We bought a 1 bed ground floor flat a year and a half ago and particularly last winter we noticed the living room was slow to heat up at 1C/hour.
The flat had a new Worcester 27CDI replacement boiler fitted Oct09 by the previous owners to the existing radiators removing the need for an immersion.
The setup now looks fairly standard but with no radiator in the kitchen, and old TRVs all around except in the bathroom. There is now a wireless thermostat in the living room. Reading all the install info that I received when buying the house the thermostat should be in the bathroom (the one with no TRV).
However, I don't think thats the cause of the slow heat-up.
The flat is fairly well insulated from c 1975 ground floor with cavity wall insulation, double glazing all round. It does have a vent in the bedroom and living room that's usually closed as they are drafty.
I have done the heat loss calcs to check the radiator sizing, and for the ones that are there they appear OK - see bottom of post.
In order to check system setup, I turned the boiler temp up to max (6), set the room start up to 26C out of the way and opened all the TRVs.
Starting the boiler, I measured all the inlet and return pipe temps with a multimeter with a K type thermocouple. I sandwiched the thermocouple against the pipe with a small towel -see attached picture;
From this I note the temperature difference across the radiators is low at less than 5C but given measuring errors even across them all. The boiler inlet and outlet differential is also low at 8C on startup dropping to 6C after the system warmed up. The boiler radiator outlet water temp stayed around 62-64C when the boiler heat setting of 6 indicates it should be approx 80C.
So the system could be 'balanced' but with low heat drops across the radiators. The combi appears not to have a variable pump speed, but does appear to modulate the gas output down. Maybe if the load on the radiators is low this could explain the small temperature differential between the boiler inlet and outlet water temperatures, and also the 62C cental heating water outlet temp.
I guess the lower boiler temperature outlet of the boiler will reduce radiator output.
The boiler works fine for domestic hot water flow and temperature.
I also notice that the STARS heat loss calcs below assume 20C differential across the radiators - do I need to balance the system for that? Would that increase the output of the radiators?
I looked at the balancing FAQ but that appeared to assume you could alter the pump speed.
Heres the heat loss calcs - I've picked the nearest radiator in the Stelrad catalog to what's already there (except the kitchen does not have a radiator);
STARS Advanced Heat Loss Calculator
External Temperature:
-3°C
Project Description:
1 bed flat
Buildings
FLAT
Flow Temperature:
80°C
Return Temperature:
60°C
Mean Water Temperature (MWT):
70°C
Pipeloss:
10%
Fast Heat Up Allowance:
0%
Hot Water Load:
0W
Room Count:
5
Rooms
Living Room
Air Changes:
1.5
Temperature:
21°C
Delta-T:
49
Radiator Count:
1
Heat Loss Requirement:
1767W / 6033BTU
Radiators
Product Code: 143709 — 1 × Compact P+ 450 × 1800 mm 1899W / 6484BTU
Bedroom
Air Changes:
1.0
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
777W / 2653BTU
Radiators
Product Code: 8468 — 1 × Elite K1 450 × 1100 mm 845W / 2885BTU
Bathroom
Air Changes:
2.0
Temperature:
22°C
Delta-T:
48
Radiator Count:
1
Heat Loss Requirement:
397W / 1356BTU
Radiators
Product Code: 8453 — 1 × Elite P1 450 × 900 mm 428W / 1461BTU
Hall
Air Changes:
1.5
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
152W / 519BTU
Radiators
Product Code: 143650 — 1 × Compact K1 300 × 500 mm 255W / 871BTU
Kitchen
Air Changes:
2.0
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
459W / 1567BTU
Radiators
Product Code: 8463 — 1 × Elite K1 450 × 600 mm 461W / 1574BTU
The flat had a new Worcester 27CDI replacement boiler fitted Oct09 by the previous owners to the existing radiators removing the need for an immersion.
The setup now looks fairly standard but with no radiator in the kitchen, and old TRVs all around except in the bathroom. There is now a wireless thermostat in the living room. Reading all the install info that I received when buying the house the thermostat should be in the bathroom (the one with no TRV).
However, I don't think thats the cause of the slow heat-up.
The flat is fairly well insulated from c 1975 ground floor with cavity wall insulation, double glazing all round. It does have a vent in the bedroom and living room that's usually closed as they are drafty.
I have done the heat loss calcs to check the radiator sizing, and for the ones that are there they appear OK - see bottom of post.
In order to check system setup, I turned the boiler temp up to max (6), set the room start up to 26C out of the way and opened all the TRVs.
Starting the boiler, I measured all the inlet and return pipe temps with a multimeter with a K type thermocouple. I sandwiched the thermocouple against the pipe with a small towel -see attached picture;
From this I note the temperature difference across the radiators is low at less than 5C but given measuring errors even across them all. The boiler inlet and outlet differential is also low at 8C on startup dropping to 6C after the system warmed up. The boiler radiator outlet water temp stayed around 62-64C when the boiler heat setting of 6 indicates it should be approx 80C.
So the system could be 'balanced' but with low heat drops across the radiators. The combi appears not to have a variable pump speed, but does appear to modulate the gas output down. Maybe if the load on the radiators is low this could explain the small temperature differential between the boiler inlet and outlet water temperatures, and also the 62C cental heating water outlet temp.
I guess the lower boiler temperature outlet of the boiler will reduce radiator output.
The boiler works fine for domestic hot water flow and temperature.
I also notice that the STARS heat loss calcs below assume 20C differential across the radiators - do I need to balance the system for that? Would that increase the output of the radiators?
I looked at the balancing FAQ but that appeared to assume you could alter the pump speed.
Heres the heat loss calcs - I've picked the nearest radiator in the Stelrad catalog to what's already there (except the kitchen does not have a radiator);
STARS Advanced Heat Loss Calculator
External Temperature:
-3°C
Project Description:
1 bed flat
Buildings
FLAT
Flow Temperature:
80°C
Return Temperature:
60°C
Mean Water Temperature (MWT):
70°C
Pipeloss:
10%
Fast Heat Up Allowance:
0%
Hot Water Load:
0W
Room Count:
5
Rooms
Living Room
Air Changes:
1.5
Temperature:
21°C
Delta-T:
49
Radiator Count:
1
Heat Loss Requirement:
1767W / 6033BTU
Radiators
Product Code: 143709 — 1 × Compact P+ 450 × 1800 mm 1899W / 6484BTU
Bedroom
Air Changes:
1.0
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
777W / 2653BTU
Radiators
Product Code: 8468 — 1 × Elite K1 450 × 1100 mm 845W / 2885BTU
Bathroom
Air Changes:
2.0
Temperature:
22°C
Delta-T:
48
Radiator Count:
1
Heat Loss Requirement:
397W / 1356BTU
Radiators
Product Code: 8453 — 1 × Elite P1 450 × 900 mm 428W / 1461BTU
Hall
Air Changes:
1.5
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
152W / 519BTU
Radiators
Product Code: 143650 — 1 × Compact K1 300 × 500 mm 255W / 871BTU
Kitchen
Air Changes:
2.0
Temperature:
18°C
Delta-T:
52
Radiator Count:
1
Heat Loss Requirement:
459W / 1567BTU
Radiators
Product Code: 8463 — 1 × Elite K1 450 × 600 mm 461W / 1574BTU
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