Small Conventional Boiler

[Dan0803]

Looking at what Razor has stated, I'd much rather have a cheaper boiler and spend additional money on insulating the house.

I had one central heating company out and I was recommended to take the old boiler and the hot water cylinder and replace with a modern combi-boiler. He suggested a 32kw boiler but I said I believed this was far too big for the house. He said he recommends this for good water pressure. I haven't had anyone else out yet - trying to do my research before inviting any other companies in.

 

[Dan0803]

It will constantly cycle

So the problem with that is possible noise and extra running costs?

 

[Dan0803]

Am looking online but cant find any boilers below 18 kw.

 

[Dan0803]

https://www.plumbnation.co.uk/site/ideal-logic-max-heat-12kw-regular-boiler-natural-gas-erp/

Found small boilers at plumbnation. This looks like a good boiler with a 10 year warranty. Any good?

 

[sxturbo]

Nothing wrong with a 18kw boiler that can modulate down to a low kw.

You current boiler is 5.8kw - 9kw, so a boiler that modulates down to below 5.8 will still be better,

This gives you more options. If you opentherm it aswell it will have better control.

But as has been said the biggest saving will be in insulation

 

[vulcancontinental]

There is not much monetary saving in fuel as NG is so cheap but an additional benefit is range rating, limiting the maximum output so the boiler output can be adjusted down and get one with an adjustable cycle rate (some boilers do not have this facility) both will stretch the cycling rate.

Nothing gives you bang per buck like insulation as mentioned but perversely it'll reduce the heat load on the building accentuating the oversizing although that is cancelled by allowing you to lengthen the anti-cycle delay.

There is an argument that more cycling will wear out the boiler components but a long warranty and a good brand will mitigate this.

 

[Dan0803]

I have come across an Ideal boiler - 12kw. It is described as 'Heat Only'. Does this mean it can not heat water to be stored in the copper hot water tank?

 

[vulcancontinental]

I have come across an Ideal boiler - 12kw. It is described as 'Heat Only'. Does this mean it can not heat water to be stored in the copper hot water tank?

No, and being old fashioned I keep tripping myself up over this. To me a heat only boiler is just that, it contains no pump or expansion vessel or valving, all that is external and it's connected to a feed and expansion cistern. A heat only system boiler contains a pump, expansion vessel and other components obviating the need for a F&E cistern. Either can heat a heating system and hot water storage cylinder.

 

[JohnD]

Nothing gives you bang per buck like insulation as mentioned but perversely it'll reduce the heat load on the building accentuating the oversizing although that is cancelled by allowing you to lengthen the anti-cycle delay.

I have oversized rads, and it seems to me that the 100litres of water gives a thermal buffer that should reduce cycling. It takes a while to heat up, and, once hot, it takes a while to cool down again.

My boiler only modulates down to 8kW

 

[Dan0803]

No, and being old fashioned I keep tripping myself up over this. To me a heat only boiler is just that, it contains no pump or expansion vessel or valving, all that is external and it's connected to a feed and expansion cistern. A heat only system boiler contains a pump, expansion vessel and other components obviating the need for a F&E cistern. Either can heat a heating system and hot water storage cylinder.

The boiler in place at moment is a baxi solo 2 - the pump is external and copper pipes lead upstairs to an cylinder hot water tank. So, is the Baxi Boiler 'heat only'?

 

[sxturbo]

The boiler in place at moment is a baxi solo 2 - the pump is external and copper pipes lead upstairs to an cylinder hot water tank. So, is the Baxi Boiler 'heat only'?

It is yes, but you can fit either a heat only or a system boiler. There isn't much difference to installing it, maybe another couple of hours removing the external pump and adding a filling loop.

Atag boiler have an adjustable cycling setup, they also have built in anti cycling.

I don't know about other boiler brands.

 

[Dan0803]

It is yes, but you can fit either a heat only or a system boiler. There isn't much difference to installing it, maybe another couple of hours removing the external pump and adding a filling loop.

Atag boiler have an adjustable cycling setup, they also have built in anti cycling.

I don't know about other boiler brands.

Thank you.

 

[sxturbo]

If you have an opentherm controller installed aswell that will also help reduce the boiler cycling.

 

[vulcancontinental]

I work for this boiler manufacturer so know this product, you can substitute others if you wish.

A 20kW Vision Plus with stainless exchanger and the EPH OpenTherm control will give you what you require including OT control of DHW and htg, DHW priority and WC can be added too.

Can be internet connected if you wish but a wi-fi gateway will be extra.

The Vision Plus will modulate to 3.4kW and you can adjust the anti-cycle delay.

The maximum output can be range rated to the minimum output.

You would need to convert your system to a sealed system.

The following efficiency improvements are general figures applicable to most boilers and system arrangements, are indicative and probably slightly conservative. I don't think it accurate to simply add them all together for a total.

SE Baxi currently around 70%
New HE boiler around 90%
Priority DHW 4.5% uplift
OpenTherm 3% uplift
WC 2% uplift
OpenTherm and WC together 4% uplift

The hit to efficiency in cycling will be around 1-2% as long as burn duration exceeds 3 minutes.

 

[sxturbo]

I would go with Vulcan recommendation, it modulates lower than the ones I've suggested, and he knows much more about boilers than I do.