system size and ductwork

[betmo]

Replacing oil furnace with heat pump, A contractor did manual j and it comes out to 2.5 ton, but the duct work he said supports only 2 ton, he proposed a lennox xp17 2 ton, with variable speed air handler(cbx32mv0 and 10kw(i think) strips. I plan to keep the temp at steady 67-71 in the winter. He says it will work fine, I am wondering if this sounds right? We have no room to add returns or supply easily. House is in Tacoma (near Seattle), WA.

[snupytcb]

i would get a couple mor estimates with manual j's.

[betmo]

I do have another, but he just looked at duct work and didn't say anything about it. This guy actually measured it.

[dan sw fl]

Replacing oil furnace with heat pump, A contractor did manual j and it comes out to 2.5 ton, but the duct work he said supports only 2 ton, he proposed a lennox xp17 2 ton, with variable speed air handler(cbx32mv0 and 10kw(i think) strips. I plan to keep the temp at steady 67-71 in the winter. He says it will work fine, I am wondering if this sounds right? We have no room to add returns or supply easily. House is in Tacoma (near Seattle), WA.

We don't judge with sound but by NUMBERS?!!!

Need R-value walls, ceiling

U-value of windows, & sizes

Infiltration ... average or loose

1,600 sq ft ?

[dan sw fl]

it sounds right to me, but that's just me listening to myself.

What were your fuel costs for the
last few years?

[betmo]

house is 1400sq ft. , my oil cost the last year was about $1600. My main question is if I get the 2 ton because the ducts can't support 2.5ton, what would happen? And if i got a 2.5ton and ducts can't handle it what then? I plan on doing more insulating in the next year(walls), attic well insulated now, have low e windows already. Being in the NW, cooling is not the concern, mainly heating.

[54regcab]

If you don't have enough ductwork you will pay to run a 2.5ton unit and only get 2 tons of cooling/heating out of it.

[RyanHughes]

Good chance the 2 ton is fine for 1400 sqft. A Manual J is only as accurate as the input data. A 2.5 ton would cost more to operate on undersized ductwork. While the XP17 is a bit short on heating btu's for a 2 ton, with a 10 kW staged heater package, you will have plenty of heat and one or both of the elements can come on if and when needed to supplement the heat pump.. What was the total heat loss as per Manual J?

[dan sw fl]

house is 1400sq ft. , my oil cost the last year was about $1600. My main question is if I get the 2 ton because the ducts can't support 2.5ton, what would happen? And if i got a 2.5ton and ducts can't handle it what then? I plan on doing more insulating in the next year(walls), attic well insulated now, have low e windows already. Being in the NW, cooling is not the concern, mainly heating.

What would happen?

Aux Heat will run longer when it's < ~35'F.
That might Not be much of an economic penalty in NW where eleCtric rates might be < $0.05 / kW-hr
Going from $1,600 OIL to < $400 for heating is a HUGE heat pump benefit.

Heat loss might be 20,000 BTU/hr at 20'F outside and 16,000 BTU/hr at 30'F.

[dan sw fl]

house is 1400sq ft. , my oil cost the last year was about $1600. My main question is if I get the 2 ton because the ducts can't support 2.5ton, what would happen? And if i got a 2.5ton and ducts can't handle it what then? I plan on doing more insulating in the next year(walls), attic well insulated now, have low e windows already. Being in the NW, cooling is not the concern, mainly heating.

What would happen?

Aux Heat will run longer when it's < ~35'F.
That might Not be much of an economic penalty in NW where electric rates are frequently < $0.05 / kW-hr
Going from $1,600 OIL to < $400 for heating is a HUGE heat pump benefit.

Heat loss might be 20,000 BTU/hr at 20'F outside and 16,000 BTU/hr at 30'F.

[beenthere]

Do you currently have central A/C, if so what size is it.

[betmo]

No a/c, just oil furnace.
My ducts start out with a 30x8 trunk, 1 6x8 supply off that then a 7x10 supply to a wall with register on both sides, trunk down to 25x7 with a 5x7 supply off that, trunk down to 20x7 and a 5x7 off that, down to 15x7 with a 5x7 supply off that, the trunk is then 10x7 to the final register about 15ft from furnace serving 2 rooms(supply in wall with register on both sides.. all registers are 12x6 4 returns about 14x7 each.

[beenthere]

2.5 tons might make some noise with the amount of supplies you have.