Weather Control or not?

[ditto]

Hi, I'm thinking of having the CH boiler changed. I've added all the radiator kW and allowed 2000W for water and this comes to 25kW. We use lots of hot water so maybe 2000W is too low - but we do not like hot bedrooms and tend to live in the kitchen diner area rather than the living room. The house is quite big and 20 years old. No cavity wall insulation but fairly well insulated loft and boarded out too for storage. Hot water is pressurised storage tank 170 lites.

I was thinking of a Baxi Megaflow but heard bad reports about circuit board failures. Now thinking of Viessmann 100 but read of 200W with weather control rather than room stat. All radiators have TRV's except kitchen diner where room stat is which is digital type.

Baxi - parts are lower cost and easy to come by if required. Viessmann I've no idea - but I guess parts will be more expensive though readily available but I hear mostly Viessmann is a good reliable boiler and of course 200W offers weather control.

Existing boiler is 20 years old and I'm thinking of trying to save heating costs.

Another boiler is the Alpha and I read the lower cost Biasi is also reliable.

So do I go for the lower cost option and be prepared to bin it if it proves unreliable or the higher end with Weather control?

My current boiler has proved reliable for 20 years - the odd thermocouple failure - its a Myson.

What do you suggest?

Thanks for any reply.

 

[cider]

cheaper boilers often mean expensive parts and a short life.
weather compensators are def good idea and will pay for itself. Viesman are good boilers.

 

[spacethegas]

viesman are good.
many baxi parts are horrendously expensive.
forget biasi. (i expect Agile to jump in).
personally i don't think you can go far wrong with alpha.

a personal opinion.

 

[ditto]

Thanks - Alpha was another I'm considering. Also, what size boiler would you recommend? Detached house normal construction. I read that the heat exhanger should be ssteel. Searching the net I find there is a Viessmann 100W as well as the 200W and the weather control sensor is an optional extra so I'm wondering what is the advantage of the 200W? What Alpha model should I look at?

Thanks again for the advice.

 

[spacethegas]

you must get an rgi in to advise you. there is only so much i can do pressing buttons.

off topic somewhat.

when i did my "efficiency ticket" i was told to use the whole house method to pass it & then immediately forget it & go back to the mears table & just bear in mind 20c differential.

 

[ditto]

Thanks for the feedback - decision made - Viessmann 100 24kW system boiler as I believe you can add weather control later and Viessmann seem to have all the bells and whistle options to control the boiler remotely - mine is in the garage. Friend of mine has a bigger house than me and he has a Baxi 24kW and his house is not cold. So 24kW it is. Only bit that puzzles me is that he tells me his is a combi but he also has a pressurised hot water tank. I thought it was one or the other, combi no tank or system and a tank?

Kind Regards.

 

[spacethegas]

the combi can run a dhw cylinder as well if required.

 

[cider]

Thanks for the feedback - decision made - Viessmann 100 24kW system boiler as I believe you can add weather control later and Viessmann seem to have all the bells and whistle options to control the boiler remotely - mine is in the garage. Friend of mine has a bigger house than me and he has a Baxi 24kW and his house is not cold. So 24kW it is. Only bit that puzzles me is that he tells me his is a combi but he also has a pressurised hot water tank. I thought it was one or the other, combi no tank or system and a tank?

Kind Regards.

make sure your not oversizing boiler by checking output on sebuk website.
your mates house may be cold cus hes a tight a with the heating or his rads are too small

 

[sooey]

Weather Control or not?

I know these new boilers are good, but they're not that good.

 

[ditto]

Friends house is marginally larger than mine and 5 years old, Baxi with 26kW heat input, 24kW output. Pressurised hot water tank and combi boiler.

I checked many of the web sites that calculate boiler size based on house type/size/location/insulation etc and all came out 24kW to 27kW.

Friends 24kW seemed to confirm this (I hope).

Current boiler is Myson Apollo 80000 BTU I believe though at times it struggled in the depths of cold winter days. Best investment seems to have been trv's and digital room stat with 0.5 deg C flat spot. I suspect the 20 year old bellows type required a lot more swing.

I looked at Sedbuk web site and Viessmann 90.5 rating and many Baxi's same order so I'm not sure what this tells me other than they are similar?

So I hope I've not oversized the boiler else I'll have to find a use for it or look into weather control again - if its an option for the Viessmann I've bought.

Kind Regards

 

[ChrisR]

2000W for water

If you use a lot of hot water, do be aware that some heat exchanger coils eg in Megaflo cylinders, are designed at 20kW, 10 times your allowance, for quick recovery.
Weather Compensation gets some people very excited. Lower intelligence means more excitement though so be warned.
Whatever you do, do not do away with an internal (room) temperature sensor. You're heating the house not the friggin garden!

"His house is warm" is not a way to judge heating requirement. WHat outside temp is it designed to cope with? How big are the radiators compared to the heat loss? Insulation?

 

[Agile]

So I hope I've not oversized the boiler else I'll have to find a use for it or look into weather control again - if its an option for the Viessmann I've bought.
Kind Regards

If you have bought a Vitodens 100 they can have an external weather compensation added and you need part number 7818116.

That can be added to any combi or system boiler in that range made since 2005.

Tony

 

[DP]

If your present boiler is rated at 20kW and you are cold in mid winter, I would be looking at 28kw instead of 'marginally' higher output that you have 'calculated'

Do you know the function of weather comp sensor? In a nutshell, this type of thermostat sets the boiler thermostat to heat the primary water to a level that will try and maintain high efficiency for long as possible. You still need an internal room thermostat. Programmable is better as it can be fine tuned to suit ones 'heat needs' over 24 hours. A digital roomstat I would not waste money on.

Personally I see nothing wrong with Vaillant range. If the present system is open vented, I would opt for Vaillant series 4 boiler (Ecomax 428). If sealed 628 and if combi 828.

Almost all boiler will modulate to match the heat requirement. Vaillant 28kw boiler will generate heat output of 6kwatts minimum to 28k max.

I would keep well away from Veissmann as their area man local to me has not had time to return many messages left on his mobile. If they cannot return calls for a sale, what chance with repair or other related calls.

 

[D_Hailsham]

I checked many of the web sites that calculate boiler size based on house type/size/location/insulation etc and all came out 24kW to 27kW.

Did you check out the Recommended Boiler Size at Sedbuk?

Current boiler is Myson Apollo 80000 BTU I believe though at times it struggled in the depths of cold winter days.

That's only 15kW. So if your rads plus HW total 25 KW it is under powered. Where did you get your rad info from to work out the output?

So I hope I've not oversized the boiler else I'll have to find a use for it or look into weather control again - if its an option for the Viessmann I've bought.[/quote]
I hope so too!! A 24kW boiler for a system with indirect HW is very large.

You say you do not have cavity insulation. You may be able to get a grant from your gas/electricty supplier for reduced cost insulation.

Check out Energy saving grants

 

[ditto]

Thanks - very good information.

Lets see if I can remember to answer all the questions.

I did try Sedbuk and it came out at just under 24kW.

Radiator kW taken from manufacturers data found on many plumbing supply sites.

Mostly showers used but washer (top loader - does not heat water and 18LB load - uses lots of water) and dishwasher on every other day.

Present boiler does not appear to shut down with stat (old bellows type) set over 20 degrees - so I guess we lose as much heat as it can make. But new stat seems to have helped a lot as have TRV's.

Cavity wall insulation - I was told I cannot have it as house is built of stone and polystyrene bonded breeze blocks - told insulation pattern cannot be guarenteed so not worth it and advised not to do it anyhow due to natural stone possibly bridging cavity in places. So I'm put off.

And thanks for the ref to the WC unit.

Finally room stat is digital type and can be programmed I believe for various times of day. Also go a wireless one that does the same but you can take it with you - now realise not a good idea to TRV's. Current stat in the kitchen diner with no TRV's and rads full on.

Any other commenys suggesting improvements to reduce gas are appreciated.

Just signed up for fixed energy deal today.

Hope I've not missed anything.
Kind Regards