New Highflow ?

[DrTannahill]

I have been advised to replace my boiler and am going to replace all my rads with reproduction cast iron rads to suit the style of the house. I currently have a worcester highflow heatslave which has been in the house for about 10+ years before i moved in it is rated at 38kw. I have two bathrooms each with baths and showers. I have two public rooms, 4 bedrooms, study, kitchen, utility room, large hall and dining room. The plumber calculated my heating requirement as 86,000BTU. He suggested a Worcester Greenstar 37CDI.
However after researching the boiler suggested i am unsure whether it would be powerful enough for my hot water demand, as we will be running two showers simultaneously. Should i get another highflow or go with the suggested ? If not what boiler would you suggest for the size of house ? The plumber also said that my gas supply may need to be upsized, is this correct ?

 

[Agile]

If you want to use a reasonable flow from each shower then thats only about 7 li/minute each.

In my view a 24 kW boiler would be needed with a 210li or better a 310li cylinder which could be unvented if you have adequate mains water flow exceeding about 24 li/min. The size of cylinder will depend on the the number of residents.

That arrangement will not require the gas supply to be upgraded.

You could also keep your old boiler and use it to feed one bathroom and also heat a cylinder to feed the rest of the house.

Tony

 

[DrTannahill]

Thanks for the speedy reply but the problem i am having is the space, i don't have room for an un-vented cylinder. The only room i have is the cupboard which the boiler is currently in. The plumber originally suggested a viessman vitodens 300 26kw and and a megaflo 210 HE but as i don't want a cylinder taking up space, he suggested the worcester combi. So would the 37 CDI suggested let me run both showers and supply my new radiators adequately ?

thanks in advance for any replies

 

[Agile]

I am sorry but you dont seem to have digested what I said!

A combi will only give about 14 li/min continuously and if you split that between two showers or baths thats only 7 li/each!!!

Have you considered putting the sylinder in the cellar or loft?

To give acceptable hot water for two bathrooms you need stored water!

How many people live there?

Tony

 

[gas4you]

A new highflow will give around 20 litres a minute I believe until the store runs out then you will be left with a very low powered basic combi, 23Kw I believe, which is basically good for nothing!

I feel that whatever you do if you have not got room for an un-vented cylinder you MUST go for a storage combi of some sort. Any normal combi will only supply one hot outlet at a time adequately.

I personally would fit the Vaillant Ecotec Plus 937, which will give 20 litres a minute hot water flow, and even when the store depletes will still give 14.5 litres / min.

Alpha also do a storage combi but I do not know the technical details of that.

The worcester highflow has a good reputation but is the size of a washing machine and awkward to work on afterwards

 

[DrTannahill]

I understand what you are saying, but the current combi i have suits my needs and will let me run two baths at the same time. The thing is i only have the space where the old boiler was, no room anywhere in the house for an unvented cylinder. and want to fit a similar combi because my old highflow is nearing the end of it's life, is there any type of combi other than buying another highflow due to the high cost ? there are 4 of us in the house.

Also would the 37 CDI combi give me similar hot water performance? I understand what you are saying about it being able to feed two showers

 

[gas4you]

The 937 is cheaper to buy but would no doubt need a larger gas supply.

As you have already got an existing highflow, I missed that bit somewhere, I would think the cheapest overall solution would be a new greenstar highflow fitting in the same place. All you will need extra is a condensate drain.

 

[scatmanjohn]

What about 42Cdi it will give 17.1 litres per minute if you have sufficient flow.

 

[Agile]

If you are happy with your existing boiler then the 937 will be about 40% better!

You have not explained why you dont apparently have a loft to put the cylinder in!.

Few of my clients would be happy with your arrangement. The idea of Scottish baths only 3" deep comes to mind!

The correct format is a 310 li cylinder and a 24 kW boiler.

To me the only advantage of the storage combi is to fill a bath quickly! Otherwise I would never fit a 14 li/min combi where it was expected to run two showers together.

Tony

 

[gas4you]

If you are happy with your existing boiler then the 937 will be about 40% better!

You have not explained why you dont apparently have a loft to put the cylinder in!.

Few of my clients would be happy with your arrangement. The idea of Scottish baths only 3" deep comes to mind!

The correct format is a 310 li cylinder and a 24 kW boiler.

To me the only advantage of the storage combi is to fill a bath quickly! Otherwise I would never fit a 14 li/min combi where it was expected to run two showers together.

Tony

Tony, a customer does not have to explain himself to an installer, let alone us on here

He has stated his requirements and the limitations as to the space he wants using, therefore us as professionals must install something that is the best solution for his/their circumstances.

Scat; I bet that uses more fuel than a space shuttle on take off

 

[DrTannahill]

will the 42 cdi give me 17lit all the time ? if so would it be ok to fit the 42 cdi or would it be oversized for my requirements ? as for my loft it is too low to fit in an unvented cylinder and there is nowhere to run the pipework for it without it going up walls and needing to be boxed in. i have recently redecorated and do not want pipes shown anywhere. i live in an old house with high ceilings ect and i do not want to damage any of the cornicing or walls.

 

[gas4you]

The 42Kw is just for water. Not certain what the ch output is on this one of the others will be able to tell you, but whatever it is boiler will modulate down to work only at the level needed for the demand at any one moment. The installer may be able to range rate it, but I don't know Worcesters that well.

 

[DrTannahill]

so is fitting a 37 or 42 CDI goin to increase my gas bills ? I already pay £180 per month.
what about the valliant someone suggested ?

 

[gas4you]

Not very much, all makes of boiler if fitted and commissioned correctly will use about the same amount of gas.

 

[DrTannahill]

i thought fitting a new condensing boiler would reduce my gas bills ?