Plumbing and heating

[nod]

I had a couple of friends down to have a look at first fixing plumbing and heating

Both fully qualified

 it conflicting opinions

 

ive 134 mtrs of UFH downstairs

Cadmans have informed me that this will need just under 10kw of boiler capacity 

 

One has said Use a system boiler 

with a storage cylinder 250 ltrs 

sites under the boiler

the othe 300 sites upstairs as shown on the drawing

 

id prefer baxi thought 40kw

told max is 32 in this type of boiler

one says to small Other say fine

Is there anywhere I can get a P&H drawing done

To sort this out 

 

Any advise pls

 

[Jeremy Harris]

First off, do you know what the heating requirement is?  10 Kw sounds high for a decent standard of build, unless the house is pretty large.  Realistically we only need about 1 kW of actual heating, even in the very coldest weather, that's for a 130m² house.

 

Hot water is far and away the largest demand.  If you have mains gas, then a combi with a high enough rating to give a decent hot water supply, plus a buffer tank in the heating circuit to stop the boiler short cycling when in heating mode, should be a reasonable option, with the boiler size being set by the hot water demand.

[PeterW]

Sounds like the first one has used the standard rad heat loss calculator for a minimum regs House. What does the heat loss calculator a la @JSHarris say you need ..?? 10kw is a lot of heat ...

 

What are your DHW requirements ...?? 40Kw is a big boiler unless it’s a combi .... and a UVC too..??

[nod]

7 hours ago, PeterW said:

Sounds like the first one has used the standard rad heat loss calculator for a minimum regs House. What does the heat loss calculator a la @JSHarris say you need ..?? 10kw is a lot of heat ...

 

What are your DHW requirements ...?? 40Kw is a big boiler unless it’s a combi .... and a UVC too..??

I will have a look through my paperwork when I get home

The 10 kw for the UFH is what Cadmans quoted as the max needed to run the UFH

[Nickfromwales]

I've recently done a conversion re-using a Baxi 40kw combi to heat a 400L thermal store, ( the TS is for DHW only ), and also 26 radiators. The radiators serve a big 7 bedroom 4 bathroom house. 

The guy who's told you the 40kw combi boiler does 32kw to heating is right, but why would anyone recommend a combi and a hot water cylinder ? I only did the above as some dickhead told the customer to  buy a combi for 7 bed / 4 bathrooms  so we reused the new boiler to save buying a system boiler. We would not have done this by design. 

As you have Ufh there is plenty of scope for a W-plan ( DHW priority ) system, utilising a system boiler. Basically you can get away with a smaller boiler as it only does either DHW OR space heating, but never the two at the same time. If DHW gets drawn off whilst the heating is running to a point where it needs to recharge, the cylinder thermostat takes priority and the boiler stops heating the Ufh and jumps across to reheat the cylinder at full speed, then, when the cylinder is hot again, the system reverts back to providing space heating. With radiators you would notice the heating has stopped serving them after a short while, but with Ufh he slab will retain heat and you'll never notice the change. 

So basically all you need is a 30-35kw boiler ( max ) and a DHW cylinder sized according to your DHW needs. 

 

Edited to add : The only reason for that size boiler is to heat the DHW cylinder quickly which you need with W-plan . . You could probably get away without w-plan tbh, if you size the DHW cylinder correctly. 250L is too small for your house afaic, so I'd go for 300L minimum. 

[nod]

30 minutes ago, Nickfromwales said:

I've recently done a conversion re-using a Baxi 40kw combi to heat a 400L thermal store, ( the TS is for DHW only ), and also 26 radiators. The radiators serve a big 7 bedroom 4 bathroom house. 

The guy who's told you the 40kw combi boiler does 32kw to heating is right, but why would anyone recommend a combi and a hot water cylinder ? I only did the above as some dickhead told the customer to  buy a combi for 7 bed / 4 bathrooms  so we reused the new boiler to save buying a system boiler. We would not have done this by design. 

As you have Ufh there is plenty of scope for a W-plan ( DHW priority ) system, utilising a system boiler. Basically you can get away with a smaller boiler as it only does either DHW OR space heating, but never the two at the same time. If DHW gets drawn off whilst the heating is running to a point where it needs to recharge, the cylinder thermostat takes priority and the boiler stops heating the Ufh and jumps across to reheat the cylinder at full speed, then, when the cylinder is hot again, the system reverts back to providing space heating. With radiators you would notice the heating has stopped serving them after a short while, but with Ufh he slab will retain heat and you'll never notice the change. 

So basically all you need is a 30-35kw boiler ( max ) and a DHW cylinder sized according to your DHW needs. 

Thank you Nick That is a massive help As I’ve already stated one heating guy has suggested siting the cylinder under the boiler

to save running pipe work across the house Is that feasible

with pipe work etc

im curious as to why the architecht has put it upstairs

so far away from the boiler

Is there anywhere that I can send my drawing off to and get a heating system design

 

Thanks again Gary

Edited October 21, 2017 by nod

[nod]

Just looking at my original Sap

It states

Boiler Worster Greenstar

model qualifier 35Di Classic system ErP

(regular boiler)

cylinder200 ltr 

Does this make sense 

Is 200 adiquate?

[le-cerveau]

@Nickfromwales will give a more qualified answer, but for a 3 bath house (from your plans) 200ltr just won't cut it!  One bath will kill the cylinder.  Even with a powerful boiler to recharge it you will struggle if more than one bathroom is used at once.  Go bigger if you have the space, but make sure it is well insulated and then get more insulation as heat loss is the biggest killer as @JSHarris will tell you.

[Nickfromwales]

The most likely reason your architect has put the cylinder upstairs is because you have an airing cupboard there and traditionally people like to have heat in there to 'air' their clothes, but more importantly it'll be central of the bathrooms ( and closer to the places you most often need hot water ) so there is less delay in getting hot water to the taps / showers etc. The only downside is it'll be further away from the kitchen sink which will result in a delay getting hot water to it.

A good system design will reduce the hot water pipework lengths to a minimum by moving the cylinder accordingly, but you could put the cylinder anywhere to be honest and fit a hot water circulation pump, commonly referred to as a 'hot return circuit' ( HRC ), which negates the problem of having the cylinder further away by circulating the hot water stored in the cylinder between it and the furthest outlets away from it. That's a neat idea IMO, and gives near instant hot water to each outlet, but looking at the layout of your house you probably could get away without one if you were happy to have the cylinder in the utility room. In my opinin you'd be better off not having the cylinder upstairs, use the utility space for plant room, and have the upstairs cupboard for clothes / linen storage, with a tiny radiator if you want a bit of heat in there. 

You can't get away from running pipework, wherever you put it, as you'll need to get heated water from the boiler to the cylinder to heat it up. The sweet spot is working out where it'll have the least losses / wasted hot water ( long hot water runs should be avoided if not having a HRC ) but if the cylinder goes into the utility room only the master bathroom will 'suffer'. 

Worcester Bosch do a new rang of hot water cylinders which I believe have very high heat recovery coils for super fast heat up times, but I'll have to look at those closely before commenting as I've no experience or knowledge of them at the moment other than a breif read here and there. Do you know the make / model / type of cylinder that has been recommended?

After dealing with hot water, you need to check you've got sufficient cold mains pressure and flow to make everything work . Have you done a survey of the cold mains supply yet? Litres per minute flow and static pressure, and do you know the size of the cold mains supply pipe that feeds the house ?

[ProDave]

I would want the cylinder closer to the kitchen. (that is indeed what I am doing) the kitchen hot tap is the one that gets used a lot and waiting ages for the hot water to get there is a pain.  Bathrooms get used once or twice a day so less important that they get the hot water as quickly.

[Jeremy Harris]

4 hours ago, ProDave said:

I would want the cylinder closer to the kitchen. (that is indeed what I am doing) the kitchen hot tap is the one that gets used a lot and waiting ages for the hot water to get there is a pain.  Bathrooms get used once or twice a day so less important that they get the hot water as quickly.

 

 

Gets my vote. 

 

I don't think there's any problem at all with waiting for hot water in a bathroom or shower room, as the chances are that a shower or bath is going to be drawing hot water for long periods and only a few times a day, and most probably in a usage pattern where one user will follow on fairly quickly from another.  The two rooms where you need hot water almost instantly at the tap are the most-used WC in the house (the downstairs one for us) and the kitchen.  Invariably these are low usage outlets, in terms of overall volume, but high frequency usage.  Hand washing, for example, is something that happens several times a day, at intervals long enough for the water in the pipes to cool down.   The same goes for washing or rinsing stuff in the kitchen .

Edited October 22, 2017 by JSHarris
typo

[nod]

52 minutes ago, Nickfromwales said:

The most likely reason your architect has put the cylinder upstairs is because you have an airing cupboard there and traditionally people like to have heat in there to 'air' their clothes, but more importantly it'll be central of the bathrooms ( and closer to the places you most often need hot water ) so there is less delay in getting hot water to the taps / showers etc. The only downside is it'll be further away from the kitchen sink which will result in a delay getting hot water to it.

A good system design will reduce the hot water pipework lengths to a minimum by moving the cylinder accordingly, but you could put the cylinder anywhere to be honest and fit a hot water circulation pump, commonly referred to as a 'hot return circuit' ( HRC ), which negates the problem of having the cylinder further away by circulating the hot water stored in the cylinder between it and the furthest outlets away from it. That's a neat idea IMO, and gives near instant hot water to each outlet, but looking at the layout of your house you probably could get away without one if you were happy to have the cylinder in the utility room. In my opinin you'd be better off not having the cylinder upstairs, use the utility space for plant room, and have the upstairs cupboard for clothes / linen storage, with a tiny radiator if you want a bit of heat in there. 

You can't get away from running pipework, wherever you put it, as you'll need to get heated water from the boiler to the cylinder to heat it up. The sweet spot is working out where it'll have the least losses / wasted hot water ( long hot water runs should be avoided if not having a HRC ) but if the cylinder goes into the utility room only the master bathroom will 'suffer'. 

Worcester Bosch do a new rang of hot water cylinders which I believe have very high heat recovery coils for super fast heat up times, but I'll have to look at those closely before commenting as I've no experience or knowledge of them at the moment other than a breif read here and there. Do you know the make / model / type of cylinder that has been recommended?

After dealing with hot water, you need to check you've got sufficient cold mains pressure and flow to make everything work . Have you done a survey of the cold mains supply yet? Litres per minute flow and static pressure, and do you know the size of the cold mains supply pipe that feeds the house ?

Thanks for that Nick

 

The only reccimendation for the cylinder Is a 200 ltr No brand

I haven’t done a mains pressure test

But our engineer informed us at the start of the project that the mains pressure is good

[Nickfromwales]

I'll update this tomorrow regarding the cylinder type / size ?

I have a feeling the WBosch may be overly expensive . 

Fyi 200L is WAY too small for your house. 250L would be the absolute minimum and I'd say you'd need at least 300L as the system should be able to match the simultaneous use of the showers in all the bathrooms at the least. Some folk here have economised their systems to suit their use of DHW and the fact they'll be staying there for the rest of their days, which is fine, but I believe systems should be designed to suit the property where there are multiple bathrooms etc.