Not much heat upstairs

[JunJun]

Hi,

I've just bought a large house complete with an Ideal Isar HE30 combi boiler fitted. (Yes, I know they are rubbish! We had one in our previous house, lasted no more than a couple of years before being switched for a Vailant but that's another story.)

When we bought the house, all the bedrooms had very small radiators (2 ft by 1 ft roughly) which weren't doing much to heat up the large 14ft x 14ft rooms (10ft ceilings). So we switched them for larger radiators and hoped the boiler would be man enough to push them. We also added a large double rad downstairs in one of the living rooms which previously had no heating.

With the heating switched on, all the ground floor rads get nice and toasty but upstairs they are cold or warm at best. I've bled the system of air and pressurised it to just above 1 bar, all TRVs and lockshields are wide open. I've also heard about balancing the system but doesn't that refer to where its hot upstairs but cold downstairs??

I've attached an (incredibly accurate) diagram of my system. Help please, winter's approaching!

 

[Whitespirit66]

If the main flow and return pipes feeding the 15mm fed rads are also 15mm, they have insufficient heat carrying capacity. 15mm main F and R pipes can only carry approx. 15,000 BTUs/4.5Kw. Add up all the 15mm fed rad outputs together, and I'm betting their combined outputs will exceed this figure. Repiping main F and R's in 22mm will probably be required. The reason the previous owners had such small rads was because that's all their 15mm fed system could satisfy.

The rads on the manifold work fine because they are fed by 22m, before the 10mm branches to each individual rad.

 

[JohnD]

you do need to balance your radiators. You are wrong to have "all TRVs and lockshields wide open" since the circulation will all flow through the easiest route.

however, whoever it was that thought it was a good idea to use 15mm to feed 3 floors was mistaken.

 

[JunJun]

If the main flow and return pipes feeding the 15mm fed rads are also 15mm, they have insufficient heat carrying capacity. 15mm main F and R pipes can only carry approx. 15,000 BTUs/4.5Kw. Add up all the 15mm fed rads outputs together, and I'm betting their combined outputs will exceed this figure. Repiping main F and R's in 22mm will probably be required. The reason the previous owners had such small rads was because that's all their 15mm fed system could satisfy.

The rads on the manifold work fine because they are fed by 22m, before the 10mm branches to each individual rad.

Thanks for the reply, very useful. And yes, you are correct, the total output of all the rads upstairs is more than 15000 BTU, two of the new column rads add up to 12,000 BTU alone. Does that mean the output of the boiler itself is acceptable? (I think the 30 in HE30 stands for 30kW?!) Repiping wouldn't be a big deal as its a Victorian house with all the pipes surface mounted but its a job for the summer.

I'm going to try closing all the valves downstairs and see how hot it gets upstairs.

Thanks again

 

[JunJun]

you do need to balance your radiators. You are wrong to have "all TRVs and lockshields wide open" since the circulation will all flow through the easiest route.

however, whoever it was that thought it was a good idea to use 15mm to feed 3 floors was mistaken.

Thanks, I will try balancing them.

 

[JohnD]

30kW is roughly 100,000 BTU. When I had a similar sized boiler in a large Edwardian house, the F&R pipes came off the boiler in 28mm, then divided into a 22mm upstairs and a 22mm downstairs circuit, which was big enough, plus a cylinder. 28mm has about twice the capacity of 22mm, which has about twice the capacity of 15mm.

Most of the time your radiators will not need to run at max output, they will need the most when they are warming up the room from cold.

If you are repiping you might like put each floor on its own zone, with a 2-port valve, and control its times/temps separately, preferably with programmable thermostats. This will work out fairly expensive, so you could just use cheap wired dial stats at first and swap them later.

A house of that size might do better with an unvented cylinder than with a combi. If you go that way, it can be run off your existing combi boiler as another zone, and timed to start heating before the CH.

 

[Whitespirit66]

If the main flow and return pipes feeding the 15mm fed rads are also 15mm, they have insufficient heat carrying capacity. 15mm main F and R pipes can only carry approx. 15,000 BTUs/4.5Kw. Add up all the 15mm fed rads outputs together, and I'm betting their combined outputs will exceed this figure. Repiping main F and R's in 22mm will probably be required. The reason the previous owners had such small rads was because that's all their 15mm fed system could satisfy.

The rads on the manifold work fine because they are fed by 22m, before the 10mm branches to each individual rad.

Thanks for the reply, very useful. And yes, you are correct, the total output of all the rads upstairs is more than 15000 BTU, two of the new column rads add up to 12,000 BTU alone. Does that mean the output of the boiler itself is acceptable? (I think the 30 in HE30 stands for 30kW?!) Repiping wouldn't be a big deal as its a Victorian house with all the pipes surface mounted but its a job for the summer.

I'm going to try closing all the valves downstairs and see how hot it gets upstairs.

Thanks again

Boiler output should be OK. However, it sounds like you have some large output rads on your system, or is the 12,000 BTU column an exception? You should add up the total output of all rads on the 15mm feeds, because if they exceed approx. 70, 000 BTUs/20KW you may even need 28mm pipes from boiler to each floor, then down to 22mm along each floor, teeing off to each individual rad in 15mm.

As mentioned above, whilst re-piping, it will definitely make your large system more efficient if you fit a zone valve and room stat on each floor - plus TRVs on all rads except the ones in the room/area where the room stats are located. If you have, or intend to have, more than one bathroom, take the opportunity to bin the combi and get an unvented cylinder (as long as your cold main in is sufficient). The Icos is on borrowed time anyway.

 

[JunJun]

Sorry to bump my old thread but thought it would be better than starting a new one as its a continuation of my previous problem.

Sooo, its the first really-cold day of the year and the top floor of our house is freezing in the morning and night. As I can't afford a completely new central heating system for probably the next few years, I was wondering whether something like in the diagram below would actually work.

Basically, the plan would be to disconnect the top floor from the rest of the system and get a plumber in to install a direct cylinder, immersion heater and pump in the middle room on the top floor, plus replace all the pipes upstairs to 22mm. Would this actually work? So its kind of like a sealed system but can be topped up using the combi-boilers fill loop if needed. I had a look at unvented cylinders too but they look dangerous! lol

 

[gigz]

Remember, the 30kw is on the hot water side. Heating is only 24kw max.

 

[JunJun]

Remember, the 30kw is on the hot water side. Heating is only 24kw max.

Sorry, I don't follow... Are you referring to the combi boiler? If you look at the pic in my last post, I plan to remove some of the load on the boiler by having a separate system on the top floor. Sorry, if I've not explained it clearly enough.

 

[Steelmasons]

 

[JunJun]

Rolleyes because it'll never work or because its not the 'proper' way to do it? I'm not looking for the proper way, just want some damn heat for a few winters before gutting the whole system!

On Googling, it seems other houses have this as standard e.g.:
http://forums.digitalspy.co.uk/showthread.php?t=1952213

 

[Steelmasons]

Crack on junjun...........too tight to call a professional will always put a bigger hole in yer pocket...

 

[JunJun]

Crack on junjun...........too tight to call a professional will always put a bigger hole in yer pocket...

Oh, we're not all as wealthy as you, Mr Plumber Extraordinaire. I'm glad I'm providing you with some entertainment. You don't seem to understand the difference between saving for a few years whilst having a temporary heating system, and saving for a few years and not having any heating at all! To put a full system in my house and replace all pipes from 15mm to 22mm will cost several thousand pounds and a lot of disruption.

 

[Steelmasons]

I would imagine a few hundred quid would have all those radiators nice and toasty...