Ground Source Heat Pumps

beardymarrow

crumbleman wrote: »

Hi,
I’m looking for some advice if anyone can help.
Shortly I will be having a house built in North East Scotland, where temperatures can often be well below freezing for days at a time. I am trying to decide which heating system to install. The developer has costed for a mains gas fuelled system boiler and suggests that as the property will have four bathrooms a system boiler provides sufficient hot water and heating. There will be underfloor heating installed on both floors.
I would like to install some renewables, taking advantage of the great interest free loans and RHI, I have considered ASHP, GSHP and solar thermal. Looking at the great MSE forums there seems to be great disparity between what the manufactures state these systems will provide and how they operate and what end users are actually finding.
One of the themes of the heat pump forums is that they seem to not be fit and forget technology in the way that a gas boiler would be, is this due to poor installation and specification from the start or is it just part of running a heat pump?
So as I’m going to be on mains gas should I even be considering a heat pump and if so any suggestions on which type?
Should there be any difference in the design of underfloor heating if the heating is provided by the system boiler or a heat pump?
Thanks in advance.

My advice, for what it's worth would be to have a gas boiler, if you're on mains gas. Even with a COP of 3.5 to make a GSHP worth it in terms of pure energy cost, but that doesn't take into account the capital outlay or the cost of repairs if it goes wrong, availability of trained engineers etc. etc. If you weren't on mains gas (like we aren't) then I'd definitely recommend a GSHP. I don't think there's any difference in UFH design if you have a gas boiler or a GSHP, but I'm by no means on expert. There certainly is for the rads though, as they need to be much bigger to cater for the lower temps of the GSHP.

Bear in mind when you take mine and Patrol's experiences into account, that we are both inveterate tinkerers, and need to know everything about everything (hence why I'm on the forum). I think a GSHP properly set-up can be fit and forget, and in fact I have forgotten about mine for the last couple of months now it's set-up right (hopefully), but as I am a curious type, every little bit of info is analysed to see where I can save money, and you just don't get that opportunity with a normal gas boiler.

matelodave

I'd agree with beardymarrow - go for gas.

We've got an ASHP which isn't as expensive to install as a GSHP and probably isn't as economical to run but the principle is similar. We've only got it because the alternatives of LPG, Oil or wood pellets didn't appeal

Heatpumps are great if you heat the house continuously ie if you are at home all day. They are very slow reacting, so not ideal if you want a quick heat up when you get home from work.

I'm also like BM and am compelled to tweak to optimise it but as said, now it's sorted I don't touch it and it gets on with it.

The RHI is nice but no where near as good as was originally promised and it's based on your EPC, so with a brand new house to the latest spec I'd guess you won't get as much as you might hope.

You really do need to do the sums to work out if it's worth while.

alastaid

Hi,


After a bit of help, have had my Greenland E11 GSHP for 9 yrs and it has purred with no probes until a few weeks ago. I got a high error on delta between gr8/gt9, I turned it off, let it cool down, cleaned all the filters, turned it back on and it worked until today, with exactly the same fault. GT8 was reading 54.3 & GT9 54.4. What is the most likely cause, do I suspect the three way valve or pump, is there an easy way to diagnose?


Thanks in advance.


Alastair

lovesgshp

Hi Alastair.
Firstly, check the full alarm log in the K2 menu, as the system will reset, so you need to see if it is a multiple problem.
Secondly, if it is a multiple alarm, you are going to have to manually check the 3 way valve operation from the service setting. You will need to remove the front cover of the pump to check the valve is switching.
Has your domestic hot water temperature increased as well, as this could also indicate a sticking valve?

alastaid

Hi,


Thanks v.much for that, yes the three way valve was stuck. Worked it free and all is back to normal. Should you put any form of lubricant on the valve, as it still feels a bit stiff, ie the spring return doesn't seem that enthusiastic, so I would think it will stick again unless I do something with it?


Cheers


Alastair

lovesgshp

alastaid wrote: »

Hi,


Thanks v.much for that, yes the three way valve was stuck. Worked it free and all is back to normal. Should you put any form of lubricant on the valve, as it still feels a bit stiff, ie the spring return doesn't seem that enthusiastic, so I would think it will stick again unless I do something with it?


Cheers


Alastair

You could try the WD40 option, which may keep it working for a while. Mine managed 1 year after a good spray of it and multiple operations from the manual switch over in the I/S menu.
However, I would suggest you change the valve ASAP to the LK version, as this is proving to be one of the most reliable. Change the whole valve, not just the electronic part.

destry

Evening all. I am renovating a leaky old 220 sq m farmhouse and trying to work out how to heat it. The walls are very thick but not cavity, so I'm losing heat that way, but doing everything I can: new windows, loft insulated, underfloor heating downstairs (probably can't afford upstairs as well), etc etc... The heat loss calc for the house (once insulated) is coming out around 14 Kw.

I have enough land for a GSHP and there is a fair amount of water flowing through - the area has a lot springs and is just below a hill. I'm attracted by a GSHP because of the low running cost, low noise, low environmental impact. I like the idea of the fabric of the house slowly heating up and retaining warmth like a thermal store. Also, I can supplement the heating (and perhaps the HW, by way of a back boiler) with wood-burning stoves as we have a small amount of woodland to harvest.

However, the area I would use for the slinkies is about 35 metres from the point in the house where the plant would be. Is that too much or does it not matter?

Am I mad to think I can heat what will always be an 'inefficient' house this way? All the guides seem a bit doubtful... And what about the hot water? I am very tall and a shameless devotee of the bathtub: my nightmare is contemplating a tub half-full of just-about-hot-water! Or, possibly just as bad, a full bath but a family complaining that I've used up the entire supply and now everyone else has to wait for an hour for the measly 300L tank to reheat (my current house has a 700L tank!).

Alternatives seem to be Calor, oil, wood pellets, or an air pump. Have also had a 'bivalent' system suggested, which seems to be a fancy term for adding a traditional boiler in case the fancy system lacks the necessary grunt. I'd like to do a GSHP installation if possible, but of course I worry that twenty grand later I'll end up being a bit cold or working the pump so hard my electricity bill goes through the roof.

Thoughts and advice welcome!

lovesgshp

destry wrote: »

Evening all. I am renovating a leaky old 220 sq m farmhouse and trying to work out how to heat it. The walls are very thick but not cavity, so I'm losing heat that way, but doing everything I can: new windows, loft insulated, underfloor heating downstairs (probably can't afford upstairs as well), etc etc... The heat loss calc for the house (once insulated) is coming out around 14 Kw.
Lots of houses here are similar to yours and yes, a 14Kw unit would be the my normal recommendation. You will need a buffer tank if it is rads and ufh.

I have enough land for a GSHP and there is a fair amount of water flowing through - the area has a lot springs and is just below a hill. I'm attracted by a GSHP because of the low running cost, low noise, low environmental impact. I like the idea of the fabric of the house slowly heating up and retaining warmth like a thermal store. Also, I can supplement the heating (and perhaps the HW, by way of a back boiler) with wood-burning stoves as we have a small amount of woodland to harvest.
If the ground loops are going uphill, then you will need to have them vented at the highest point to prevent airlocks. Wet ground is perfect.

However, the area I would use for the slinkies is about 35 metres from the point in the house where the plant would be. Is that too much or does it not matter?
You can normally go to that distance, but you will need well insulated feeds to the pump. I would not suggest slinkies, but single lines, as slinkies are not as efficient.

Am I mad to think I can heat what will always be an 'inefficient' house this way? All the guides seem a bit doubtful... And what about the hot water? I am very tall and a shameless devotee of the bathtub: my nightmare is contemplating a tub half-full of just-about-hot-water! Or, possibly just as bad, a full bath but a family complaining that I've used up the entire supply and now everyone else has to wait for an hour for the measly 300L tank to reheat (my current house has a 700L tank!).
You can have a 500ltr or 700ltr tank if you want. The 160 ltr one here takes about 20 mins if it is drained completely.

Alternatives seem to be Calor, oil, wood pellets, or an air pump. Have also had a 'bivalent' system suggested, which seems to be a fancy term for adding a traditional boiler in case the fancy system lacks the necessary grunt. I'd like to do a GSHP installation if possible, but of course I worry that twenty grand later I'll end up being a bit cold or working the pump so hard my electricity bill goes through the roof.

Thoughts and advice welcome!

Welcome to the forum destry. Have answered the best I can to your information. Hope it helps

destry

Many thanks, Lovegshp. I'll remember to ask about venting the pipes at the highest points. Does the pump use more energy because it has to push the fluid uphill?

I'm interested that you don't recommend slinkies, which most installers seem to suggest are just as efficient but cheaper to install. Apologies if you have covered this elsewhere, but what's the thinking here?

I have an advisor saying the feed from the manifold to the pump should go underground and will therefore just be picking up more heat from the ground (albeit less efficiently) as it travels the 35 metres to the house - and as such won't need to be insulated until it pops up to pass through the back wall. Does that make sense to you?

Finally (newbie question alert...) can you really get a steaming hot bath out of these critters in the height of summer?

Many thanks again!

Cardew

destry wrote: »

Finally (newbie question alert...) can you really get a steaming hot bath out of these critters in the height of summer?

Notwithstanding that 'lovesgshp' gives excellent advice - the best on MSE - I really cannot see the case for any heat pump(ground or air) with the price of oil these days.


Oil is currently as cheap as mains gas at about 3p/kWh(30p/litre)*


A well installed GSHP could achieve a system COP of, say, 3.0. That would be above average - see the Energy Saving Trust trials.


With electricity at 12p/kWh that is an effective 4p/kWh i.e. higher than oil even allowing for a boiler inefficiency.


Then there is the issue of capital costs for installation. From posts on MSE it seems a GSHP will cost in the region of £25,000.


An oil CH system with tank is £5k to £6k?. Even at today's rock bottom interest rates you can get over 2% after tax on a long term investment - that is £400pa on the 'saved' £20k.


Noise isn't a problem as you can have the boiler outside if you wish.


Whatever the Heat pump enthusiasts might say, it cannot compete with a conventional CH system that can 'instantly' blast out water at 80C and warm a house very quickly - and provide the 'steaming hot bath'.


* I do accept that oil prices have been volatile in the past, but all the informed advice I read is that cheap oil is here to stay.