Advice on replacing my CH system

[pyounger]

I live in a conventional 3 bed terrace House, which has an old conventional boiler (the sort with header tank in the loft) with a 1500kw output (I’m told), it has gravity fed hot water and pumped heating to the rads.

I have been worried about the boiler simply because of its age and I want to extend and refit the kitchen, so feel the time is probably right to replace my present system while the kitchen is being done.

I have spoken to two CH engineers, the one who serviced it last year wants me to go all out and swap out for a new Combi boiler system. I am not happy about combi’s because I know so many people who seem to be forever calling out engineers to fix theirs - it seems to me they were made to give engineers a money stream! Like newer cars, so complex the diy mechanic can’t keep pace! Anyway, to replace my system, it would need new reworking of pipework and checking all the pipework can take the extra pressure etc, a new pump & valves, and the system requires more space. Approx cost £3,500

the other engineer says no, I wouldn’t benefit from a Combi which are better suited (economically) to larger properties. His suggestion is to replace with a similar system but, modern building regs state that these newer boiler versions of what I have do not have gravity fed hot water, which means that in addition to the cost of the boiler, a new Thicker pipe from the Meter to the boiler would have to be installed, New valves and a new hot water cylinder (because it needs a different coil on this proposed system). Total cost about £3k.

both engineers agreed that any savings gained by a proper Combi system, would be minimal.

I’m on a bit of a budget and wondered about the opinions of professionals within this group, or if you guys have alternative solutions and is it true that you can’t buy conventional boilers which can be a complete swap out of what I have?

 

[muggles]

It's not a 1500kW boiler, that's big enough to heat a large factory. Could be 15kW. What make/model is it?

I think you're generally very confused about the information you've been given, and have mixed up the advice on combi boilers with the advice on a heat-only direct replacement for what you have now.

A new boiler of any type, combi or otherwise, won't be a money stream for anyone in the short to medium term. Many combi boilers now carry a 5-10 year warranty which means you won't have to pay to fix anything that might go wrong for at least 5-10 years. Look at Intergas boilers - only four moving parts so very little to go wrong, and they're very well made. If you're on a budget then the Rapid might well suit you. You wouldn't need a new pump and valves with a combi - the pump is built into the boiler. Combi boilers are generally suited to smaller properties with a single bathroom.

You've not given the make and model of boiler you have, so it's impossible to say whether a direct replacement is available, but unless it's a back boiler and fire front then generally speaking there should be something out there which would work. The only change is that gravity hot water is no longer acceptable, systems must be fully pumped, so there would be a small pipework alteration to accommodate that. You wouldn't have to change your cylinder though, unless it's a Primatic type.

 

[pyounger]

Thanks for the info. My current boiler is an Ideal RS 50 with a pretty standard looking old copper tank, which, as I understand it, would be removed and so A new Combi boiler could perhaps go in the airing cupboard making more cupboard space in the kitchen???

I guess which ever way I go, I am still going to have to rip up the newly laid bathroom floor and as the boiler is currently directly below the bath, probably have to rip that out too!

 

[Harry Bloomfield]

If a combi is fitted to replace an open vented system, then in all likelihood the combi boiler will need to have a higher output and a larger gas supply pipe to supply it. Many of the people I know who have swapped from an open vented system to a combi have regretted it. Combi boilers are certainly more suitable for a property which is occupied irregularly, they are also more compact/cheaper to install than an open vented from scratch.

If your copper tank (hot water cylinder) is bare copper, with no insulation, then it will need to be replaced with a modern, well insulated one if your present open vented system is retained.

My open vented was installed in the mid 1980's and is now on its third boiler from new. The house is usually occupied. The last two replacement boiler installers have tried to persuade me to switch to a combi, which would have involved a larger gas supply pipe run around the outside of the property. My present supply pipe is completely buried in the floor, from meter, to the boiler. I also didn't like the idea of the boiler firing up, every time the hot water tap was turned on, nor the long wait/slower flow of hot at the taps. The long wait can me mitigated if a combi uses a small store of hot water.

 

[bernardgreen]

he other engineer says no, I wouldn’t benefit from a Combi which are better suited (economically) to larger properties.

The reason he believes this is because a combi has to have a high kWatt rating in order to provide hot water on demand. This high kWatt rating is far too high for heating a small house. Even if the boiler can modulate ( reduce ) its heat output down to 1/5 it is still too much heat for a small house. Hence the boiler has to cycle ON and OFF which puts wear and tear on the boiler. It is also inefficient in this mode of operation.

The irony is that a large house is likely to have more demand for hot water and hence an even larger boiler may be required to provide adequate hot water on demand.

is it true that you can’t buy conventional boilers which can be a complete swap out of what I have?

It is NOT true, there are many heat only boilers on the market which can heat a house and a cylinder of hot water.

A Heat Only boiler has pumps and control gear outside the boiler casing. Makes servicing much easier, the pump(s) and control gear can be freely selected to suit the requirements of the house.

A System boiler is heat only but comes with the pumps and control gear fitted inside the boiler casing. Can be a pain to service or replace parts. The pump(s) and control gear are what comes with the boiler and may not be the optimum for the requirements of the house.

This page is old but still valid LINK

 

[Mottie]

Each to their own depending on circumstances and budget I suppose. I had my conventional system with a 20 year old heat only boiler changed to a sealed system with unvented hot water. Kept the original boiler but had the pipe work modified and a new unvented hot water cylinder fitted. Did away with tanks in loft, replaced the old two way diverter valve with two separate valves and bypass valve, pressure relief valves etc. Had a powerflush at the same time. Advantage for me was a better insulated hot water cylinder which was quicker to heat up, an immersion heater in the cylinder for backup and of course, near mains pressure hot water. Then, like you, a few years later when I felt I may be pushing my luck with the boiler, I just had it swapped over for a modern condensing heat only boiler. It just suited me doing it that way, your circumstance may be different though.

 

[Harry Bloomfield]

It is NOT true, there are many heat only boilers on the market which can heat a house and a cylinder of hot water.

A Heat Only boiler has pumps and control gear outside the boiler casing. Makes servicing much easier, the pump(s) and control gear can be freely selected to suit the requirements of the house.

So very much easier to repair and fix any problems yourself, without recourse to a gas engineer.

 

[ianmcd]

This high kWatt rating is far too high for heating a small house. Even if the boiler can modulate ( reduce ) its heat output down to 1/5 it is still too much heat for a small house. Hence the boiler has to cycle

Google range rating Bennyboy

 

[bernardgreen]

Google range rating Bennyboy

Provide information instead of derogatory comments

 

[ianmcd]

Provide information instead of derogatory comments

quality boilers have potentiometers on the PCB where you can change the max output on the heating side , the DHW stays the same

 

[bernardgreen]

where you can change the max output on the heating side

Please expand,

What is the range of this max heat setting in terms of percentage of HW heat setting ?

Can it be as wide as from 10% up to 100% ? For example 3.5 kW to 35 kW on a boiler rated at 35 kW for hot water supply.

What is the variation of efficiency over the range ?

I am aware that the answers will be different for different makes and models of boiler.

 

[ianmcd]

Please expand,

What is the range of this max heat setting in terms of percentage of HW heat setting ?

Can it be as wide as from 10% up to 100% ? For example 3.5 kW to 35 kW on a boiler rated at 35 kW for hot water supply.

What is the variation of efficiency over the range ?

I am aware that the answers will be different for different makes and models of boiler.

Yep depends on the boiler and yes the efficiency alters as the boiler is measured at max rate, some give a table at what the difference is at what output, but not all

 

[pyounger]

Thanks for all your advice, I haven’t quite worked out yet if it’s all made me wiser or more confused, but I am certainly grateful for it!

A further question, if I may: after reading some replies would I be correct in thinking that with a Combi the hot water flow will be slower? That would be a problem as we already have a fairly slow flow and presumably our shower (mixer tap on the bath) would become unusable.

 

[denso13]

would I be correct in thinking that with a Combi the hot water flow will be slower?

Not necessarily, it depends how slow it is at the moment. The hot and cold will both be at mains pressure so showers generally tend to be better (depending on water pressure/flow of course).

Some gravity hot water flows are very poor and are helped by installing a combi.

 

[Mottie]

Perhaps get your flow rate and pressure checked first?