Another which boiler thread with smart controller

[Secret_Sipper]

After the best part of 30 years old (we reckon), we are retiring the old girl (Baxi Solo WM50/4) due to it being in the way of our plans for an extension. I think we are due a new one anyway!
My dad has a Worcester 30kw CDi that he had installed a few years ago, no problems.
A visit from the one of the guys tonight has put my idea of Worcester out the window as he said they are a nightmare to work on and full of plastic fittings.
Now I sympathize being an engineer myself and I do fit products that are easier to maintain for my self but it being hard work to work on isnt a priority as I can't really work on it myself. Reliability is.
He recommended a Baxi 825 or a main which I'd never heard of myself until finding out it was part of the Baxi group which makes sense.
I figured I'm gonna get less biased feedback from here as you lot have nothing to gain from helping a fellow member out. Any insight would be massively appreciated.

I'm also looking at the smart controller side too, again not quoted yet but I'd say he may plug for the Baxi usense. I believe it needs hardwiring in which isn't ideal. Again any advice would help me greatly.

I fear due the current boiler age, I'm massively out of touch with how things have moved on!

 

[muggles]

Avoid Baxi, the modulation range on them is rubbish and there are very few installer parameters available to allow them to be set up for the system they're fitted to. They're a boiler for installers who just want to chuck it on the wall and run away. Are you looking for a combi boiler or are you keeping your hot water cylinder?

 

[Secret_Sipper]

Thanks for your reply!

I know alot are putting hot water tanks in at the moment due to having solar etc but it's not something I want to navigate at the moment. Very possible in the future as I think it's just how it's gonna have to go.

Yes a combi is more than suitable for our needs. The tank will be making way for a shower tray, I hope

 

[muggles]

OK, in that case the first thing you need to know is your incoming mains pressure & flow rate. That will give you some idea of the hot water performance you can expect and thus help to inform your choice of boiler.

You also need to know the heat loss for your home (IE how much heat it actually requires, which is almost certainly less than you think). Since June last year it has been a requirement of Building Regulations in England & Wales to carry out a full heat loss survey in order to determine the most appropriate boiler power for a property.

You can get a good approximation yourself using this handy chart

Once you have these two facts, you can start to choose a boiler. I'd suggest looking for one that accepts OpenTherm controls unless you're happy using manufacturers own modulating controls

 

[Secret_Sipper]

I'd say we are in the 40-65w/m2 bracket having cavity wall, 200mm loft insulation, solid floors and upgrading all of the rads with TRVs and convectors (75 % done)

We have good mains cold water pressure (could rig up a gauge on a tap) but I'd be useless at measuring the flow rates.

Didn't even check any of those last night.

It will require a new 22mm gas feed to the boiler as it's currently only 15mm.

 

[muggles]

What's the total floor area (not footprint) of the existing in m²? What's the floor area of the extension?

Flow rate is easy to do. Get a bucket of known capacity, and stick it under your cold bath tap (if connected to the mains rather than the loft tank) or outside tap. Time how long it takes to fill up with the tap running at full rate, then convert that figure to litres per minute.

If the person who visited last night didn't bother to even check pressure and flow rate, they really are just a boiler slinger and it's time to find a different installer

 

[Secret_Sipper]

Thanks again for the above!

Going forward, not very confident in what he's offered so far. After looking at what modulation is and understanding it abit better/comparing it to a WB (easier as I've heard my dad's run and it run pretty well, from ambient temp outside 8 degrees to 16 didn't take long to get up to temp at all) they are miles apart albeit cheaper which isn't a bother if I can see a difference in quality, reliability and longevity.

From above, total floor area is 89 sq m existing and 14 sq m for the new extension.
Approx 2.5 / 2.7 bar pressure (allowed for gauge) and 13 litres per min.

 

[muggles]

89m² old side @ say 50w/m² = 4.45kW
14m² new side @ 30w/m² = 0.42kW

Total heat load therefore about 5kW when it's -3°C outside with an internal target of 21°C. Heat loss is a function of the difference between internal and external temperatures, and as such on a day when it's 9°C that heat load will drop to 2.5kW. Now you'll hopefully see why modulation is important.

13l/min points to around a 30-35kW combi.

So, to options...
Vokera Vibe Max 30C is very keenly priced, OpenTherm compliant, and modulates to 4.0kW. 5 year warranty, stainless heat exchanger.

Intergas Xclusive 36 is a different combi boiler design which has removed the need for a plate heat exchanger, diverter valve, and air pressure switch. Only 4 moving parts for great reliability. OpenTherm compliant, modulates to 3.6kW. Large bore copper waterways encased in an injection moulded aluminium heat exchanger. 12 year warranty. All metal construction, no water carrying parts pass through any plastic sections. Not the quietest boiler on the market at full chat.

Navien NCB700 42kW. More power than you need but modulates to 3.5kW so not a problem. The lower power 500 series have a higher minimum output. Well priced for a boiler with this power rating. OpenTherm compatible, or Navien's own controller works well with it and comes with an app. Stainless heat exchanger, 12 year warranty.

Viessmann 200-W 35kW. Amazing modulation down to 1.9kW. Stainless heat exchanger, 7 year warranty as standard but can be upgraded to 12 years. Most expensive boiler listed here, and only works properly on weather compensation, using Viessmann's own controls.

Worcester 8000. 30kW modulates to 3.0kW, 35kW modulates to 3.5kW and is probably the one I'd go for. Aluminium heat exchanger, 10 year warranty, can be upgraded to 12 years for £150. Need to use Worcester's own controls to get the best out of it.

Vaillant ecoTEC Exclusive 35kW. Stainless heat exchanger but very narrow waterways which are very dirt sensitive and almost impossible to flush, so system needs to be absolutely sparkling from day 1. Modulates to 3.4kW, 10 year warranty when fitted by an Advance installer. Needs Vaillant's own controls to get the best out of it.

Hope that helps

 

[Secret_Sipper]

I cant thank you enough for taking the time to help out.

Absolutely amazing detail

Some brands I've never heard of their so I'll get my researching head on this weekend

 

[Secret_Sipper]

But of an update, first guy has quoted for main eco compact (3100), Baxi 800 (3800) and WB 8000 (4200) but has recommended the main (as we thought)

Last night we have had an accredited WB installer round and has recommended the 4000 over the 8000 mainly due to the additional depth needed and might require batoning off the cupboards (if we put it inside one) The place of install is close to a window which is only 300mm deep (it's not on the same wall as the opening window and more than 100mm away from it)

I'm slightly worried the rated 10 litres per min of the 4000 might hinder us but potentially if it does, does the pump throttle back or will we just get slightly cooler hot water?

Also recommended the Hive over WB easy control which having looked online doesn't sound as though it's as good to use and not totally intuitive.

Mark

 

[muggles]

WB 4000 is OK. Modulates to 3kW. 30kW does 12.3l/min at 35°C temperature rise. Running water through faster will just result in cooler water. Heat exchanger is a bit more dirt sensitive but a well flushed system will ensure it's ok. Hive won't provide any form of load compensation, it's a completely unintelligent on/off switch so the boiler would be less efficient than on EasyControl.

 

[desktop987456]

@muggles. I have looked at chart on your post#4 and have calculated heatloss at my property on two floors.

It gets very cold on first floor so I have used a factor of 100 to calculate heating requirement. For downstairs which is much warmer than upstairs I have take the factor at 80. My total heating requirement or w/m2 comes out 18-19kw. I understand that this heating requirement is for a very cold day which will be couple of weeks at the max in my area. On normal or sunny days I may not be needing these many kws. For optimum efficiency would a 15kw boiler do the job since Ground floor will be needing less heating than upstairs?
Secondly, I live in a hard water area and limescale build up could be an issue, Which boiler is less sensitive to this issue.
Thanks

 

[gazfen]

Worcester is an easy boiler to work on. Most boilers are plastic.

 

[desktop987456]

Worcester is an easy boiler to work on. Most boilers are plastic.

Thanks, would a 15kw inverter do the job. Secondly, which series in worcester has pump and expansion vessel built in?

 

[gazfen]

Don’t know, I don’t do installations. Only repairs