How to design a domestic plumbing and heating system

[Annker]

I am starting a large victorian renovation and it will involve, (amongst everything else) installation of an entirely new heating and plumbing system.

 

Plumbing, like most trades, seems to have two main aspects; design and installation.

The installation part on my last two projects was painful. The plumbers seemed happy to work to a wider tolerance that I'd deem acceptable. I had to repeatedly check and correct the setting out of 1st fix & associated ware positions. I seemed to spend much time overseeing a supposid specialist trade and in frustration I frequently said to myself I could do this myself!

 

Clearly I wouldn't have the knowledge or speed of an experienced plumber, but being a carpenter by trade and therefore well experienced "on the tools" I believe I'd have the dexterity to install a large amount of plumbing/heating system. Perhaps then enlist a plumber on a day rate for soldering, final connections, etc.

 

Currently I don't have the knowledge to design the system. I see a lot of commentor's on this sub-forum design their own systems. Perhaps it's something I could design if there was a suitable "design your own" resource.  

From reading various threads here I have a basic idea of some very general specifics for the system but clearly this is far from a working design:

• The house is Victorian with solid brick external walls. I won't install EWI, neither IWI due to the risk of interstitial condensation so I'm not chasing thermal efficiency with the refurbishment works. In such situation I understand that a gas fired CH system with radiators to be the most suitable
• Pipework in Hep20 or similar to facilitate a simpler install     
• All F&R to radiators on individual loops from a manifold
• Domestic feeds similarly from a manifold  
• My rear facing roof surfaces are perfectly orientated to capture sun rays so I would like to instal solar panels although I have no idea how these will be integrated into the MEP system
• I believe the house will be far from airtight so no MVHR but  

I've worked on large scale projects where the MEP system is designed by specialist MEP consulting engineers but does anyone know if there are smaller MEP engineers that design the plumbing & heating system for domestic projects and if this is a common procurement route for a self-builder? 

Has anyone had a design drawn up this way? Maybe someone can recommend an designer.

[Annker]

Just to add further description of the property:

• Semi detached Victorian 
• Floor area ~216 m sq /2325 ft sq. Laid out on Cellar, Ground and First floor
• 4 ensuite bathrooms (no main bathroom)
• 1 cloakroom wc 

 

[Annker]

Anyone at all able to chip in with any kind of advice on my post above? 

[Big Jimbo]

On my daughters, i split the gas central heating into Two. Upstairs, and downstairs. Ran a 22mm flow and return to upstairs, and downstairs. Ran 15mm tails from manifolds to each radiator. Works well. The only thing a mate told me was to try and make the 15mm runs less than 6meters.  I will need to start designing mine soon.

[Annker]

3 hours ago, Big Jimbo said:

On my daughters, i split the gas central heating into Two. Upstairs, and downstairs. Ran a 22mm flow and return to upstairs, and downstairs. Ran 15mm tails from manifolds to each radiator. Works well. The only thing a mate told me was to try and make the 15mm runs less than 6meters.  I will need to start designing mine soon.

Thanks Jimbo, that's helpful.

Keeping the runs <6m isn't so easy in even a moderately sized house, certainly points towards having the plantroom or (manifold at least) centrally located if possible. I've a cellar so that gives me a bit of flexibility on where to locate all that gear on the floor plan. 

[TonyT]

Heating system will have to be designed to 55degc or lower for a gas installtion 

 

its over 150m2 so needs at least 2 zones.

 

not sure if you are going gas or heat pump.

 

I would do a heat loss calculation as a starting point and I would design my system if I could with 40 deg in mind so that if I had to go heat pump in 10 plus years the pipework has been sized to suit and minimises future fabric disruption

 

i like manifolds and lots of full bore isolation, let’s maintenance proceed without draining down everything, upsetting occupants etc

 

can you do a vertical riser?

[SimonD]

IMHO the best place to start with system design is with the industry manual: Domestic Heating Design Guide - Everything is in there with regards to heat loss calculation (although the BH community tend to use the calculator designed by Jeremy - you'll find a link to it on the forum), pipe sizing and emitter sizing. For manifolds specifically, I've found scant info on the design but made my own using the the above linked design guide to size all the primary and secondary pipework sizing. Works all fine. My manifolds were copper, soldered with full bore level valves on flow and return to each rad.

 

As already mentioned, you'll need 2 zones but that's pretty simple in the grand scheme of things.

 

One thing not covered in the design guide however is priority hot water setup (sometimes referred to as X-plan) with the heating system which is more efficient than your typical S or Y plan. Select your boiler on its ability to support different DHW and CH temp outputs, its modulation and likewise compatible controls that will modulate boiler output.

[Annker]

1 hour ago, TonyT said:

Heating system will have to be designed to 55degc or lower for a gas installtion 

 

its over 150m2 so needs at least 2 zones.

 

not sure if you are going gas or heat pump.

 

I would do a heat loss calculation as a starting point and I would design my system if I could with 40 deg in mind so that if I had to go heat pump in 10 plus years the pipework has been sized to suit and minimises future fabric disruption

 

i like manifolds and lots of full bore isolation, let’s maintenance proceed without draining down everything, upsetting occupants etc

 

can you do a vertical riser?

Hi Tony thanks for the response.

 

The house is 1870's semi, currently no wall insulation.

I can't do EWI as it would cover my attractive brickwork and I'm against IWI on solid walls due to the risk of interstitial condensation 

As such I believe heat pump is may not have the sufficient high temp output for a building fabric with such relatively poor thermal efficiency. Gas fired CH seems to be the best option AFAIK.

 

The plan is the located the plant room in the cellar, and I have some flexibilty which part of the cellar the plant room will be located in, so have scope for a centrally located vertical riser.  

[Annker]

2 minutes ago, SimonD said:

IMHO the best place to start with system design is with the industry manual: Domestic Heating Design Guide - Everything is in there with regards to heat loss calculation (although the BH community tend to use the calculator designed by Jeremy - you'll find a link to it on the forum), pipe sizing and emitter sizing. For manifolds specifically, I've found scant info on the design but made my own using the the above linked design guide to size all the primary and secondary pipework sizing. Works all fine. My manifolds were copper, soldered with full bore level valves on flow and return to each rad.

 

As already mentioned, you'll need 2 zones but that's pretty simple in the grand scheme of things.

 

One thing not covered in the design guide however is priority hot water setup (sometimes referred to as X-plan) with the heating system which is more efficient than your typical S or Y plan. Select your boiler on its ability to support different DHW and CH temp outputs, its modulation and likewise compatible controls that will modulate boiler output.

Hi Simon,

Great that Design Guide sounds exactly like the kind of resource I'm looking for, that's evening reading sorted for the next few weeks!

Thanks for the other points also.

 

Did you solely design your system or did you both design and install it as well, and if so did you weld the manifolds up yourself?

I guess the key is to pressure test what you install. I think the manifold system also facilitates this as you can isolate testing and potential leak points a little easier  

[SimonD]

53 minutes ago, Annker said:

Did you solely design your system or did you both design and install it as well, and if so did you weld the manifolds up yourself?

I guess the key is to pressure test what you install. I think the manifold system also facilitates this as you can isolate testing and potential leak points a little easier 

 

Design and install myself including welding up the manifolds. Ironically, I've trained and become Gas Safe registered since doing it! Yes, pressure test. There are some fairly cheap pressure testers you can get off ebay for one off use.

[SteamyTea]

8 hours ago, Annker said:

I'm against IWI on solid walls due to the risk of interstitial condensation 

As such I believe heat pump is may not have the sufficient high temp output for a building fabric with such relatively poor thermal efficiency. Gas fired CH seems to be the best option

You can design the condensation risk out with a bit of thought.

Temperature is not power, or energy. As long as your thermal emitters have a large enough surface area, then they can deliver enough thermal energy at quite low temperature differences.