Is my boiler suitable?

[GuidancePlease]

Dear all.

Loft conversion recently started in my 1950’s 3 bed house with 1 bathroom & 2 shower rooms, adding 2 beds + shower room. Two or maybe all three showers are thermostatically controlled. Gas Safe Plumber outlined options for new coffin tank & pump, or Megaflow (pointing out size needed for bathrooms), or new combi/condensing boiler. I wanted to keep existing reliable boiler Potterton Kingfisher 2 CF80 (no repair costs for 10 years). House on South coast near Brighton.

When plumber realised chimney was to be removed loft work was correctly stopped because existing open flue can not be diverted (BS5440art 1:2000). Only solution was new boiler, and quickly to continue work. Told me changing for Worcester really good combi boiler.

Fitted a Junior 28I at £2,500 including power flush etc. CH is OK, but DHW now has issues. Problems:
- First floor main bathroom shower (Mira) is controllable on full flow, but if bathroom hot tap used then shower temperature drops; also temp drops to luke warm and flow slows right down if either ground floor kitchen hot tap or cloakroom shower used.
- The En Suite shower (8 months old, Pura Bathrooms Ltd) can’t fully test yet as it only gives uncontrolled full heat now (previously OK with/without pump on, plumber going to fit a pressure reducer).
- The old cloakroom shower (maybe thermostatic, called Power Shower Deluxe) is controllable but pipes appear to be reversed (turn from off and it starts hot and gets colder as you turn further).
- If bathroom hot tap on, when kitchen hot turned on temp drops and flow reduces considerably in bathroom.

Not happy that with a single shower in use the temp is greatly affected by one shower or tap elsewhere in house. Also the stabilised temp at hot taps (nothing else being used) seems to vary slightly each time you use them.

Flow rate at hot taps & showers was OK with old tank gravity feed & old boiler, but is better now. Plumber estimated new flow rate with measuring “cup” at kitchen hot (approx 11 litre/m) & cold (approx 18 litre/m), although this is a mixer tap with small flexi connection pipes so might be a lower flow rate than other taps.

So is this boiler suitable for my home? Come to that, is it suitable for a 1 bed flat if you don’t want the shower temperature dropping when someone uses a tap? Your views will be appreciated.

 

[tamz]

In one word. NO.

For the amount of bathrooms you have, no combi would be suitable and certainly not a 28.
You would need an unvented cylinder of approx 300 litres capacity to come near to it.
This would be very much dependant on the incoming mains pressure and flow rate.

All is not as bad as it seems tho as the combi can be altered to feed say the kitchen or one bathroom on the hot water side and changed to an S plan to heat the unvented cylinder.
Get it fixed now or forever regret it.

 

[Blackcatgas]

In one word. NO.

For the amount of bathrooms you have, no combi would be suitable and certainly not a 28.
You would need an unvented cylinder of approx 300 litres capacity to come near to it.
This would be very much dependant on the incoming mains pressure and flow rate.

All is not as bad as it seems tho as the combi can be altered to feed say the kitchen or one bathroom on the hot water side and changed to an S plan to heat the unvented cylinder.
Get it fixed now or forever regret it.

Agree 100% with the above.

 

[Reg Man]

Oh my word! Combi's are great, but not for your demand. Poor new boiler is struggling to provide for your needs. Average combination boilers are great for a small house or flat, not for several bathrooms/shower rooms ect. 28i will give you 13.4 l/min at 30 degree rise down to 10 l/min at 40 degree rise.

 

[GuidancePlease]

Tamz. So even the existing boiler could be OK with an S Plan. No need to press for a bigger combi like 42CDI or maybe 440CDI? Would an S Plan mean rescuing the old immersion tank & valves etc with a coffin tank in the loft and pump for the loft shower?

 

[Reg Man]

Yes. You require a higher capacity hot water system.

 

[tamz]

A 42cdi will still give unsatisfactory performance max hw output is 18 litres at 30º rise (shower temp) The only combi that would come near your needs is a 550 highflow or similar storage combi.
A 28kw should be big enough for your heating needs but it should be checked. (42 cdi and 550 highflow have 30kw to heating).
|Your best bet would be to use the 28 to feed the hot water to either your kitchen or one bathroom and fit an unvented cylinder to feed everything else.
The incoming pressure and flow rate would need to be checked to make sure you have enough.
The central heating side of the fitted 28 should be altered to an S plan and also heat the cylinder. This is easily done and is about the only way you will get enough hot water. How many people live in your house ie realistically how many showers may be running simultaneously?

 

[Blackcatgas]

Tamz. So even the existing boiler could be OK with an S Plan. No need to press for a bigger combi like 42CDI or maybe 440CDI? Would an S Plan mean rescuing the old immersion tank & valves etc with a coffin tank in the loft and pump for the loft shower?

A Storage combi such as a Viessman 222F or tthe Worcester Bosch one (550?) would do the job a 42cdi would still struggle, or as Tamz has said use the 28si on a s plan to run an new unvented (megaflow type) cylinder. You could probably re use your old tanks etc if they are still there, although you might struggle with pressure if your putting a bathroom in the loft, the tanks would have to be in the apex of the roof which might not be possible.

EDIT, Tamz beat me to it.

 

[GuidancePlease]

Thanks to all. Reg Man, I assume your Yes is to everything I outlined to Tamz as the solution?

I am still surprised that the boiler DHW can't cope with the limited use of one shower plus one tap/shower elsewhere in the house. Even in a flat this is a reasonable expectation, or is there something wrong with my boiler?

 

[tamz]

EDIT, Tamz beat me to it.

I'm off to bed. Got a lovely recently separated woman to cheer up for valentines day (give her a boiler that works)

 

[GuidancePlease]

Sorry Tamz, we overlapped. Number in house varies with us two plus one at Uni and one here then there....

 

[Blackcatgas]

Thanks to all. Reg Man, I assume your Yes is to everything I outlined to Tamz as the solution?

I am still surprised that the boiler DHW can't cope with the limited use of one shower plus one tap/shower elsewhere in the house. Even in a flat this is a reasonable expectation, or is there something wrong with my boiler?

Sounds about right, a combi will give 1 good shower.

 

[Reg Man]

Fully support Tamz and Blackcatgas. The guy you had do the work does not understand the hot water demand for the property you describe.

 

[Blackcatgas]

I'm off to bed. Got a lovely recently separated woman to cheer up for valentines day (give her a boiler that works)

Nice one!, have a good one, Ive got another can of Carling to finnish before i go.

 

[tamz]

Sorry Tamz, we overlapped. Number in house varies with us two plus one at Uni and one here then there....

Well unless you put your foot down and make it clear no water is to be run when you are in the shower i'd get it sorted now.
No point in having a lot of bathrooms that can only be used one at a time and if you have daughters that won't happen

I'm off to bed before i start billing you

 

[GuidancePlease]

Fantastic all - enjoy your night!!!!

 

[Bartdude]

As the other lads have stated already,you need a hot water storage system. A unvented cylider of at least 250 litres if you've got a good enough pressure and flow rate on your incoming main. I'd get that checked first as that could limit you options.

It seems strange that your plumber initially gave you the option of a cylinder but then went for a small combi. I'd expect to fit a 28kw in a 1 bathroom property,and even then you have to explain that a bath will fill slowly. There are storage combis,I've fitted a couple Vaillant 937's when a cylinder hasn't been an option and they work pretty well. But if you have high water demand then having storage is always the preferred option.

I would suggest you talk to your installer and see what you can work out together,there's always a solution somewhere!

 

[fuzzy]

how long are the pipe runs?
cud you use the boiler to supply some hw outlets but also heat a cylinder for the rest? say kitchen sink off combi and bath off cyl?

 

[GuidancePlease]

Tamz, Blackcatgas, Reg Man, and Bartdude, with your advice I realise a 250 to 300 litre storage is needed for most of the HW. I referred to using a tank and cylinder, with a pump for the loft HW and maybe all the showers. Wouldn't this be a vented cylinder feeding HW on gravity/pump?

You all mentioned an unvented cylinder which I thought is for mains pressured HW output?

The mains pressure is good, but flow varies when cold taps are used or toilets are flushed. I assume this would affect the cold and hot flow to showers. Wouldn't a gravity / pumped system using a tank and a vented cylinder supplying Hot & cold to the showers give a more consistent flow?

Not sure if you will look at this thread again, but if you do many thanks

 

[Reg Man]

Unvented hot water vessel would be good, but you need to ensure you have adequate volume of flow and pressure coming into your property at all times.

The first unvented system I ever fitted back in 1988 caused me a problem, because the property was on the end of a road. When I tested the flow and pressure during the day, all was fine. Installed the unit, all was fine. In the evening customer calls because of poor hot water trickling from taps. Went back the next morning, nothing wrong all working fine. Got another call the following evening, no hot water. I went round immediatley, no hot water. Found out that when everyone in the road comes home from work and runs a bath :etc, this house is on the end of the supply and gets short change on the water supply. An other lesson taught for someone who always tried to do the job to the book. Customer was great about it when I explained and an alternative solution was put in place.

 

[yorkieplumber]

22mm pipe incoming water main needed for unvented cylinders which a 1933 semi house probably will not have , you can get the waterboard to upgrade incoming water main (they will charge) or Viessmann have come out with a new unit which only requires 15mm incoming main it is called a Viessmann 222-F combi it has a cylinder underneath and comes in 2 sizes, check it out, i know its a bit late now but your installer should have known a ordinary combi is no good for your hot water demands, like Reg Man says unvented cylinder good but in coming mains water needs checking out, hope this helps,

Steve.

 

[fuzzy]

unvented wud be good, i was trying to think of alternative that would save money

 

[Plucky]

If you need a proper plumber to come and sort it out for you then give me a shout on here.

I am in the Brighton area