Potential Boiler / Heating Options Going Forward

pmartin86

Hi All

Just after a bit of advice in general in the very early days of replacing a boiler. Some basic facts to start - I'm fortunate enough to live in a large house (Joys of being in Wales with its property values) which is 5/6 bedrooms, 2 en suite, one master bath and a downstairs toilet. Theres also a kitchen, a large living room and 3 "additional" rooms, dining room, "sitting room" and a study. Currently the house is supplied by a Greenstar Highflow 440CDi boiler, that ive been told is "fine" and will last for "years" - but I'm looking towards the future as I dont ever intend to move from here untill I'm going to the forever home in the dirt.

I've been reonvating over the last year we've been here, and replacing the 30+ year old pipes and rads etc, aiming to give each room enough BTUs to eventualy cope with a heatpump, and turning down the locksheilds. Looking forward, we are having a 7.7kw solar array fitted early next year and I've been wondering how to possibly utilise the "spare" generation in the summer for my hot water needs. I've replaced the en-suite shower with an electric shower anyway (Mainly for redundancy should the boiler decide its had enough) but was thinking of a hot water storage cylynder that would somehow use the excess generation to pre-heat? I assume this wouldnt work with the existing combi and would need a "normal" boiler and Cylynder setup?

Can anyone advise on how I might get started with looking into things? How to compare efficencies etc? Assuming we are looking at a 5 year timescale before the change (lots of renovation, limited time and budget) is there anything else I need to be doing "now" to prepare? I've allready upped the CH feeds to larger bores etc to cope with the heatpump needs, should I be doing anything with the hot water feeds?

Thanks In Advance
Paul

FreeBear

pmartin86 said: is there anything else I need to be doing "now" to prepare?

Insulate as much as you can, and then add more insulation. I've got ~300mm of loft insulation, and am in the process of insulating the walls best I can - 75mm of Celotex type boards on most of the walls upstairs (solid brick on the upper half). New windows & doors all round. Plugged all the nasty draughts, especially ones coming in around the old badly fitted windows.

pmartin86

FreeBear said:

pmartin86 said: is there anything else I need to be doing "now" to prepare?

Insulate as much as you can, and then add more insulation. I've got ~300mm of loft insulation, and am in the process of insulating the walls best I can - 75mm of Celotex type boards on most of the walls upstairs (solid brick on the upper half). New windows & doors all round. Plugged all the nasty draughts, especially ones coming in around the old badly fitted windows.

Yes, should have mentioned I'm adding insul;ation where appropriate as I renovate - Most rooms are "back to brick" to ideal time really. The one thing that really stands out about this house is the insualtion though, previous occupants were rather obessed it seems, all the floors are filled with rockwool, the walls are allready well insulated, the loft has between 500 and 550 (yes, five hundred...) so most of what I need to do it just touching up where theres been modifcations - Its lovely to be fair, I can turn the heating on for an hour when its been minus figures outside and it stays warm for most of the day!

Ectophile

If you get a hot water tank, with an immersion heater, then you can buy a solar "diverter" that detects that you are exporting electricity, and sends some of that spare electricity to the immersion heater.  With such a large solar installation, you could find that you have more hot water than you could need during the spring and summer.

In the winter, you'd need to heat the water from the gas boiler.

benson1980

You can use a combi boiler with a cylinder so I would look at heat pump ready cylinders and see if they are compatible. Ours is indirect HP ready (whether we end up converting I don’t know but good to have the option) and hooked up to a heat only boiler- they are a bit more expensive but not prohibitively so.

then you can look at using the panels to heat the cylinder via the immersion as well.

pmartin86

Ectophile said:

If you get a hot water tank, with an immersion heater, then you can buy a solar "diverter" that detects that you are exporting electricity, and sends some of that spare electricity to the immersion heater.  With such a large solar installation, you could find that you have more hot water than you could need during the spring and summer.

In the winter, you'd need to heat the water from the gas boiler.

Thanks - This is sort of what I was hoping for - I should have mentioned that we are also getting batterys for the solar install, so there will allready be a diverter - do you happen to know if its possible to "daisy chain" devices? The installer informs me that the Energy generated by the panels will first be "used" by any devices drawing power, then fill the batteries, then export whats left, idealy I'd like the "water" to be last on the list before export? Is this something I need to discuss with the installer in advance?

pmartin86

benson1980 said:

You can use a combi boiler with a cylinder so I would look at heat pump ready cylinders and see if they are compatible. Ours is indirect HP ready (whether we end up converting I don’t know but good to have the option) and hooked up to a heat only boiler- they are a bit more expensive but not prohibitively so.

then you can look at using the panels to heat the cylinder via the immersion as well.

Thank you - Wasn't aware you could combine a combi and a cyclinder, very good to know though as I dont want to replace the boiler if its "working".

FreeBear

benson1980 said: You can use a combi boiler with a cylinder so I would look at heat pump ready cylinders and see if they are compatible.

I had been looking at the Intergas range of combi boilers - These have the option of running just hot water or central heating. Handy if you are doing a staged installation and just need one or the other. Not a cheap boiler though, but some of them have a 10/12 year warranty available.

benson1980

pmartin86 said:

benson1980 said:

You can use a combi boiler with a cylinder so I would look at heat pump ready cylinders and see if they are compatible. Ours is indirect HP ready (whether we end up converting I don’t know but good to have the option) and hooked up to a heat only boiler- they are a bit more expensive but not prohibitively so.

then you can look at using the panels to heat the cylinder via the immersion as well.

Thank you - Wasn't aware you could combine a combi and a cyclinder, very good to know though as I dont want to replace the boiler if its "working".

Indeed not...I think the way you are looking at approaching it makes sense. We did struggle though to find a plumber who had the slightest clue about HP ready cylinders. We ended up getting someone in who had diversified into heat pumps, and we contacted Vaillant tech support as well who confirmed it would all work. I believe the only difference is the coil design that has improved heat transfer properties (larger surface area presumably) so all in all you'll still be getting a slightly more efficient cylinder anyway, even if you heat it from the gas boiler.

We are also considering installing a diverter at some point, as we have panels- maybe next year.

ThisIsWeird

pmartin86 said:

Hi All

Just after a bit of advice in general in the very early days of replacing a boiler. Some basic facts to start - I'm fortunate enough to live in a large house (Joys of being in Wales with its property values) which is 5/6 bedrooms, 2 en suite, one master bath and a downstairs toilet. Theres also a kitchen, a large living room and 3 "additional" rooms, dining room, "sitting room" and a study. Currently the house is supplied by a Greenstar Highflow 440CDi boiler, that ive been told is "fine" and will last for "years" - but I'm looking towards the future as I dont ever intend to move from here untill I'm going to the forever home in the dirt.

I've been reonvating over the last year we've been here, and replacing the 30+ year old pipes and rads etc, aiming to give each room enough BTUs to eventualy cope with a heatpump, and turning down the locksheilds. Looking forward, we are having a 7.7kw solar array fitted early next year and I've been wondering how to possibly utilise the "spare" generation in the summer for my hot water needs. I've replaced the en-suite shower with an electric shower anyway (Mainly for redundancy should the boiler decide its had enough) but was thinking of a hot water storage cylynder that would somehow use the excess generation to pre-heat? I assume this wouldnt work with the existing combi and would need a "normal" boiler and Cylynder setup?

Can anyone advise on how I might get started with looking into things? How to compare efficencies etc? Assuming we are looking at a 5 year timescale before the change (lots of renovation, limited time and budget) is there anything else I need to be doing "now" to prepare? I've allready upped the CH feeds to larger bores etc to cope with the heatpump needs, should I be doing anything with the hot water feeds?

Thanks In Advance
Paul

You've given this quite a bit of thought! Including the all-important upsizing of rads in order to provide enough output when run on a 'cooler' energy system like ASHPs.

Something I don't know is whether a Thermal Store is required for an ASHP system, but it would certainly appear to be a useful addition in your sort of case as you'll have more than one way to heat it, so I think I'd be looking at this as being a 'must have'. Meanwhile, until you do go ASHP, I understand that combi boilers can operate like 'system' boilers, and their CH output is simply diverted by external 2-port valves - one for CH and one for stored DHW - so they can do both. The 'instant DHW combi' output doesn't actually have to be used, but you may still wish to do so - your call.

So, afaIk, your 440CDi can be used as a system boiler right away if that is what you wish. 

Looking at the most popular immersion heater diverter - the Marlec iBoost+ - that prioritises domestic consumption first, then diverts any unused to the hot cylinder - like all of them. But I also notice it has something like 'compatible with batteries' printed on the box these days, so suspect it's as you would wish - domestic consumption first, then batteries, then immersion heater - but you'd need to confirm. I'd be astonished, tho', if far more comprehensive controllers were not available to add to PV systems that could be set to do exactly what you want.

Miser1964

For your immediate plans of gas boiler plus using solar for domestic water heating, I'd be thinking of using a Priority Domestic Hot Water (PDHW) design with sealed tank which also has an immersion heater. The system boiler can heat the house via rads/underfloor, but then prioritise heating water in the cylinder when there's been insufficient solar power to reach the target temp on cylinder thermostat.

There are some clued-up installers on YouTube (eg. "Urban Plumbers" and "Artisan Electrics") covering PDHW, ASHP and solar installs.

From what I see on Youtube, people are realising that ASHP are not quite good enough in British winters to be used in older houses without requiring secondary heating and gas boilers are being used for that! The alternative of a 3kW+ electric water heater built into the ASHP unit itself is just too expensive to run...

If you are combining ASHP with a gas boiler as backup/supplemental heating then some sort of manifold/low loss header seems to be needed to combine the flows and avoid them pumping water to each other.