Combi Boiler / poor pressure

[brucej]

On the advice of British Gas we recently had a new Worcester Bosch

28CDi combination boiler installed in our loft space (previously had a backboiler+gas fire in lounge). unfortunately this does not work during times of high demand, due to problems with low pressure in our area. We are currently having our mains supply replaced and separated from our neigbours, but I'm not holding much hope of this improving things, as the problem seems to be affecting most people in our area.

British Gas have recommended the next step being to install a hot+cold water tank, and a timer. I am reluctant to use this as an option since this will remove all the advantages of a combi boiler ie space saving and hot water available at any time of day.

I have seen an article in a newspaper where they recommend a pumped supply from a cold water tank to the combi boiler which can be set to an appropriate setting eg 1.5bar. This would seem to avoid the need for a hot water cylinder, and continue allowing hot water on demand at any time of day.

I don't seem to be able to find much info on such a system... does anyone know where I can find it?

thanks Bruce

[IMM]

Did BG fit it? If they did then they should have tested the mains pressure. For low pressures the best are the Ferroli's, with the lowest being 0.1 bar. Get BG to replace the combi as they have F***** up big time, that is if they have fitted it of course. If they did not fit it, then get in touch with the people who did.

Cold water storage tank or cylinder?

You can fit a 50 gallon poly tank and have a normal "one sided" power shower type pump off this suplying the combi. Or a two sided, and have the combi suppy off one side and the other cold water oulets off the other. Stuart Turner can supply pumps just for this use.

Wait until the new mains pipe is fitted. Have a 22mm dedicated cold water pipe all the way to the combi and only full-bore valves in this line. Do not tee off it for any other cold supply. That may do it without pumps and tanks.

If BG fitted it.,they should pay for the tank in the loft if one is needed. They should test the mains supply. No one in their right mind would fit a combi that requires a high mains operating pressure in a low pressure district.

[Niel A. Farrow]

Would the combi have to be moved to the first floor (I'm assuming a first floor bathroom) in order for the cold tank to provide an adequate head (pressure) of water? Neil

[Mike Hibbert]

Not in my case, I have the combi in the integral garage and I want to build a shower room also on the ground floor. This sounds like a great solution to me, has anyone else done this and does it work well? I take it that drinking water wouldnt have to go through the combi (and therefore plastic tank)?

[IMM]

No.

Yes. But it is best to have the cold under pressure too as when you have a mixers, especially shower mixers, pressure is equal on hot and cold so a nice mix and good adjustment.

A hot and cold two ended pump will automatically switch off and on, so no need for a timer.

See the makers info. they will give you min and max cold water inlet pressures. they differ from make to make.

[IMM]

Yes.

Correct.

Yes. 80 gallons if supplying hot water only as I am assuming in low periods the cold water mains will be just a trickle (a bath is approx 100 gals at

43C). 100 galls if doing hot and cold. Make it 100 galls plus if 2 bathrooms and all cold off the poly tank.

[Mike Hibbert]

Ok, sorry to keep asking question, but I want to make sure I have this straight in my head.

I have checked the info and the combi will accept a cold water input of up to 10 bar, so I could get a 3 bar pump and a 50 gallon cold water tank and push the water from the tank through the combi!? This sounds like a great plan, but what about drinking water? Would that be from the tank or from the mains? Would I have to split the two somehow?

Thanks in advance.

Mike

>

[Mike Hibbert]

I saw your other reply, thanks a lot!

Mike

[IMM]

Correct. But if the mains is so bad the tank may not fill up fast enough up as you are drawing off. A bath is approx 100 litres, so get yourself at least a 100 litre poly tank (note litres now). If having a bathroom and a shower then go higher. The one pump will do both hot and cold with an impeller either end of the motor, as is a normal power shower pump.

Direct off the mains.

Yes.

When the mains is uprated in the area the tank and pump can be disconnected. If you have a date when the water company is to put the pressure right, then this tank is obviously a temporary thing, and a cheapish power shower pump from B&Q will do for a couple of years or so. Get one with a good guarantee.

Stuart Turner make v good, but expensive pumps.

[IMM]

An advantage of the poly tanks and pump is that if it is fitted say over an airing cupboard, I assume you still have one and heat it, without insulation under the tank, it will act as a pre-heater for the incoming water, so giving a pretty constant operation.

[Ed Sirett]

Our road is at the end of the pipe being the last road in this area in LB Barnet, and thus the end of the 3 Valleys supply area. The people at the top of the road have poor pressure. We had zero pressure for 2 hours the other morning. You don't happen to live in N10 by any chance?

[Mike Hibbert]

Hi,

Thanks for all your help on this one, I understand the principle now and will probably have a go myself. I think that I will retain mains water to the toilets and have pumped hot and cold to all the sinks, baths and shower (except the kitchen cold tap). My only last question would be the washing machine/dishwasher they have a hot feed and therefore it would have to be a pumped feed wouldn't it? Is that a problem?

Again, thanks a lot for your help!

Mike

[IMM]

No.

pleasure.