Please help with this heat pump dilemma

NedS

Sandwich said:

QrizB said:

Sandwich said:

I’m looking for advice on a heat pump install and facing a few issues. The biggest problem is space: my current airing cupboard (which holds a cylinder linked to a back boiler system) has a depth of just 480 mm. E.ON told me the Ideal system they offer needs at least 650 mm, and the Vaillant AroTHERM won’t fit either. Is there a good heat pump system with a narrower cylinder that would fit in this space?

This Grant cylinder claims to be 478mm diameter:

https://www.wickes.co.uk/Grant-QRSC150SL-Quick-Recovery-Single-Coil-Slimline-Cylinder---150L/p/293890

Grant heat pumps aren't the best-of-the-best but they're OK, my parents have one.

Data sheet here (see page 2 for the slimline models):

https://media.wickes.co.uk/is/content/wickes/GPID_5000122857_TECH_0

Alternatively, is there any scope that you could just demolish the cupboard then re-build it around your new cylinder? Is it just studding, or are we talking load-bearing walls?

The space is wide enough and tall enough. It's something like 700mm wide, but only 480mm deep. I can'd demolish behind it because it's a load bearing wall, and I don't want to build out because it's in a hallway and would look wrong. 

I do have a cupboard in what's going to be the home office that is nearly big enough, but I'd have to extend it a bit. Not ideal, but doable. 

Another alternative, my neighbour who didn't have space indoors had their 'plant' cited outside in a well insulated lean-to shed constructed by the installers, next to the heat pump unit. Do you have any attached out buildings or anywhere else it could be accommodated? Not ideal, as there will be substantial heat loss, and it's always better for that heat loss to occur within the heated envelope of the property.

QrizB

benson1980 said:

As for refrigerant, I don’t get that. The refrigerant is in the unit outside. How would it leak under the floorboards?

Suspended timber floors need ventilation, otherwise they get damp and rot. So it could seep in through the air bricks.

I'm not convinced it's a significant risk, but I'm not the one putting my name on the bit of paper that says it's safe!

FreeBear

benson1980 said:

Sandwich said:

benson1980 said:

Do you have a loft space that could accomodate a cylinder?

To answer the other queries suspended floors have no bearing (other than insulation properties or lack thereof) on choice of ASHP specifically so not sure what they are talking about there. Furthermore I'd also be asking for reasons as to why the existing pipework is deemed to be insufficient (flow restrictions etc). 

I do have loft space, but the technician said the cylinder weighs 180kg when full, so I'd probably need a survey and work done. 

The issue with the Vaillant system is supposedly that because it uses R290 refrigerant, if it leaks it could accumulate under the floor and be a fire hazard. Don't know if that's true. 

I’d definitely explore the loft option. You can get horizontal cylinders, or reinforce/ spread the load if installing a vertical. Plenty of installs (including ours) have it in the loft.

Getting a tank up in to the loft space may not be an option if the hatch is on the small side. Most HP manufacturers also give a limit on pipe runs to a tank. And as NedS points out, it is preferable to keep the tank within the thermal envelope of the building - It reduced the heat loss from the tank, and the "waste" heat contributes to keeping the house warm.

benson1980

QrizB said:

benson1980 said:

As for refrigerant, I don’t get that. The refrigerant is in the unit outside. How would it leak under the floorboards?

Suspended timber floors need ventilation, otherwise they get damp and rot. So it could seep in through the air bricks.

I'm not convinced it's a significant risk, but I'm not the one putting my name on the bit of paper that says it's safe!

That is such a tenuous risk if that is the reason, and never heard of that before. There might not be any air bricks anywhere near the proposed installation site and even if there were, the minimal risk could be designed out I am sure. In short it'd be worth getting another installer opinion I believe.

benson1980

FreeBear said:

benson1980 said:

Sandwich said:

benson1980 said:

Do you have a loft space that could accomodate a cylinder?

To answer the other queries suspended floors have no bearing (other than insulation properties or lack thereof) on choice of ASHP specifically so not sure what they are talking about there. Furthermore I'd also be asking for reasons as to why the existing pipework is deemed to be insufficient (flow restrictions etc). 

I do have loft space, but the technician said the cylinder weighs 180kg when full, so I'd probably need a survey and work done. 

The issue with the Vaillant system is supposedly that because it uses R290 refrigerant, if it leaks it could accumulate under the floor and be a fire hazard. Don't know if that's true. 

I’d definitely explore the loft option. You can get horizontal cylinders, or reinforce/ spread the load if installing a vertical. Plenty of installs (including ours) have it in the loft.

Getting a tank up in to the loft space may not be an option if the hatch is on the small side. Most HP manufacturers also give a limit on pipe runs to a tank. And as NedS points out, it is preferable to keep the tank within the thermal envelope of the building - It reduced the heat loss from the tank, and the "waste" heat contributes to keeping the house warm.

Yes access may indeed be an issue. Heat loss not so much on modern cylinders. Even on the coldest days ours loses about 2 degrees through the day.

Reed_Richards

QrizB said:

benson1980 said:

As for refrigerant, I don’t get that. The refrigerant is in the unit outside. How would it leak under the floorboards?

Suspended timber floors need ventilation, otherwise they get damp and rot. So it could seep in through the air bricks.

I'm not convinced it's a significant risk, but I'm not the one putting my name on the bit of paper that says it's safe!

If this is the issue, then it's an issue with where the heat pump is sited.  Guidance states not to put a heat pump using R290 (Propane) refrigerant close to a drain for the reason stated, nor close to an air brick, presumably.  You would not want a leaky heat pump to fill the space under your floor with propane that might then be ignited.  

benson1980

Reed_Richards said:

QrizB said:

benson1980 said:

As for refrigerant, I don’t get that. The refrigerant is in the unit outside. How would it leak under the floorboards?

Suspended timber floors need ventilation, otherwise they get damp and rot. So it could seep in through the air bricks.

I'm not convinced it's a significant risk, but I'm not the one putting my name on the bit of paper that says it's safe!

If this is the issue, then it's an issue with where the heat pump is sited.  Guidance states not to put a heat pump using R290 (Propane) refrigerant close to a drain for the reason stated, nor close to an air brick, presumably.  You would not want a leaky heat pump to fill the space under your floor with propane that might then be ignited.  

Useful info-thanks. Indeed it looks like there is an ‘exclusion zone’ around the sides/base of the r290 units. The risk does seem really minimal though that any escaped refrigerant would directly flow into an air brick before seeping into the ground…even if it was right behind the unit

Reed_Richards

I agree that the real risk is probably minimal but it's also predictable as something that could happen, hence the advice to take steps to avoid that possibility.   This is from a US website: https://www.hocongas.com/blog/can-propane-tanks-explode/

the Consumer Product Safety Commission estimates that there are only about 600 propane tank explosions a year. That number is not very large considering that propane is used in about 11.9 million households, according to the National Propane Gas Association.

matelodave

A quick shufti on t'interweb suggests that the maximum amount of R290 in a heat pump is around 150gm but it could also be less depending on your system.

(It is classified as a flammable substance, and its charge amount is subject to strict regulations. In Europe, the maximum safe charge for R290 in hermetically sealed systems is 150g per circuit, as per IEC 60335-2-40 safety standards)

As 1kg of liquid propane =0.546cum of gas, in the great scheme of things, the actual volume of gas that's likely to be released from 150gm isn't really all that much.

It might take your eyebrows off if you were leaning over it but I cant see it causing much of a problem out in the open air - seems like "elf' n safety" gone mad. Especially when you see several 47kg propane bottles with flexible tails propped against house walls together with the regulator for cooking an heating.

I carry up to 20kg of the stuff in plastic cylinders in my caravan 

michaels

Sandwich said:

benson1980 said:

Do you have a loft space that could accomodate a cylinder?

To answer the other queries suspended floors have no bearing (other than insulation properties or lack thereof) on choice of ASHP specifically so not sure what they are talking about there. Furthermore I'd also be asking for reasons as to why the existing pipework is deemed to be insufficient (flow restrictions etc). 

I do have loft space, but the technician said the cylinder weighs 180kg when full, so I'd probably need a survey and work done. 

The issue with the Vaillant system is supposedly that because it uses R290 refrigerant, if it leaks it could accumulate under the floor and be a fire hazard. Don't know if that's true. 

I am guessing they are proposing a split system rather than a monoblock?

Does the 480 existing cupboard depth measure from inside the door?  With a slim cylinder it might be possible to have the plumbing all done to the side but it is obviously easier to plumb/maintain if it is in front.

Finally afaik it is entirely possible to mix and match cylinders and heat pumps from different manufacturers (although obviously not for split systems)