Combi boiler for a 4 bathroom house - Advice please

[Howsie]

Unless pipework is horrific and house has a 28mm 40m run to bathroom I wouldn't waste wonga on pump. Spend more in electricity and replacement pumps than u will save! Lagg pipes well, remove oversized and unused legs make system as "sporty" possible

But some people don't like waiting for their hot water never mind the wastage.

 

[timmyjane]

The ACV unit may well provide the flow rates required but you need to look at the plumbing system as a whole. If you've got long pipe runs to the showers you need to be looking at a secondary circulation system for the hot water to minimise the wait for hot water. I'm not familiar with the ACV unit and it may have the facility for a secondary return but there is no point in using a space saving option if it doesn't provide the performance you require.

How does an unvented boiler get around this? Situation could be unvented horizontal cylinder in the loft (Boiler likely ground floor as this is where gas inlets are) with a shower on the ground floor and loft. Same length of run, for either system. Would a secondary system be needed in both situations. Very reluctant to put anything 1st floor other than pipe runs.

Note room heights around 230 cm, ground and 1st floor at the mo. Max house footprint 10 metres square. Does this help. Absolute max pipe run I would envisage could be 13 metres long?

 

[timmyjane]

Queries

Heatmaster 85tc, out I think on cost alone, along with potential meter problems etc, to get full potential of it may have to upgrade pipework in the house, so too much to consider.

Still weighing pros and cons of 35/45 tc unit. easier connection all round. Still base cost will be more than decent sized unvented cylinder and system boiler. Back down to a lower flow rate with this one but still ok I think.

1. price consideration, which is going to cost me less to run over 5 years.

300 lt with great boiler say 30 - 40kw. Guess I'd have to heat a tank in the morning (majority used 1st thing), need a little during the day and say half a tank in the evening. It has to be at optimum heat between. 6 - 8.30 in morning and 5.30 - 8.30 in evening. Presume would need Boiler on heating 3 hrs a day.

The 45tc, 100 litre tank combi system. So still need to pre heat 100 litres in morning (1/2 hour), ready for morning rush. But rest could be on demand say another hour. 1.5 hrs a day. I have no idea how much gas is!

Then theres the central heating, which I presume would be same for both? On this basis think heating cost overall would be half, but may have that totally wrong.

2. One thing bothering me about both systems, seems both would be subject to a certain amount of limited pressure in the system and the same pipe sizes delivering the water throughout the house. Is there any reason from a pressure point of view one would be better than the other, remembering I want 3 showers running at exactly same time and rather it wasn't 3 dribbles? Question is about pressure rather than heat now for feel either system could deliver the hot water.

Guidance appreciated:confused5:

 

[SafeGasInstall]

any run over 12m must have a secondary return

 

[SafeGasInstall]

pressure wil not be a problem and running 3 showers at the same time from UHWC
You can pre set HW to be heated 30 to 45min before the demand and during the demand time

 

[Howsie]

Get a decent plumber in. They will cover all of this with you before you next birthday.

 

[timmyjane]

UHWC? would both systems (The combi with hot water tank, and the cylinder with standard boiler) be the same in terms of pressure delivered to showers.

 

[SafeGasInstall]

UHWC? would both systems (The combi with hot water tank, and the cylinder with standard boiler) be the same in terms of pressure delivered to showers.

sorry I dont understand that .
As Howsie said , time for a descent plumber to design and install , and not before your next birthday but before this Xmas

 

[timmyjane]

Would like to, but kinda want to have a good idea about what I want before the plumber I choose just suggests his favourite system, which he gets a discount for at his local yard. I'm an untrusting sort. Did put a request for a plumber on this forum, waiting for responses.

 

[SafeGasInstall]

where are you timmyjane ?