Ground-source heat pumps and hot water cylinders
Discussion
Does anyone have a ground-source heat pump central heating system? I understand they are best for underfloor heating but that it is possible to use oversized radiators. I'm going to replace the CH system in a cottage that currently uses oil, mains gas isn't available so the only options are electricity or oil (lpg too dear). It'll be used as a holiday let so mimimal maintenance and lowest possible running costs are important. The cavity-walled cottage will be well insulated apart from existing concrete floors so underfloor heating isn't an option. There's plenty of land to take the collection pipes for a heat pump.
Any thoughts? I have no experience of these so any input would be welcome.
Also, to any plumbers on here, is it possible to place a pressurised hot water cylinder in the roof space? Presumably as it's at mains pressure, it doesn't need any head? It currently has a vented system but space is tight in the bathroom and I'd like to get rid of the cylinder currently in there.
Thanks in advance.
Any thoughts? I have no experience of these so any input would be welcome.
Also, to any plumbers on here, is it possible to place a pressurised hot water cylinder in the roof space? Presumably as it's at mains pressure, it doesn't need any head? It currently has a vented system but space is tight in the bathroom and I'd like to get rid of the cylinder currently in there.
Thanks in advance.
rovermorris999 said:
Also, to any plumbers on here, is it possible to place a pressurised hot water cylinder in the roof space? Presumably as it's at mains pressure, it doesn't need any head? It currently has a vented system but space is tight in the bathroom and I'd like to get rid of the cylinder currently in there.
It's possible to place a un-vented hot water cylinder such as a Megaflow (many cheaper alternatives) in your loft space, no problems.You have to have good mains pressure (3 bar min constantly through out the year), do you have this?
rovermorris999 said:
The water pressure could be an issue, I'm at the end of the line in a rural area, it can vary quite a bit.
These rely on good water pressure to work. Without it, come the summer months when everyone has their hose pipe out, it won't work.Edited by Gingerbread Man on Sunday 27th September 16:38
Don't see why you would need a minimum of 3 bar all the time for a mains pressure cylinder, no reason why it won't work down to much lower pressures.
Ground sourced heat pumps can be made to work with radiators. The whole point about heat pumps is the efficiency varies with the temperatures required. The bigger the radiator, the lower the temperature required and the higher the efficiency. Underfloor works so well because you can go down to 35 degrees.
The issue I suspect you will have is going to be the capital cost.
If you want to know how to heat the hot water cylinder with the same heat pump let me know - and it doesn't involve heating all the water up to high temperatures.
Ground sourced heat pumps can be made to work with radiators. The whole point about heat pumps is the efficiency varies with the temperatures required. The bigger the radiator, the lower the temperature required and the higher the efficiency. Underfloor works so well because you can go down to 35 degrees.
The issue I suspect you will have is going to be the capital cost.
If you want to know how to heat the hot water cylinder with the same heat pump let me know - and it doesn't involve heating all the water up to high temperatures.
Thanks for that. I'm a bit worried about the capital cost although I can get the groundworks for the collector pipes done for not much as I know someone with a JCB. I'd have to do some sums comparing with oil. I have to replace the oil boiler and hot water cylinder anyway, and possibly the radiators as they look pretty grotty. Oil is getting dearer and dearer so the running costs will make a big difference I think.
Any further information would be very welcome, I'm at the learning stage and it's good to be as much up to speed as possible when the time comes to talk to firms who want to to sell me stuff.
Any further information would be very welcome, I'm at the learning stage and it's good to be as much up to speed as possible when the time comes to talk to firms who want to to sell me stuff.
Anyone who is thinking of fitting an unvented cylinder should more or less forget about pressure issues. As low as 2 Bar is going to be useable, but it's the FLOW rate that is critical and also less achievable.
The plumber I work with won't consider an un-buffered unvented below 25 litres a minute MINIMUM. True, some places may not have 2 bar, but of all the cylinders I have specified I have never failed to get 2 Bar.
The problem with roof space mounting unvented cylinders is that G3 of the Building Regs requires a visible warning of safety valve failure. Recent changes now allow discharge into soil systems, but only if the tundish at the cylinder end is visible since the other end will not be. Therefore a discharge pipe MUST be run to within 4" of the ground and any part of it must be be caged to prevent anyone touching it. This pipe MUST be one size larger than the discharge valve and run no more than 9 metres (I think it is) before it needs to be increased in size again. The pipe MUST be metal.
Get hold of someone with an unvented ticket for a more reliable set of current info and bear in mind that the Health and Safety Executive require that the cylinder must be installed by someone with the correct ticket.
The plumber I work with won't consider an un-buffered unvented below 25 litres a minute MINIMUM. True, some places may not have 2 bar, but of all the cylinders I have specified I have never failed to get 2 Bar.
The problem with roof space mounting unvented cylinders is that G3 of the Building Regs requires a visible warning of safety valve failure. Recent changes now allow discharge into soil systems, but only if the tundish at the cylinder end is visible since the other end will not be. Therefore a discharge pipe MUST be run to within 4" of the ground and any part of it must be be caged to prevent anyone touching it. This pipe MUST be one size larger than the discharge valve and run no more than 9 metres (I think it is) before it needs to be increased in size again. The pipe MUST be metal.
Get hold of someone with an unvented ticket for a more reliable set of current info and bear in mind that the Health and Safety Executive require that the cylinder must be installed by someone with the correct ticket.
jaybkay said:
Don't see why you would need a minimum of 3 bar all the time for a mains pressure cylinder, no reason why it won't work down to much lower pressures.
Sorry, I missed that comment. This is very true and as I said above FLOW RATE is FAR more important. Remember that when you open a hot and cold bath tap at the same time ALL the water from those two 22mm valves may be coming up a 15mm internal pipe from the road.
Hooray for Building Regs. Not. The work will be done by a local plumber recommended to me but I like to know all the ins and outs beforehand so that I know what to ask for and so that I recognise a proper job.
I'll check the flow rate when I get the chance and before any decisions are made. I've had another poke around and I think I may have found another location for a vented cylinder which may be a cheaper/simpler option, at least I understand them!
I presume a low pressure would rule out a combi boiler as well? My only experience of them was when they first came out and I was put off by the poor flow rate of hot water. Have they improved in recent years? Oil ones are available but I've only ever seen a gas one.
I'll check the flow rate when I get the chance and before any decisions are made. I've had another poke around and I think I may have found another location for a vented cylinder which may be a cheaper/simpler option, at least I understand them!
I presume a low pressure would rule out a combi boiler as well? My only experience of them was when they first came out and I was put off by the poor flow rate of hot water. Have they improved in recent years? Oil ones are available but I've only ever seen a gas one.
There is a post on here by someone who recommends an air exchange unit over a ground source for a retro fit.
I think it is the "how are you going to be ECO thread"
Anyone else have an Eco Friendly Plan
I think it is the "how are you going to be ECO thread"
Anyone else have an Eco Friendly Plan
Edited by elster on Sunday 27th September 16:11
I think you will find that running a ground source heat pump without underfloor heating is going to be pretty costly in electricity terms; I might be wrong on this and stand to be corrected but it could be as a bad as 4 units of electricty to produce one of heat. If this place is rural and not in 24/7 use have you considered a wood burning boiler?
rovermorris999 said:
Hooray for Building Regs. Not. The work will be done by a local plumber recommended to me but I like to know all the ins and outs beforehand so that I know what to ask for and so that I recognise a proper job.
I'll check the flow rate when I get the chance and before any decisions are made. I've had another poke around and I think I may have found another location for a vented cylinder which may be a cheaper/simpler option, at least I understand them!
I presume a low pressure would rule out a combi boiler as well? My only experience of them was when they first came out and I was put off by the poor flow rate of hot water. Have they improved in recent years? Oil ones are available but I've only ever seen a gas one.
Make sure the plumber shows you his Unvented card, because you WILL need to have paperwork to support the unvented installation. It used to be the case that you actually had to notify Building Control of your intention to fit one. Please be aware that unvented hot water has the potential to be more dangerous than a gas explosion in the wrong hands.I'll check the flow rate when I get the chance and before any decisions are made. I've had another poke around and I think I may have found another location for a vented cylinder which may be a cheaper/simpler option, at least I understand them!
I presume a low pressure would rule out a combi boiler as well? My only experience of them was when they first came out and I was put off by the poor flow rate of hot water. Have they improved in recent years? Oil ones are available but I've only ever seen a gas one.
Low pressure, as I said before, is an issue, but not a major one. Be warned that in all my years in the construction industry I've never met a plumber worth his salt that thought Combination Boilers were much cop on more than a couple of outlets, despite what the industry might try to tell you. This is real-life experience. In fact, a boiler manufacturer told me a few months back that he could see the end of the Combination Boiler in the fairly near future. It doesn't lend itsef to integration into a decent renewable fuel scenario.
There was a thread not so long ago about this very subject - one of the comments were about getting more efficient radiators as an alternative to underfloor heating. 'GetCarter' from here built his place a few years back using ground source (it was a new build) and ran a blog detailing how it went. Sure he'll be along eventually.
Ken Sington said:
I think you will find that running a ground source heat pump without underfloor heating is going to be pretty costly in electricity terms; I might be wrong on this and stand to be corrected but it could be as a bad as 4 units of electricty to produce one of heat. If this place is rural and not in 24/7 use have you considered a wood burning boiler?
The manufacturers' websites that I've seen suggest 1 unit in, between 3-4 out, but on an underfloor installation. I think that efficiency should be similar for radiators as the boiler will work just the same but the issue is whether they get hot enough to warm the room. I'm hoping that if they're big enough at 35 degrees C they should do the job but I'd like to hear some real world experience.It is a rural property but it'll be a holiday let so it needs to be a completely hands-off push-button heating system. Having run a holiday let before I've learned never to underestimate the dimness of the general public, so much so that I'm loathe to let them have an open fire or log burner! I don't want the place burnt down. And the less maintenance, the better. A heat pump is pretty much maintenance free, reputedly.
I specced a system running air-source with rads in two small offices and a kitchen area for an industrial unit. The rads were specced for 50 degrees instead of the normal 80 and were (I think) bigger than the ratio of those tempertatures would suggest. I was impressed with the outdoor temperatures at which the rads were capable of operating though....
Some more thoughts.......
The other advantage with an underfloor system is that becomes an energy storage device as much as a heating system - and if an air sourced unit is fitted (much lower cost) you can take advantage of the relative warmth of the day to make a heat pump more efficient.
with radiators you tend to have to heat when it's cold outside, so a ground sourced unit will be more efficient.
However if the house you want to heat is a rental, I would be tempted to install radiators and an air sourced unit (I could supply an 11.9kW unit for under a thousand) - and have the ability to turn the system on and off by remote control via mobile phone. Keep it simple, air sourced unit going straight round radiators, no buffer tanks or thermostatic valves, one master thermostat and a time clock.
The other advantage with an underfloor system is that becomes an energy storage device as much as a heating system - and if an air sourced unit is fitted (much lower cost) you can take advantage of the relative warmth of the day to make a heat pump more efficient.
with radiators you tend to have to heat when it's cold outside, so a ground sourced unit will be more efficient.
However if the house you want to heat is a rental, I would be tempted to install radiators and an air sourced unit (I could supply an 11.9kW unit for under a thousand) - and have the ability to turn the system on and off by remote control via mobile phone. Keep it simple, air sourced unit going straight round radiators, no buffer tanks or thermostatic valves, one master thermostat and a time clock.
I don't know any of the gory details, except that the vertical borehole is supposed to be a better solution (depending on the geology I guess). The thing is that the drilling of the vertical borehole makes one hell of a mess.
The old's had one installed on a site which is about an acre, they parked the cars off-site on the warning of the drillers, and they still had to clean them. Muddy gloppy stuff splattered everywhere!
The old's had one installed on a site which is about an acre, they parked the cars off-site on the warning of the drillers, and they still had to clean them. Muddy gloppy stuff splattered everywhere!
Arthur Jackson said:
Recent changes now allow discharge into soil systems, but only if the tundish at the cylinder end is visible since the other end will not be. Therefore a discharge pipe MUST be run to within 4" of the ground and any part of it must be be caged to prevent anyone touching it.
My muppet plumber installed mine so that the discharge pipe discharges directly over my front door! Step outside and get a scalding shower!Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff