New Build: Do I need an immersion on the tank

893bet

In middle of new build. Heating is oil. Will be 3-4 zones etc.

Also will have 3 plate solar on south roof.


Do i need an immersion for back up for DHW? the plumber has suggested no electric showers as there is no need with the solar. He has suggested power showers only. My fear is running out of hot water and having none. Power showers use alot of water so if someone empties the tank I have no hot water then till the solar heats it up or the heating is on.

Which would be most efficent. Putting the DHW heating zone on for a half hour or the immersion?

Any advice appreciated!

Prenderb

If it were my build, I'd put one in.

It does sound like you will have hot water covered with the solar and oil, though. It's just that an immersion is comparatively inexpensive and I think you might enjoy the flexibility on autumn or spring days where solar isn't heating enough, but the oil mightn't be on for too long, if that makes sense.

Also as you say you have a fear of running out - have you answered your own question? put one in! :P

freddyuk

In summer use immersion/solar and in winter use oil/solar. As you have the heating on in winter opening the DHW valve wastes no extra energy. Avoid running DHW alone as it needs to heat the pipes from boiler to cylinder. A decent immersion programmer can allow several switch time options with simple override if required. By having a cylinder stat wired in you will not use the timed immersion if you have sufficient hot water depending on where you site the stat on the cylinder. I would have it high and just heat enough for showers/washing up if needed.
In summer the immersion is cheaper to run (and repair) then the boiler.
Make sure you have a big enough cylinder for the solar input and your usage pattern. No point in having a small cylinder and wasting solar input when it is available. If you top load you can have the cylinder hot at the top first then switch to the bottom rather than heating from the bottom only.

Wearb

893bet wrote: »

In middle of new build. Heating is oil. Will be 3-4 zones etc.

Also will have 3 plate solar on south roof.


Do i need an immersion for back up for DHW? the plumber has suggested no electric showers as there is no need with the solar. He has suggested power showers only. My fear is running out of hot water and having none. Power showers use alot of water so if someone empties the tank I have no hot water then till the solar heats it up or the heating is on.

Which would be most efficent. Putting the DHW heating zone on for a half hour or the immersion?

Any advice appreciated!

Oil is cheaper.

Like other poster, I would put in one electric shower. Then it wouldn't really matter about the immersion, but as said, for the relative cost, why not put one in.
I am not sure about this, but I think it may be necessary anyway, to keep water at a temp that prevents Legionnaires Disease.

Wearb

freddyuk wrote: »

In summer use immersion/solar and in winter use oil/solar. As you have the heating on in winter opening the DHW valve wastes no extra energy. Avoid running DHW alone as it needs to heat the pipes from boiler to cylinder. A decent immersion programmer can allow several switch time options with simple override if required. By having a cylinder stat wired in you will not use the timed immersion if you have sufficient hot water depending on where you site the stat on the cylinder. I would have it high and just heat enough for showers/washing up if needed.
In summer the immersion is cheaper to run (and repair) then the boiler.
Make sure you have a big enough cylinder for the solar input and your usage pattern. No point in having a small cylinder and wasting solar input when it is available. If you top load you can have the cylinder hot at the top first then switch to the bottom rather than heating from the bottom only.

Nonsense.

agusta

893bet wrote: »

In middle of new build. Heating is oil. Will be 3-4 zones etc.

Also will have 3 plate solar on south roof.


Do i need an immersion for back up for DHW? the plumber has suggested no electric showers as there is no need with the solar. He has suggested power showers only. My fear is running out of hot water and having none. Power showers use alot of water so if someone empties the tank I have no hot water then till the solar heats it up or the heating is on.

Which would be most efficent. Putting the DHW heating zone on for a half hour or the immersion?

Any advice appreciated!

Yes,there is always a fear of running out of hot water.I have 3 power showers in my house,except in the main bathroom i have a triton t90 fitted on the opposite wall to the power shower.Its the best of both worlds really.The shower tray that i have in main bathroom is 1200x 900 quadrant.I agree with wearb that using the DHW heating zone is far cheaper than using the immersion

freddyuk

Wearb wrote: »

Nonsense.

OK by how much?

gctest50

this much ?

Wearb

freddyuk wrote: »

OK by how much?

By enough to matter. Why would you make those claims that I highlighted?

There is loads of information here on boards about those costs and also on the SEAI site. AND that was before oil costs fell by over 30%

Edit: see post above. It was posted while I was typing.

Irish Steve

going slightly off the exact topic, but I think it's close enough to be worth throwing into the pot for consideration.

We're oil heated, with backup immersion, but the one thing I did a few years ago which is a very helpful trick is to put the radiator in the main bathroom on to a dedicated supply loop that gets heated if the pump is running, regardless of which zone is active, so the bathroom is heated if the hot water or either of the heating zones is active. The bathroom is branched off the main supply and return before any of the motorised zone valves, so if the pump is running, the bathroom loop get heat. The radiator has a thermostatic valve to avoid over heating that area.

In the winter, that usually means that we can fire the boiler in the morning, which gives us hot water, and at the same time, the bathroom is heated as well.

To make that even more effective, and allow us to use the radiator for drying towels and the like, the bathroom radiator is oversized by 100%, which was done by fitting a double panel radiator where the sizing was based on a single panel. It works very well.

Another thought that's worth mentioning is that I don't use an internal coil in the hot tank, I have a small external (pumped) heat exchanger, which means that the water is heated to close to 60 C in one pass through, so if we only want half a tank, we can run the boiler for (about) 20 minutes, and the top half of the tank is at 60, and the rest of the tank is at whatever temperature it started at, which is a lot more effective than an internal coil.

I'd also suggest giving serious consideration to trying to put in a hot water loop, circulated by a small bronze pump, to minimise the wasted water when the hot line hasn't been run for a while, given the change in emphasis on water costs now. Having to run a tap and waste maybe 5 litres of water every time you want hot water may not have been an issue previously, but with the way that charging is now going, that sort of wastage is not a good idea,

OK, it's slightly off the original question, but given that it's a new build, now is the time to be giving some of these things an airing, I know if I didn't have tiled floors throughout the ground floor, I'd be looking at some significant changes to our pipe layouts to save more money.

Hope this helps

bluemartin

Are power showers a good idea? what with impending water charges and all that

Flood

I installed a willis heater instead of an immersion, never did the maths on whether its more efficient than an immersion or not.

freddyuk

Wearb wrote: »

By enough to matter. Why would you make those claims that I highlighted?

There is loads of information here on boards about those costs and also on the SEAI site. AND that was before oil costs fell by over 30%

Edit: see post above. It was posted while I was typing.

The numbers on paper are not that far apart as has been presented above. I think I pay €0.18 per unit (I had not included night rate which is perfect for topping up a cylinder for early morning use). Oil had dropped temporarily but we have to talk averages not spot rates as it will go back up.
You however conveniently forget the costs of servicing and maintaining boilers/storage tanks against zero added costs of a simple immersion @100% efficiency. If you want maintain your boiler warranty you will need an annual service charge added on to the capital cost. Even an old boiler needs regular servicing? If you have long pipe runs there will be losses in a boiler system if the boiler is next to the cylinder it can be negated. You can argue over the amount of system losses all day but each installation is different with varying flow rates and heat losses but it is a factor to consider. An immersion goes straight into the tank zero losses.

Legionnaires is a complete red herring BTW. In an average DHW the water is replaced each day so there is nil risk and no one has ever died from this source of infection.

Wearb

freddyuk wrote: »

The numbers on paper are not that far apart as has been presented above. I think I pay €0.18 per unit (I had not included night rate which is perfect for topping up a cylinder for early morning use). Oil had dropped temporarily but we have to talk averages not spot rates as it will go back up.
You however conveniently forget the costs of servicing and maintaining boilers/storage tanks against zero added costs of a simple immersion @100% efficiency. If you want maintain your boiler warranty you will need an annual service charge added on to the capital cost. Even an old boiler needs regular servicing? If you have long pipe runs there will be losses in a boiler system if the boiler is next to the cylinder it can be negated. You can argue over the amount of system losses all day but each installation is different with varying flow rates and heat losses but it is a factor to consider. An immersion goes straight into the tank zero losses.

Legionnaires is a complete red herring BTW. In an average DHW the water is replaced each day so there is nil risk and no one has ever died from this source of infection.

Freddie, I have often read your posts with interest and agree with a lot if them, but you sometimes go into convoluted arguments to try and stand by an erroneous statement that you made. That is the case this time.

Those seai figures still gave oil and gas as better options even when oil was a lot dearer.

As for legionnaires, slight risk in domestic., but would you want to subject your family to that risk? Especially when whole families vacate their properties for holiday breaks.

gctest50

freddyuk wrote: »

....
Legionnaires is a complete red herring BTW. In an average DHW the water is replaced each day so there is nil risk and no one has ever died from this source of infection.

the point is not to be giving it places to hide out no ?

An estimated 10-15% of otherwise healthy people who contract Legionnaires’ disease will die due to problems like these.


In 2010, there were 38 deaths from Legionnaires’ disease in England and Wales.

freddyuk

gctest50 wrote: »

the point is not to be giving it places to hide out no ?

Please do not insult my intelligence. Go and find one case of a death in a domestic household of an otherwise healthy individual? Don't just read the first Google result you come across.

If you want to keep your DHW at 60c then you should fit a TMV to prevent accidental scalding. If you want to check the number of accidents and fatalities from scalding it may temper your argument about a 1 in a million chance of legionella.

And mind how you cross the road.....but this is going off the subject.

"Wearb" - I fully accept your comments but in real life I know what the immersion is costing me exactly and for a quick blast into the cylinder to top up for immediate use is not costing much. I have more difficulty calculating the unknown and known losses involved in the oil heating system and therefore recommend my approach as a balance between solar and a backup. I am not advocating using electric for all the heating but it has a place in a system and is underestimated I feel when used in a controlled way. If you run out of oil on 1st May you will either have to buy a fill up for € 1,000 and store it all summer or use immersion costing maybe €0.50 for an hours worth of immersion heating in a morning.
Sorry if that is convoluted but it is one view. So far in a minority!

Irish Steve

There are indeed service costs on an oil based system, but given that the majority of use of an oil system is space heating rather than DHW heating, it's not a major factor. We use our oil system all the year for DHW, partly for cost reasons, and partly because it means the boiler and pump are being regularly used, rather than sitting cold and idle for prolonged periods, and it seems to work for us, I've had to do some repair and maintenance on things like motorised zone valves, but apart from that, I've had very few problems with the system, the boiler is cleaned etc regularly, and I've had to free up the occasional stuck valve stem on the some of the thermostatic valves.

The biggest hassle I've had has been limescale in the heat exchanger, and that was eventually solved when we put a salt based softener in, and it removed the limescale issue from the system completely, and at this stage, the softener has more than paid for itself in reduced maintenance and reduced bills for soap, and other related things like washing machine tablets, detergent, and the like, we use far less than we used to have to use.

Wearb

@Freddy

Don't let being in a minority stop you from posting.

I agree with a quote from Rumpole of the Bailey, "I disagree totally with everything you say, but I will defend to the death your right to say it".

I think we have given the op lots of opposing info to help decide.

freddyuk

It won't!

893bet

So..... Clear as mud for me so!

Will prob wire one in so. Better to be looking at it than looking for it!

Wearb

893bet wrote: »

So..... Clear as mud for me so!

Will prob wire one in so. Better to be looking at it than looking for it!

Well you have both sides of the argument, what more could you ask for?

agusta

Wearb wrote: »

Well you have both sides of the argument, what more could you ask for?