Combi or Standard Boiler?

[bernardgreen]

I agree Bernard. The old ways are the best.

They were and some still are the better option.

One advantage of the old ways was that many of the items involved could be understood and maintained by average person. Modern technology involved with heating systems is well beyond the average person's ability. Sadly it is also beyond the abilities of some "professionals"

 

[Harry Bloomfield]

They were and some still are the better option.

One advantage of the old ways was that many of the items involved could be understood and maintained by average person. Modern technology involved with heating systems is well beyond the average person's ability. Sadly it is also beyond the abilities of some "professionals"

In addition to which, for absolutely everything which can go wrong with a complex combi, strictly speaking a gas qualified engineer is needed to open it, diagnose the issue and hopefully attempt a repair.

Obviously, the more combi type boilers are installed, the more work is generated for the gas qualified engineers in repairing them, even the minor easy fixes which a DIY'er could resolve if most of the points of failure were not packed inside the combi.

 

[vulcancontinental]

Obviously, the more combi type boilers are installed, the more work is generated for the gas qualified engineers in repairing them, even the minor easy fixes which a DIY'er could resolve if most of the points of failure were not packed inside the combi.

Yes but 30% less CO2.

Just need to calculate which is greater, a visit from the engineer with spares or putting 30% more CO2 into the atmosphere each day. A difficult calculation.

 

[gas112]

Combis are no more complicated than a standard boiler they way some on here are speaking they are trying to make them sound like rocket science .
Mine is around 22 year old and has had one pump and a couple of diaphragms

 

[fixitflav]

Yes but 30% less CO2.

Where does that figure come from?

 

[vulcancontinental]

Where does that figure come from?

A gravity boiler Band G would be typically around 50-60%, a Band A boiler would be typically 80/90%

 

[Harry Bloomfield]

Yes but 30% less CO2.

I think you are not comparing like with like. Modern heat only boiler is at least as efficient as a combi, all things considered probably more so..

 

[jeff the gasman]

Baby Jesus, Mother Mary and the poor wee donkey! I feel hedgermicayted.

 

[vulcancontinental]

I think you are not comparing like with like. Modern heat only boiler is at least as efficient as a combi, all things considered probably more so..

Obviously, if I was comparing like for like the figures would be the same. A gravity boiler similar to that which the OP has, as I explained, has a very poor efficiency compared to a modern Band A boiler. That is notwithstanding the additional efficiency losses incurred comparing the control system and unnecessary system losses of one to the other.

 

[gas112]

I think you are not comparing like with like. Modern heat only boiler is at least as efficient as a combi, all things considered probably more so..

in what way would it be more so ?

 

[Harry Bloomfield]

Obviously, if I was comparing like for like the figures would be the same. A gravity boiler similar to that which the OP has, as I explained, has a very poor efficiency compared to a modern Band A boiler. That is notwithstanding the additional efficiency losses incurred comparing the control system and unnecessary system losses of one to the other.

That, we can agree on, but the OP question was about whether he should opt for swapping to a combi, or not..

 

[oldbutnotdead]

I can see a PhD thesis coming on here- compare hot water costs from a typical combi household and a typical cylinder household.

For me (living alone) the combi in summer is probably cheaper- shower or 2 a day, bit of washing up if I can't be faffed with the dishwasher, shave if I'm venturing Outside .The heat I'd be losing from a full cylinder would (I am quite certain) outweigh the start/stop waste from the combi. Both cases I'd be losing a pipe run full of hot water every time.

For a larger household I'm not so sure- my instinct says the boiler will burn more efficiently on a long burn (to replenish the cylinder) than a series of short burns. Flip of that of course is with the combi you have infinite hot water (long as the gas is on) but at a limited flow rate (filling a bath is tedious).

Especially nowadays I believe the cylinder has that chunky advantage of alternate heat sources (wet or PV solar, heat pump, woodburner).

But I have a horrid suspicion that the time and money invested in such things will never actually be recouped (not in my lifetime anyway) unless you can write off the capex element (someone else did the work then you bought the place).

Dunno. I know Shell are going to give me slaver again this month for zero gas consumption (been going swimming of a morning and availing myself of the showers there).

 

[Harry Bloomfield]

Both cases I'd be losing a pipe run full of hot water every time.

It will take time and some gas burn, to get the heat exchanger up to temperature, before it can even begin to fill the pipework. When you switch off, there will then be wasted heat left in the boiler. Short runs of the boiler are not good economy.

Flip of that of course is with the combi you have infinite hot water (long as the gas is on) but at a limited flow rate (filling a bath is tedious).

Yep, that as well. My heat only when I run a bath, assuming it is enabled, will fire up and replace the used hot water before I get out of the bath, one single constant burn, gradually ramping down to off once the cylinder is back to temperature. I fill the bath up with me in the bath, adjusting the H&C taps to get the temperature I want. It fills so quickly.

My gas usage at the moment is also miniscule - £1.9054 per week standing charge, versus an average of £2.04 per week for actual gas usage. The use includes a bath usually every second day at the moment, interspersed with electric showers; a full session of washing up and a full cooked meal in the gas oven each day. Cylinder is kept at 60C from around 9am to 8pm everyday.

 

[cdbe]

How old is a spacesaver 2? I'm sure mine was way over 40 years old when I replaced it 5 years ago. I replaced everything - pipework, cylinder (new unvented), controls, rads etc - it was all in a **** state (but never ceased to amaze me every day when it would clunk into life without fail). If yours is anything like mine was, a combi would be a vast improvement, an unvented a vast and a bit improvement. I would say that if you get a combi make sure it isn't just connected to the old big bore gravity hot water pipework - it might travel halfway round your house before it gets to your kitchen tap. Given current gas prices a cheap combi with a decent warranty might save you a bit of money while you see what the future is - heat pumps, solar, hydrogen etc - none of which (in my opinion) are worth investing in at the moment.

 

[oldbutnotdead]

In the winter (when woodburner is on so the thermal store gets used) the mains pressure hot water from the plate hex is lovely. Not checked pressure at the bathroom tap but it's dumping 25 litres/min so think it's fairly healthy