Air Source heat pump heating vs wood pellet boiler heating

[Freddyjersey2016]

Trying to choose best solution for heating my friends house - it is a 4 bed detached house on a large plot in a country location in Bedfordshire, not on mains gas. In the past it had been heated with oil, that was replaced about 20 yeas ago with a massive central electric storage heating system. House will be rented out long-term, so need a solution that is economical to run, and simple for tenants to cope with.

Have discounted propane and oil as cost is only going one way and need to refill them.

Wood pellets look a possibility, but are they actually made in the uk - seems crazy to me to import them from the USA... and the boilers seems to me to be likely to need regular maintenance, ash clearance... not ideal

has anyone got experience of airsource heat pumps? Economics look good, little maintenance, no supplies to buy - what's not to like? The house does not currently have solar panels, but has roof that could take them

 

[Beau]

Try the Navitron forum. Lots of ASHP users on there. Have a ground source heat pump myself but would not recommend it for rented accommodation due to folk being unfamiliar with them and how to make them work optimally. http://www.navitron.org.uk/forum/

I know a few pellet users. They do need a bit of maintenance and as you say a lot of pellet is imported. Recently looked into the impact of importing/exporting heavy goods but was surprised how small an amount of fuel was required per tonne to move goods long distances. Not sure what the RHI on pellet is like now but one chap I know is making a tidy sum from the payments but to be fair it's not why he installed the system.

First port of call is usually insulation first. If you can do this to a high standard the heating system can be much smaller and cheaper.

 

[treeturner123]

Freddy

In my opinion steer clear of wood pellets. It's not so much the cost of transport, but the cost of sourcing, cutting, processing etc that is the problem added to the fact that large swaths of US and Canadian forests are potentially at risk. Don't forget that the higher the latitude, the slower the growth of timber (this is why the UK wanted Baltic pine rather than home grown as it is denser due to the low growth). Clearly this will have an impact on the ecology and probably the planet's climate (oh sorry, forgot, Trump says there is no human influence on this!!!!!).

If the property will be rented for a significant time, then the simplest system is best. Pellets need to be ordered and delivered just like gas or oil!

Phil

 

[doctor Bob]

I have a ground source heat pump, more efficient throughout the year than an air source pump.
Just received my first RHI payment, £530 a quarter for the next 7 years, basically means it has cost me nothing.
My heating should be 1/4 of the cost of gas.

If he has the land then I'd recommend it, feels like free heat.

 

[MusicMan]

I don't have it yet but have been into it fairly thoroughly as I have ordered a system to be installed in April. As long as the RHI is kept on, it seems an economic solution, and the professional opinion that I have had is that the heat pumps themselves need very little maintenance, much less than a boiler. Mine is a fairly large house and needs 2 x 9kW units (Samsung).

I am using DHS renewables, who seem both honest and competent though probably not the cheapest. I was impressed by the technical survey that they had to do and the information they provided. The economics seems to work out even taking out a loan, and if you have the capital it is a good investment.

That said, if I had a large country plot I would look seriously at a ground source heat pump. Bob is right, they are more efficient but do need the area (or a deep borehole) and installation is more hassle. I didn't have the area. You need about 700 square metres for a 8 kW system. This is to collect the solar energy as it is all solar in the end (unless you are sitting on a geothermal source).

Keith

 

[Freddyjersey2016]

Based on replies to date - I am going to discount wood pellet.

I have a ground source heat pump, more efficient throughout the year than an air source pump.
Just received my first RHI payment, £530 a quarter for the next 7 years, basically means it has cost me nothing.
My heating should be 1/4 of the cost of gas.

If he has the land then I'd recommend it, feels like free heat.

Doctor Bob - Is yours a trench based or borehole based ground heat pump - the plot I am looking at does not have enough land for trench based system, but there is space to get a borehole in quite easily - from the example costs for borehole systems they seem surprisingly expensive

 

[Beau]

The snag with GSHPs is they need good levels of insulation and a large radiant surface for delivery ideally being under floor heating. This way you can keep the temperature of the heating water as low as possible. If you have a small radiant surface like conventional radiators and poor insulation to meet heating demand you need to run at higher temperatures but then with a heat pump the COP drops off badly. There is some good info on the John Cantor site including this interactive calculator. http://heatpumps.co.uk/heatpumpcalculator.html. Also they are best left to tick over running nearly constantly on the coldest days of the year unlike conventional systems which can deliver lots of heat quickly ie leaving the heating off during the day and turning it on when you want heat. Heat pumps do not like to work like this regardless of what the salesman like to say.

 

[doctor Bob]

Hi,
My GSHP is trenched, needed about 700m of trench digging, we are on an acre.
As mentioned in the last post, we are all low temperature underfloor heating, and the house is extremely efficient in terms of insulation, max water temp is 50deg c, where as conventional systems run at 60-65.

We have a plant room and pipe hot water from there to the house, the necessary insulated pipe is very pricey to keep the hot water hot. 50 in the plant room and 48 on entering the house.

 

[Keithie]

I have some observations/opinions for the op, based on experience of friends& my research when the RHI was first announced

1. ground source heat pump good.. espec with rhi ...if you have the space
2. solar pv good with rhi (subject to any ongoing issues with inverter supply and shape of roof / amount of land if you want to farm solar)
3. air source heat pump ...not typically great at all
4. biomass boiler ...good if your energy demands are small (or larger) commercial or v large property/estate, but not great for medium - large houses.
5. Rural fuel for houses (when no mains gas) ... elec/oil/propane ....propane typically the worst choice, oil the cheapest subject to environmental spill risk management

We have mostly log fires and an oil aga with a backup oil boiler for when its properly cold
Neighbours mostly solar pv & ground source heat pumps or just oil

For those who biomass round here (big places) they tend to be able to use wood chip/pellet and grain (oats/wheat etc) and wait for deals to come up. Typically boiler is in an external building (barn/shed) which incorporates a large hopper feeding the boiler via an auger.

If you do decide to go down the pellet boiler route maybe consider buying a pellet maker ?
If you know a few woodturner types then you may have a large free supply of woodchippings /turnings to pellet up!

If I was letting out a rural property with expensive elec heating (storage or otherwise) I'd probably just leave it as it is and make sure the rads had trvs etc (obviously sort the insulation as well)

good luck!

 

[Beau]

Hi,

As mentioned in the last post, we are all low temperature underfloor heating, and the house is extremely efficient in terms of insulation, max water temp is 50deg c, where as conventional systems run at 60-65.

:shock:

Bob 50 deg C is very high for heating with a GSHP. Are you sure it runs at this or is that for DHW? Ours never needs to get over 30C

 

[MusicMan]

I don't know about ground source but for air source our system will also be 50 C. Plus an important 60 C run once a week to avoid legionella.
30 C would not be warm enough for a shower. Note this is for hot water and radiators, not heating only, which of course does not need legionella prevention.

 

[Beau]

I don't know about ground source but for air source our system will also be 50 C. Plus an important 60 C run once a week to avoid legionella.
30 C would not be warm enough for a shower. Note this is for hot water and radiators, not heating only, which of course does not need legionella prevention.

May be talking at cross purposes. Sub 30c for the heating system but yes near 50C for direct hot water (DHW). Run our DHW at 46c but any lower and there are complaints

 

[doctor Bob]

Yes sorry hot water 50c and heating lower, max the house can get to when all rooms set to same temp is about 25c, whack the log burner on and shut down a few rooms and we can hit 30c but that is like a sauna.