Hi all... instant hot water?

[kev-in-spain]

Hi, I've just joined the forum and thought I'd introduce myself with bit of background about my abilities and a brief insight into my project together with my question regarding instant hot water circuits.
I ran my own commercial interiors company (office fit-outs and hospital refurbs mostly) in uk for more years than I care to remember. I was never shy about getting stuck in myself, whenever I could get away from the paperwork, and have always been interested to know the ins and outs of all the different trades involved and, over the years, have acquired a substantial insight into what's what with most of what goes on in a refurb.
So, having had enough of the rat race in uk, I have moved to Spain and recently started a project to extensively refurbish my old house here. I say refurbish but, it's actually more of a 'rebuild'. Because of the age of the house, the local authorities insist that the facade stays intact so, apart from the facade, the middle supporting wall and the rear wall up to 1st floor level and a few of the original floor beams, everything else has been demolished.
As I have a clean slate, all the plumbing and heating will be completely new installations, aside from the combi boiler that I salvaged from the rip-out.
Getting to the point, I need some reassurances on the following: I will be installing an 11 zone underfloor heating system which, I've been told, is ok to run off a combi and I would like to run hot water loops to the kitchen and 2 bathrooms for instant hot water. I'm ok with the underfloor heating as I installed it in my house in uk. I'm not so clear on the hot water loops... how does this function with a combi? Would I need an additional circulation pump?
I know the obvious answer will be 'get someone in who knows what they are doing' but, apart from the fact that we are on a very tight budget, I am keen to learn and want to do as much of the project as I can myself.
I have made several searches of the forum to see if there are any existing threads on this subject but have found nothing.
Thanks in advance for any pointers
Kev

 

[snowhead]

I'm ok with the underfloor heating as I installed it in my house in uk. I'm not so clear on the hot water loops... how does this function with a combi? Would I need an additional circulation pump?

Won't work with a conventional Combi,
The Combi won't fire until there is a water loss in the system, there won't be a loss if you are circulating.

Conventional DHW secondary circulating systems use a Bronze / Stainless pump to circulate from / to the Cylinder.

 

[Ch4 plumbing]

Hello Kev, you can't run a hot water loop with a combi boiler as the boiler provides instantaneous hot water on demand, a hot water loop or circuited will only work with cylinder type installations.
Just run a hot to each tap and you should be fine.

 

[efficiencyman]

In sunny Spain I would install Solar Thermal into larger cylinder to supply 2 bathroom / showers etc. Scrap the combi, you can then get rid of the heat loss dead legs and use circuited instant DHW. Use a system boiler for top up if / when needed, why burn gas when the sun is free ?

There are many reasons to get shot of the used combi, to have had a combi boiler for ten years and have no trouble is truely amazing. Diverter valves, nct's, fans, plate heat exchangers, ev's, gas valves, pcb's, pressure switch's. even the best of them, faults on them all, and if you cant get the part for a few days or more than a month or even longer, there's always trouble with parts & frustration getting them repaired.

As I said these are my thoughts, and its how I`ve earn`t my living, but go to any plumbers merchant ask the plumbers for their recommendation, they tend to want a sale of what`s in vogue, slim chance you'll find any of them agree, the boiler you thinks great, we've seen the lemon.

 

[kev-in-spain]

Hello Kev, you can't run a hot water loop with a combi boiler as the boiler provides instantaneous hot water on demand,

Thanks for the straight answers snowhead & ch4 plumbing. Now you put it in writing, it's actually quite obvious that it wouldn't work.:blush5:

efficiencyman... I have looked at installing Solar Thermal but have decided against it for 2 reasons. 1) although we will have 2 bathrooms, we don't actually use a great deal of water and, as we need a boiler to run the heating system (which we do need in the region of Spain we live in 🙂 ), it makes sense to not over complicate things with two systems. 2) The South facing section of the new roof is not that big and will be covered with solar panels for the batteries leaving no room for the vacuum tubes.

I will take on board your advice about the combi and look into maybe changing it.... see how the money goes! :-/

Thanks all.

 

[bigads28]

I'd just run a conventional system with a unvented tank. Put a secondary return in for the hot taps and the hot water will be very quick and at mains pressure.

 

[markfxy]

Keep the combi use it to supply water to the kitchen only, fit an unvented cylinder with hot water return, combi will heat cylinder and underfloor heating

 

[voivod]

Saw a lot of solar hot water cylinder on the ground in spain...no room?

 

[kev-in-spain]

Based on the advice and knowledge received, here's what I've decided to do.
Ditch the combi. It's given over 7 years of trouble free service so, based on energymans theory, it's sods law it will break down pretty soon after I reinstall it.
Fit a conventional boiler to run the underfloor heating and heat a domestic hot water cylinder. I have calculated that I may have a bit of room on the roof for thermal tubes if I downsize a little on the solar panels. Voivod, the only place I get sun all year round is on the roof, so a ground system is out of the question. Anyway, The jury is still out on that one but it wont hurt to add a couple of tees into the system for 'just in case'. I also intend to use energy from an open fireplace to heat the hot water cylinder.
The only thing I'm stuck on is the instant hot water loop/return.
The way I see it, there are 2 options:
1. A single circuit throughout the whole house with tees off to each shower/bath/sink etc.
2. Separate legs to each area.

The up side of option 1 is, only one valve so, cheaper & less to go wrong but, I'm concerned about the length of the circuit (about 50m) and the scenario of one shower/tap robbing hot water from another when both are open at the same time.

Option 2, a bit more complex to install, 3 valves is more expense and more to go wrong (I'm assuming I could run all 3 with one circulator) but a lot more efficient as each leg/loop is only between 8 and 14m from the water cylinder.

Thanks again for all previous input and advice. I'd be really grateful for any opinions on my last part of the install.
By the way, I haven't mentioned it before as I didn't think it relative but, maybe, it is...? As we have no mains pressure at all, the whole system is pumped via a massive (10,000 ltr) underground water deposit.

All the best
Kev

 

[kev-in-spain]

Based on the advice and knowledge received, here's what I've decided to do.
Ditch the combi. It's given over 7 years of trouble free service so, based on energymans theory, it's sods law it will break down pretty soon after I reinstall it.
Fit a conventional boiler to run the underfloor heating and heat a domestic hot water cylinder. I have calculated that I may have a bit of room on the roof for thermal tubes if I downsize a little on the solar panels. Voivod, the only place I get sun all year round is on the roof, so a ground system is out of the question. Anyway, The jury is still out on that one but it wont hurt to add a couple of tees into the system for 'just in case'. I also intend to use energy from an open fireplace to heat the hot water cylinder.
The only thing I'm stuck on is the instant hot water loop/return.
The way I see it, there are 2 options:
1. A single circuit throughout the whole house with tees off to each shower/bath/sink etc.
2. Separate legs to each area.

The up side of option 1 is, only one valve so, cheaper & less to go wrong but, I'm concerned about the length of the circuit (about 50m) and the scenario of one shower/tap robbing hot water from another when both are open at the same time.

Option 2, a bit more complex to install, 3 valves is more expense and more to go wrong (I'm assuming I could run all 3 with one circulator) but a lot more efficient as each leg/loop is only between 8 and 14m from the water cylinder.

Thanks again for all previous input and advice. I'd be really grateful for any opinions on my last part of the install.
By the way, I haven't mentioned it before as I didn't think it relative but, maybe, it is...? As we have no mains pressure at all, the whole system is pumped via a massive (10,000 ltr) underground water deposit.

All the best
Kev

 

[markfxy]

best advice would be to get a plumber in, sounds like a disaster waiting to happen:smartass:

 

[Worcester]

Depending upon the type of solar thermal you install, you need a special cylinder for the solar thermal, you can't just "tee" in...

A little bit of knowledge is a dangerous thing....

 

[Centralheatking]

Worcs is dead right Solar Thermal systems need carefull consideration as they can reach some very high temperatures - this looks like a world that you are not competant to deal with and you could be considering putting together a domestic time bomb CHKing

Depending upon the type of solar thermal you install, you need a special cylinder for the solar thermal, you can't just "tee" in...

A little bit of knowledge is a dangerous thing....

 

[solutions]

I agree with my fellow forumites that this kind of install and the work you are contemplating is best left to professionals. However I wanted to point out it may ne worth investigating solar pv panels that have integrated solar thermal tubes. I cant recall brand names but they do exist. The advantage being you dont have to compromise your roof realestate to have 1 over the other particulatly as pv has better output when cooler which the solar thermal should achieve by drawing the heat away to use in your cylinder.

 

[kev-in-spain]

I appreciate all the warnings and, as was pointed out, a little knowledge can be dangerous. Well, that's why I'm on here asking questions before going ahead with anything.
As I said in an earlier post, a solar thermal installation is, at the moment, just a consideration. If I do decide to install it, I will study it further.
My question was really more to do with the domestic hot water installation. Any thoughts on that would be helpful.

Thanks

 

[Worcester]

Your system now though is getting very technical and well beyond 99.9% of non-professionals and also actually beyond 95% of normal heating installations. To illustrate this, there are only 1200 registered solar thermal installers in the whole of the UK... . You should really use a competent specialist. I bet that less than 10% of 'plumbers' have ever seen a pumped secondary return system, let alone know what to do with it, know why it's needed and what it does, or configure it.