Older house heating/hot water system questions

[tommy8884]

Hello,

We are currently in the process of moving house. The house is a 1967 build and seems to have a traditional gravity fed hot water and heating system running on an non condensing bolder (Potterton Netaheat). We are trying to get an idea on how expensive this system will be to run, how it will meet our demands, how I can put programmers in (it just runs of non programmable thermostats). Also, ideally, budget allowing we would increase the tank size and fit a new condensing system boiler or combi (also to sack off the tanks in the loft in a new system). However, for the life of me, I cant work the configuration out. We don't have permanent access to the building yet, so I only have a few pics.

The boiler only has water 2 pipes (and one gas). I assume these to be flow and flow return for the central heating, but also the hot water???? I can see no mains water entering the boiler.

Annotation 2021-01-10 151356

• tommy8884
• 10 Jan 2021

Just to the top left of the boiler is, what I assume to be, the hot water control. the wire seems to trace back to a valve on the other wall.

On the opposite wall to the boiler we can see the pipes, pumps and valves

PXL_20210108_122255301

• tommy8884
• 10 Jan 2021

Annotation 2021-01-10 151506

• tommy8884
• 10 Jan 2021

Now we know there are at least 2 heating circuits controlled by 2 room thermostats (dumb). I have only been able to find 2 thermostats and the control by the boiler. In the configuration we can see 3 valves (T1, T2 and HW). 2 of these are for the heating circuits (T1 and T2). Q: could the 3rd (HW)be for the hot water????? Ive never heard of a system where the hot water and heating runs off the same pump controlled by but valves? I can only assume that the mains water must be going to the loft and feeding the system from there?

For info here is a really poor shot of the tiny hot water tank and of the cold water tank in the loft. Sorry for the terrible shots that give little info, by this point the estate agent thought i was very strange.

Lastly, here is a diagram that I *think* represents the system we have (minus the second heating circuit). Would you agree?

 

[ianmcd]

you have a standard open vented system, nothing special about it, same as thousands of other homes , and stop calling it a gravity system, it isnt it is S+ open vented system, a gravity system is something else

 

[tommy8884]

thank you for the reply. Noted i will call it the correct thing now i know.

If we were looking to replace the boiler with a condenser and increase the tank size, would it be best to leave this as a vented system or install an unvented tank? I'd be looking to future proof the system to possibly allow to be used with heat pump, or solar in the future, so whichever water tank would ideally be future proof for this. Also ideally to clear the loft of tanks, I assume unvented mains fed is the only option for the hot water and also the boiler would need mains water to pressurise the heating when needed?

 

[HERTS P&D]

by this point the estate agent thought i was very strange.

You are worrying too much, just move in and take each day at a time making a list of what work needs to be done weather it be building/decorating work and upgrades. Also note that a combi will be no good if you want to have a second bathroom eg loft conversion.

Andy

 

[tommy8884]

Thanks Andy. Agree on the combi, although we have one in our current house without too much issue, it kills the shower if any other tap is on. I have 2 daughters and a wife and there is no way the current tank in suite will do even 1 shower, let alone 4! So getting a bigger tank will be high on the priority list when we move. Also changing to a condenser will be high on the list with the refurb for efficiency reasons. Clearing the loft of those tanks so we can store stuff (we have a loft full now), would also be a priority.

I'm thinking a condenser boiler with a new unvented tank would be the way to go

 

[JohnD]

the colour of the cylinder (it is not a tank) suggests you are in Ireland, is that right?

The Netaheat is a very good boiler, and if looked after by someone who knows them, should be kept until it becomes irrepairable. The cost of change will not be repaid by improvements in efficiency, and the Netaheat may well last longer than a new boiler.

You could reasonably fit a larger hot water cylinder. A bath takes round about 100 litres and a modern cylinder will reheat from cold in around half an hour. It is modern practice to have a cylinder that holds about two bath's worth, so you will not run out even if somebody else is doing lots of washing up or running another shower or bath at around the same time.

If you can estimate the actual dimensions of your cylinder we can estimate its capacity.

If you have sufficient incoming water flow to the house from the mains (around 20litres per minute) then you would get the best performance from an unvented cylinder. This may mean replacing some pipes and valves with larger bore to improve the flow.

 

[flameport]

If we were looking to replace the boiler with a condenser

All new boilers are condensing, so when the existing one needs replacing, it will inevitably be a condensing type.

There is no point in replacing a working boiler. A new one will use less gas, but it will be a decade or more before those savings even cover the cost of the new boiler, by which time the 'new' boiler will be end of life and need replacing again.

Far greater savings can be had for a fraction of the cost of a boiler by replacing the controls with modern ones, such as programmable thermostats.

would it be best to leave this as a vented system or install an unvented tank?

Two different things.
An open vent vs sealed is totally unrelated to the hot water cylinder.

Your existing system is open vent. A new one would normally be a sealed system. One can be converted to the other fairly easily. New ones are usually sealed, and that gets rid of the small cold water tank in the loft. Older systems may leak if converted as the operating pressure is higher.

The hot water cylinder is either supplied from a large cold water tank in the loft (what's there now), or it can be supplied direct from the cold mains water supply, which is an unvented hot water cylinder.
Loft storage tank = can be used on any water supply, but pressure at the hot outlets will be low as it relies on the height of the cold water storage relative to the outlets. Pump(s) can be fitted to provide a higher pressure for showers and/or hot taps.
Unvented = higher pressure, but can only be installed if the incoming cold water supply has sufficient pressure and flow. Doesn't require any cold water storage in the loft, but that's only relevant if you intend to convert the whole loft into a living space.

, I assume unvented mains fed is the only option for the hot water and also the boiler would need mains water to pressurise the heating when needed?

It's one option, and a good one if the incoming water supply is suitable. If the water supply isn't suitable then it will be totally useless.

The boiler doesn't need mains water, the system can be filled / pressurised from any convenient location on the pipework - if the system is converted to sealed, which would typically only be done if a new boiler was installed.
Replacing the hot water cylinder is unrelated to installing a new boiler.
One can be replaced without the other.

 

[tommy8884]

thanks for the reply. Actually we are in England.

Last question (i think). Is it possible to put an unvented tank in this system without making alterations to the heating system and without replacing the boiler? Thinking about it, I would still need the expansion tank in the loft for the heating system so wouldn't gain the space in the loft.

 

[tommy8884]

All new boilers are condensing, so when the existing one needs replacing, it will inevitably be a condensing type.

There is no point in replacing a working boiler. A new one will use less gas, but it will be a decade or more before those savings even cover the cost of the new boiler, by which time the 'new' boiler will be end of life and need replacing again.

Far greater savings can be had for a fraction of the cost of a boiler by replacing the controls with modern ones, such as programmable thermostats.


Two different things.
An open vent vs sealed is totally unrelated to the hot water cylinder.

Your existing system is open vent. A new one would normally be a sealed system. One can be converted to the other fairly easily. New ones are usually sealed, and that gets rid of the small cold water tank in the loft. Older systems may leak if converted as the operating pressure is higher.

The hot water cylinder is either supplied from a large cold water tank in the loft (what's there now), or it can be supplied direct from the cold mains water supply, which is an unvented hot water cylinder.
Loft storage tank = can be used on any water supply, but pressure at the hot outlets will be low as it relies on the height of the cold water storage relative to the outlets. Pump(s) can be fitted to provide a higher pressure for showers and/or hot taps.
Unvented = higher pressure, but can only be installed if the incoming cold water supply has sufficient pressure and flow. Doesn't require any cold water storage in the loft, but that's only relevant if you intend to convert the whole loft into a living space.


It's one option, and a good one if the incoming water supply is suitable. If the water supply isn't suitable then it will be totally useless.

The boiler doesn't need mains water, the system can be filled / pressurised from any convenient location on the pipework - if the system is converted to sealed, which would typically only be done if a new boiler was installed.
Replacing the hot water cylinder is unrelated to installing a new boiler.
One can be replaced without the other.

Very informative. Thanks so much for the reply. I'm taking my existing smart controls from my current house (i have 2 as its a new build with 2 heating circuits). Those can also do hot water although don't have to right now as we have a combi.

The only reason I'm looking to replace a working boiler so soon, is to utilise the green deal grant which is only valid until the ned of march, so my savings could be realised much sooner.