Worcester Combi Junior 28 i

[NGUY]

We are thinking of installing a new Worcester Combi Junior 28i boiler and were told that we may have problem with water pressure. Howver, our boiler fitter said that there should not be so long as we have our pipe work reconfrigured. Does any know whether it is true of what our boiler fitter said. Also what is the difference between a Combi boiler and a Condensing Combi boiler

Many thanks
Mrs Nguy

 

[bripl]

28i jnr is worc entry level combi gives approx 10litres hot water with 35 degree temp rise nice little boiler.for best results hw should be reran in 15mm pipe connecting to existing 22mm will give probs at the bath with temp of hw.worc do a 24i but most fit the28i.condensing boilers reuse the latent heat of the flue gases to increase the effiency.greenstar is worc condenser nice boiler but expensive,have fitted lots of jnr only had probs with one worc out same day changed part never been back,hope this is of some help.

 

[bripl]

sorry i should of asked has your installer measured water pressure/flow at various times to check suitability for a combi, boiler requires 22mm gas supply.i assume you are using a corgi reg installer to satisfy legal req/warranty.

 

[croydoncorgi]

Assume a Combi boiler needs 22mm GAS supply pipe. This is because all combis use a LOT of gas when doing hot water, which a 15mm pipe cannot supply.

There is a lot of urban myth about HOT WATER pipe sizing. IDEALLY, for most small combis, there should be 15mm pipe to all the outlets. Even so, a small combi will NOT be able to drive a sensible volume out of more than one tap at a time. The water will be flowing through the boiler too fast to get hot! Larger/ storage-type combis (spec'd for at least 15 litres/minute) will drive 2 taps or 1 shower plus 1 tap without water going cold.

If a conventional system with 22mm pipes to the bath taps is converted to a combi, the volume of water coming out of a full-on three-quarter inch hot tap may be more than the boiler can manage - hence cool or cold water. Reduce the flow through the tap and the water will heat up. The installer may put some sort of restriction in the pipe (eg. a half-closed Ball-o-fix) to limit the flow and ensure that the water comes out hot. Another consequence of 22mm pipes is that there will be a longer delay between opening the tap and boiler lighting, before hot water actually arrives. It's not worth tearing a bathroom apart to change 22mm pipes to 15mm just to correct this non-fault.

 

[PEDANTICVINDICTIVEMAN]

Surely the boiler will only let through it's maximum flow rate regardless, if not the ballofix idea seems best.