Dual heat sources for 4 bed detached. Bad Idea?

[lavadiy]

Edit: added models of current equipment

Hey.

I''m considering something for ease but not sure if its a bad idea.

I have a largish 4 bed detached bought recently. Owners had left the country and house had a flood so was a bit of a do-up project.

They had an ASHP installed in combination with a V old Gas boiler and vented system but it was done V badly. See here for a bit more info.

ASHP = Viessmann Vitocal 300A,
Hot Water Tank = Viessmann Vitocell 300B) (2 coils, pressurised HWT)
Also have a Solar Thermal set up to feed into the Vitocell largest coil.

Vitocal 300A + controller
Vitocell 100e
Vitocell 300b
Solar System Vitosol 100f ???

Starting from scratch as all pipes and old rads ripped out.
Having UFH downstairs using panels (www.floorheater.co.uk) but cant afford it upstairs plus all the cost to get the ASHP to do the hot water or run low temp rads upstairs
I'm having a nightmare with costs of getting the system up and running. 1 quote has come in as around 10k EXCLUDING the heat destinations e.g UFH or Rads + hot and cold mains around the house. (Can do that myself).

Question:

1. Is it a bad idea to use the ASHP for UFH downstairs only, (Ideal for UFH as uses low temps + weather compensation), then use a Gas boiler to do the hot water, and standard Rads upstairs?

2. If its a bad idea anyone got any tips or advice on this: run Gas boiler which i know can mix down for UFH to low temp, but then run standard rads upstairs, do the HW + use Weather Compensation?

Thinking of a Viessmann 200 system boiler if going Gas route.

I'm not sure on the Gas system running weather comp yet needing dual temps for upstairs + downstairs. May cost a lot to run??

Any help appreciated. If any serious plumbers around i'm in staffordshire not too far from Stoke-on-Trent.

 

[Agile]

I strongly suggest using ASHP for the UFH and a small gas boiler say 18 kW for the HW and upstairs rads.

That will be cheapest and most efficient. Perhaps from £2k.

Tony

 

[dcawkwell]

The simple solution is have the air source heat pump and
and boiler connected together.

The air source will do most of the requirement for most of the year
with the gas boiler coming in and acting as a booster.

Otherwise the rest of the house is standard central heating set up.

 

[lavadiy]

The simple solution is have the air source heat pump and
and boiler connected together.

Wondered this, but the costs of doing that are Very high. I also think a buffer tank is needed for this set up which i do have, but can get rid of if dont try and run 2 systems.

I dont have a Gas boiler see and setup costs of the ASHP into the HW tank and all the plumbing etc from the quote i've had is high.

I thought if the ASHP does UFH its a simple 2 pipe send return to UFH manifold, then a Gas boiler and rads to do upstairs and the HW tank should be fairly easy to plumb in and more plumbers familiar etc. I can run most of the Rad pipe work in myself see as have done before a few times.

I will save on using normal Rads see (convector ones still) rather than having to either oversize by about 40% or use low temp rads for the low temps of ASHP, which is what's pushing the cost high.

 

[dcawkwell]

The simple solution is have the air source heat pump and
and boiler connected together.

Wondered this, but the costs of doing that are Very high. I also think a buffer tank is needed for this set up which i do have, but can get rid of if dont try and run 2 systems.

I dont have a Gas boiler see and setup costs of the ASHP into the HW tank and all the plumbing etc from the quote i've had is high.

I thought if the ASHP does UFH its a simple 2 pipe send return to UFH manifold, then a Gas boiler and rads to do upstairs and the HW tank should be fairly easy to plumb in and more plumbers familiar etc. I can run most of the Rad pipe work in myself see as have done before a few times.

I will save on using normal Rads see (convector ones still) rather than having to either oversize by about 40% or use low temp rads for the low temps of ASHP, which is what's pushing the cost high.

Easy to set up get other quotes.
My preference would be a low loss header that both air source and gas boiler feed. From that you tap off what you like.

 

[lavadiy]

You will need a buffer vessel here to do this properly, not just a low loss header. Complete overall control of a complex system such as this is not a simple matter.

Indeed, which starts driving the cost up. I do have a buffer vessel that was installed and dont forget currently i DONT have a gas boiler.

I'm trying to find the most effective method.

- UFH is a definite requirement downstairs now.
- I've got the ASHP, HW tank + buffer cylinder already so would like to use them as they've cost me nothing, but i dont have 10k just to get it all set up as the single heat source.

However i dont want to put a system in that a) costs a fortune to install (dont have the funds) and b) is incredibly complex due to people fixing in the future.

Hence wondering if it was a bad idea to have simple ASHP driving UFH then a separate Gas boiler (to buy) and do normal temp rads + HW.

My thinking on the latter is cost of a boiler could be recouped by just buying normal rads. I can do a normal rad first plumb fit myself to again reduce cost and then get someone to install the boiler, connect up HW tank etc. As that would be fairly standard it shouldnt cost the earth.

The ASHP would be simple set up so costs of plumbing to UFH manifold and then just commissioning should be within budget..

In future i could always add UFH upstairs and get the heatpump to do that??

I just dont know if a) this is normal practise b) if i should just sack off the ASHP altogether. Just seems a shame.

We will be in this house for a long time and as i've got all upstairs flooring up its ideal time. I've got no bathrooms in the house (all ripped out).

 

[dcawkwell]

Systems can always be changed in the future.

If you have a buffer tank my suggestion would be choose a place in the house (outside wall) where you can house the gas boiler and buffer tank if you have one. On the outside wall will be the air source heat pump.

All piping should come to this point.

By all means connect the air source up to just the underfloor.

You can chop and change as you like in the future should you find the air source not giving the underfloor enough in very cold weather.

I suggest location of air source should be south facing wall to get the
most from the air source if possible.

Connecting up the system shouldn't be that costly. It is only
a few flows and returns.

Having two boilers even if one is an air source shouldn't present any problems.
A two boiler cascade set up.

 

[lavadiy]

Thanks for that.

Indeed the ASHP is on a south wall in the garage. The ducting is all good quality install (separate company did the ducting).

I've also moved my HWT vitocell 300b into the garage to be near the ASHP and if i decide to buy a gas boiler hopefully will have room for that too.

Indeed i would'nt have thought the plumbing costs should be that hight to get it all connected. Plumber wants around 3.5k to plumb in the heat pump, to the tank. basically just the plumbing in the garage. Then the commissioning guys wants 1.5k + there's some pumps and heat exchange and other bits needed which brings it to near 3.4k. There's another 1.5k + parts to do the solar.

 

[dcawkwell]

Thanks for that.

Indeed the ASHP is on a south wall in the garage. The ducting is all good quality install (separate company did the ducting).

I've also moved my HWT vitocell 300b into the garage to be near the ASHP and if i decide to buy a gas boiler hopefully will have room for that too.

Indeed i would'nt have thought the plumbing costs should be that hight to get it all connected. Plumber wants around 3.5k to plumb in the heat pump, to the tank. basically just the plumbing in the garage. Then the commissioning guys wants 1.5k + there's some pumps and heat exchange and other bits needed which brings it to near 3.4k. There's another 1.5k + parts to do the solar.

3.5k to connect a flow and return pipe and switch the electric on seems a bit steep.

 

[Agile]

You do seem to be getting some very high quotes.

Could it be that the system is too complex for them to get their heads round and they are giving a high quote to cover themselves?

None of what you describe seems very coimplicated but it can be daunting if you are showing them an empty house when you are expecting to do much of the work yourself.

Better to do what you plan to and THEN call them so they can better assess the requirements.

Tony