Mains supplied water heater to supply shower, bathroom sink and kitchen sink.

locky76

I’m helping a mate of mine renovate a property and we’re looking at a mains fed electric water heater for the mixer shower and the kitchen and bathroom sinks.
What lite capacity would this need to be?
Would 100 liters be sufficient?

antoinolachtnai

How will you provide for storage of an adequate amount of water? It sounds like it would be contrary to the building regulations and Irish water regulations to me. I would not do this if it could be avoided.

EdgeCase

You might be better off looking at an instantaneous gas water heater like a combi boiler. Very few electrical systems can reasonably produce enough heat and flow to do tankless.

Sleeper12

EdgeCase wrote:

You might be better off looking at an instantaneous gas water heater like a combi boiler. Very few electrical systems can reasonably produce enough heat and flow to do tankless.

This cannot come off the mains either though. Only to coldest tap in the kitchen can come off the mains. Everything else should come from the cold water tank.

The regulations could be different if op has their own well.

EdgeCase

Sleeper12 wrote: »

This cannot come off the mains either though. Only to coldest tap in the kitchen can come off the mains. Everything else should come from the cold water tank.

The regulations could be different if op has their own well.

Are you sure that's actually in the regulations?
I know two houses in Dublin where it's mains fed.

Also what is the logic of that? Is there something wrong with the water mains in Ireland?

Interesting article in the Engineers Journal:

http://www.engineersjournal.ie/2015/04/07/engineering-waterborne-bacteria-building-water-systems-part-2/

Sleeper12

EdgeCase wrote:

Are you sure that's actually in the regulations? I know two houses in Dublin where it's mains fed.

I'm a plumber. It's definitely the regulations. Connecting a combi boiler to the mains supply is not the correct way to install a combi boiler in Ireland. It plays havoc with showers. Showers require equal cold and hot pressure to work correctly.

One plumbing company told the client that to change the temperature of the shower shed have to get out of the shower & adjust the temperature at the boiler instead. This isn't practical. Most plumbers won't install a combi off the mains supply.

EdgeCase

Surely you provide hot and cold water to a thermostatic valve at the shower?!!

A combi boiler is not intended to operate as the thermostat for a shower, rather be a source of domestic hot water at a steady temp 50-60ºC

antoinolachtnai

If the cold supply is coming from attic tank and hot supply is coming from combi then the thermostatic valve can’t and won’t work correctly. Even a regular mixer tap will hardly work. But this is what often passes for plumbing.

EdgeCase

In the case of that house in Dublin there is no tank. House is mains fed entirely.

What in just surprised at is that the Engineers Journal article above is basically describing cold water storage tanks as a significant health hazard and that they should be avoided where possible, while the plumbers seem to say the opposite.

Sleeper12

EdgeCase wrote:

Surely you provide hot and cold water to a thermostatic valve at the shower?!!

Yes but you can't adjust hot and cold at different pressure at the shower itself.

The correct way to install a combi boiler to take all water from the cold water tank & pump it to the boiler and throughout the house for cold. This gives even hot & cold pressure

1874

Sleeper12 wrote: »

I'm a plumber. It's definitely the regulations. Connecting a combi boiler to the mains supply is not the correct way to install a combi boiler in Ireland. It plays havoc with showers. Showers require equal cold and hot pressure to work correctly.

One plumbing company told the client that to change the temperature of the shower shed have to get out of the shower & adjust the temperature at the boiler instead. This isn't practical. Most plumbers won't install a combi off the mains supply.

When I saw this thread earlier, I knew you could not/should not connect mains supply to a bathroom in Ireland, that said mains does not only go to the cold tap in the kitchen as you mentioned earlier but also to the storage tank (maybe thats obvious to you so you did not mention it).
Im not a plumber, so how else is a combi boiler to be connected?

My understanding is they are connected to the mains supply pressure? and then supply hot water, are you saying they are tank fed?

maybe this isnt the case in Ireland but I thought it was a requirement for combi boilers, Ive seen some in the UK (I know different region/and better water pressure) but it seems to be standard means to connect a combi boiler, otherwise, where is the pressure coming from?
A would not use a combi boiler here, no problem with them in the UK for a small installation.


As for the OP, capacity would depend on demand, electric heating isnt the cheapest form of heating either, what type of property is it?

Sleeper12

EdgeCase wrote:

In the case of that house in Dublin there is no tank. House is mains fed entirely.

Plumber should have installed a tank. Tank can go ground level if there is no attic as it'll be pumped anyway

EdgeCase

Seems to be working absolutely perfectly as is.
Can't see it being changed to a more complex arguably worse system somehow.

All I'd say is Ireland has absolutely weird plumbing by European standards.

Is there something seriously wrong with the specification of the water mains here or something? I'm genuinely curious as to what the logic of this stuff is.

antoinolachtnai

antoinolachtnai wrote: »

If the cold supply is coming from attic tank and hot supply is coming from combi then the thermostatic valve can’t and won’t work correctly. Even a regular mixer tap will hardly work. But this is what often passes for plumbing.

That would be classed as a nonsensical plumbing design and wrong on many levels.

EdgeCase

EdgeCase wrote: »

Seems to be working absolutely perfectly as is.
Can't see it being changed to a more complex arguably worse system somehow.

All I'd say is Ireland has absolutely weird plumbing by European standards.

Is there something seriously wrong with the specification of the water mains here or something? I'm genuinely curious as to what the logic of this stuff is.

I would suggest it’s to do with poor water supply often heating systems don’t work because the incoming supply drops below the required working pressure, combis can put greater strain on the water supply.

OP a lot of times wall hung 100ltr electric stored water heaters would be used.

Sleeper12

1874 wrote:

My understanding is they are connected to the mains supply pressure? and then supply hot water, are you saying they are tank fed?

The correct way to install a combi boiler is to take the cold water for the house from the cold water tank and run it to a pump. Some prefer to run separate supply bypassing the pump for the toilet. This cuts out pump noise in the middle of the night. The water suppling the combi boiler should come from the cold water tank, to the pump and onto the boiler. This way hot and cold water has equal pressure and you meet building regulations.

Sleeper12

Sleeper12 wrote: »

The correct way to install a combi boiler is to take the cold water for the house from the cold water tank and run it to a pump. Some prefer to run separate supply bypassing the pump for the toilet. This cuts out pump noise in the middle of the night. The water suppling the combi boiler should come from the cold water tank, to the pump and onto the boiler. This way hot and cold water has equal pressure and you meet building regulations.

No combi boilers are purely designed to be mains fed and as such the main selling point is constant hot water, the pump and break tank add on is a local response to a local requirement which leaves a restriction on hot water performance.

Sleeper12

gary71 wrote:

No combi boilers are purely designed to be mains fed the break and as such the main selling point is constant hot water, the pump and break tank add on is a local response to a local requirement which leaves a restriction on hot water performance.

Of course you are totally correct. What I should have said was the correct way to install one in Ireland is with a water tank rather than off the mains

antoinolachtnai

It also undermines the economic case. The economic benefit of the combi boiler comes in large part from not needing a tank or a pump. When you need a tank and a pump then there isn’t that much benefit anymore.

Sleeper12

Sleeper12 wrote: »

Of course you are totally correct. What I should have said was the correct way to install one in Ireland is with a water tank rather than off the mains

We’re both right:D

antoinolachtnai

antoinolachtnai wrote: »

It also undermines the economic case. The economic benefit of the combi boiler comes in large part from not needing a tank or a pump. When you need a tank and a pump then there isn’t that much benefit anymore.

Also the space the stored cold water takes up can be the same as the space the hot water cylinder took up killing the usual space saving you get fitting a combi.

Sleeper12

gary71 wrote:

We’re both right

I've never done gas & haven't put a heating system in well over 20 years. I bow to your knowledge every time.

Sleeper12

Sleeper12 wrote: »

I've never done gas & haven't put a heating system in well over 20 years. I bow to your knowledge every time.

Jesus...don’t be listening to me

Flyingsnowball

I never agreed with these boilers in Ireland. The reliability of mains pressure rules them out.

I think it’s lazy plumbing recommending them. Same price but a bit less work as far as I’m concerned.

I want a few litres of water in my attic if the mains is stopped for a few hours.

Flyingsnowball

Flyingsnowball wrote: »

I never agreed with these boilers in Ireland. The reliability of mains pressure rules them out.

I think it’s lazy plumbing recommending them. Same price but a bit less work as far as I’m concerned.

I want a few litres of water in my attic if the mains is stopped for a few hours.

There are plenty of areas with decent mains pressure also combis work perfectly well, every appliance when fitted incorrectly causes mayhem and your few liters does you little good if you don’t have your tank high enough.

Flyingsnowball

gary71 wrote: »

There are plenty of areas with decent mains pressure also combis work perfectly well, every appliance when fitted incorrectly causes mayhem and your few liters does you little good if you don’t have your tank high enough.

My tanks in the attic. Mains pressure could be atmospheric at certain hours and 3 bar at others. This is in Dublin not carrickfergus.

To have a combi I’d need attic storage tank, booster pump to combi to take it up to minimum level the combi needs if not getting it,
There are new instantaneous heat exchangers on the market now. I’ve fitted a few in bigger set ups than houses and they are amazing.
Work like hot water cylinders but way better.
I’d say they are the way forward.

Flyingsnowball

Flyingsnowball wrote: »

My tanks in the attic. Mains pressure could be atmospheric at certain hours and 3 bar at others. This is in Dublin not carrickfergus.

To have a combi I’d need attic storage tank, booster pump to combi to take it up to minimum level the combi needs if not getting it,
There are new instantaneous heat exchangers on the market now. I’ve fitted a few in bigger set ups than houses and they are amazing.
Work like hot water cylinders but way better.
I’d say they are the way forward.

You don’t use a putter to tee off, you look at the requirements of a install and use the best solution that meets the given requirements be it new technology or old.

OP another thing that maybe thought about is holding your stored hot water at higher temperatures and useing a temperature control on the draw off to make the hot water go further reducing the amount of hot water required to be stored.

Dtp1979

Combis need high constant water pressure to work. They don’t care, and don’t know, if it’s coming from a mains supply in the UK, or a pumped supply in Ireland. All they want is the water.
Ideally, a tank and pump should be installed outside in a shed to reduce the noise. Sometimes that’s not feasible so we use the attic tank. A simple invention called a lid, will stop contamination.
Again, a combi will only work well where there’s usually low hot water demand, In places where there’s 1 or 2 bathrooms max. They are more economic than you heating a 150l cylinder and maybe only using 60L of that water. Intergas have only hell of a combi on the market.

Dtp1979

Dtp1979 wrote: »

Combis need high constant water pressure to work. They don’t care, and don’t know, if it’s coming from a mains supply in the UK, or a pumped supply in Ireland. All they want is the water.
Ideally, a tank and pump should be installed outside in a shed to reduce the noise. Sometimes that’s not feasible so we use the attic tank. A simple invention called a lid, will stop contamination.
Again, a combi will only work well where there’s usually low hot water demand, In places where there’s 1 or 2 bathrooms max. They are more economic than you heating a 150l cylinder and maybe only using 60L of that water. Intergas have only hell of a combi on the market.

Combis don’t care very true but pumped hot water adds difficulties to a installation that many installers don’t take in to account which are not present with mains fed combis, the manufacturers instructions are mains fed based and not tank fed.

Combis when fitted with the home owners requirements adhered too will work perfectly no matter what path is used to get to the top of the mountain.

Flyingsnowball

gary71 wrote: »

Combis don’t care very true but pumped hot water adds difficulties to a installation that many installers don’t take in to account which are not present with mains fed combis, the manufacturers instructions are mains fed based and not tank fed.

Combis when fitted with the home owners requirements adhered too will work perfectly no matter what path is used to get to the top of the mountain.

What would such difficulties be?

Flyingsnowball

Flyingsnowball wrote: »

What would such difficulties be?

The main one is Incorrectly sized stored cold water restricting the amount of hot water available, the positioning of the pump and noise issues is another one,
different hot and cold tap pressures around the house can also make things funky.

I’m sure there’s a few more but I’m not anti tank/pump fed combis im anti bad installer, when a appliance is fitted badly it doesn’t help anyone in the industry. The requirements of the homeowner or the fitting requirements of the combi are rarely thought of when the boilers are being fitted but when they are fitted correctly their perfect.

jhenno78

This thread is a great example of how we're so used to having crap infrastructure that we don't even realise how crap it is.

Anyway, sounds like OP should try and measure mains pressure/flow rate. You could argue that pumped isn't even such a great idea unless the mains flow-rate exceeds the pumped, or you have a really massive tank.
Re: hot vs cold pumped supplies - what would the reason be for not putting the pump straight after the tank, totally mimicking a mains-pressurised system (bar kitchen tap).

Dtp1979

gary71 wrote: »

The main one is Incorrectly sized stored cold water restricting the amount of hot water available, the positioning of the pump and noise issues is another one,
different hot and cold tap pressures around the house can also make things funky.

I’m sure there’s a few more but I’m not anti tank/pump fed combis im anti bad installer, when a appliance is fitted badly it doesn’t help anyone in the industry. The requirements of the homeowner or the fitting requirements of the combi are rarely thought of when the boilers are being fitted but when they are fitted correctly their perfect.

Never heard of incorrectly sized tanks tbh. If it’s too small, add another me thinks. I find using a submersible pump in the tank as a fantastic counter to the noise. But if I had a choice it’d always be outside

Flyingsnowball

With all this hassle why not just get a normal boiler.

jhenno78

Dtp1979 wrote: »

Never heard of incorrectly sized tanks tbh.

If theres a poor mains supply the pump empties the tank quicker than the mains can fill it. A good shower and someone who likes a long shower/a few showers in a row can empty the tank.

jhenno78

Flyingsnowball wrote: »

With all this hassle why not just get a normal boiler.

Its much handier to not have to plan your showers/dish washing in advance and not get caught short if you''ve a lot of demand at the same time.

Flyingsnowball

jhenno78 wrote: »

Its much handier to not have to plan your showers/dish washing in advance and not get caught short if you''ve a lot of demand at the same time.

Ah the joys of a good insulated cylinder. The water comes on for an hour twice a day. Probably costs me an extra 20 pence a day than a combi but I can afford it seeing as I’m saving the money on not needed to run a mains booster pump all day.

Dtp1979

Dtp1979 wrote: »

Never heard of incorrectly sized tanks tbh. If it’s too small, add another me thinks. I find using a submersible pump in the tank as a fantastic counter to the noise. But if I had a choice it’d always be outside

Very common sadly and easy to spot when your running the tap to Commision the boiler also the work you do isn’t the same as some who are fitting boilers.

Flyingsnowball

Flyingsnowball wrote: »

With all this hassle why not just get a normal boiler.

Swapping over to a combi can free up a lot of room and improve flow rates or simplify a new installation, they have their uses and many people are happy with them.

jhenno78

Flyingsnowball wrote: »

Ah the joys of a good insulated cylinder. The water comes on for an hour twice a day. Probably costs me an extra 20 pence a day than a combi but I can afford it seeing as I’m saving the money on not needed to run a mains booster pump all day.

Current house has an excellent cylinder and it does help a lot - still nothing like as good as a properly set-up combi.

Simply, it's nice when everything just works without having to put any thought into it.

jhenno78

gary71 wrote: »

There are plenty of areas with decent mains pressure also combis work perfectly well, every appliance when fitted incorrectly causes mayhem and your few liters does you little good if you don’t have your tank high enough.

IMO it would be a lot more sensible to remove the cold storage requirement from
the regs but require councils to bring in local rules for each supply area so that places with a good enough supply can use mains-pressurised but in other areas people are protected from getting it wrong.

jhenno78

jhenno78 wrote: »

IMO it would be a lot more sensible to remove the cold storage requirement from
the regs but require councils to bring in local rules for each supply area so that places with a good enough supply can use mains-pressurised but in other areas people are protected from getting it wrong.

That’s what’s done anyway even by councils, that water reg must be the most ignored in the country.

jhenno78

gary71 wrote: »

That’s what’s done anyway even by councils, that water reg must be the most ignored in the country.

Fair enough, I've seen it (very rarely) but didn't know if it was common or not.

Flyingsnowball

gary71 wrote: »

That’s what’s done anyway even by councils, that water reg must be the most ignored in the country.

Well that and washing machine into the rainwater gully.