I would like the communities well informed views on high temperature heat pumps and how they can be used for boiler replacement to improve heat pump takeup in the UK.
Last year I replaced my 1990’s oil boiler installation with a high temperature Heat Pump operating at 35 to 50 deg C for my radiator heating and 68 deg C for heating a standard UK indirect 120 litre tank. No additions or changes to the internal pipe work were carried out except for a new pump, flush and filter. After a winters season I have found that the cost of running at these higher temperatures is only 6% to 8% more than the ‘normal’ 30 to 45 deg C range for Heat Pump with radiators.
The advantage is that the existing radiators and tank can be reused and no plant room is required with a considerable reduction in cost, disruption and internal space required on smaller properties.
If there is an existing indirect storage tank in the property then it can be reused but alternatively there is the option of a much smaller tank that can be reheated in 30 minutes to 60 deg C to effectively provide ‘continuous DHW’ with the right heat exchanger (the heat output is rated 11kW on my 8kW Samsung HTQ at 70C @ 2C ambient!)
The re-use of the existing components is a low carbon option in itself that more than compensates for the small reduction in SCOP.
From my experience any heating technician could fit one of these replacements easily knowing that a higher temperature option can always be set to compensate for an older property with varied and indeterminate heat loss. (running at 55 to 60 deg C radiator temperature is perfectly ok with these heat pumps, I have tried it)
Insulation and/or radiator upgrades can be added as a separately costed ROI project if required at a later date.
The most important issue here is how can we convert older properties more quickly at lower cost and resources whilst more easily meeting the customers expections.
Do we think this approach could lower installation costs and the skills required for the big switch over?
Do we think MCS should embrace high temperature installations?
I am very aware that the current level of the BUS grant will soon have be dramatically reduced when/if the take up improves. The right sort of tariff subsidy based on grid demand smoothing might be a better option.(although I already average 15p per kW on Octopus cosy which I highly recommend)
PS I am not disregarding the importance of improving home insulation, which is obviously necessary to allow a smaller heat pump to be fitted, just want more heat pumps installed of any size.
more about high temperature heat pump and the impact it could have on our older leaky UK housing stock here.
I agree, it should possible to install the simplest system possible.
In my mind that might be cut down to:
a heat pump that includes everything (filters, expansion vessel, controller, WiFi, oat sensor, frost protection etc).
use whatever is cheapest, easiest for hot water. It’s not a big part of the bill, so it doesn’t really matter. You can always use less water.
as you say allow high temp.
Use energy usage to size the heat pump.
don’t require per room heat loss calculation, just assume the existing system works, as you would for a boiler. Verify that the sum of radiators are big enough at the chosen flow temperature. And that the pipes are big enough (give clear processes on that, to stop the 22mm everywhere brigade).
reduce electricity prices relative to gas to make up for the loss of efficiency.
include more sensors and better intelligent controls, so it sorts itself out. And be diagnosed remotely as a last resort (with all data available).
Thanks for the reply. Simple is best. I chose the high temperature boiler replacement option to test the manufacturers claims and it worked for me. I think it could work for most of the UK housing stock. Studies have shown that up to two-thirds of UK homes could be fitted with heat pumps with no additional home upgrades required.
There are 29 million households in the UK and probably 75% will need to find an alternative to fossil fuels for heating in the next 25 years. The current grant system would cost the government £165 billion which clearly will not happen. The cost of a heat pump conversion needs to be around a third of what it is now for an average home without government subsidy.
An interest free loan scheme recovered through future electricity bill savings might be a more realistic funding option.
Your system is an interesting example of what a simple approach can achieve. I’ve been following along on the various threads you have contributed to, where you share different insights but wanted to bring some of the key stats together here for easier reference:
Samsung HTQ 8kW (~approx £3.9k for the heat pump).
Weather compensation setting:
50C flow temp @ -2C outside
35C flow temp @ 15C outside
SPF 3.2 (from the Samsung display)
Standard 120 L indirect hot water tank (flow temp peak 68C)
Vented system with header tank
Pipework: 28mm to hot water tank, 15mm elsewhere
4 bed detached brick, with modern extension (cavity filled). Double glazed, 300mm loft insulation.
Previous system: Oil boiler (18kW Wallstar, 25 years old)
It would be interesting to know if the installer quotes you received included upgrading radiators. It seems that £12-15k quotes without radiator upgrades are not uncommon.
I was quoted £12.5k for the heat pump and hot water cylinder with no radiator upgrades. I installed the whole lot myself in the end for a material cost of £4.7k (£2400 for the heat pump, £1000 for cylinder and £400 copper pipe and fittings, £600 radiators, £300 misc). At the time my over-inflated heat loss suggested my low temperature heat pump would not have been able to run the existing radiator system but I now calculate based on an accurate heat loss that I could have actually run the existing system with no upgrades at a design flow temp of 47C, which technically even my low temp heat pump could supply. If I had realised this at the time I would have tried it, if only for heating science… after a very thorough flush of that older system.
Is the real lesson or point that your making, not necessarily low temp vs high temp, but that it can be possible to install a heat pump in a simple bolt on approach to an existing oil boiler heating system where there is an existing cylinder in place and that with careful tuning of control settings (crucial!) a better SPF is possible than almost 90% of the systems on the Electrification of Heat trial (https://eoh.heatpumpmonitor.org/)!
If there was no BUS and MCS to distort the market, perhaps this type of try it, tune it and see approach would be more common.
The elephant in the room is the additional costs beyond materials when paying for professional installation, that gets to a sensitive subject. Installers often express that they see their work devalued by discussion of cutting these costs and that these costs reflect what it takes to run installation businesses with all the overheads involved (costs that many of us don’t see when we try and make sense of the difference between materials and total install cost).
Your example is a good example of how it can be possible to simplify the installation down to a minimal intervention and it would be interesting to hear from some installers if they would be willing to price up that specific installation type, to give a fair price comparison with the pipework change + cylinder but perhaps no rad upgrades.
Hi Trystan, That’s a great summary and I will try to install a monitor next heating season if only for the heating science. I have left a space for it.
The preliminary quotes I got did include two radiator upgrades but I was never really going to wait for MCS and BUS approval and arguing with the EPC if I need yet more insulation, finding plantroom space or all new bathroom radiators with electric heaters in them etc. etc. It all costs money, time and resources. I just wanted to get on with it!
My thoughts are that any heating engineer can assess an existing DT50 radiator boiler setup in a few hours. Checking the gas bill for heat loss estimation, what are the flow rates, is it working to the satisfaction of the home owner etc. There should be nothing to stop a direct replacement with a suitably designed HP by any qualified heating engineer IMO. They are designed for direct boiler replacement with compatible flow and temperature deltas. I predict this will become the ‘new normal’ for the UK heat pump roll out and dedicated plant rooms costing more than the external monobloc HP will a be a thing of curiosity in the decades to come. UK housing stock does not have the space.
If a hot water tank already exists then it can be used but if you are replacing a combi boiler (most likely) then an independently wired flow water heater can be fitted where the old gas boiler was in most small homes. (or 8 hours of the off peak cosy tariff spread over the three sessions will keep a standard tank hot all day at a reasonable cost)
This type of installation would solve the three issues holding back heat pumps -uncertainty, disruption and cost. There is predictability with simplicity, minimum internal rebuilds and much lower cost of installation as you can use standard trades with healthy competition. (yes I know there have to be regulations in place but lets keep it simple and flexible)
Octopus Cosy turbo is designed to run up to 65 deg C radiator temperature on cosy tariff. Now that would be interesting to monitor!
Shame the Heat Greek mini store is so costly for what it is! Fits in the space of a combi boiler.
I can’t convince myself that for most installs a spare £5ķ (lower if PV being installed) is better spent on improved COP then home battery.
But a basic heatpump install needs a unreasonable level of understanding from the residents for a landlord to cope with the educational overheads on each tenant charge.
A landlord may choose a direct replacement of the existing boiler with something like the Cosy Turbo set to a higher flow temperature range to simplify the installation. The operating cost is borne by the tenant. The weather compensation will be preset and locked. The tenant can adjust the target temperature and schedule but will soon understand that the heating has to be on for most of the day rather than the quick evening boost they were used to.
Then the tenant will likely start taking up the landlords time, so best to keep to simple combi boilers untill tenants arrive pretrained in how to live with a heatpump.
Also landlords needs every possible meaningful EPC point they can get, and heatpumps don’t give points.
