1 house - 2 Independent Boilers

[Bream]

Hi Everyone, This is my first post and I think it may be a rather atypical situation, so I will provide some background information, but will try and keep it brief.

Seven years ago we bought half of a house. It is over 100 years, 3.5m ceilings, all one level, solid wall brick construction, external wall insulation. Total of about 190sqm. The house had long ago been divided (or perhaps originally designed as two joined by a common entrance and corridor). We did a complete renovation of our side of the house (90sqm) including all plumbing and heating. A 20KW gas combination boiler provides hot water to 1 bathroom and a small kitchen and heat to the radiators. It works great, and we are very happy with the performance. No complaints.

Three children later and feeling a bit squeezed we have just purchased the remaining half (100sqm) of the house from the elderly couple next door. The new side of the house will require some serious renovation work, including plumbing and the heating system, which must be replaced. There is a VERY old inefficient gas boiler that has to go.

We plan to join the two halves as one seamless home. The old half will be the sleeping area, and will require only a few minor modifications. The new half a large kitchen, open plan dining/living, 2nd bathroom, large entrance corridor, and an additional bedroom (small).

Clearly our existing 20KW boiler won’t handle the load of the 2 bathrooms and extra 100sqm. The simplest option is to replace it with something bigger to run the entire house. Or does it make good sense to install a 2nd boiler for the new half, and run it as a 2nd independent zone?

To complicate things further – the new half of the house has suspended floors, and I may (it isn’t clear yet) end up lifting most of them and replacing – tiles for the bath/kitch/corridor and hardwood for the living area. Would seem like a great opportunity to install wet UFH. In this situation would it make even more sense to install a second, high efficiency condensing boiler to run the UFH, and leave the original boiler for radiators in the bedrooms and hot water to the taps? I should add that the open plan area will also have a fireplace.

Thank you in advance for sharing your thoughts and experience.

 

[dcawkwell]

The old boiler is 20kW so will possibly run 13 radiators.

If you will have less than this you can simply add an unvented cylinder to supply a good supply of hot water to the entire property. Assuming you have a good mains supply to the property. It also give you an immersion heater backup for hot water should the boiler fail.
The combi can heat a hot water tank.

Given the combi is old and only 20Kw I would be upgrading it to something bigger.

Stick with radiators for the whole house.

 

[Blagard]

It's a tricky think to answer especially if the property is in Poland as I have no idea what the ground rules are out there!

One thing that occurred to me is you presumably have two electrical supplies, two gas supplies and two water supplies.

Unless you are merging into one property properly and have one supply of each I would stick with two systems that allow you to split the property back again in the future if you want to.

If you use one boiler will the supply be adequate for good flow rates to the whole assuming you want to use a combi again. If not that is another reason to keep them separate.

I appreciate you have not mentioned electrical work but in the UK I think you could run into problems if a room is created from two that have different supplies, possibly on different phases.

 

[Bream]

Thanks for taking the time to respond. You may be right that the existing 20KW combi is big enough to heat the whole house, I hadn’t approached the problem that way. The cylinder with immersion heater backup is something I will consider.

Blagard – Leaving the possibility to split the property again in the future is a big plus, but not a strict requirement. There are single mains water/gas/electric connections terminating in the house, all which then divide into 2 metres for each service. Water and electric I’ll have run off a single supply, but will have the services designed in a way that leaves a future split possible. The gas supply is a question mark for me – if I do opt for two separate systems I’ll have the installer decide what is best. Your advice to stick with 2 systems is based solely on the ability to separate in the future, or are there other considerations involved?