Changing CH plumbing to be able to only heat HW

System

This discussion was created from comments split from: Domestic Solar PV Quotes 2024 - No PM requests - See Mod note post #1.

marco_polo

https://www.boards.ie/discussion/comment/122147887#Comment_122147887

Good question we do have gas CH but lack a seperate water zone so in summer need to turn off rads etc and only works ok we find really in terms of the balance between house too warm and enough hot water. Considering it as much for the convenience factor than pure financially really I think. I don't think they have listed the price separately so ignorance is bliss :).

On a smart rate rather than an EV plan as well although obviously that could be easily fixed.

graememk

https://www.boards.ie/discussion/comment/122149804#Comment_122149804

Possibly look into adding a separate zone for your domestic hot water, (and then a tank thermostat too)

marco_polo

https://www.boards.ie/discussion/comment/122150146#Comment_122150146

Thanks I will look into it would there generally be much work in that I had figured there would be a good bit of new plumbing involved so hadn't seriously considered it. Boiler would be old enough too probably in its last few years of life.

graememk

https://www.boards.ie/discussion/comment/122150658#Comment_122150658

Really depends on how your house is plumbed, the DHW should just have a feed that is split from the flow from the boiler, possibly all that is needed is a motorised valve or 2 so the DHW can be heated on its own

And then the tank thermostat is to turn it off when the tank reaches temperature.

deezell

https://www.boards.ie/discussion/comment/122150658#Comment_122150658

A zone valve operated by a room stat on the CH flow, not the HW, will close of CH during the the summer. Timing events on the boiler will then only heat HW. Little plumbing required If you can find a point where all CH Flow diverts from HW flow. Unfortunately, it's often the case the HW flow is tapped off the upstairs CH flow, with no easy way of closing all CH and leaving just HW connected. If you're considering a new boiler, you could get either a two circuit model, and have the cylinder plumbed directly to one. Alternatively, you could get a system boiler with a direct HW outlet which feeds hot taps on demand, no need for a cylinder, but a fair bit of plumbing required also. Final option is smart TRV's on all rads to close them.

Zoning the cheapest if the cylinder is fed flow and return immediately from the boiler hot flow outlets, then the CH can be zoned off by a single stat controlled valve. Apologies , this is the wrong thread for this, mod can move it to home heating automation if he wishes.

graememk

https://www.boards.ie/discussion/comment/122150831#Comment_122150831

Needs a valve on the CH for that to happen too and going on the state of some plumbing I've seen/heard i wouldn't be surprised if there was one.

Only thing that would put a spanner in the works is if the DHW is just a "radiator" in the middle of the rad loop somewhere.

conor_mc

https://www.boards.ie/discussion/comment/122151055#Comment_122151055

my house is like this, but also need CH to heat non-TRV towel rails even during summer. All other rads are TRV controlled so just get turned down by me during summer (family will swelter if I get hit by a bus!). Considering a timer switch for immersion to run on EV rate electricity overnight - Eddi can do this but I think cheaper/simpler to just use a dumb timer switch. I’m a fan of simple more so than cheap in this case.

graememk

https://www.boards.ie/discussion/comment/122155656#Comment_122155656

I've thought about switching the towel rail to dual fuel (an electric element in them, but then also need power)

I'll spin this discussion into its own thread now.

deezell

The term DHW us usually reserved for Direct Hot Water, distinct from generic HW, which is generally HW from a storage cylinder heated by an external source. DHW is hot water straight from the boiler, heated on demand, no intervening HW cylinder other than the small pressure cylinder in the boiler itself.

Where the HW cylinder has its own built in souce of heat, such as burner or an immersion, and this is the only method of heating, no external boiler heat exchangers, such cylinders are often referred to as DHW, but in a domestic environmentit's only true if your cylinder is immersion only, no oil/gas boiler heat exchanger coils. This is highly unlikely here, except homes with no boiler heat source, such as older homes with only electric radiant or storage heaters, or perhaps new homes with heat pump heating and cylinder/immersion HW, though the latter is often a function of the heatpump in HW mode.

When commenting I always use the term HW to refer to the HW circuit of a storage cylinder heated by the external oil, gas or HP source, but with an internal immersion element available. This is the vast bulk of Irish home installations, the complete opposite of the continent where DHW reigns.

conor_mc

I’ve seen DHW (Domestic Hot Water) used in the context of heat pumps, hence assuming storage cylinders would be involved.

deezell

https://www.boards.ie/discussion/comment/122156315#Comment_122156315

That makes sense, the water in the heating circuit is seperated from the hot water out of your tap, so that circuit is usual referred to as CH, on valves and timer relays. The same sealed flow going to the cylinder is HW. What comes out the tap never mixes with the hot flow from the boiler, so referring to that actual water as DHW is fine. Domestic,or Direct if comes straight from the boiler on demand. Such installations don't have the complexity of zones valves for HW, but may have more than one CH zone. When using Direct HW boilers, some of the smart thermostats such as Tado can control the temperature of the HW to the tap from the App, provided it is connected to the boiler using a digital two wire control using the Opentherm protocol. Lots about this on the (long) Home heating automation thread.

graememk

Yeah I've seen it as domestic hot water , and used it as such

bullit_dodger

https://www.boards.ie/discussion/comment/122155656#Comment_122155656

Since you already have TRV valves on the rads, have you considered Tado?

https://www.tado.com/gb-en

They'll replace your existing thermostatic valve with a wifi powered one. Usually you can do that without even getting a wrench out of the toolbox. It would convert your house into a "zone" for each room, and then you can set a temp on each rad. Like 16C in the bedrooms and if it's summer obviously with it being warm, the valves would be closed without you doing anything.

Great system. And handy. I can turn on the radiators from my phone before leaving work, or have it scheduled to come on at specific time(s). Also detects when there's a window open and turns off rads in that room.

https://www.youtube.com/watch?v=i8Fx-NfAGgw

graememk

https://www.boards.ie/discussion/comment/122156702#Comment_122156702

Gotta be pedantic lol

They aren't WiFi.. but are wireless 😂

With some clever wiring you could have it run your HW when you have the rest of your rads off

bullit_dodger

https://www.boards.ie/discussion/comment/122156711#Comment_122156711

True as Graeme mentions, it's not actually wifi as it's ~850mhz or so which the lower frequency helps for range and power, but the main point is that the valves are wireless. So no dragging cables or anything back to a central box. You can set a room up which has an existing TVR valve in about 5 mins (no joke!) as a zone in the app and you're done. If you don't have TVR valves, then it gets a little messier as you have to replace them with TVR and that can mean draining the rad. Not "hard", but it's not 5 mins.

Have nearly all my rads on this (the one/two I don't have are in rooms which are typically off all year round anyway). In your case, @marco_polo in summer if you turn on the central heating for hot water, assuming the rooms temps are above what you have set the desired each tado unit for, they will be closed (automatically) so then the boiler will only be heating the Hot water.

Big Lar

I would love some of those but the price is steep, whats the downside to the cheap Zigbee alternatives on Aliexpress, was thinking to pair with HA.

deezell

https://www.boards.ie/discussion/comment/122168229#Comment_122168229

When the cheap ones turn on, they have no connection to the boiler to turn it on also and heat the room. You may be able to buy and configure a relay to do this from the Zigbee trv app. Tado uses a wired wall stat to the boiler which the TRVs can wirelessly use as a boiler relay.

graememk

https://www.boards.ie/discussion/comment/122168359#Comment_122168359

Or the wireless extension kit.

https://www.boards.ie/discussion/comment/122168229#Comment_122168229

Id go native ZigBee in home assistant and control them directly.

Using the generic thermostat in home assistant you could have that for each room, and then a relay board (possibly running esphome) to control your boiler.

Disadvantage is that it's all DIY, and there's not many people around that would be able to fix it if your not there.

Big Lar

I have the house divided into two zones Up/downstairs Its just that in the morning I am heating the whole ground floor so that the kitchen can be heated so I think that I would leave the heating on the timer, the wife and kids in this house have no problem using the boost button😥so not fussed about boiler control.

@graememk Disadvantage is that it's all DIY, and there's not many people around that would be able to fix it if your not there.

That the story with a lot of things around the house.