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boiler/central heating and hot water cylinder questions

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Found 23rd Jun 2016
hey everyone

wondering if I could pick the brains of the plumbers in our forum.

renovating a house, will end up with 2 to 3 bathrooms, maybe 4. now ive called a couple of people round for a quote and just deciding who to go for. im getting conflicting advice. some saying that having a boiler wih a unvented hot water cylinder will make a big difference and one guy saying no, that a good solid high capacity boiler will do the job.

essentially I want to be able to run 3 showers at the same time without any one of them losing power. I thought the idea behind the cylinder was that it allowed that, but this one guy says no, you wont get full power on all 3 at the same time. he said a good solid boiler with large capacity is just as good as a boiler/cylinder combo.

secondly he said with a cylinder, the boiler is on all the time as its making sure the water is kept hot. I thought the cylinder heated the water independently but this guy was saying nope, boiler connected to the cylinder and boiler will stay on to heat the water in the cylinder.

so im right royally confused now so looking for some consensus on the issue from the helpful/knowledgable people here.

also, any reliable places where I can source about 15 radiators from? need a mix of vertical and standard convector ones. obviously cheapest possible really.

thanks for reading
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62 Comments
Definately not wanting electric showers? This might solve your issue quick. But will have to wire up 3 independent mcbs.
bigweapon07

Definately not wanting electric showers? This might solve your issue … Definately not wanting electric showers? This might solve your issue quick. But will have to wire up 3 independent mcbs.



never been a fan of electric showers as I feel they don't give as much power as the gas ones. but I could have one as a electric I guess.
bigweapon07

Definately not wanting electric showers? This might solve your issue … Definately not wanting electric showers? This might solve your issue quick. But will have to wire up 3 independent mcbs.



well im doing a rewire anyway so should not be a issue.
EN1GMA

never been a fan of electric showers as I feel they don't give as much … never been a fan of electric showers as I feel they don't give as much power as the gas ones. but I could have one as a electric I guess.



with that many bathrooms have one electric shower at least that way any boiler issues you aren't washing in cold water
Whether or not your boiler comes on running a shower will depend on the size of your tank. The thermostat that calls for heat from the boiler is nearer the bottom of the tank so it won't be until you've used all the water above that first before the boiler switches on.

There is also the possibility that you could have a direct cylinder instead of indirect and just have several elements within the tank that heat the water rather than the boiler?

With regard to the 'power' of the showers, an unvented tank will only put out water as fast as the water going in so if your pressure/flow is rubbish coming into your house this may not work for you.
EN1GMA

well im doing a rewire anyway so should not be a issue.


Would be worth it as a backup aswell. You never know with boilers when they want to throw a wobbler and refuse to work even if they are new.
Some good tips guys, thanks. might go for one electric if I can get a bathroom in the attic. I just needed confirmation that the boiler was not always 'on' powering the cylinder/hot water. when he said that it threw me back abit and im thinking, then what's the point of the cylinder.....

ive made some more google queries at it seems the guy was wrong. the cylinder does have its own programmer which has a thermostat which regulates the temp thus no need for the boiler to do that.
Hallsie

Whether or not your boiler comes on running a shower will depend on the … Whether or not your boiler comes on running a shower will depend on the size of your tank. The thermostat that calls for heat from the boiler is nearer the bottom of the tank so it won't be until you've used all the water above that first before the boiler switches on.There is also the possibility that you could have a direct cylinder instead of indirect and just have several elements within the tank that heat the water rather than the boiler?With regard to the 'power' of the showers, an unvented tank will only put out water as fast as the water going in so if your pressure/flow is rubbish coming into your house this may not work for you.



thinking of getting a 200 ltr tank.
EN1GMA

thinking of getting a 200 ltr tank.


We're in the process of having building work done and recently replaced our Combi Boiler with a Mega-Flow System (275 litre) along with a Vaillant Eco Tec 637 boiler. The Mega-Flow also comes with an electric back up to keep water heated just in case (we're currently using it this way). However, a point to note is; it does require extra additional space as it's quite big (smaller capacity ones are available). We've put both in an outhouse/shed and hope this helps in some way...
You need an unvented system without a doubt
EN1GMA

never been a fan of electric showers as I feel they don't give as much … never been a fan of electric showers as I feel they don't give as much power as the gas ones. but I could have one as a electric I guess.



Electric showers are supplied by mains pressure which is as powerful a system as you can get without fitting pumps to a water cistern.

And if you are having 3 showers on a pumped system you will need one hell of a big cold water cistern & hot water tank or an unvented pressurised system .
What's the best way/simplest/cheapest way to zone my heating system via floors? Bear in mind I'm re plumbing the house, might as well do this now. Just wanted to know my options
EN1GMA

What's the best way/simplest/cheapest way to zone my heating system via … What's the best way/simplest/cheapest way to zone my heating system via floors? Bear in mind I'm re plumbing the house, might as well do this now. Just wanted to know my options



After having your radiators balanced for flow rate i would just have them all on TRVs. Thermostatic radiator valves. So you can adjust yourself. Obviously the further up the house the lower youll need them as heat rises in the house and the heating system. And bedrooms might be even lower.
EN1GMA

What's the best way/simplest/cheapest way to zone my heating system via … What's the best way/simplest/cheapest way to zone my heating system via floors? Bear in mind I'm re plumbing the house, might as well do this now. Just wanted to know my options



I suggest you go to a plumbers website for advice. You wont get much on here.

First I would advise u don't bother with electric showers. The flow rate is not that good especially in the winter.
If u go for a unvented tank it has a back up immersion heater if the boiler ever fails so you will never be without hot water.
The problem you face is the mains pipe size and pressure coming in the house. The flow at any one time will be based on how much water and the pressure the water is coming into the house. Then it will either go into the boiler for instant hot water or a unvented tank. Either you will go by the hot water flow rate on the boiler or the mains flow rate pushing the water through the tank.
If u go with 2 showers you will get decent flow but pressure will be distributed between the 2 showers, 3 showers on at any one time will produce a lower pressure and flow rate. So if it was 9lts a minute u would get around 3ltrs of water to each point.
The way around without dropping pressure is stored cold water tanks with pumped hot water system. Which can work out expensive but work out worth while if need be.
But what are the chances in reality that 3 showers will be used at the same time ?
Also u can go for a combo boiler with a unvented tank. As a combo boiler is a system boiler with added extra of producing instant hot water.
Go to mrcentralheating for your boiler and rad package as they are the cheapest and ibath for the vertical rads. Hope it helps and confusion just ask. Good luck.
Another shower to consider is a pumped electric. Doesn't get affected by any flow as it requires stored cold water tank. Theses aren't affected by any mains pipe and you can have as many as you want without loss of pressure but require a bigger storage tank as you increase the amount of showers. But personally I would suggest a unvented tank with a mains pump fitted to increase flow. With a system or combi boiler powering it.
Also the benefits of going with a tank system then just a combo boiler alone is that if u use hot water on the combi boiler the heating stops. So a big negative in the winter in large houses. A hot water tank does not get affected by this problem.
bigweapon07

After having your radiators balanced for flow rate i would just have them … After having your radiators balanced for flow rate i would just have them all on TRVs. Thermostatic radiator valves. So you can adjust yourself. Obviously the further up the house the lower youll need them as heat rises in the house and the heating system. And bedrooms might be even lower.


Would having TRVs mean I'd have to adjust the dials on the rads myself?

Basically it's a 4 storey house and what I would ideally like is to zone the house so only the heating on those floors come on which I want. Controlling every rad is overkill but if I can control the rads of each floor, that would mean that when I switch on the rads, the whole houses rads are not on as that would cost me a lot to run.

I don't fancy manually adjusting the thermostat for each radiator everytime.
kash2013

Another shower to consider is a pumped electric. Doesn't get affected by … Another shower to consider is a pumped electric. Doesn't get affected by any flow as it requires stored cold water tank. Theses aren't affected by any mains pipe and you can have as many as you want without loss of pressure but require a bigger storage tank as you increase the amount of showers. But personally I would suggest a unvented tank with a mains pump fitted to increase flow. With a system or combi boiler powering it. Also the benefits of going with a tank system then just a combo boiler alone is that if u use hot water on the combi boiler the heating stops. So a big negative in the winter in large houses. A hot water tank does not get affected by this problem.


Yeah, agreed that with a unvented hot water cylinder, the rads can be on and the shower/sink etc would not be affected in terms of water flow.
If u fit a zone valve before the tank which u should anyway this is controlled by a timer. So the hot water in the tank comes on at certain times. So most at night and if your at work the boiler will not be able to heat the water in the tank.
If u want to zone certain areas in the hose you will need to fit zone valves on the flow pipe feeding those areas. Also u may need to increase the pipe size for the heating if u want 15 rads or 2 heating pumps to stop radiator cold spots. I wouldn't call the second plumber back. Don't think he has enough knowledge for large houses.
YouDontWantToKnow

I suggest you go to a plumbers website for advice. You wont get much on … I suggest you go to a plumbers website for advice. You wont get much on here.


On the contrary, the information I get from people on this site is amazing. Lots of people with lots of real time actual knowledge based on experience. This place is actually one of the first few places I come to.

But you're right, I'll probably have to visit a plumbers merchants to get more info.
Nash

We're in the process of having building work done and recently replaced … We're in the process of having building work done and recently replaced our Combi Boiler with a Mega-Flow System (275 litre) along with a Vaillant Eco Tec 637 boiler. The Mega-Flow also comes with an electric back up to keep water heated just in case (we're currently using it this way). However, a point to note is; it does require extra additional space as it's quite big (smaller capacity ones are available). We've put both in an outhouse/shed and hope this helps in some way...


Is it true that the boiler and unvented hot water cylinder need to be close together? Would you mind if I ask how much the boiler and cylinder cost you?
kash2013

First I would advise u don't bother with electric showers. The flow rate … First I would advise u don't bother with electric showers. The flow rate is not that good especially in the winter.



lol

Pressure will be circa 3bar the same as a combi. Flow rate will be the same because of the 15mm pipework (the same as a combi)
EN1GMA

Yeah, agreed that with a unvented hot water cylinder, the rads can be on … Yeah, agreed that with a unvented hot water cylinder, the rads can be on and the shower/sink etc would not be affected in terms of water flow.


A tap, shower, flushing a toilet etc will all affect water pressure at any one time as there all points of pressure loss.
Edited by: "kash2013" 24th Jun 2016
kash2013

Another shower to consider is a pumped electric. Doesn't get affected by … Another shower to consider is a pumped electric. Doesn't get affected by any flow as it requires stored cold water tank.



Rubbish. You only pump the cold water
EN1GMA

On the contrary, the information I get from people on this site is … On the contrary, the information I get from people on this site is amazing. Lots of people with lots of real time actual knowledge based on experience. This place is actually one of the first few places I come to. But you're right, I'll probably have to visit a plumbers merchants to get more info.



Sorry to say that on this thread you are being fed a load of rubbish.
kash2013

A tap, shower, flushing a toilet etc will all affect water pressure at … A tap, shower, flushing a toilet etc will all affect water pressure at any one time as there all points of pressure loss.



Because the house is gutted and I'm doing the plumbing from scratch, more or less, then might as well get all this done now.

Appreciated for the advice. Just trying to get my head round everything.
kash2013

A tap, shower, flushing a toilet etc will all affect water pressure at … A tap, shower, flushing a toilet etc will all affect water pressure at any one time as there all points of pressure loss.



No. They reduce flow rate not pressure.

Yet another incorrect statement.
YouDontWantToKnow

lolPressure will be circa 3bar the same as a combi. Flow rate will be the … lolPressure will be circa 3bar the same as a combi. Flow rate will be the same because of the 15mm pipework (the same as a combi)


It's normally a 22mm inlet on a unvented tank. But a combi would not be suitable for a large house. As the a open hot water tap would stop the heating. If they are running a bath in the winter the heating in the entire house would stop until the turn of the hot water tap.
YouDontWantToKnow

Rubbish. You only pump the cold water


Yes you pump the cold from a stored water tank to a electric shower. 20 years a plumber and have a property maintenance business. I think I know what I am talking about. Maybe with such a large thread I may have jumbled a few words but it's late night and I am tired.
Edited by: "kash2013" 24th Jun 2016
kash2013

It's normally a 22mm inlet on a unvented tank. But a combi would not be … It's normally a 22mm inlet on a unvented tank. But a combi would not be suitable for a large house. As the a open hot water tap would stop the heating. If they are running a bath in the winter the heating in the entire house would stop until the turn of the hot water tap.


That's the issue with my current house. But it's a small house. In winter, I have to time the rads to come on before people wake up, then switch off before everyone gets up. Otherwise if the rads are on and shower starts, the rads go off. With kind of learned to live with it in our current house but with the refurb in the new house, good opportunity to redo things how we want. So if I can have a system where rads could be on whilst people could use the shower without loss of flow/pressure then happy days.


Edited by: "EN1GMA" 24th Jun 2016
kash2013

If u fit a zone valve before the tank which u should anyway this is … If u fit a zone valve before the tank which u should anyway this is controlled by a timer. So the hot water in the tank comes on at certain times. So most at night and if your at work the boiler will not be able to heat the water in the tank. If u want to zone certain areas in the hose you will need to fit zone valves on the flow pipe feeding those areas. Also u may need to increase the pipe size for the heating if u want 15 rads or 2 heating pumps to stop radiator cold spots. I wouldn't call the second plumber back. Don't think he has enough knowledge for large houses.



If I go for a zoned system, then is each floor piped individually?

Any place I can see a simple diagram of how the piping looks in a zoned system. I like to know so I know the plumber ain't chatting bubbles.

I'm thinking of going for the evo/honeywell system to zone. It's a 4 storey house and I don't want to zone each floor but at leach basement and ground floor together and 1st floor and 2nd floor together would be fine.

Wanted a zoned system as when the rads come on, don't fancy the whole houses rads come on when we are only downstairs. In a small house it's fine but this new house is bigger and would like to have some control of the bills and usage.

Also, does the boiler and unvented hot water cylinder have to be next to each other? Or can I have the boiler in the bathroom and cylinder in the basement?
Edited by: "EN1GMA" 26th Jun 2016
EN1GMA

Also, does the boiler and unvented hot water cylinder have to be next to … Also, does the boiler and unvented hot water cylinder have to be next to each other? Or can I have the boiler in the bathroom and cylinder in the basement?



If is unvented you can put the cylinder anywhere & boiler anywhere but you will obviously obtain extra costs to the pipework that may run into many hundreds.
Oh & I would make sure you get a proper professional. 4 baths, 3 showers, rads & underfloor heating all through a 15mm 3bar mains is going to be very expensive. You will probably be advised to do at least 2 electric showers & electric underfloor heating & unvented..
Edited by: "YouDontWantToKnow" 26th Jun 2016
YouDontWantToKnow

If is unvented you can put the cylinder anywhere & boiler anywhere but … If is unvented you can put the cylinder anywhere & boiler anywhere but you will obviously obtain extra costs to the pipework that may run into many hundreds.


Thanks for the response. There is a place in the attic I could put the boiler, just need to see if the pipe on the boiler can be vented out. Otherwise I'll have to stick the boiler in the bathroom and the tank in the attic if not in the basement.
YouDontWantToKnow

Oh & I would make sure you get a proper professional. 4 baths, 3 showers, … Oh & I would make sure you get a proper professional. 4 baths, 3 showers, rads & underfloor heating all through a 15mm 3bar mains is going to be very expensive. You will probably be advised to do at least 2 electric showers & electric underfloor heating & unvented..


It's going to be one bath and two showers. And about 15 rads.

The house has 90% been gutted so I hopefully it makes the plumbers and electricians jobs easier to work on.

It's a good thing I got this place for unbiased advice. I'd like to think all the trades know what they are doing.
EN1GMA

It's going to be one bath and two showers. And about 15 rads



You changed your mind then..
YouDontWantToKnow

You changed your mind then..


I don't think so. It was always going to be 1 bath and 2 showers, at a push 3 showers but I don't think the third shower is going to be practical. It's one toilet, shower off the kitchen and 2 bathrooms on the 1st floor(one with bath the other with shower)

What's a good yet inexpensive zoning system? 4 zones are going to be overkill so I'll have to settle for 2(basement and ground floor and the other is 1st and 2nd floor)
EN1GMA

I don't think so. It was always going to be 1 bath and 2 showers, at a … I don't think so. It was always going to be 1 bath and 2 showers, at a push 3 showers but I don't think the third shower is going to be practical. It's one toilet, shower off the kitchen and 2 bathrooms on the 1st floor(one with bath the other with shower) What's a good yet inexpensive zoning system? 4 zones are going to be overkill so I'll have to settle for 2(basement and ground floor and the other is 1st and 2nd floor)




renovating a house, will end up with 2 to 3 bathrooms, maybe 4


Edited by: "YouDontWantToKnow" 26th Jun 2016
YouDontWantToKnow


Apologies for the confusion. I originally meant 3 bathrooms/shower rooms. So one bathroom with a bath, toilet and sink and the other 2 with a shower and toilet and sink. House is big but not that big to accommodate 4 bathrooms and 3 shower rooms lol
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