These questions come from an experienced electrician but an inexperienced plumber! I'm just buying a house which needs just about everything replacing. The house currently has a Creda electric warm air heating unit (original from 1967) housed in a huge cupboard in the kitchen. We would like to do away with this and remove the cupboard if possible to give us a lot more space in the kitchen. What are these electric warm air units like in terms of efficiency, reliability and cost to run? Hot water is currently provided by means of an immersion heater in the cupboard on the landing. A loft room is planned and the staircase will go straight through this cupboard. We now need a solution for a central heating system (fortunately it all looks like it needs replacing anyway). I'm thinking a combi' boiler is the only real option, but is it possible to fit the combi' in the loft and vent the flue up and out of the pitched, tiled roof? It is a mid-terrace house without any real options for mounting it on an external wall, except in the dining room, which is far from ideal. The other concern that I have is the pressure of the hot water. What is the pressure of the hot water dependant on? Is it the incoming mains pressure or the boiler size or type, or is it something else? With the combi, we'll be doing away with the cold water tanks; does the cold water supply the cold taps directly or does it go via the boiler first to regulate the pressure? I've been told not to oversize the boiler and to size the boiler so that it's just about the right size so that it runs flat out. Is this correct and why so if this is the case? I've been looking for textbooks to help me learn about plumbing and central heating but it's hard to find one that's a good balance between the DIY virgin and the technical industrial gas and controls engineer; any recommendations? Any advice on my plans or alternative ideas would be much appreciated and well received. Many thanks, Liam.
Lots of questions for you knowledgable people...
- Thread starter spark
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i am not a plumber or heating engineer, but i can tell you that the cold water comes direct from the mains supply if you have a combi boiler.
the hot water pressure is dependant on the incoming cold water pressure
there are lots of opinions on this forum regarding combi boilers, but you may want to start by clicking here
the hot water pressure is dependant on the incoming cold water pressure
there are lots of opinions on this forum regarding combi boilers, but you may want to start by clicking here
spark said:
By the way my Ma used to moan, very inefficient, very expensive, the only way she could get warm was to sit in front of the "grill"!! Also, in my opinion, gas is a much more efficient (on is on, off is off) source of heat/cooking (will BG give me a discount if they read this
) and also a hell of a lot cheaper, look at the farce that is known as night storage heaters !!Sponsored Links
Check mains water flow rate as well as pressure, and check it when your neighbours are using water too. If you are having a bath in your house you may find fill time irritating if the flow rate is low. If you are having a mains shower, the pressure will be affected if another hot tap is turned on. I have recently been looking at thermal stores (www.gledhill.net) (usual disclaimer) which allow the boiler to cycle longer, and may or may not overcome some of the above problems.
As you are in a mid terrace you can get your heat losses down very low with lots of loft insulation, as well as rockwell you could look at multi-laminate foil from (at least) Enigma Insulations at Norwich and I don't have any connection with them either. The foils are about 6mm thick and give an insulating performance to 200mm of wool for RADIATION losses. They are not conduction insulations. Once you have super insulation you may be able to live with the electric thermal stores, which though more expensive to run are lower maintenance costs (IMHO) I don't say they are cheaper than other fuels but we have storage heaters, and servicing costs have been zero for 20 years.
As you are in a mid terrace you can get your heat losses down very low with lots of loft insulation, as well as rockwell you could look at multi-laminate foil from (at least) Enigma Insulations at Norwich and I don't have any connection with them either. The foils are about 6mm thick and give an insulating performance to 200mm of wool for RADIATION losses. They are not conduction insulations. Once you have super insulation you may be able to live with the electric thermal stores, which though more expensive to run are lower maintenance costs (IMHO) I don't say they are cheaper than other fuels but we have storage heaters, and servicing costs have been zero for 20 years.
Agree with oilman except that I can't see the attraction of thermal stores.. They seem to have problems of their own. Look at a condensing system boiler and an unvented hot water cylinder. Ie no loft cisterns needed. Check that mains is 3bar + and gives around 20 litres /min at agarden tap. Then you get good flow for showers, electric back-up, and a system that's standard enough to maintain easily.
I love the maintenance costs of electric storage heaters (£0), usually) but the enegy costs... If a wet, gas (or oil!), system is installed properly with good quality bits it should last a long time with little attention.
I love the maintenance costs of electric storage heaters (£0), usually) but the enegy costs... If a wet, gas (or oil!), system is installed properly with good quality bits it should last a long time with little attention.
That's an idea I hadn't even thought of Chris. Would that work the same way as a conventional boiler system with an indirectly heated cylinder and pumped central heating, except doing away with the cold tank and the F&E tank? Presumably if this is the case the cylinder would be fed from the mains cold water supply, would store hot water at mains pressure and supply the taps with hot water at mains pressure? Would the cylinder need an expansion vessel and some kind of pressure release valve or warning system? I'm assuming this cylinder will be indirectly heated by the boiler, but is it also possible to get a cylinder with immersion heater elements (as a back up if the boiler packs up) like a normal indirect cylinder? Presumably the unvented hot water cylinder could be mounted up in the loft with the boiler (assuming the boiler can be fitted in the loft and vented through the tiles) because it's fed with mains cold water not gravity fed stored water? Lot's of questions I know, but I've picked up bits and pieces of how plumbing systems work but don't know enough to make a complete picture in my head. Thanks, and any further info from anyone is still much appreciated.
spark said:
Blimey Spark you wanna the ins and outs of the lot dont yer
what you are talking about in an UNVENTED HOT WATER CYLINDER to service and install one of these you MUST a provenly competent installer.
In my opinion this kind of work is NOT DIY you must call in an installer to carry out the preliminary checks and to carry out the work do not be tempted to do it yourself as these appliances (they come in a pack wit all the necessary gear) are extremely dangerous if not installed correctly.
again Not a DIY job
Go here and look at the Megaflow cylinders to give you an idea.
http://www.heatraesadia.com/
spark said:
Blimey Spark you wanna the ins and outs of the lot dont yer
what you are talking about is an UNVENTED HOT WATER CYLINDER to service and install one of these you MUST a provenly competent installer.
In my opinion this kind of work is NOT DIY you must call in an installer to carry out the preliminary checks and to carry out the work do not be tempted to do it yourself as these appliances (they come in a pack wit all the necessary gear) are extremely dangerous if not installed correctly.
again Not a DIY job Inow your a sparks but this is a fish of and entirely different colour
Go here and look at the Megaflow cylinders to give you an idea.
http://www.heatraesadia.com/
That's a useful link thanks corgiman. I was actually going to get a competant person to install the boiler and test the pipework, I was just going to install the pipework and leave 'tails' (is that what you call them in plumbing?) near to the boiler position for the heating flow and return, mains cold water feed, DHW out and gas. Presumably I could still do that with the unvented cylinder? I understand the potential seriousness of a fault with this type of cylinder could be huge and for that reason alone I would not be happy connecting up my self. Surely if I get a competant person to actually connect and commision the boiler and cylinder and do final connections to the gas at both ends and all safety systems are in place, then the worst that can happen is that I get wet... ?
?All your assumptions are correct, spark! You can go through the roof vertically or horizintally. Unvented HW cyls can go in lofts, with matters like frost, strength, sorted out. Beats the hell out of a combi, but does cost more.
Things like Megaflo's have a pocket of air inside which needs re-establishing every several months or so - you know when the pressure relief pipe starts to dribble on heating the water. You can stick an external expansion vessel on a Megaflo, or the "other" sort of UVHW cylinder, which avoids the small task .
You do need a reasonable mains supply - better than for a for a combi really cos you can draw hot water much faster. Say 20litres/min at garden tap and 3bar + static pressure. Yousometimes have to get a bigger mains pipe put in - most of the cost is in diggin the trench 800mm or so deep across your front garden/driveway... Depends how old your house is - if it's modern you may be OK.. Ancient and a flattened 1/2" lead main won't feed a combi either.
You can put your own systems in - with reservations. You can run ALL the pipes except gas. I wouldn't have any problem connecting up an UVHWC which someone else had put in place with primaries etc handy. Get the installation instructions up front and you'll see what has to be done - not onerous. Main thing is copper discharge pipe has to go to ground somehwere. Best to get someone lined up before you start though. Yes I do have the "Unvented ticket" & Corgi. Water authority has to be informed of UVHW installation - no big deal. 95% aren't though!
By the way the Megaflo's primary water coils are high wattage - like 24kW, so they heat up FAST - no need for a monster. Other makes are cheaper . Megaflo's are arguably top of the tree and covet that position.
In the UK all makes come with at least 3 protective devices - 5 if indirectly heated only! I have a picture somewhere of what's left of a French school where there weren't enough. Luckily it was before the place had people in.
Things like Megaflo's have a pocket of air inside which needs re-establishing every several months or so - you know when the pressure relief pipe starts to dribble on heating the water. You can stick an external expansion vessel on a Megaflo, or the "other" sort of UVHW cylinder, which avoids the small task .
You do need a reasonable mains supply - better than for a for a combi really cos you can draw hot water much faster. Say 20litres/min at garden tap and 3bar + static pressure. Yousometimes have to get a bigger mains pipe put in - most of the cost is in diggin the trench 800mm or so deep across your front garden/driveway... Depends how old your house is - if it's modern you may be OK.. Ancient and a flattened 1/2" lead main won't feed a combi either.
You can put your own systems in - with reservations. You can run ALL the pipes except gas. I wouldn't have any problem connecting up an UVHWC which someone else had put in place with primaries etc handy. Get the installation instructions up front and you'll see what has to be done - not onerous. Main thing is copper discharge pipe has to go to ground somehwere. Best to get someone lined up before you start though. Yes I do have the "Unvented ticket" & Corgi. Water authority has to be informed of UVHW installation - no big deal. 95% aren't though!
By the way the Megaflo's primary water coils are high wattage - like 24kW, so they heat up FAST - no need for a monster. Other makes are cheaper . Megaflo's are arguably top of the tree and covet that position.
In the UK all makes come with at least 3 protective devices - 5 if indirectly heated only! I have a picture somewhere of what's left of a French school where there weren't enough. Luckily it was before the place had people in.
ChrisR, I was interested in thermal stores instead of unvented cylinders because of the maintenance/annual test cost of the unvented cyl. Are the thermal store problems significant? They seem attractive as the potable water is at mains pressure, but the large volume energy store is unpressurised.
ChrisR said:
Spot on chris but with a couple of pointers
Spark you said you would run the gas pipe for the boiler, I know this has been discussed before but I would ask your CORGI man if he is happy with this first
And if you are going to run the discharge pipe, especially from the loft, makes sure it is of an adequate size do your sums and dont just whop some 22mm in and think thats ok cos if the temp/pressure valve goes your going to have a lovely hot shower from the tundish
I will consult my 'CORGI man' before I do anything anyway because like electricians, everyone has preferences and different ways of doing things. If he says he would prefer to run the pipe himself, then I'll just have to do all I can to clear the route for the pipe as possible, but I'd have thought that if he can test the pipe and he can inspect it throuout it's length then he'd be happy. I looked on the heatrae website and the it seems the cylinders are supplied with a tundish with a 15mm entry and a 22mm exit anyway. Would heatrae not have tested to confirm that these sizes are satisfactory? In what instances would 22mm not be large enough? In the event that for some reason the 22mm discharge pipe was not large enough, is it possible to buy a 15mm/28mm tundish? What sums would enable me to calculate the diameter of the discharge pipe required? I do not want to cut corners and would like to know all there is to know(short of qualifying to be a plumber ); is there a book available so I could learn about these things myself without asking everyone all these questions? Thanks for all your time and info people.
); is there a book available so I could learn about these things myself without asking everyone all these questions? Thanks for all your time and info people.DIYnot Local
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