your boiler is probably obsolete at that age with either zero part availability or difficulty in sourcing certain bits

[Simon]

It's certainly on my list.

It's also under the counter top in the corner of my kitchen with makes accessibility a bitch for the poor BG man who comes and services it. It needs moving up to be in one of the upper wall cupboards, so it'll probably all be done at the same time when we have a new kitchen in a year or two (or move before!).

[Swervin_Mervin]

What's your views on combis @jamcg ?

It always seems like some in the industry hold them in really low regard. We're looking at spending a Viessmann when we do our refurb and we've had combis trouble free for 20yrs now (vaillant at last place and WB here).

[mik]

I may not be @jamcg but I much prefer a system boiler + water tank when you have multiple bathrooms/en-suites. A couple of houses back we had a 36kW combi, but running a HOT Bath in winter required a reduced flow rate.

With a system boiler & hot water tank there is no issue with 2 or even 3 people showering simultaneously*.

* even in different bathrooms

[Jobbo]

Agree with Mik - these modern cylinders don’t lose much heat and will heat up very quickly too. The one downside of good pressure and flow rate can be that teenagers still run you out of hot water So get a f—k off big cylinder.

We have a halfway house; there was no need to replace our boiler so we got a 250l hot water cylinder called a Harlequin Heatstream. It works with an vented system; it’s just basically a well-insulated thermal store, with mains pressure water heated up to temperature by passing through a coil in the cylinder. Works really well, no need for pressure relief valves and annual services.

[jamcg]

What's your views on combis @jamcg ?

It always seems like some in the industry hold them in really low regard. We're looking at spending a Viessmann when we do our refurb and we've had combis trouble free for 20yrs now (vaillant at last place and WB here).

Combi boilers are great- in the right situation. Single bathroom house with 2 people living in it- great

Multi bathrooms with teenagers- fuck no. You need hot water storage then, preferably unvented. If you run it on an all day setting, letting the thermostat control it running out shouldn’t be too much of a problem as the recovery time is really short

[Swervin_Mervin]

I only ask as my.mum and dads place has one of the 40+kw WB combis and it will merrily run 2 showers at the same time amd still leave enough flow for the washing machine or someone to wash up. I'd always just assumed it was because the combo was big enough and being a new house it will likely have had at least a 25mm supply pipe.

My aim is to try and replicate that - they visit fairly regularly in a normal year and so it's useful to be able to cater for 4 adults showering (and a child that will obvs want to start showering themselves on a couple of years) without running out of water.

We've had a new supply moled so flow is hugely improved. But our cd24 is out of its depth and I suspect we have some limiting internal pipework - 1 shower is the limit. Anybody turns on a tap and the flow drops to a trickle. Hence thinking about a new combi bit also checking the internal pipework and upping the if necessary

[jamcg]

I only ask as my.mum and dads place has one of the 40+kw WB combis and it will merrily run 2 showers at the same time amd still leave enough flow for the washing machine or someone to wash up. I'd always just assumed it was because the combo was big enough and being a new house it will likely have had at least a 25mm supply pipe.

My aim is to try and replicate that - they visit fairly regularly in a normal year and so it's useful to be able to cater for 4 adults showering (and a child that will obvs want to start showering themselves on a couple of years) without running out of water.

We've had a new supply moled so flow is hugely improved. But our cd24 is out of its depth and I suspect we have some limiting internal pipework - 1 shower is the limit. Anybody turns on a tap and the flow drops to a trickle. Hence thinking about a new combi bit also checking the internal pipework and upping the if necessary

I’d never recommend a combi in a house with more than one bathroom, regardless of the size you install it’s still a compromise- I’m surprised your parents place works that well to be honest. If you’re looking to get that much hot water you’d be better off with an unvented hot water system, but they’re quite an expensive job. If you go for the combi it may work but there’s no guarantees it’ll do what you want- also bear in mind if you’re in an old property your incoming gas main might not be up to the job of supplying a 40kw+ boiler, and your existing internal gas pipe work definitely won’t be- you either need the meter next to the boiler or a good chunk of the gas line in 28mm pipe

[V8Granite]

I only ask as my.mum and dads place has one of the 40+kw WB combis and it will merrily run 2 showers at the same time amd still leave enough flow for the washing machine or someone to wash up. I'd always just assumed it was because the combo was big enough and being a new house it will likely have had at least a 25mm supply pipe.

My aim is to try and replicate that - they visit fairly regularly in a normal year and so it's useful to be able to cater for 4 adults showering (and a child that will obvs want to start showering themselves on a couple of years) without running out of water.

We've had a new supply moled so flow is hugely improved. But our cd24 is out of its depth and I suspect we have some limiting internal pipework - 1 shower is the limit. Anybody turns on a tap and the flow drops to a trickle. Hence thinking about a new combi bit also checking the internal pipework and upping the if necessary

I’ll need to check the model but our combi was supposed to be for a 5 bed house and ours is a small 3 bed. With my wife scalding herself having a shower I can fill the washing up bowl and she won’t notice.

Maybe this wouldn’t happen with a power shower but we have good water pressure and seems to work really well.

Maybe in a bigger house it couldn’t keep up as you’re heating up loads of pipe work too with much farther to send it.

Dave!

[Carlos]

It's all subject to mains water pressure but you can get Combi's that will pump 20l/min + of hot water which will easily cope with 2 really hot showers.

Our new one only pumps 12.2l/min so I'll check in the morning if 2 showers simultaneously are ok.

My kids go in the shower for hours so hot water on demand is a big benefit.

[Swervin_Mervin]

My parents is a 46CDI IIRC which will pump about 17l/min. Our 24 will only do 10-11 and it's 20yo so probably past its best anyway.

Most of the house supply has been upgraded in the past so I've no qualms about that - the water main was the main thing to have done. We're on about 16-17l/min supply now so vastly up on where we were (I think it was about 8-9l/min). When we had the downstairs bog removed from the garage it has exposed some of the gas supply pipe between meter (front of house) and boiler (rear) and it's 28mm. The builders were surprised to see that and made specific comment about it, so that bodes well as well.

I did look at the WB Highflow combis for a while but at over 20l/min there seems little point given the incoming flow isn't that high. I eventually settled on the Viessmann Vitodens 111-W with >18l/min and a 40l integral hot water storage tank. The latter we had similar on our Vaillant at the last place and it was a bonus - running the hot tap until it gets hot is bloody infuriating with the old WB in our current place!

[jamcg]

Showers use between 10-15 l/min, that’s spread across hot and cold though

If your gas supply is already 28mm it’s probably an old primary from a gravity boiler

From experience with any appliance that combines two functions into one there’s always a compromise or a shortcoming somewhere down the line, so tread carefully (have experience with the vaillant you describe but not the viessmann)

[Swervin_Mervin]

The Vaillant was a PITA in that every 2-3 years there was one part that needed replacing - you'll probably know what from my description. It was a plastic valve IIRC that was designed to deform in the event of a certain type of fault and it would cut off the gas supply. Only trouble was it would also deform gradually over time. Always eventually failed in winter, mid-shower!