Central heating for new build bungalow

Hi all,

Long time reader, first time poster.

I am in the process of project managing our long planned self build bungalow and am trying to stay a couple of steps ahead of the next decision I have to make!!

We currently live in a small semi-detached with a fairly old combi boiler running off LPG (rural area - no natural gas). Granted, we only have one bathroom and one extra sink in the kitchen but I really love the fact I can get hot water any time. There is myself, my husband and 2 children under 5.

Our new build is also outside mains gas but larger (2500sq ft) with one main bathroom, 2 en suites, one of which I envisage installing an electric shower in. I am hoping given the amount of insulation we are putting in, the heating will not need to be on for quite a few months in the summer, therefore making me lean towards a new, higher powered combi boiler.

However (and I realise this question has been posed and discussed before) I appreciate we will have significantly more demand for hot water than currently. My problem is that I am dealing with projected pressures and flow rates given by the water service which do not seem great......they are quoting the minimum pressure at 1.5 bar and minimum flow rate of 9l/minute. The main water pipe is due for an upgrade but goodness knows when they will get around to it.

My understanding is, even with a system boiler and cylinder I would still need good flow rate and as my preference is to lean towards combis, I then began investigating the storage combis (mainly Valliant ecoTec Plus 937 / Viessman Vitodens 222-F 35kW / Gloworm Ultracom 2 35 store / Alpha CD50) but now my head hurts and am getting more confused the more I read!!! I also looked at the higher powered WB combi boilers but again, my understanding is that the output is only as good as the cold water input.

I believe the mains water pipe coming from the mains to the house will be 25mm.

Can any of you nice forum people give me any words of advice??

Yours in hope........

Steer clear of a combi in your situation, with a growing family it will just lead to disappointment.
With 9 lpm coming in you're going to need some sort of storage, break tank and pump set.
A nice fast recovery unvented cylinder, with an lpg system boiler, immersion back up that can obviously be linked up to pv panels if you wanted at some point.
Combis have there uses but with 3 bathrooms before long you'll wish you hadn't.

The GW Ultracom Store is a decent bit of kit and will hold it's own against unvented cylinders if the incoming main pressure and flow is sufficient.

It is one heavy beast though so allowances will have to be made for wall construction.

Ted

I'd be looking to install a heat pump with a small boiler to top it up on the coldest days or a wood-chip fired system. Underfloor heating and a HW cylinder would be favourite. If you have a large building plot then use ground source or bore hole type and air source if you are tight on space. Solar heat panels would also give you cheap HW.

More importantly you would get paid to run them! Look up the Renewable Heat Incentives (RHI) web site. You will be surprised how much they will pay you per kW to use them.

(And a final comment, LPG gas boilers are extremely expensive to run as you probably already know. Oil may be cheaper if you have to go conventional or combi-boiler)

I assume you can get a free biomass boiler for a new build.
Just had my biomass installed for free.

Tipper said:

I'd be looking to install a heat pump with a small boiler to top it up on the coldest days or a wood-chip fired system. Underfloor heating and a HW cylinder would be favourite. If you have a large building plot then use ground source or bore hole type and air source if you are tight on space. Solar heat panels would also give you cheap HW.

More importantly you would get paid to run them! Look up the Renewable Heat Incentives (RHI) web site. You will be surprised how much they will pay you per kW to use them.

(And a final comment, LPG gas boilers are extremely expensive to run as you probably already know. Oil may be cheaper if you have to go conventional or combi-boiler)

Click to expand...

I agree , Heat pump or even biomass is a better option, with heat Pumps your heating design is crucial, underfloor heating in screed is highly recommended as you can run an ASHP during the day when outside air temperatures are higher and store the energy in the screed, biomass is ok with ufh or radiators, or even wall heating. And the best bit is the RHI will pay you to generate your own heat, and because hot water is generated so cheaply ditch the solar panels,

Would it not be more efficient to run the ASHP on an off peak tariff?

Norcon said:

Would it not be more efficient to run the ASHP at night on an off peak tariff?

Click to expand...

It all depends on what the outside air temperature is, the higher heating demand is usually when the outside temperature is lowest, not many people understand the effect low temperatures have on ASHP`s especially in our moist climate, many manufacturers boast 16 kw output but this is probably at +10 deg C the same unit will only produce 8 kw at - 10.
At this point backup immersion heaters are employed so the off peak electricity gain is cancelled out, plus the moisture in the air at colder temperatures cause more frequent defrost cycles especially ASHP`s with a small evaporator surface area, and again there is no point running a radiator heating system at night, it must be ufh in screed as a thermal store.10 years in the business has taught me a lot.

Greenerheat said:

Norcon said:

Greenerheat said:

Tipper said:

I'd be looking to install a heat pump with a small boiler to top it up on the coldest days or a wood-chip fired system. Underfloor heating and a HW cylinder would be favourite. If you have a large building plot then use ground source or bore hole type and air source if you are tight on space. Solar heat panels would also give you cheap HW.

More importantly you would get paid to run them! Look up the Renewable Heat Incentives (RHI) web site. You will be surprised how much they will pay you per kW to use them.

(And a final comment, LPG gas boilers are extremely expensive to run as you probably already know. Oil may be cheaper if you have to go conventional or combi-boiler)

Click to expand...

I agree , Heat pump or even biomass is a better option, with heat Pumps your heating design is crucial, underfloor heating in screed is highly recommended as you can run an ASHP during the day when outside air temperatures are higher and store the energy in the screed, biomass is ok with ufh or radiators, or even wall heating. And the best bit is the RHI will pay you to generate your own heat, and because hot water is generated so cheaply ditch the solar panels,

Click to expand...

Would it not be more efficient to run the ASHP at night on an off peak tariff?

Click to expand...

It all depends on what the outside air temperature is, the higher heating demand is usually when the outside temperature is lowest, not many people understand the effect low temperatures have on ASHP`s especially in our moist climate, many manufacturers boast 16 kw output but this is probably at +10 deg C the same unit will only produce 8 kw at - 10.
At this point backup immersion heaters are employed so the off peak electricity gain is cancelled out, plus the moisture in the air at colder temperatures cause more frequent defrost cycles especially ASHP`s with a small evaporator surface area, and again there is no point running a radiator heating system at night, it must be ufh in screed as a thermal store.10 years in the business has taught me a lot.

Click to expand...

I must add not all Heat Pump installations employ back up immersion heaters, Greenerheat install high quality units from IDM Energie, never have we installed a system with electric back up.

Would you install an ASHP as the sole means of providing CH and HW?

When they breakdown then a customer can be left in a right pickle.
And maybe parts difficult to source.

Norcon said:

Would you install an ASHP as the sole means of providing CH and HW?

When they breakdown then a customer can be left in a right pickle.
And maybe parts difficult to source.

Click to expand...

We have installed many GSHP and ASHP`s over the years, only one was with a back up boiler because the largest ASHP we had available in single phase 240 volt at that time was rated at 10.5 kw @+2 deg C (we now have 17 kw 240 volt) plus at the property was a renovation the existing first floor radiators remained in place and underfloor heating was installed on the ground floor, so the ASHP could not achieve 100% heat load,
Apart from the occasional soft starter problem we do not have breakdown or under performance issues on any installations and this is down to good design good product and good installation. we can never compete on price but can compete on quality. In this sector you get what you pay for. we do not install any other than IDM Energie.
out latest models take advanced information from the met office so automatically adjust output to compensate for sudden temperature changes.