Combi or Sytem Boiler????

Sprinkles02

I am confused over which route to go down in replacing my 25 year old boiler. There are 3 of us (me partner and a 6 year old) living in a extended 3 bed detatched house with 1 downstairs loo, one bathroom and an en suite shower room.

I thought we were being quoted for a combi but our plumber has recommended a sytem boiler with cyliner.

I'm more than happy with the make (Worcester Boch, seems to be recommended everywhere) but am not sure which type. The thought of being without a back up tank/immersion should the boiler go wrong worries me but why heat a load of hot water that may not be used? I understand with a combi you can lose the water pressure when someone uses another tap etc. My partner & I have showers twice a day, my son has either a shower or a bath daily. I'll have the odd bath every few weeks too probably (instead of a shower)!

Are system boilers more expensive to run? The difference in installation between the 2 is approx £500 but I don't want to make the wrong choice. We're being quoted £4800 inc vat for the new system/cylinder option with 6 new rad valves, a powerflush, hot water clock on cyliner and a programmable room stat.

Any advice appreciated.

Magentasue

We've had both. In our old house, a system boiler was recommended because there was a long run to the downstairs shower room, and with six of us in the house, we were told a combi wouldn't cope. This house, ten years on, we went for a combi. We will only have one bathroom but were told even if we had a shower downstairs, a combi would be fine because they're much better than they used to be. Water pressure does drop if we're running a bath and turn another tap on but that doesn't bother me. I prefer the combi - instant hot water being the advantage. I feel it's cheaper to run but I don't have evidence for that.

As you say, the big disadvantage is if the boiler packs up for a week. Haven't had to deal with that yet!

aelitaman

I would make sure that you get more than one quote. As you are being quoted twice what I paid 3 years ago and the boiler I purchased was 1100 GBP and I had the boiler moved to a new location so had to have new pipes layed to conect to the exisiting pipework. All in all, it took about two and half days to remove old boiler, seal up the old connections, lay new connecting pipework, and install new boiler. There were two working and one labourer, so 7.5 man days. So if they want to earn 50K per year then 50 / 260 (working days in a year) = 192 gbp per day x 7.5 = 1440 GBP . This is about what I paid from memory it was arou d 2500 GBP inc VAT.

Onto the boiler I got multiple quotes and they were all different recomendations in configuration but not one recommended a combi, I think that there is a lot of sceptitsm about combis in the trade. Anyway I got a combi, the largest one that Worcester Bosch made at the time. I will admit that it takes a long time to run a bath about 25mins but I have a shower with a 10inch head and the flow rate is fine, not power shower levels but plenty enough to keep me wet and happy and this is with the water temp set at 55C so I am not adding much cold water to boost the flow rate.

This flow rate is because my combi has an internal tank in it where hot water is stored so you get instant hot water and an increased flow rate that means that I can run two taps at the same time with acceptable flow.

So my recomemdations to you are get the largest combi you can, with the highest hot water flow rate, as this should be a 25 year investment, I have the space for a floor stander. Make sure it has the internal hot water tank.

Canucklehead

Good evening: A system boiler with an unvented cylinder would fit the bill.....lots of hot water at mains pressure....more here We have a combi in our own home (good mains flow/pressure at the property)) but we have only one bathroom. The OH fits Vaillant, Viessmann or Remeha (all have stainless heat exchangers vs. aluminium with the WBs).

HTH

Canucklehead

allan673

im a big fan of combis now, mine is saving me a small fortune in gas costs since ive had it fitted 30% easily, instant hot water - no need to heat a tank full etc as it heats what you need on demand. the flow rate is excellent too, it seems the same as the old system boiler we had removed.
your quote seems way too expensive, by a couple of grand in my opinion.

ive got a worcester bosch and its fantastic, 2 year guarantee with next day call out should anything go wrong, worcester also do a boiler cover too after the guarantee has expired.
although my parents have had no problems with there worcester at all, theyve had it years.

Cozworth806

The only thing to consider is the size of the boiler for the two types.
A system boiler can be much smaller and lower powered due to having the time to heat the water, and you could consider solar water heating at the same time if you were that way inclined.
It means that the boiler is working at peak efficiency more of the time, rather than being under used through summer, with a 12 or 15Kwh boiler rather than a 24kwh+ condensing boiler.

I have had combi and the modern two I have had were very good (condensing Baxi's) but the older non condensing WB was noticeably worse.

Sprinkles02

aelitaman wrote: »

I will admit that it takes a long time to run a bath about 25mins .

Would it really take 25 mins to fill a bath with a combi???

Does that mean that no heat goes to the radiators whilst the demand is for the bath??

Pssst

System boiler with cylinder,either open vented or pressurised if your budget will stretch. Think how invigorating your shower will be !

Magentasue

Sprinkles02 wrote: »

Would it really take 25 mins to fill a bath with a combi???

Does that mean that no heat goes to the radiators whilst the demand is for the bath??

No, five to ten minutes, I'd say. Will time it tonight if I remember.

darich

Sprinkles02 wrote: »

Would it really take 25 mins to fill a bath with a combi???

Does that mean that no heat goes to the radiators whilst the demand is for the bath??

Our combi can fill the bath in nowhere near 25mins....more like 10mins.

Can't say if no heat goes to radiators but I'd imagine it makes little to no difference. Although it could depend on the pressure from your mains and how good your combi boiler is.
Ours can heat 8 radiators in about 10mins and we need to turn them all off again.

Couple of advantages include only heating what is required.
Also because the water comes off the mains and is heated, the pressure is great. We bought a mixer shower which is basically a big mixer tap - no pumps, or boxes on the bathroom wall - just large tap to adjust the flow and temperature. Hot water at high pressure gives a great shower.

Sprinkles02

Magentasue wrote: »

No, five to ten minutes, I'd say. Will time it tonight if I remember.

WOW! That's kind!

Thanks for the replies everyone.