Can you have a storage tank with a condensing boiler?

ey143 · 27 Nov 2015

My parents house had a combi boiler fitted in 1995 and we got rid of the 1970s water tank we had in the property as part of a house renovation and loft extension. That boiler was replaced with a Worcester Bosch 28CDi Junior condensing boiler about 5 years ago. We now plan to add a downstairs bedroom for my elderly parents.

Given the water demand has now changed considerably since the house was a 3 bed and soon to be a 5 bed and with 3 bathrooms rather than the one, is it possible to have some sort of small hot water thank (say 100 litres), stored somewhere but connect to the existing condensing boiler? I'm trying to avoid having to get a new boiler when the old one is perfectly fine.

If we have good mains pressure (blue mains plastic pipe), can I assume that when someone is showering, it will not go bone dry if the kitchen tap is opened or indeed if someone else decides to have a shower too?

muggles · 27 Nov 2015

A blue plastic mains pipe is no guarantee of good flow/pressure, but you can certainly add a hot water cylinder to your existing system

cross thread · 27 Nov 2015

yes you can,get somebody in to check mains pressure /flow rate and have a small unvented cylinder installed

Agile · 27 Nov 2015

You need to have the dynamic flow rate from the mains measured. It may be marginal for two showers or outlets.

You can have a hot water cylinder with any kind of boiler.

But unless the hot water use is going to be very high its often better to just have a small electrically heated cylinder.

Tony

ey143 · 27 Nov 2015

Trying to avoid heating water electrically at any cost.

What would happen to a combi boiler when a tap is opened (if you have a cylinder) - it no longer activates?

Agile · 27 Nov 2015

A combi boiler provides hot water as a priority.

So the central heating and cylinder heating is interrupted until the hot water demand ceases.

But the cylinder reheating takes less than 30 minutes and would normally be timed to daily reheat early in the morning.

Electrically heating is by far the simplest so why are you so against it.

How many times a day will this cylinder need reheating? Better what is the volume of hot water it needs to supply daily?

These two elderly parents are going to have a whale of a time in a three bathroom and five bedroom house!

Tony

cross thread · 27 Nov 2015

you leave some taps supplied by the combi and others off the new cylinder,who ever fits will advise on best set up

ey143 · 2 Dec 2015

Agile said:
A combi boiler provides hot water as a priority.

So the central heating and cylinder heating is interrupted until the hot water demand ceases.

But the cylinder reheating takes less than 30 minutes and would normally be timed to daily reheat early in the morning.

Electrically heating is by far the simplest so why are you so against it.

How many times a day will this cylinder need reheating? Better what is the volume of hot water it needs to supply daily?

These two elderly parents are going to have a whale of a time in a three bathroom and five bedroom house!

Tony

Elderly parents with other adult family members in the household, so house is full.
ok I didn't know you can split the use of a combi to do both hot water on demand and a storage tank. No problem then for a Worcester Bosch 28 CDi Junior?

Re electrical heating, as mentioned I thought cost would be the bigger issue. Can you pls point me to some example electric water heaters. Could this be used for a bedroom that is far away from others and save having to install a secondary return value?

St0rmer66 · 2 Dec 2015

The boiler does not know whether it's heating radiators or a cylinder, it just provides heat as demanded. The heating and cylinder would need separate motorised valves and thermostats so that it knows when to stop and start heating each one that's all.

ey143 · 2 Dec 2015

So if the new (5th) bedroom is going to be a newly built after knocking down a garage, and we dont have any enough pressure to run kitchen taps together with a shower or two showers at the same time, is it perhaps better to put an electric shower in the new ground floor bedroom. What can we use for electric instant hot taps (just a thought at this stage)?

St0rmer66 · 2 Dec 2015

Any outlet still needs a water feed, no matter what it's heated by (gas or electric) so having electric won't help the poor flow rate.

JohnD · 2 Dec 2015

Energy from electricity now costs four times as much as energy from gas.

Can anyone not see a reason for avoiding an electric heater?

Nige F · 2 Dec 2015

Have you heard of Economy 7

a distant bedroom with a small elec. stored water heater and timeswitch would be viable Vs. the amount of water in a deadleg - How come they burn gas to make elec. We could go back to gas lighting and save a fortune.

dilalio · 2 Dec 2015

ey143 said:
So if the new (5th) bedroom is going to be a newly built after knocking down a garage, and we dont have any enough pressure to run kitchen taps together with a shower or two showers at the same time, is it perhaps better to put an electric shower in the new ground floor bedroom. What can we use for electric instant hot taps (just a thought at this stage)?

As already mentioned in this thread...

Before you begin pondering which way to go, you need to ascertain what "working pressure" and "dynamic flow" you have available to you.

For pressure you need a gauge which are a few quid to buy, along with flexi to connect to outside tap or washing machine feed. Check static pressure first (no outlets open except one to gauge). Then open kitchen cold and take reading again at outlet to gauge (working pressure).

For flow: use a measuring jug and bucket(s). Over a minute, fill bucket(s) from cold tap and then use jug to count how many litres you got. Repeat with kitchen tap open to get your dynamic flow. This'll give you your litres/minute.

If possible, repeat these tests upstairs at the shower hose or bath taps, as height affects your mains pressure.

Then you can consider options!

Agile · 2 Dec 2015

Instead of an electric shower I would choose a small electrically heated cylinder to supply shower and basin.

Certainly electricity is about three times the cost of gas but for just one room that's not going to be much more expensive.

The alternative is to have flow and return pipes from the boiler and controls to cover its operation and the extra cost and providing a routing would be a lot of cost and bother compared with a simple electric immersion heater.

Tony

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Can you have a storage tank with a condensing boiler?

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