System advice

[b21playa]

My crude drawing, how does that look. Each radiator would have a 15mm flow & return from the manifold.

Also need to work out costs for this versus the zone valve route

Your thoughts are welcomed

 

[b21playa]

What are the opinions on a high flow combi v system boiler?

 

[BlueLoo]

I like your diagram. I'd do similar.

Needs a valve on the HW as you don't want that heating all the time.

No zone valves means local control at the rads and a central programmer.

3 floors is big, so pump on the middle floor, perhaps use a variable speed one to help modulation.
I'd do some check calcs for load swing from min (one rad) to max (all)

I'm answering this because nobody else has. I'd suggest professional design though.

I don't like combi boilers, especially for big houses. Too many compromises for my liking.
I don't like system boilers. I don't see the point of jamming everything into a tight box if you don't have too.
I don't like pressurised systems. You can't work on them and they are more complex than a bog std vented system.

Let the stoning begin.

 

[DP]

From a professional angle, manifold installation requires bigger pipe runs as source is the manifold and final the radiator. Imagine a floor with 6 radiators- there would be 12 pipes from the manifold to the radiators. Now visualise these 12 15 mm pipes below a flooring with limited space.

Next a boiler. On a new system I would fit a combi boiler and an unvented cylinder. Solar panel additional to cylinder.

If house is a big one, woukd fit two combis to split the load, have done it before and worked very well so no single source of heat to fail taking the whole house down.

 

[b21playa]

I like your diagram. I'd do similar.

Needs a valve on the HW as you don't want that heating all the time.

No zone valves means local control at the rads and a central programmer.

3 floors is big, so pump on the middle floor, perhaps use a variable speed one to help modulation.
I'd do some check calcs for load swing from min (one rad) to max (all)

I'm answering this because nobody else has. I'd suggest professional design though.

I don't like combi boilers, especially for big houses. Too many compromises for my liking.
I don't like system boilers. I don't see the point of jamming everything into a tight box if you don't have too.
I don't like pressurised systems. You can't work on them and they are more complex than a bog std vented system.

Let the stoning begin.

Thanks for that. Yes I missed the HW valve on my excellent drawing.

I am just planning on locations for all the items and how to stage all the work.

I was looking at the actual kit and found some ufh manifolds that I could use, with actuators to control each ‘zone’ using the heatmeiser wiring centre and smart thermostats for each room paired to the zone. Only issue with this setup is the costs seems to be going up, I priced just the manifolds & controllers at over £2k, plus there’s a few rads on the other side of the house where I will struggle to run their own 15mm feed & return

 

[bernardgreen]

I don't like combi boilers, especially for big houses. Too many compromises for my liking.
I don't like system boilers. I don't see the point of jamming everything into a tight box if you don't have too.
I don't like pressurised systems. You can't work on them and they are more complex than a bog std vented system.

I agree with BlueLoo on these 3 points

 

[b21playa]

From a professional angle, manifold installation requires bigger pipe runs as source is the manifold and final the radiator. Imagine a floor with 6 radiators- there would be 12 pipes from the manifold to the radiators. Now visualise these 12 15 mm pipes below a flooring with limited space.

Next a boiler. On a new system I would fit a combi boiler and an unvented cylinder. Solar panel additional to cylinder.

If house is a big one, woukd fit two combis to split the load, have done it before and worked very well so no single source of heat to fail taking the whole house down.

Thanks for the reply.

The number of pipes is what is the issue for me. On the first floor I’d have 7 radiators, ground floor would be 10, plus 3 in the loft. I am contemplating about just going for the standard S plan+ I have now but upgrading all pipework to 22mm and only teeing off in 15mm for each rad. Would this work?

Interesting about combi and tank, how would that work?

 

[DP]

Convention and good option is to have all the controls where the hot water cylinder is. In fact there are hot water cylinders with MVs already installed.

Unless you have really old property, 22mm runs to each floor should suffice with finals and branches to suit. A 15 branch might even feed more than one radiator depending on pipe loop loading.

The combi would supply on tap hot water in utility and kitchen unless the hot run is long. Combi also has integral expansion vessel which you most likely have where the hot water cylinder is. Often the kitchen is on first floor and boiler in garage in which case the the hot water to kitchen tap from boiler would take a while to flow hot due to long pipe run

 

[b21playa]

Convention and good option is to have all the controls where the hot water cylinder is. In fact there are hot water cylinders with MVs already installed.

Unless you have really old property, 22mm runs to each floor should suffice with finals and branches to suit. A 15 branch might even feed more than one radiator depending on pipe loop loading.

The combi would supply on tap hot water in utility and kitchen unless the hot run is long. Combi also has integral expansion vessel which you most likely have where the hot water cylinder is. Often the kitchen is on first floor and boiler in garage in which case the the hot water to kitchen tap from boiler would take a while to flow hot due to long pipe run

luckily boiler & tank are being sited centre of the house, just below bathroom and will actually be in the new kitchen so pipe runs for hw are not very long.

yes I already have 3 circuits but the whole pipework needs replacing, luckily I can reuse mv’s as they are only a few years old

 

[b21playa]

I think I’ve settled on a conventional system with pressurised tank. Running all them pipes is going to be difficult.

I’ll get new boiler and tank fitted first and then slowly connect up rads floor by floor. First thing is to get a new water main sorted

I’ve also today upgraded my hive controls to Drayton wiser unit, and as rads are replaced will get smart trv’s

 

[fezster]

I had a large system like yours put in about 10 years ago. Vaillant 438 boiler, 3 zones (u/s, d/s, hot water). 28mm primaries from boiler, reducing to 22mm throughout the house and then 15mm to rads.

With multiple zones and a large boiler (in particular the vaillant, because of the pump head required to overcome the restrictive hex), a low loss header resolved many of my problems, including being able to spec 2 domestic CH pumps, instead of a large and expensive semi commercial pump.

I tried wiser for a while and for me it just wasn't effective enough to justify the cost. Unless doors between rooms were kept closed, you'd end up with the heat spreading uniformly across individual floors.

I would, however, highly recommend weather compensation and priority hot water with an unvented tank. Not only for efficiency but comfort too.

 

[b21playa]

I had a large system like yours put in about 10 years ago. Vaillant 438 boiler, 3 zones (u/s, d/s, hot water). 28mm primaries from boiler, reducing to 22mm throughout the house and then 15mm to rads.

With multiple zones and a large boiler (in particular the vaillant, because of the pump head required to overcome the restrictive hex), a low loss header resolved many of my problems, including being able to spec 2 domestic CH pumps, instead of a large and expensive semi commercial pump.

I tried wiser for a while and for me it just wasn't effective enough to justify the cost. Unless doors between rooms were kept closed, you'd end up with the heat spreading uniformly across individual floors.

I would, however, highly recommend weather compensation and priority hot water with an unvented tank. Not only for efficiency but comfort too.

Hi

That’s interesting….how far did you run the 28mm primaries (doesn’t the boiler have 22mm connections). Reading up a lot don’t like the 438 we have. How does the low loss header with twin pumps work?

I’ve got the Drayton just as 3 channel at the moment, ordered a trv to test its functionality but may just leave it as each floor, I guess I have the option now as the hive trv’s are supposed to be rubbish.

 

[fezster]

Hi

That’s interesting….how far did you run the 28mm primaries (doesn’t the boiler have 22mm connections). Reading up a lot don’t like the 438 we have. How does the low loss header with twin pumps work?

I’ve got the Drayton just as 3 channel at the moment, ordered a trv to test its functionality but may just leave it as each floor, I guess I have the option now as the hive trv’s are supposed to be rubbish.

28mm primaries for the first 5m or so. That's how the original installation was done and I've subsequently been told many times its a good thing and recommended.

The pump arrangement is very simple. The primary pump is controlled by the boiler with overrun. The secondary is on the 3 MVs SL.

 

[b21playa]

Hi all, Happy New Year

I finally got around to measuring each room and using an online calculator to work out but. If I add all rads plus allow 10,000btu/3kw for the tank I get a total of 100,000btu. By the time I get the rads, some will be over sized so I estimate 110,000 btu.

Does this then equate to a 32kw boiler? Have I missed anything I needed to consider? Want to ensure someone isn’t going to under specify or over specify a boiler

Thanks in advance

 

[b21playa]

Hi all

just to update, I had a heating engineer around yesterday and he recommended a Worcester 35kw or a vanillant 37kw.

Does this sound right or too excessive?

thanks