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I have 8mm plastic pipework to my rads so I’m thinking it’s going to a big job.
Heat Pumps: anyone have one/thought about it?
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I assumed it was 8mm. If yours was 10mm plastic did you have any pipework replaced? Did you have any new radiators? I’ve read Octopus won’t touch microbore 10mm that is. And I assume it’s working great for you?
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This is my pipework. Has to replace a section as it was sludged up.
I’ve got 10mm plastic microbore and no replacement needed in my install. My total heat loss is just under 6kw.
10mm plastic is usually 10mm OD, ID is just over 8mm as they have plastic inserts which fit into the end of the pipes at the joints. 8mm is usually copper.
Yes, loads. 5 upstairs, 3 downstairs.
They will do an anything down to 10mm micro bore. It works fine for me and my house/heat loss.
10mm puts a lower cap on how much water (and therefore heat) the system can supply to a radiator as it can’t flow as much water as say a 15mm copper pipe.
It effectively caps the maximum output of a radiator at a lower level than 15mm copper. As long as you are below that cap for that room, you are fine.
You can of course have multiple radiators to a single room to get around any limits, larger rooms probably already have more than one radiator already anyway to help spread the beer around the room.
Edit: your house looks fairly modern so probably doesn’t have a huge heat loss and will probably be fine on 10mm
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My install is 8mm copper to each radiator from 22mm main distribution headers. There are two separate problems to calculate and resolve:
1. Your heat loss per room at your design condition
2. Head (predominantly friction) loss in each circuit.
Your case sounds worth doing detailed calculations to identify your worst case circuit. In my case it was my living room that is furthest away from the heat pump with greatest length of 8mm, and also the highest heat loss at around 1.3kW when it's -5 outside. The most water you can get down 8mm copper is worth around 1.1kW at dT of 5. I got a Nibe heat pump that runs with a dT of 7, and also the other rooms have capacity to balance the living room.
So far it's worked well. We've not had -5 but the house has kept a steady 18C throughout since July. If you want to investigate in detail or better yet find out if the installers you are talking to are willing to put some thought into it, check out this heat geek article and video:
HeatGeek: What to do with microbore pipework on heat pumps
For heat pumps to work efficiently we need flow, and this does 2 things. It will mean the heat pump’s plate heat exchanger will work at maximum efficiency AND
www.heatgeek.com
Heat Pump Piping: Do You Really Need to Upgrade Your Pipes?
Get expert guidance on heat pump piping sizing! Our comprehensive guide covers everything you need to know about heat pump piping sizes.
www.heatgeek.com
Once you've gone through these if you're keen and have any questions there are some knowledgeable folk here and on other forums.
It's not perfect with 8mm (or effectively 8mm if you have 10mm plastic which has greater friction inside as well as the inserts) but there are ways to resolve it, or you could repipe.
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Thanks both. House built in 2003 so no wall or floor insulation. In the last 12 months I’ve replaced all windows and last week new Endurance door. This has helped. I had the loft partially boarded properly. There are some things I want to sort out in the loft. Install thermahoods for spots and top up insulation on the sides. For instance tonight I haven’t put the heating on since last night and it’s holding just above 18 degrees. Last night it was on for 30 minutes set to 18. Mind you it’s 8 outside so not freezing.
House is 4 bed detached. 1800 square foot.
@b0rn2sk8 do you have wall insulation?
House is 4 bed detached. 1800 square foot.
@b0rn2sk8 do you have wall insulation?
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Yes, your house was built the same year as mine. You should have cavity wall insulation and floor insulation. I’m pretty sure cavity wall and ground floor insulation was compulsory form the early 90’s.
Sure it’s not as thick as what you’d get in a 2020 new build but it should have some and way better than say an 80s build which will have nothing. They will build that into their assumptions.
Your heat loss will probably be in the region of 6kw if you have topped up the loft to ~300mm. That is absolutely no problem on 10mm plastic microbore and 22mm flow/return on the central heating.
Ours is slightly smaller 4 bed detached at 130 square meters. Our heat loss is about 5.5kw with terrible double glazing and a minimum of 250mm in the loft. It’s higher where it isn’t boarded (~50%) but they used 250mm for the purpose of the survey.
We have a 6kw Daikin unit (which is just a software de-rated 8kw heat pump), when it’s on tickover it draws about 400w. The most I’ve seen it draw is 2.2kw when on full charge doing hot water at 55C flow temperature.
We have a gas fire in the lounge, this added a huge number to the heat loss, 1000w if I recall correctly. We’ve never used it and the gas was being disconnected as part of the install. They ignored it for the purpose of the survey and I filled the flue with expanding foam before they installed. I’ve not got round to removing it yet and bricking up the hole, it’s a job for the spring.
Sure it’s not as thick as what you’d get in a 2020 new build but it should have some and way better than say an 80s build which will have nothing. They will build that into their assumptions.
Your heat loss will probably be in the region of 6kw if you have topped up the loft to ~300mm. That is absolutely no problem on 10mm plastic microbore and 22mm flow/return on the central heating.
Ours is slightly smaller 4 bed detached at 130 square meters. Our heat loss is about 5.5kw with terrible double glazing and a minimum of 250mm in the loft. It’s higher where it isn’t boarded (~50%) but they used 250mm for the purpose of the survey.
We have a 6kw Daikin unit (which is just a software de-rated 8kw heat pump), when it’s on tickover it draws about 400w. The most I’ve seen it draw is 2.2kw when on full charge doing hot water at 55C flow temperature.
We have a gas fire in the lounge, this added a huge number to the heat loss, 1000w if I recall correctly. We’ve never used it and the gas was being disconnected as part of the install. They ignored it for the purpose of the survey and I filled the flue with expanding foam before they installed. I’ve not got round to removing it yet and bricking up the hole, it’s a job for the spring.
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Just booked Octopus in for Monday. £200 refundable deposit for a survey. Their quote is throwing the default £15k with 7.5k grant. That includes an asbestos check (not required), a water tank (I am hoping my 2 year old vented Kingspan is sufficient) and a re-pipe. If I can get it down to £1500 installed I might consider it. I can then sell the Vaillant second hand and re-coup maybe £500 or so.
The house just works so bloody well at 50*C flow temp, but it lets the heat out a fraction too quick and I hate the boiler cycling.
Can these things be wall mounted and the pipework ran externally into the attic?
The house just works so bloody well at 50*C flow temp, but it lets the heat out a fraction too quick and I hate the boiler cycling.
Can these things be wall mounted and the pipework ran externally into the attic?
Soldato
Mine routes to the loft for my water cylinder. Manifold is behind a false front in a cupboard.
You’ll need a new cylinder, somewhere for a small volumiser and a pressure vessel. Your system will need to be converted to unvented.
Pipework can be routed externally but make sure you ask for trunking or they’ll just clip the insulated pipes direct. Most of my pipe work is in the attic, including the volumiser, the cylinder and pressure vessel are in the middle of the house.
They had to install a separate D2 pump as I don’t have any existing pipework to my old vented system or a way to easily link to existing plumbing. The outlet for the D2 pump runs back outside along the same route as the flow/return.
I doubt you’ll get them down to £1500 mind.
Edit: I’m generally running at 30-35c flow temps at the moment. That will rise a bit over this week when the temperature drops.
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Soldato
Watched a video at the weekend (EV Man), not that he went into much details, but he had a Valiant UniTower, which seemed to contain pretty much all the internal stuff.
We have a massive floor standing Worcester Bosch boiler (19 years old) in our utility room, and that tower would fit nicely in there.
There's not a lot of info about the UniTower, anyone got one?
We have a massive floor standing Worcester Bosch boiler (19 years old) in our utility room, and that tower would fit nicely in there.
There's not a lot of info about the UniTower, anyone got one?
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How are some people paying £500 then? The tank they've included in the £15k is £750.
My entire heating setup is in the attic - heating circuit, hot water circuit, mains cold.
Octopus pricing is a bit of a mystery from what I’ve seen but those with £500 costs tended to have smaller houses with a low heat loss.
Mine was £3600, 4 bed detached ~140sqm, 2003 build.
Heat loss post survey was just under 6kw and I needed 9 radiators changed.
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OK, I'll let the survey run then. It is £200 refundable so no love lost. I won't be changing radiators as the floor is now final fixed.
Does your heatpump go as high as 50 degrees? That is my "factual" starting point for being right sized/insulated.
Soldato
93% of UK installations require substantial work to the central heating system, and many require complete replacement. So you, with 8mm pipes you are going to need new radiators and pipes.
This is the "undoing" of the system in the UK. It's a great idea, but given the cost of upgrading the central heating and insulation, it makes it prohibitively expensive for most people. Even with government subsidies, they will never make their money back. Having said that, if you go in to this thinking "save the planet" then you can't go far wrong, but if you go in to it thinking "save money" you most certainly can go wrong.
I am honestly surprised that the government push heat pumps so much. They are not the best choice for many homes in the UK.
But then the government think that Fusion power will be mainstream by 2035
And that a hydrogen economy will actually work
Yes, the design temperature is 50C at -2C, I think I have my WC curve down at 50C at -8C at the moment, the next few days will test if that’s too low.
As for rad swaps, they’ll be built into the price, most of mine used the same foot print as the originals. Given how much work you have done, you’ll probably need to go round with the surveyor room by room as otherwise they’ll assume it’s solid walls and nothing under the floor.
Your statements on heat pumps are factually incorrect, I’ll leave it there.93% of UK installations require substantial work to the central heating system, and many require complete replacement. So you, with 8mm pipes you are going to need new radiators and pipes.
This is the "undoing" of the system in the UK. It's a great idea, but given the cost of upgrading the central heating and insulation, it makes it prohibitively expensive for most people. Even with government subsidies, they will never make their money back. Having said that, if you go in to this thinking "save the planet" then you can't go far wrong, but if you go in to it thinking "save money" you most certainly can go wrong.
I am honestly surprised that the government push heat pumps so much. They are not the best choice for many homes in the UK.
But then the government think that Fusion power will be mainstream by 2035
And that a hydrogen economy will actually work
Soldato
Yeah, I only spent 40 years designing heat pumps, control software, and BEMS installations, and HVAC, what do I know? I'll leave it there.
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Ah 50C would be easy for me then. Not sure I'd see much more of a cost saving but I think house comfort would be exponential - sick of yoyoing up and down and being mindful about running the heating for too long.
If my rads are at the right BTU for the room (and oversized) - what is there to replace them with?
Well given many don’t need a complete replacement, you can install them on 8mm copper, you can install them in pretty much any property and you don’t need to go to any special measures regarding insulation….
To install a gas boiler correctly (e.g. so it meets its quoted efficiency range), you have to design the attached radiator system in the exact same way.
They have never been about ‘making your money back’, it’s transitioning away from fossil fuels for other reasons. You also need to redesign the system once, the house could be there for another 100 years.