What choice HW tank for cottage renovation?

[Caddy]

Hello All

 

I have only recently found this forum and have been reading the posts with great interest.

 

I have just moved into a 2 bed cottage in the countryside in need of some renovation and some advice on my DHW and heating situation would be appreciated.

 

Current situation:

 

• Small 2 bed cottage, 1 upstairs bathroom, livingroom and kitchen downstairs.
• Thick solid stone walls but no insulation, slate roof with tatty 100mm of insulation in loft, ground floor is I think old flagstone covered in concrete skim and carpet.
• Property (and village) not on gas network.
• HW from direct vented system with electric shower. 
• HW tank 2 immersion elements, bottom one on E7 (no timer) and top one manual switch.
• No boiler or wet central heating.
• Multifuel stove in livingroom and 1 old looking storage radiator in livingroom as well.
• Convection heaters on wall in both bedrooms and bathroom.
• I live on my own and I work from home but light user of electricity normally. Laptop use and cooking, washing up and shower daily.

 

Plan so far is to insulate where I can before winter and I have a 3.5Kw solar PV system being fitted at the end of this month. I hope to use most of the energy myself for my day to day use with any spare being diverted to my HW tank by a Myenergy Eddi. My thoughts were to leave the bottom immersion element on the E7 feed but maybe add a timer so it wasn't solely relying on the element thermostat to turn off and potentially be on for 7hrs a night. Then hook the Eddi unit to the top (more mid) level immersion element so that could top up the HW with any spare energy during the day. Do you think that sounds reasonable?

I would also like to get rid of the electric shower as its power hungry and a pretty crap shower. I was thinking of changing to an unvented system (which got me looking at this forum) and I also started looking at things like the Mixergy tank and Sunamp. I'm an engineer and always interested in technology but I'm trying to not get seduced by the shiney new toys available. I don't have loads of money spare and some posts on this site made me think to keep the current vented HW system and fit a pump to create a decent shower. So I'm undecided whether to go unvented or to improve my vented system to get rid of the electric shower?

The solar install is costing about £5500 and I have about another £5000 to spend on my current upgrades. About £500 of that has been spent on some insulation for the loft and some internal walls and I was thinknig about how to spend the rest to get the most bang for my bucks. I though a new unvented HW system would be around £1500 (?) or fitting a pump around £500 (?). I was considering batteries for my solar system (£3-3500) and I still need to sort out a better heating system than wall mounted convection heaters. Maybe a couple of new storage rads or IR panels (~£2000)?  Luckily I'm from Yorkshire originally and don't mind the cold at the moment and the stove is enough. There is also a second output from the Eddi and I was thinknig of maybe electric unfloor heating for the bathroom, but not looked into the cost of this yet. I'm happy to spend money on the HW and heating before worrying about decorating and garden etc.

 

Sorry for the long post, it was good to actually wite it all down and clarify (a bit) what I'm trying to do. An all electric house for HW and heating is the expensive option at the moment (my decent current tariff runs out in Feb, gulp) and any ideas for making this house as efficient and cost effective as possible would be much appreciated.

  

 

[Iceverge]

Welcome, 

 

Plenty of good info on here. Here's 2 to get you started. 

 

 

 

 

 

[SteamyTea]

Welcome.

Your current DHW setup, and lifestyle are similar to mine.

I have an E7, 200lt cylinder, but most of the time I could get away with 100lt.

Now I very really need to top up my cylinder because it runs out of hot water. And I only heat mine to around 45⁰C.

If I do top up, because I have friends staying, I just turn the top element on. 30 minutes and the job is done.

So I would wire the PV diverter into the bottom element, and out the top element on the E7, but with a secondary timer set for the last hour I.e. 6AM to 7AM.

I use a pumped shower, it works well. Cost 100 quid for the pump, and not much for the tap with a shower takeoff. With the RCD and pipe and stuff, less that 200 quid.

That was 15 years ago.

 

Spend all your money on insulation and airtightness improvements.

The only bit of hi tech you need is an energy monitor and logger.

[Caddy]

@SteamyTea I read some of your posts about not bothering with an unvented cylinder and just using a pump and it got me thinking. I don't have heavy HW demands at all and the purpose of the unvented tank was going to be at least 80% just about water pressure so I could remove the electric shower. I'm thinking of removing the bath and just having a nice shower. The bathrrom needs updating sometime and whatever I do with the HW is with that re-furb in mind.

 

Both replies have emphasised  the need to insulate and make air tight first before deciding on energy requirements of a heating system. I agree with this, and I'm currently starting on this already. Insulation levels are bad but I think the house is pretty airtight. There are only 4 windows and 1 door. The windows are double glazed and the door is wooden but has a small covered in porch over it that stops direct wind ingress. The porch is only single skin brick and single glaze windows though so I might do some improvement to this area as well.

 

The only insulation is about 100mm of dirty mouse crap covered loft insulation. I'm stripping all this out and I have sourced some cheap 100mm PIR from a local for between the ceiling joists and will add 170mm loft insulation over that, trying to be careful about ventilation. The walls have nothing and I'm a bit wary of reducing the room size of an already small cottage too much. I also a bit worried about stopping the building breathing if I insulate too much as the walls are stone and lime mortar construction. Maybe some wool based insulation and Fermacell boards would still breathe? Is it worth worrying about insulating the stud partition internal walls or is this overkill? 

 

The ground floor would be the next task but that seems a pretty big job. I would need to did up the living room and kitchen floor and lay some PIR with a floating floor maybe. Would need to consider if then would be a time to fit under floor heating or if its necessary. I don't like a too warm house.

 

Questions, question, always more questions. Thanks for the replies so far.

[Jilly]

The Haynes Manual for Period houses is a good read. The worry is interstitial condensation.

 

I think you could safely put a lot more insulation in the loft, up to 400mm so long as you don't block up the eaves vents. Most people advocate just topping up the existing stuff (presumably because pulling out the old stuff will create an almighty mess and have to go into landfill anyway). Chopping PIR in the loft will be quite a dire job, much quicker to just roll out rock wool or whatever in opposite directions. 

[SteamyTea]

This 'letting buildings breath', where is the moisture coming from?

A brick, or block, or even a bit of stone laid in the same fashion as sometime in the past, will have the same problems.

As far as I can see, it don't matter what sort of concrete, render or mortar us used, if the damp us getting into the structure, stop the damp.

Usually good, controlled, ventilation is all that is needed.

Re the windows. My windows are old (34 years), I just changed the glass to ones that had 16mm gap instead of 4mm gaps.

 

Just about to drive 300 miles home, so shall ponder more on the way.

[joe90]

2 minutes ago, SteamyTea said:

This 'letting buildings breath', where is the moisture coming from?

Depends if it was built with modern damp proof courses in floors and walls, also the occupants with cooking, showering etc will give off some moisture. 

[SteamyTea]

4 hours ago, joe90 said:

Depends if it was built with modern damp proof courses in floors and walls, also the occupants with cooking, showering etc will give off some moisture. 

That is my whole point, it is not the materials, per sec, it is the techniques that out them all together.

 

Within 2 miles of home, need milk.

[Caddy]

Just got my first quote for an Joule 200l unvented direct cylinder fitting, £2800. Looks like it will be vented and and pump after all. Wow....

Edited November 18, 2021 by Caddy

[ProDave]

You can buy a Telford stainless UVC for about £1000

 

Are you really saying your plumber is going to charge £1800 to fit it?  That would be 6 days labour at £300 per day to do what is probably no more than 2 days job.

 

Try a different plumber.

[SteamyTea]

25 minutes ago, Caddy said:

Just got my first quote for an Joule 200l unvented direct cylinder fitting, £2800. Looks like it will be vented and and pump after all. Wow....

And you can fit it all yourself, except maybe the pump wiring.

[Caddy]

1 hour ago, ProDave said:

You can buy a Telford stainless UVC for about £1000

 

Are you really saying your plumber is going to charge £1800 to fit it?  That would be 6 days labour at £300 per day to do what is probably no more than 2 days job.

 

Try a different plumber.

 

I think it's worse than that. I could get a quality 200l tank for ~£500 easily. No central heating connection required, HW only direct. The quote is so high it makes me think they don't want the job and so priced it to fail. 

[Caddy]

The only potentially awkward part of this install could be routing of the drain for the pressure valves to the outside. I could do this myself in advance to save time (and money). Is this just a run of solvent weld jointed 20mm plastic pipe? I know it has to be to a low level drain so you are not potentially shooting hot water out of an upstairs drain and burning someone.   

[ProDave]

7 minutes ago, Caddy said:

The only potentially awkward part of this install could be routing of the drain for the pressure valves to the outside. I could do this myself in advance to save time (and money). Is this just a run of solvent weld jointed 20mm plastic pipe? I know it has to be to a low level drain so you are not potentially shooting hot water out of an upstairs drain and burning someone.   

No, 22mm or possibly 28mm copper, with a set number of bends and a defined discharge position.

 

I did this myself and the plumber who connected and comissioned the tank was happy, but this was a plumber I knew and with his prior agreement.

[Caddy]

On 09/11/2021 at 12:53, SteamyTea said:

Welcome.

Your current DHW setup, and lifestyle are similar to mine.

I have an E7, 200lt cylinder, but most of the time I could get away with 100lt.

Now I very really need to top up my cylinder because it runs out of hot water. And I only heat mine to around 45⁰C.

If I do top up, because I have friends staying, I just turn the top element on. 30 minutes and the job is done.

So I would wire the PV diverter into the bottom element, and out the top element on the E7, but with a secondary timer set for the last hour I.e. 6AM to 7AM.

I use a pumped shower, it works well. Cost 100 quid for the pump, and not much for the tap with a shower takeoff. With the RCD and pipe and stuff, less that 200 quid.

That was 15 years ago.

 

Spend all your money on insulation and airtightness improvements.

The only bit of hi tech you need is an energy monitor and logger.

 

@SteamyTea I agree with how you advised to set up my system and that is installed. The PV is fitted and the diverter is wired to the bottom element and the top element is fitted to the E7 feed. As suggested I would like to fit a timer to this secondary feed to turn on for the last hour of E7 to heat the top of the tank for the morning and let the PV heat the rest during the day if there is spare. I purchased a fused spur with built in electronic timer to control this but I may have run into a problem. My E7 comes from a split feed meter and the E7 feeds into a secondary smaller CU with 2 mcb's, for 1 HW element and 1 storage radiator and I pressume only comes live after 12am. Am I correct in thinking this would mean the timer would be running from the battery back up for 17 hrs a day to retain the time programing? The timer is a Timeguard FST77 and it says the built in battery retains the programs for 720 hrs, but I'm not sure if it's designed to be used in this way, going on to battery backup every day. Maybe a mechanical timer would be better?

[SteamyTea]

1 hour ago, Caddy said:

timer is a Timeguard FST77

Shall see what my timers are when I get home. Not had any problems with them for over a decade.

[Caddy]

If I do get a new unvented hot water tank is there any way to measure the temp of the water inside? Are there wifi enabled sensors that can track the temp at several depths maybe? This site has unfortunately got me tracking every Watt I generate and use and next on the list might be tracking my HW usage and temperature. I thought I'd read something somewhere that some tanks come with pockets (?) that can have sensors attached. Did I dream this?

[SteamyTea]

I use a Raspberry Pi Zero W with 3 1-wire DS18B20 temperature sensor.

One is on the input pipe, one on the output pipe and the other is in the cold storage tank in the loft.

Not ideal, but gives a good idea of what is happening.

[Caddy]

On 18/11/2021 at 13:06, ProDave said:

You can buy a Telford stainless UVC for about £1000

 

Are you really saying your plumber is going to charge £1800 to fit it?  That would be 6 days labour at £300 per day to do what is probably no more than 2 days job.

 

Try a different plumber.

 

On 18/11/2021 at 14:50, Caddy said:

 

I think it's worse than that. I could get a quality 200l tank for ~£500 easily. No central heating connection required, HW only direct. The quote is so high it makes me think they don't want the job and so priced it to fail. 

 

Got another quote from a different plumber. If I supply the new tank, drain down the old one and remove the header tank myself, he will fit and commision new tank for £400+vat. He said it would be an easy install as all pipes are in the right vacinity and its HW only (Direct). That's more the price I was thinking it would cost. Very tempted now.