Really old install - should I change things

[Buffy330]

Hi

first post and please excuse me if my terminology and understanding of this dark art is poor.

My 5 bed house started out as a 2 bed cottage , and I bought it in its extended state.
It would appear that the heating system has been extended in a haphazard way.

I fully understand that the vented system with a floor standing boiler and a pump for the CH and a second pump for hot water is dated , but it is what it is , and is reliable.

So my problem:

The CH pipes from the boiler are 22mm and as you would expect , the flow and return run upstairs to a cupboard with the hot water cylinder.

To start with , at ground floor level , there is a 15mm loop buried in the floor feeding 4 old radiators.
This pipework is set in concrete and I suspect is leaking , so I propose to dig up and replace with 22mm , and feed the new rads with 15mm tails - is that ok ?

Secondly , in the airing cupboard there is another 15mm loop feeding 2 upstairs radiators. These get very hot.

Thirdly , there is a single straight spine of 22mm flow and return running down the centre of the house , with several long 15mm loops attached.

Naturally trying to balance all this is a real nightmare , and some rads just dont get hot.

So , my proposal .

As above - set the downstairs 4 rads in 22mm with 15mm tails.
Then , get rid of the straight run upstairs of 22mm with all of its loops , and instead run from room to room in 22mm to create an arc so to speak , so that the 22mm is closer to the rads , and have short 15mm tails to the rads.

This way I will eliminate all of the upstairs loops and effectively have a single circuit upstairs.

This might sound naive , and maybe not even logical , but I need to do something.

All opinions are most welcome

thanks

Steve

 

[SJB060685]

If you're prepared to go to such lengths to rectify an existing problem why not consider a complete redo, ie new boiler and system? You can eliminate the two pumps situation and zone the DHW and CH, possibly having two separate zones for heating, one up and one down. Of course this will be quite a chunk out of your pocket but if designed and executed properly you will have a modern high efficiency boiler and system.

 

[gmartine]

Just a thought, IF the boiler has been kept throughout the development and extension of your house does it even have the capacity to heat it fully as you'd like? If it is the first thing to do is some rough heat loss calculations and make sure it can.

 

[SJB060685]

Just a thought, IF the boiler has been kept throughout the development and extension of your house does it even have the capacity to heat it fully as you'd like? If it is the first thing to do is some rough heat loss calculations and make sure it can.

Very good point and one i overlooked. Schoolboy error

 

[gmartine]

Very good point and one i overlooked. Schoolboy error

Back to Andrew Millward's design school for you sir, (recognise the avatar).

 

[SJB060685]

Back to Andrew Millward's design school for you sir, (recognise the avatar).

So who are you then. Obviously I'm in the same group as you

 

[gmartine]

I'll introduce myself to you when I'm on the forum sometime, I hardly use it tbf but AM is a generous and knowledgeable resource that's for sure.

 

[SJB060685]

He has a very good understanding yes. Certainly taught me a lot my college didn't.

 

[siricosm]

As gmartine suggested, first thing is to know for pipe sizing is the total heat load for the house, and for each area that you would like to run a "main" to.

I would run 22mm from the boiler where convenient, and then take 15mm spurs off that to feed 2 or 3 rads each, unless they are small. I don't think it matters how "close" the 22mm gets to the rads. I would probably keep the single 22mm run going upstairs, going room to room with 22mm is just a waste. Just make sure you don't have too many rads on a single 15mm run off the 22mm main.

To put things in perspective, a 15mm pipe has a cross sectional flow area of 3.14 * ((15-2)/2)^2 = 132 mm^2, and a 22m has 3.14 * ((22-2)/2)^2 = 314 mm^2, so the 15mm has almost 1/2 the heat carrying capacity of the 22mm (although it reduces a little because the 15mm has relatively more fluid friction).

A two pump system is not bad, in fact it can often be better than 1 pump and zone valves, but it is more expensive in the short term. As unituitive as it seems, pumps last longer, and are more reliable than zone valves.

If you are worried about balancing, I would buffer it and use TRVs.