Radiator sizing

[MetManMark]

All

We have just got a quote in for central heating (below) while we are largely happy with it I am slightly concerned that the rads are undersized. The house is listed, has solid walls, large single glazed windows, rooms that are about 15*15 feet and 2.8m high (yes I know I have mixed my units!).

What are people's thoughts? I am slightly surprised that he hadn't stipulated double rads throughout?
I have looked up the rads on the DeLonghi pages and know the BTU output. What is the best webpage to put in the room sizes to find out the required rad size? I know there are basic calculators out there but I want to factor in the fact that the windows are singly glazed etc.

cheers
Mark

• Supply and fit new Baxi Duo Tec 40KW combination boiler in ground floor store room with the flue terminating vertically through the roof tiles.
• Supply new Honeywell ST9100A Single Channel 7 Day timer.
• Supply new Honeywell Analogue Wireless Room Thermostat.
• Run a new gas supply underneith the floor boards and through to the store room.
• Supply and fit the following radiators in the rooms listed below : ( K2 = Double radiator, K1 = Single radiator)

1. Dining room 600 x 1200 K2
2. Lounge 600 x 1200 K2
3. Ground floor hall 600 x 1200 K1
4. Ground floor office (through lounge) 600 x 1000 K1
5. Kitchen 600 x 1000 K1
6. Store room 300 x 500 K1 (i added this as i felt it will be useful during cold weather and also help to dry washing etc)
7. Bathroom 600 x 1200 Chrome Towel Rail
8. Bathroom 300 x 900 K1
9. Main bed (rear) 600 x 1200 K1
10. Bedroom 2 (front joining main bed) 600 x 1400 K1
11. Bedroom 3 (joining bathroom) 600 x 1200 K1
12. Bedroom 4 (smallest) 600 x 600 K1
13. 1st floor hall 600 x 600 K1

• All radiators will have Thermostatic Control Valves fitted to increase the efficiency and comfort of each room.
• Plumb-in new hot and cold supplies to bathroom, WC and kitchen sink from boiler room.
• Run new copper flow and return pipe work from boiler room to all radiators.
• Treat the new system with Sentinel X400 Cleanser to remove any dirt/soldering flux that may be in the pipe work. Finally, treat with Sentinel X100 Inhibitor to prevent the build up of iron oxide and prolong the life of major components inside the boiler.

 

[MetManMark]

OK I have found some online calculators. By means of a follow up question - should you just put in what the calculators tell you or should you oversize somewhat (10% etc)?
Cheers
Mark

 

[Paulus]

It's up to you at the end of the day. To be on the safe side you could oversize a bit and install TRV's to provide room by room control of the temperature. It's what I would probably do on an old house with single glazing.

 

[doitmyself]

OK I have found some online calculators. By means of a follow up question - should you just put in what the calculators tell you or should you oversize somewhat (10% etc)?

I wouldn't trust online calculators as they make too any assumptions.

Download Stelrad Stars. It's more complicated but will give a more accurate result.

Most calculators have a built-in oversize of about 10-15% as this gives quicker heating up in the morning; it also provides some headroom for very low temperatures (below -1C). What is not taken into account is the fact that boilers are more efficient at lower temperatures. Rad outputs are quoted for a 75C/65C temperature difference while boilers work better with a 75C/55C difference. This means oversizing the rads by a further 20%.

TRVs need excess heat to be able to operate otherwise, if the rad is only just large enough, the TRV will have to remain fully open to maintain the required temperature.

 

[diamondgas]

Stars is a good piece of kit but takes a bit of getting use too! It'll also sugest their brand rad sizes as well as boilers! Give you a room by room print out etc.

 

[gaspastemania]

If you concerned just P+ them may cost a bit extra but may be worth it in long run ,
If i am mistaken no magna clean on list ??

 

[EPH]

The Quinn app is quite good on the move and lets you email the details easily to your PC or suppliers

 

[RoryD]

Seems to me that if you're questioning the bloke at this stage, then perhaps he's the wrong man? Ensure you get a number of quotes from reputable companies, then compare