Condensing boiler with hot water tank?!

BigAunty

Baffled by heating and hot water set-up in new house. Energy bills v. high.

The property has a modern Worcester Bosch Greenstar 40 cdi conventional condensing boiler and just one bathroom.

Had a WB Greenstar in a previous property with 2 bathrooms which gave me instant hot water for the mixer tap shower and all kitchen and both bathroom taps, low bills.

For some reason, the previous owners got it rigged it up to a hot water tank above the boiler which operates on a timer (shares a thermostat with heating but allows a separate timing schedule to be set for the water).

This means there is no hot water on demand, it has to be set on a timer to fill the tank. Half an hour on the timer barely heats it up sufficiently to do the washing up. A long time on the timer barely fills up a bath. Sometimes I can't get any water at all out of the downstairs kitchen tap or just a trickle.

There is a separate 'water heater' wall switch in the kitchen that doesn't seem to have any function as far as I can tell.

Any reason why someone would rig up a modern boiler with an old fashioned hot water tank? (Lack of water or gas pressure? ex owners were perhaps big users of hot water and tank provides more capacity - there were twice as many family members when they had it installed compared to me?)

What are my options? Get a plumber to strip out the tank and put the hot water back on instant?

I just find it bizarre to have a relatively modern boiler yet have the kind of primitive and expensive access to hot water I recollect from living in social housing some decades ago....

thanks

Mankysteve

Hot water tanks are not old fashioned.

All new boilers have to be condensing. A condensing boiler can either be a combi boiler(ie instant hot water like what you had) or hot water tank(what you have now).

There are advantages and disadvantages to both systems. Which I wont go into here but basically if you've got a lot of bathrooms you need a hot water tank.

I would suspect that what happened in this case is the old boiler died and the old owners has just swapped over a modern boiler without the cost of converting to a combi system/new tank.

Is the hot water tank an old copper uninsulated one?

Basically you need to the hot water heating cycle for much longer to get a full tank as we've got a modern well insulated tank ours is never switched off as it makes so little difference in Gas usage.

It does sound like something up with your system though as should not be getting low pressure at your taps, even if there's no hot water in there. Personally if its old tank I would swap it out with a more modern insulated tank and get a plumber to find the pressure fault.

To switch a combi system you will need an entire new boiler.

BigAunty

It's an insulated copper tank. There's only 1 bathroom.

I like your theory that the previous owners elected to retain their tank when they got a new boiler.

It's a shame to have to spend 2-3k on a new boiler to get instant running water when there's nothing defective about the boiler itself.

I've had years of instant hot water and hate the way I now have to plan a bath and wait until the timer cycle has ended before doing the washing up - I find it 'old fashioned' because that's what I endured in social housing decades ago.

I will switch on the hot water heating cycle as you have suggested for longer and monitor gas usage. I assumed that a longer cycle would make the energy consumption sky-rocket but perhaps that's due to the childhood fear instilled in me about ruinous costs of hot water tanks by my father....

I moved to a smaller property (4 less rooms to heat), better insulated (as it's fully double glazed) and with a condensing boiler versus an antique combi boiler at my last place. With barely a bath since I've been here, the energy consumption is much higher, gas and electric.

It doesn't help that the thermostat has been hardwired into a drafty hallway which means a couple of the main rooms get overly stuffy so I will look into getting a wireless one so I can put it in the living room.

thanks for your advice.

Mankysteve

Also some people don't like combi as they are not as reliable as hot water tanks.

Your thermostat will only control the radiators it won't affect the temp of the tap supply.

If you haven't already got them have trv values installed on all your rads it will help to stop some rooms getting silly hoter than others.

Better_Days

Mankysteve wrote: »

If you haven't already got them have trv values installed on all your rads it will help to stop some rooms getting silly hoter than others.

We have a very old boiler and old wired thermostat. When we moved in the heating was basically on or off. We have recently had TRV's fitted (Pegler Yorkshire) and they work very well and much better than the ones we had at our previous property. I have also started fitting programmable TRV's so I can zone upstairs during the day when I don't need the CH on. We also have a HW tank and found during the summer (when CH off) having the HW on an hour in morning and hour in the evening was ample to keep the water in the tank hot.

Actually we have the opposite problem to you OP, our HW is too hot in the winter as we have a gravity HW system with no valve so we can't currently have CH on and HW off.

Is there a difference in wall/loft insulation between your old and new properties which would account for increased fuel usage?

Ectophile

I don't get this idea that you have to "plan to have a bath" with a stored hot water system.

I have an "old fashioned" system - a Worcester Bosch condensing boiler and modern well-insulated tank. The boiler is on a timer, so it heats up a tankful of water every morning. That normally lasts me a day. I don't have to do anything or plan anything.

If I needed more hot water, I could just set the timer to come on twice a day instead. There's a thermostat on the tank, so it wouldn't matter if I set the timer for too long or too often - the boiler just shuts off when the tank is up to temperature.

daveyjp

No surprise your heating bill is high. How many dozen radiators are being served from a 40kw boiler? That is huge for a conventional system.

Plumber90

I have my hot water come on a couple of hours in the morning and a couple of hours in the evening and it works fine for us,.

southcoastrgi

daveyjp wrote: »

No surprise your heating bill is high. How many dozen radiators are being served from a 40kw boiler? That is huge for a conventional system.

as above, where do you live Buck House ?

Mankysteve

southcoastrgi wrote: »

as above, where do you live Buck House ?

The op said they downsized by 4 room and now only have one bathroom. That me susgests at most a three bed people on here need toread post better.

BigAunty

It's a 3 bed, 1 bathroom, 2 reception room terrace with 2 occupants. The insulation should be the same or better than my previous property as it has lower ceilings, similar type of build/era, more double glazing, insulated roof, better general draft proofing.

As well as putting on the water timer for longer, getting a plumber out to identify why the hot tap in the kitchen sometimes runs dry or trickles, and getting a wireless heating thermostat so it can take readings in a regular room rather than a draft hallway, I will look into zoned TRVs.

I have already performed an energy comparison and switched provider to reduce my bills. Now I am tackling consumption.

Just had a count. There's only 5 radiators in regular use whereas my last place had 7/8 in use. In this current property, there are 9 radiators installed. Some of the rooms here have two radiators but the second radiators don't have working valves to switch them on, there's no rad in the kitchen, and we keep a couple of lesser used rooms unheated.

I had a quick browse of the WB website and it does seem that this size of boiler suits larger properties. I haven't gone through the complex calculations to identify if it's overspecced for the property though. I did unearth this rule of thumb guidance though.

"Generally speaking if you opt for a combi and you live in an apartment or a terraced house with up to 10 average size radiators and 1 bathroom, you will require a boiler with an output of between 24-27kW. A medium to large 3-4 bed house will require a combi boiler with a higher output of at least 28kW. For a property with one bathroom and up to three bedrooms, a regular or system boiler of 12-15kW will do the job. A larger 4 or 5 bed property with one bathroom and an ensuite shower room will require a boiler with a higher output, typically 30kW."

Thanks for the advice.