DIY Doctor UK DIY Forums

We have entered the confusing world of replacing our central heating boiler! We have a 3 bed semi with a bathroom with bath/shower, and we may add another shower downstairs soon.

We have decided upon a non vented indirect cylinder with a gas boiler, both located in the loft (which is fuly boarded with good space). My questions are:

1. Is supplementary solar power a cost-effective option.
2. For any sugested option (solar or non solar)
a. What is optimum boiler output?
b. What is recommended size of cylinder?
(solar has twin coils and some companies have priced 250L cylinders)

We feel that unless you manually turn the hot water off and on when the cylinder runs out then you may not benfeit to much from the solar power effect. It only assists during the daytime (on some days!) by which time the gas boiler has probably already heated the tank fully. (ave 20-25 min full tank reheat). So unless you have showers/baths/use a washing machine during sunny days you might normally only save max 100 pounds per year. Twin solar panels would therefore take about 15 years to pay for themselves assuming 2500 intial installation and and increase in gas prices.

We would be grateful of any advice/comments.

Hi, Answers to your questions,
1) In my opinion NO
2) a) Would depend on size of floor area and size of radiators, but I would suggest a 28kw unit should be OK
b) a 210-250L would be ok for two bathrooms.

p.s. If money is no object then I would recomend the vac tubes instead of panels, they give more heat, if the companey you use know their job they will install the correct controls to make maximum use of the tubes.
Hope this helps. :D

Many thanks. It confirms our conclusions.

Hi just to add a bit, we have evac.tube panels, place is all electric, no gas available, solar heating is all we need for most of year.
3 bed detached bungalow, have immersion heater fitted for top up on 'bad days', timed for early evening, so if it comes on timer but panels have worked, tank already at 65c+ and heater stays off!
There is a 2nd coil fitted so if we had a 'wet' boiler system it could be controlled in same way, it was fitted 2 years ago, cost too much, but i figured to pay my lifetime water heating bills up front while still earning ok wages, so less to pay when retired as cost of heating can only go up!
You don't ask when your 'fridge, TV, washing m/c will pay back, treat it the same way & be smug about 'doing your bit for the environment Hi, Hi!!!
regards SPARX

Thanks SPARX I'll give it serious thought.