It's all a bit of a mess...

[vetinry]

Morning everyone

I am in the midst of renovating a property that we bought last year and (probably a little too late) am now considering options for the central heating and hot water.
Currently the house (approx 3000 sq ft, built in 1987) heating and hot water is supplied by an oil boiler (Boulter Camry 5?)

Heating

The central heating is "Y" plan and a single zone, and before we moved in, all rooms (14 of them) were supplied by radiators. There was insulation in the various loft spaces but I have been topping it up as and when there is an offer at B&Q - I'm aiming for min 300mm but it is actually deeper than this in some places.
We have already renovated the Kitchen and opted for Wet underfloor heating under a tiled floor and over 70mm insulation to achieve u-values.
Underfloor heating is not an option everywhere in the house because we want to put carpets and not have to worry about low tog values.
In one of the upstairs bedrooms, I am about to install skirting board heating to see how I get on with that.
And in the upstairs bathroom, we want to tile so we are considering either wet or electric underfloor heating.

Domestic Hot Water

The water is supplied by a cylinder, which I think I calculated as about 160litres and which seems to be a little bit small for a 5 bedroomed house.
In addition, the immersion heating is broken, and the cylinder is built into the eaves of upstairs making it's removal without removing the tank rather difficult.
In the upstairs loft, there are 2 huge water tanks (gravity system) and there are 3 shower pumps scattered throughout the house.
When the house was built, copper must have been pretty cheap because there are literally hundreds of metres of copper pipe running through the loft spaces. For example, each of the 3 showers are fed by their own 22mm supply and they are scattered throughout the house.
The hot water is also linked to a secondary circulation system due to the sheer distance that water has to travel to the various tap points.
I've checked mains pressure (about 4 bar) and flow (about 25 litres per minute)
Just before Christmas we had an oil delivery and 2500 litres at 75p per litres gave me a bit of a shock.
And now, I'm going to need a little bit more oil to get through the summer (boiler still supplying hot water)
Therefore I'm researching different options, principally to reduce our demand on oil and improve efficiency

Questions

I have some fairly basic questions which I hope you might be able to help with
How much of the oil is being used to heat the property vs hot water production.

1. Is it very inefficient to have a DHW system which runs seperately from the CH. I've seen an indirect cylinder with built in air source heat pump which looks like it could supply all of my hot water at a fraction of the cost that I currently spend on oil
2. If the oil boiler is on, does it make any difference whether it is heating lots of rooms or just a few? The reason I ask this is that I will still need to heat the underfloor heating, and rooms with carpets where radiators or thermal skirting will be used. But in the bathroom, for example, it would be much less expensive to install electric underfloor heating but if the boiler is already on, am I just spending twice on energy?
3. Seperating the house into zones. I definitely want to zone off the kitchen ufh but wondered how close to the "centre" of the system the zone valves need to be placed. ie could you have the zone valves operating close to the rooms or is this inefficient since you are still heating pipework prior to the zone valves?

Really hope that you might be able to shed some light on all of this

Thanks
Steve

 

[SimonG]

Hi Steve,

1. Don't know but others will, but have you looked at unvented cylinders? Plus is your secondary return on all the time or on a timer for peak hot water requirements?

2. Yes it does make a difference and as you update you will be adding thermostatic controls to your rads or thermal skirtings. As far as the bathrooms go the feedback I get from customers is that they find the electric underfloor heating quite expensive to run, but I dont have first hand knowledge of this, however I would also have a radiator or towel rail even if just to dry/warm your towels.

3. Zoning, my preference is close to the boiler where you've got plenty of elbow room to change/maintain things, might not be so easy on an existing system but sounds like the mods you are planning will lend themselves to this.

Hope it helps.

 

[vetinry]

Hi Simon
Thanks for your quick reply. The secondary pump was running continously when we first moved in but I've put a single channel 5+2 day honeywell controller on it to just circulate the water for an hour in the morning and evening when the boiler is on.

I did install electric ufh in a kitchen in my old house but ended up not using it because the electricity bills were so high. So, I'm leaning toward wet UFH, perhaps using the wavin plywood with 10mm pipes built in (depending on heat output) to maintain floor height. We're probably not going for a full wet room, perhaps a flush fitting or low profile shower tray instead.

Zoning close to the boiler would theoretically be possible but the boiler is in its own room next to the garage and this is a considerable distance to the hot water cylinder and 3 way valve. I was therefore wondering if I continue with the single run to the current valve and then think about zoning from there.

I am also wondering whether converting to mains pressure hot and cold would be a viable option but am struggling with whether an unvented cylinder (with ASHP on top) or a thermal store might be better for me.

There is also a second mains supply in the double garage attached to the house, which is supplying a couple of outside taps and which could be used to supply mains cold and hot if a new cylinder went in the garage - the problem with the existing cylinder location is height (it's in the eaves) and diameter (between trusses) so I'm probably limited to either adding a second cylinder of similar size or moving the location.

Steve

 

[Bartdude]

Zoning the house is a good move to make for fuel efficiency,the UFH should be on a different circuit to the radiators really as underfloor heating needs to be running for much longer periods than radiators.It doesn't matter too much where on the circuit the zone valve is positioned,you won't be heating water behind it as there won't be any circulation whilst it is closed.

An unvented cylinder would be my choice for hot water,and the shower pumps could be removed,solar thermal could be an option for heating water too,it will be supplementarty though,you will still need top up from the boiler.I don't know about the ASHP combo,never seen one of those.

I'm not a big fan of electric underfloor heating really,in my experience it's quite expensive to run.

 

[vetinry]

That's good news about the zone valves.

I probably should have realised that there wouldn't be any flow through the pipes.

So, to give me good control, I could effectively break up the house into a number of different areas, each controlled by its own valve.

Can these all link back to provide boiler switching?

Steve

 

[SimonG]

Aye, through the two port valves microswitch.

 

[HHP Ed]

I agree with Bartdude. The firm that i work for zone off all the larger houses that we work on. It does help with the fuel efficiency and allows much greater flexibility for your heating. Dont go with electric underfloor heating (got it in my kitchen and the cost is ridiculous, i ended up putting in radiators), also heating dhw with an immersion is expensive, even compared to oil.

 

[vetinry]

Thanks for all of the replies

What I've concluded so far is that I definitely need some zones in the house, and that an unvented cylinder is probably the way forward with regards to hot water.

I will have to consider the capital outlay for solar panels and how much hot water they can provide (are there any easy ways to calculate hot water energy requirements?)

If I zone up the house and need individual control, can that be achieved by programmable thermostats in each of the zones which also switch the boiler, or will it be more efficient to have a central control which manages all of the zones and also the boiler control - can anyone provide good recommendations - I've found the honeywell stuff, and also a product from Heatmiser.

Finally - is there a way of calculating how much of the oil will be used to provide hot water vs central heating or a simple rule of thumb eg 40% hot water, 60% heating

Steve

 

[HHP Ed]

Steve. If you want a rough idea of the cost of solar panels my boss could give you a ring/quote (free) depending on where you are, pm me if you want any more info.
I would advise seperate room stats in all the areas that are zoned, thats the best way to utilise the zones and give you the most control over temperature and to save money. We always go with honeywell and very rarely get any problems. And definetly go with an unvented cylinder as the are the dogs bits for giving decent pressure and saves having extra pipework and pumps for showers etc.