Heating engineer needed north west London

[HRP123]

Hi there, I've already posted on the forum but I need an experienced heating engineer to determine what changes to make to my system - please let me know if you can suggest anyone covering north west London (not far from Watford) who can deal with system design and complicated wiring. Thanks!


Summary of the situation

The house is 15 years old, I moved in around 12 years ago. Built to good standards, no major issues with construction design. However about 10 years ago I replaced the original boiler system with a new one because it was not delivering enough heat. Originally there was an obscure Geminox boiler around 24kw with hot water priority. However the hot water would kick in so often that the heating would not work sufficiently.

Since gas prices were cheap, I asked my plumber to basically put in a V8 engine of boilers to make sure I could run everything at any time. He put in a WB 40cdi system boiler with a low loss header and separate zones for

• Underfloor heating – approx 160sqm ground floor only, off the LLH on a pump, going to two separate UF manifolds (without their own pumps) with room thermostats on actuators controlling each zone (7 zones)
• Radiators – one circuit with its own pump with two zones with 8 on first floor and 4 on second floor – controlled by Nest
• Towel rails – on a timer operation, 6 rails – simple Honeywell 7 day programmer
• Cylinders – 2 x 300 litre original Geminox EBS 200 tanks connected in parallel

The wiring connected up in a relay switch system so any zone can call for heat. There are 5 pumps – 1 to LLH, 1 to each circuit. There is also a secondary hot water circulator as it is a big house with irregular usage – which needs to be on all the time most day hours (if there was a smart control, I would be able to adjust this sometimes).

1. The boiler is consuming a crazy 70,000-80,000 kwh of gas annually. I’ve done a heat loss calc on Heat Engineer. It suggests 20kw of heat loss with total annual energy demand of 56,000 kwh (see attached). So there should be capability to reduce the gas consumption.
2. I don't think there is weather compensation currently setup – the flow is 65 degrees to suit the HW circuit plus see point 3 below.
3. I’m not sure if the blending valve on the UF circuit off the LLH is distorting the temperature inside the LLH, as even when the boiler flow is 65 degrees, I measure input flow into the cylinders of 50 degrees (which is what I currently set the UF blending valve in order to work the system more efficiently – floor temp around 30 degrees on the tiles). I’m not sure if this is a measurement issue or a system design fault with the return from the UF distorting the LLH header temperature.
4. The two cylinders have never worked together properly. One cylinder always seems to drain much faster than the other and we haven’t been able to identify why.
5. The 40cdi can only modulate down to 9kwh min gas usage. This may be too high if just one or two zones are calling for heat – like a V8 powering the needs of as 3 cylinder. However sometimes, we need a V8 if all circuits are open. That said I have range rated the boiler down to 75% the last few weeks and it has been fine.

I am looking for a recommendation of a revised system design – to consider:

• Replace the boiler with a more modern option that can operate down to 2/3kwh min.
• Introduce more up to date weather control.
• Introduce DHW priority – assuming it can recharge the cylinders quick enough without compromising heat.
• Look at replacing the cylinders with one if this makes more sense. Consider adding a solar boost to use current excess solar being exported to grid on sunny days.
• Consider whether to replace current hot water secondary recirculator with a more modern efficient one eg Grundfos auto adapt.
• Look at an alternative option of ASHP alongside existing boiler to power just the UF circuit. Use existing boiler for HW, CH and towel rails.